Chapter 6: The Heart in the Living System
“The heart governs the blood and the vessels of the body.” If that sentence is read only as “the heart is master of the vessels,” it is still too thin. A fuller reading is this: what the heart governs is not a set of isolated tubes, but a whole network that can adjust, feed back, compensate, and lose the power to compensate. The previous chapter showed how the four chambers, the valves, the heart wall, the coronary arteries, and the cardiac cycle turn a pump into a precise organ. This chapter steps farther back. It watches how that pump is set inside the closed loop of the systemic and pulmonary circulations, how the microcirculation carries out the real work of nourishment, and how the heart is bound up with the steady state of blood pressure, with the relations of heart and lung, heart and kidney, and heart and spleen, with the reins of the autonomic nerves, and with the ordinary facts of daily life: pressure, lipids, glucose, tobacco, movement, and sleep. Without a view of the whole system, there is no way to understand why blood pressure rises and falls, or why a wound in one place at the heart sets the five organs trembling. There is also no way to turn “the heart governs the spirit” from a slogan into a workable form of care for the whole person.
The heart in the living system is, in physiological terms, the coupling of circulation, breathing, nerves, hormones, and immunity. It is also the echo, in modern language, of the holistic view in Chinese medicine. The older writers spoke of the mutual relations among the five organs, and of qi and blood moving through the channels. Writers today speak of feedback loops, homeostasis, and network medicine. The names differ. The facts they point toward are close. Health is not the isolated normality of a single organ. It is a dynamic balance that many systems hold across time. An ordinary reader does not need to memorize the English abbreviation of every chemical messenger. The reader does need a few main lines: how the closed loop runs, where nourishment actually happens, how pressure is regulated, how the organs drag one another down or nourish one another, and how daily habits become a maintenance manual for the system. This chapter is the hinge of the book, the turn from the organ to the whole of a life. The organ explains how the pump works. The system explains how the pump lets the whole body live with clarity. The next chapter, on the heart of awareness, asks how the experience of that clarity is related to the heart.
From the standpoint of ordinary life, the heart in the system has a familiar face. It explains why the pulse feels tight the day after a sleepless night, why the vision goes dark when a person stands up suddenly, why chronic kidney disease can burden the heart, why sleep apnea makes the right side of the heart work harder, and why treating only the heart sometimes fails to relieve palpitations and shortness of breath. The more precise a scientific description becomes, the more it ought to show connections, so that prevention starts earlier, panic is rarer, and effort in one place can benefit many. After this chapter, a reader may be less tangled in the question of which single number matters most, and clearer about how the whole net is held up by ordinary days. The intelligence of the sovereign organ was never a lone charge. It lay in using the chancellor and the hundred officials well, and in keeping qi and blood moving in order.
1. The Closed Loop: Systemic and Pulmonary Circulation as a Figure Eight
In the adult, the circulation is formed by the systemic circuit and the pulmonary circuit placed in series. The shape is a figure eight lying on its side, or two rings joined end to end. When the left ventricle contracts, it ejects oxygen-rich arterial blood into the aorta. That blood travels through arteries of successive sizes and reaches the capillary beds of the whole body. There, oxygen is exchanged for carbon dioxide, and nutrients are exchanged for metabolic waste. Venous blood then gathers through the venae cavae into the right atrium and passes into the right ventricle. When the right ventricle contracts, it pumps that venous blood into the pulmonary artery and on to the capillaries around the air sacs of the lung, where gas exchange is completed. Oxygenated blood returns through the pulmonary veins to the left atrium and then to the left ventricle. The circuit repeats without a pause. In fetal life the foramen ovale and the ductus arteriosus still shunt blood aside. After birth the pulmonary circulation opens and those shunts close, and the clear double loop of adult life is formed. If a congenital shunt remains, or if some other abnormal channel persists, oxygenated blood and blood that has not been oxygenated mix out of place. At the level of the system, the clean division of labor inside the closed loop is broken.
The systemic circulation can be pictured as the long journey out to the whole body. The pulmonary circulation is the short trip to the lung, where the blood changes its air. Neither journey can be spared. The pulmonary path is short and the resistance is low, so a relatively thin wall of the right ventricle is enough for the work. The systemic path is long and the resistance is high, so the left ventricle must be thicker and stronger. If the heart is compared with the waterworks at the center of a city, the aorta is the trunk network, the microcirculation is the tap at each door, the veins are the return pipes, and the lung is the treatment plant. What is treated there is the gas exchange that life requires. Blockage, leakage, or a disorder of pressure at any link shows itself as symptoms at a distance. Congestion in the lungs can cause shortness of breath and frothy sputum. Congestion on the systemic side can cause swelling, an enlarged liver, and distended veins in the neck. When the tissues are under-perfused, the result can be fatigue, clouded consciousness, and even shock. Failure of the left heart and failure of the right heart often follow one another, because the two loops stand in series. When one side fails to compensate for a long time, it changes the filling pressure or the resistance faced by the other side.
A more direct path runs like this:
Left ventricle → aorta → arteries of the body → capillaries (exchange of gas and nutrients)
→ veins → right atrium → right ventricle → pulmonary artery → capillaries around the air sacs (exchange of gas)
→ pulmonary veins → left atrium → left ventricle …
A closed loop means that the total volume of blood is roughly conserved, that the direction is roughly one way, secured by the valves, and that pressure falls in a gradient from one segment to the next. Arterial pressure is high and drives the blood forward. Pressure in the capillaries is moderate, high enough for exchange and low enough to limit excessive leakage. Venous pressure is low. Return to the heart depends on the muscle pump, the respiratory pump, and the valves in the veins. The rhythmic contraction of the muscles in the legs works like a second heart, squeezing blood toward the chest. During long sitting, or on a long flight, that muscle pump stops. Venous blood pools, and the risk of thrombosis rises. That is a gap in the closed loop at the level of behavior. Negative pressure in the chest increases during a breath in, and helps draw venous blood toward the right heart. That is another mechanical coupling of heart and lung. Straining with the glottis closed, a violent cough, ventilation with positive pressure, or a tension pneumothorax can all change the blood returning to the heart and the output the heart can deliver. Circulation does not happen only inside vessels. It also happens inside the rhythm of pressure in the chest.
The vessels themselves are not inert pipes. The large arteries are rich in elastic fibers. In systole they expand and store part of the energy of ejection. In diastole they recoil, and that recoil smooths a pulsatile stream into a relatively continuous perfusion. After the arteries stiffen with age, pulse pressure widens and diastolic pressure tends to fall. Diastolic perfusion of the coronary arteries and of the brain can then suffer. Small arteries and arterioles are the resistance vessels. A small change in their caliber can markedly change peripheral resistance and the local distribution of flow. During exercise, vessels in skeletal muscle dilate. During digestion, flow to the abdominal organs increases. In the cold, vessels in the skin constrict. This distribution puts a limited cardiac output where it is most needed at that moment. In fever and infection, dilation of skin vessels helps the body shed heat, and it can also leave the effective circulating volume relatively short. In the compensatory phase of shock, the heart and the brain are protected first, and the skin and the abdominal organs are sacrificed. Cold, clammy hands and feet are often a danger signal. The venous system has a large capacity and serves as a reservoir. About six to seven tenths of the blood volume ordinarily rests on the venous side. Sympathetic activation can raise the tone of the veins and increase the blood returning to the heart, which supports cardiac output under stress. The lymphatic system assists the return of fluid from the tissues and takes part in immune surveillance. Swelling is not only a matter of too much water. The channels of return may have failed, or the colloid osmotic pressure, the pull exerted by proteins in the blood, may have fallen. A leak of chyle, and local lymphedema after lymph nodes have been removed, show from another side that unobstructed return matters as much as the arterial supply.
Look back at this closed loop from the statement that the heart governs the blood and the vessels. What the vessels require is flow that does not cease, and a rising and falling that stays in order. The systemic and pulmonary circuits in series are a large anatomical and physiological footnote to the older phrase “one qi circulating throughout.” The firmness and suppleness of arteries, the storage and overflow of veins, and the seepage and irrigation of the microcirculation can be read against outward signs: the pulse, the complexion, and the warmth or coolness of the limbs. A hasty pulse, a choppy pulse, or a pulse that is knotted or regularly intermittent often corresponds to some abnormality of heart rate, resistance, rhythm, or effective blood volume. A pale or dusky face, and blue-purple lips and nails, often mean that perfusion or oxygenation has gone wrong. The sovereign organ does not have to walk in person to the tips of the toes. It does have to keep the vessels open out to the four extremities. Once the closed loop stops at some point, or blood backs up there, the spirit and the whole body know it quickly. Care of the closed loop protects the heart and the valves, and it also protects arterial elasticity, venous return, and the cooperation of the respiratory pump. Walking, deep breathing, and avoiding long periods of immobility are ordinary maintenance for this figure-eight net.
2. The Microcirculation: Where Nourishment Actually Happens
If the large arteries are highways, the microcirculation is the lanes and the doorways that finally carry the goods to each household. The capillary bed is where oxygen and nutrients leave the blood, and where carbon dioxide and metabolic waste are taken back. At the same time, some fluid enters the spaces between cells and returns through the lymph. Chinese medicine returns again and again to the claim that the five yin organs and the six yang organs are thereby nourished. At the level of the system, that claim can almost be translated directly. Effective perfusion pressure is present. The small vessels open and regulate as they should. The blood carries enough oxygen and enough substrate. The cells can finish their metabolism and are not drowned in toxins and acidosis. Without that last mile, even a powerful cardiac output is only idling on the main road.
Regulation of the microcirculation is fine, and it is layered. When local products of metabolism increase, among them adenosine, carbon dioxide, and hydrogen ions, the arterioles dilate and flow rises. That is supply according to demand. Endothelial cells, the cells that line the vessels, release substances that widen vessels, such as nitric oxide, and substances that narrow them, such as endothelin. Between those signals, the tension of the wall is held in balance. After the endothelium is injured, the capacity to dilate falls, and thrombus and inflammation find a place to settle more easily. Shear stress, the frictional force of flowing blood on the wall, itself regulates the genes and the behavior of the endothelium. The moderate shear that comes with regular exercise helps keep the endothelium in a state that resists inflammation and clotting. Regions of turbulence and of low shear more readily become the ground where atherosclerotic plaque takes hold. The tone of the sphincters before the capillaries, and of the small veins after them, decides how much blood enters the bed where exchange occurs, and how much fluid filters out into the tissues. If hydrostatic pressure is too high, as in the congested lung of heart failure, if colloid osmotic pressure is too low, as when the blood is poor in protein, or if the vessels have become abnormally leaky, as in inflammation, the tissues swell. In pulmonary edema, gas exchange worsens, the whole body lacks oxygen, and a vicious circle forms. High-altitude pulmonary edema after a rapid ascent, and the leaky lung of acute respiratory distress syndrome, are extreme lessons in what happens when the microcirculation and its barrier fail.
Shock is microcirculatory failure in its extreme form. The cause may be a low blood volume after major bleeding, pump failure that produces cardiogenic shock, severe infection that produces distributive shock, or an obstruction such as pulmonary embolism. The common point is that the tissues are not perfused. Cells lack oxygen. Lactate accumulates. Organ function collapses. Here, a clouded spirit is not a figure of speech. The brain is extremely sensitive to a lack of blood flow and a lack of oxygen. A few minutes of severe under-perfusion can cause injury that cannot be reversed. In severe anemia, flow may still be present, and nourishment still fails, because the blood cannot carry enough oxygen. Diffuse clots in the small vessels are like barricades stacked at the mouths of the lanes. Blood is present in the large vessels and absent at the door of the cell. The small-vessel disease of diabetes, and the remodeling of arterioles by long-standing high blood pressure, are chronic and silent discounts on nourishment. The back of the eye, the kidneys, and the endings of nerves are often the first to call for help. What classical language calls the injury of the vessels by sugar-toxin can be seen under the microscope as a thickened basement membrane, a narrowed lumen, and abnormal leakiness. High blood pressure thickens the walls of the small resistance arteries, narrows their lumen, and leaves autoregulation less able to do its work.
Nourishing the heart is therefore more than nourishing the force of the pump. It is also nourishing the openness of the far end of the circulation. Quitting smoking protects the endothelium. Keeping glucose in range reduces the injury of glycation. Moderate exercise improves the density of small vessels and the function of the endothelium. Staying warm, and avoiding long stillness, reduces pooling. These habits sound small. At the level of the microcirculation they are the practical support of nourishment. Cold constricts vessels at the periphery and lowers perfusion of the hands and feet. People with angina often have attacks in the cold, in part because the microcirculation and the resistance of the coronary vessels worsen together. When older physicians observed the warmth or coolness of the hands and feet, the bloom or the withering of the complexion, and the small vessels under the tongue, they were in part reading the outward projection of perfusion. Examination of the retina, a small amount of albumin in the urine, and the oxygen saturation at the toe translate the same question into measures that can be counted. Disturbance of the microcirculation sometimes explains chest pain when the angiogram of the large vessels is normal. The large vessels on the surface of the heart are open, while the tone of the small vessels is disordered, or the endothelium is not working as it should. This pattern is relatively more common in women and in people with diabetes. A diagnosis that takes the system seriously cannot stop at the large pipes.
The microcirculation also holds a fact that is easy to pass over. A cardiac output recorded as normal does not mean that every organ is fed. Early in shock, blood pressure may still look acceptable while the abdominal organs are already short of blood. In people with high blood pressure, the curves of autoregulation in the brain and in the coronary circulation shift to the right. If pressure is brought down too far and too fast, dizziness and a darkening of vision from under-perfusion can appear. In sepsis, vessels dilate widely. Blood sits in the pipes and still cannot generate an effective perfusion pressure. What the heart in the living system requires is a distribution that fits the need, and a single handsome number is not that distribution. The signs that nourishment has succeeded include a clear mind, a reasonable output of urine, warm skin, and a lactate that is not high, along with the partial pressure of oxygen on a laboratory report. Those combined signals are the language, at the bedside, of whether the microcirculation is alive.
3. Blood Pressure: A Key Measure of the Steady State
Blood pressure is the sideways pressure of blood on the vessel wall. It is usually written as systolic pressure over diastolic pressure. A simplified relation says that mean arterial pressure depends roughly on the product of cardiac output and peripheral vascular resistance, and that cardiac output equals stroke volume multiplied by heart rate. Anything that changes the force of contraction, the preload (the blood returning to the heart), the afterload (the resistance the heart pumps against), the heart rate, or the caliber of vessels can rewrite the pressure. Over short periods, regulation is neural. Pressure sensors in the carotid sinus and in the arch of the aorta sense stretch. After the brainstem has integrated that signal, sympathetic and parasympathetic tone are adjusted. If pressure rises abruptly, the heart rate slows and vessels widen. If pressure falls abruptly, the heart rate quickens and vessels narrow. This is the baroreflex. It is an important protection against fainting at the very moment of standing. Massage of the carotid artery, violent vomiting, or a state of excessive vagal tone can trigger the reflex too strongly and cause a slow heart rate or even syncope. The reins need a proper degree of tightness, and they also need a proper degree of slack.
Over longer periods, regulation depends more on the kidneys and on the fluids of the body. The renin–angiotensin–aldosterone system is activated when perfusion of the kidney falls, or when sympathetic activity rises. Angiotensin II narrows vessels. Aldosterone promotes the retention of sodium and water. Blood pressure comes back up. Antidiuretic hormone, the natriuretic peptides, and other signals also take part in the fine adjustment of volume and of tone. When the atria and the ventricles are stretched, they release natriuretic peptides. Those peptides promote the excretion of sodium and a mild widening of vessels. They are biological markers in common use for the diagnosis of heart failure and for judging its outlook. In the language of hormones, the body is saying that the volume is too great. Endothelial function, the elasticity of arteries, sleep and breathing, emotion and pain: each of them leaves a mark on this net. High blood pressure is rarely the single story of one pipe drawn too tight. It is a steady state that has been shifted upward by many factors stacked together. Genetic background, a diet high in salt, obesity, resistance to insulin, chronic kidney disease, sleep apnea, too much alcohol, and sustained mental strain can all push the set point higher. Secondary hypertension is a minority of cases, and it should not be missed. Narrowing of a renal artery, primary aldosteronism, pheochromocytoma, Cushing syndrome, and disordered function of the thyroid need to be remembered when pressure is hard to control, begins early in life, or arrives with special clues.
The harm of high blood pressure lies in a long and quiet injury to the organs it targets. Faced with a sustained high afterload, the heart first thickens in order to compensate. Diastolic function then declines, and the course can end in heart failure. Atherosclerosis speeds up. The risk of coronary events and of stroke rises. The small arteries that enter and leave the filtering units of the kidney harden. Filtration declines, and high blood pressure is worsened in return, so that heart and kidney injure each other. Hardening and bleeding of the arteries at the back of the eye can damage sight. Systolic pressure and pulse pressure matter especially in older people, because they reflect the stiffness of the large arteries more closely. The older image of excessive pressure on the sovereign, with the chancellor and the hundred officials all bearing the burden, hardly needs translation here. The Inner Canon says that when yin is level and yang is well kept, the spirit is in order. The steady state of blood pressure is one expression of that balance in the mechanics of flow. Pressure that stays too high is like an excess of yang scorching the system. Pressure that stays too low is like a deficiency of yang that never arrives. Both leave the spirit unsettled. Among the patterns of dizziness, headache, and ringing in the ears described in Chinese medicine, some are related to swings in blood pressure. Dizziness has other sources as well. Low perfusion, a problem of the vestibular system, anemia, and anxiety can all appear as dizziness. Pressure should be measured, and the cause should be distinguished. Stopping a medicine, or adding one, on one’s own authority is a poor course.
Low blood pressure, and a fall in pressure on standing, deserve the same seriousness. When a person stands suddenly, gravity pools blood in the legs, and the blood returning to the heart falls for a short time. If the baroreflex is sluggish, as it may be in older age, with certain medicines, in disease of the autonomic nerves, or after a long time in bed, perfusion of the brain fails for a moment. Dizziness, a darkening of vision, weakness, or fainting follows. Dehydration, anemia, acute loss of blood, severe infection, and a sharp fall in cardiac output can also bring the pressure down. A fall in pressure after meals is not rare in older people. After a large meal rich in carbohydrate, vessels in the abdomen dilate, and the effective volume in the systemic circulation falls in relative terms. Care of the heart includes a blood pressure that sits in a middle range. Lower is not always better, and a high reading is not something to tolerate in silence. Anxiety about numbers can drive the pressure down too far. The feeling that nothing is wrong can delay treatment that is already due. Measurement at home, orderly follow-up, and a target set for the individual reflect the real steady state more faithfully than a single reading in the clinic. White-coat hypertension and masked hypertension remind us that a full picture, clinic and home, day and night, comes closer to the truth of the system. Monitoring through the day and night helps show whether a dipping pattern is present. In health, pressure at night should fall to a moderate degree. A pattern that fails to dip, or that rises at night, is often related to damage in the target organs and to a worse outlook. Sleep apnea is a common cause.
For an ordinary person, the steady state of blood pressure also has a practical layer. Restricting salt is a way of reducing the load of volume and the reactivity of vessels. Loss of weight and regular movement can improve sensitivity to insulin and lower sympathetic tone. Taking medicine on a regular schedule re-anchors a steady state that has been shifted upward. Rising slowly in the morning, and avoiding a sudden change of posture, gives the baroreflex time to work. Alcohol widens vessels over a short period and raises pressure over a long one. Among medicines for pain, the nonsteroidal anti-inflammatory drugs can affect the kidney and the blood pressure, and they should be used with that knowledge. Behind a measurement there is always a network of life that can be adjusted. The measurement is for seeing the network. A change of habit, and advice followed from a clinician, are for rewriting it.
4. Heart and Lung: The Chancellor and the Work of Exchanging Air
Chinese medicine says that the lung holds the office of chancellor, and that regulation and order issue from it. The lung governs qi and manages breathing, and it helps the heart to move the blood. All the vessels meet at the lung, and the lung presides over the rhythm of that meeting. In modern language, the lung is the place where blood receives oxygen. Changes in pressure inside the chest assist the return of venous blood. A lack of oxygen, and a rise in carbon dioxide, act through chemoreceptors to change heart rate, the tone of vessels, and the drive to breathe. Chronic disease of the lung, and disordered breathing during sleep, can remodel the pressure in the pulmonary circulation and burden the right side of the heart. Heart and lung were never colleagues at neighboring desks. They are partners in one office, sharing one schedule. Qi commands the blood, and blood is the mother of qi. When oxygen is lacking, the blood moves weakly, and the heart compensates with a faster rate. When blood is deficient, qi has nothing to rest on, and shortness of breath comes easily. That classical mutual dependence is still plain on an analysis of blood gases and on the curve of cardiac output.
Gas exchange is completed across the membrane between the air sacs and the capillaries. Breathing that is too shallow for the need, a barrier to diffusion, or a mismatch between ventilation and blood flow will all lower the oxygen in arterial blood. Lack of oxygen stimulates the small arteries of the lung to constrict. When that constriction persists, pulmonary hypertension follows, and the afterload of the right ventricle rises. The right ventricle thickens and enlarges, and the course can end in failure of the right heart. Swelling of the legs, congestion of the liver, and distended veins in the neck may then be seen. Chronic obstructive pulmonary disease, chronic bronchitis, severe asthma, fibrosis of the lung, and recurrent emboli in the lung can all travel this path. Older physicians may not have spoken of pressure in the pulmonary artery. In panting, in a blue cast of the skin, and in swelling, they already saw lung disease reaching the heart. High pressure in the pulmonary veins, caused by failure of the left heart, can also back up into the pulmonary circulation and produce a reactive rise in pulmonary artery pressure. Left and right then drag each other down in a spiral. Widening the pulmonary arteries alone, or strengthening the heartbeat alone, may not be enough. The filling pressure of the left heart has to be lowered, and the volume of blood has to be brought into a better range, at the same time.
Sleep apnea is one of the representative problems of heart, lung, and system in our own time. The upper airway collapses again and again. The result is intermittent lack of oxygen, violent swings of negative pressure in the chest, sleep broken into fragments, and bursts of sympathetic activity. Blood pressure rises at night. High blood pressure by day becomes hard to control. The risk of disordered rhythm, including atrial fibrillation, increases. Pressure in the pulmonary artery can rise as well. People with this condition often snore loudly, wake choking, are sleepy through the day, and have headache in the morning. A partner’s account sometimes finds the problem earlier than the person who has it. Loss of weight, sleeping on the side, and continuous positive airway pressure, among other measures, often improve blood pressure, heart rhythm, and the load on the right heart together. Work done in one place benefits the system in many. Enlarged adenoids in a child, obesity and a receding jaw in an adult, and alcohol or sedative-hypnotic drugs that relax the muscles of the throat are common precipitants. Treating sleep is often the treatment of high blood pressure that will not yield, and of atrial fibrillation that has seemed to have no cause.
Infection and inflammation couple heart and lung as well. Severe pneumonia can cause a lack of oxygen and sepsis together, with depression of the heart muscle and leakiness of the capillaries at the same time. An embolus in the lung is an emergency of obstruction in the circulation. Acute enlargement of the right ventricle can be fatal within a short time. Sudden breathlessness, chest pain, coughing of blood, or fainting calls for a high degree of attention. Long sitting, cancer, and the period after surgery for a fracture are important parts of the background. Even at the scale of ordinary days, mouth breathing from a blocked nose, chronic inflammation of the sinuses, and inflamed airways from years of smoking quietly raise the work of breathing and the burden of oxidative stress, and they add to the load on the heart and vessels. The benefit of quitting tobacco reaches the lung, the heart, and the quiet of the endothelium and the platelets. In the years after a person stops, the risk of myocardial infarction and of stroke falls markedly. Among interventions aimed at the whole system, this is one of the highest in return.
Read through the idea of regulation and order, the relation of heart and lung is this. The lung exchanges gas, and it also takes part in setting the rhythm of qi and of blood flow through the body. Breathing that is too shallow and too fast, as in the over-breathing of anxiety, can change the blood gases and the excitability of the nerves, and can bring on palpitations and numbness of the hands and feet. Slow breathing that uses the abdomen often raises vagal tone and lowers the heart rate. That is a shared lesson of the autonomic nerves and of the respiratory pump. During exercise, ventilation and cardiac output rise together. A person who is trained uses oxygen more efficiently, and the same activity costs less of the heart and less of the lung. Rehabilitation of the lung and rehabilitation of the heart overlap in method, because the two are two faces of one process. To nourish the lung is, in part, to nourish the heart. Stay clear of smoke and of heavy pollution. Treat disease of the airways that can be treated. Receive the vaccines that are appropriate, and thereby lower the chance of severe infection of the respiratory tract. Take snoring and choking at night seriously, so that the chancellor can truly share the worry of the sovereign.
5. Heart and Kidney: Water and Fire in Balance, and the Cardiorenal Syndrome
Chinese medicine speaks of the heart and the kidney in communication, and of water and fire already supporting each other. The heart belongs to fire and dwells above. The kidney belongs to water and dwells below. Fire of the heart warms the yang of the kidney from above. Water of the kidney assists the yin of the heart from below. Then the spirit is calm, and the essence is secure. When heart and kidney fail to meet, a person may have restlessness and insomnia, soreness of the lower back and the knees, dizziness and ringing in the ears, and seminal emission or trouble with sexual function. These findings cannot be matched, item by item, with a modern mechanism. The intuition that the upper and the lower have failed to aid each other is still strikingly close to the modern account of heart and kidney injuring each other. The balance of water and fire stresses traffic between them, and a check on each by the other. Fire without water is dryness, agitation, and sleeplessness. Water without fire is cold congealing into edema. Modern clinical profiles of heart failure, described as dry and cold or as wet and warm, use different words. They too describe combined states of perfusion and congestion, of cold and heat, of deficiency and excess.
In heart failure, cardiac output falls and perfusion of the kidney falls with it. The renin–angiotensin–aldosterone system and the sympathetic system are strongly activated. Sodium and water are retained. The load of volume increases and burdens the heart further. Congestion of the kidney itself also damages renal function. In chronic kidney disease, accumulated toxins, anemia, disordered metabolism of calcium and phosphorus, too much volume, and high blood pressure injure the heart muscle and the vessels together. The risk of disordered rhythm and of heart failure rises markedly. This worsening in both directions is called, in the clinic, the cardiorenal syndrome. The classification is complex. The core fact is simple. Heart and kidney share a fate of perfusion, of volume, of neural and hormonal signals, and of inflammation and oxidative stress. Removing excess fluid, widening vessels, restraining the renin–angiotensin–aldosterone system, correcting anemia, and controlling blood pressure and volume often require cardiology and nephrology to work as one. Mutual support needs water and fire in cooperation. An assault from one side alone misses the relation. Diuresis pushed too far can leave the blood volume short, the creatinine rising, and the electrolytes disordered. Volume that is ignored can produce edema of the lungs and failure of breathing. A sense of proportion is the soul of treating heart and kidney together.
The kidney also takes part in the long-term control of blood pressure, through excretion and through its own hormones. When renal function declines, the capacity to excrete sodium is limited, and high blood pressure that is sensitive to salt becomes more common. When erythropoietin is insufficient, anemia follows, and both the oxygen supplied to the heart muscle and the peripheral resistance change. Active vitamin D, and the secondary over-activity of the parathyroid glands, affect the calcification of vessels. Disease of the heart muscle in uremia, and inflammation of the pericardium, were more common in the era before dialysis. Dialysis and medicines have improved the outlook, and events in the heart and vessels remain among the main causes of death in people with chronic kidney disease. In the other direction, long-standing high blood pressure and diabetes are the two great drivers of chronic kidney disease. As the kidney disease advances, blood pressure becomes harder to control. The older sense that essence and blood share a source, and that what is inborn and what is acquired nourish each other, receives a footnote here from pathophysiology. Insufficiency of kidney essence can appear as abnormal production of blood and abnormal metabolism of bone. Insufficiency of heart blood leaves the spirit unnourished and the tolerance for effort reduced. In treatment, tonifying the kidney and nourishing the heart are often carried out, in contemporary practice, as protection of the kidney function that remains, correction of anemia, management of minerals and of bone, and attention to heart failure and to the risk factors for coronary disease. The aim is still to restore traffic between what is above and what is below.
A practical reminder follows. Renal function and protein in the urine should be checked before the legs are swollen through. A person with heart failure needs attention to changes in creatinine and in the electrolytes. A person with kidney disease needs active screening by electrocardiography, by ultrasound, and by the pattern of blood pressure across the day and night. Before and after contrast material, or certain drugs that can injure the kidney, the risk should be weighed. More urine at night, urine that is foamy, swelling of the eyelids, and anemia or bone pain that is hard to explain may all be the kidney sending an alarm through the system. The mutual support of water and fire is a poetic name for daily monitoring and for intervention that comes early. Protecting the kidney protects the heart, and protecting the heart protects the kidney. Written into a way of living and into a sheet for follow-up, that sentence has more force than it has when it is written into a slogan.
6. Heart and Spleen: The Making of Qi and Blood, and the Hub of Transport
The spleen is the source from which qi and blood are generated and transformed. The spleen governs transport and transformation. Spleen and stomach receive grain and water, ripen them, and turn them into a refined essence. That essence is presented to the heart and transformed into red blood. It is dispersed to the liver, it fills and nourishes the lung, and it irrigates what lies around them. The classic picture of deficiency in both heart and spleen includes palpitations and insomnia, forgetfulness, a sallow complexion, poor appetite, abdominal distension, loose stool, and fatigue. In modern terms, that picture often corresponds to undernutrition, anemia from lack of iron, chronic loss of blood, poor digestion and absorption, and the disordered appetite and autonomic function that accompany anxiety and depression. Anemia directly weakens the capacity of blood to carry oxygen. The heart rate quickens in compensation. The balance between the oxygen the heart muscle needs and the oxygen it receives grows more fragile. Severe undernutrition leaves the heart muscle short of the substrates that supply its energy, and immunity and repair decline. A lack of iron, even before anemia has become severe, can affect the function of mitochondria and the tolerance for exercise. In people with heart failure, restoring iron can sometimes improve symptoms. That is a modern footnote to a source of generation and transformation that has run short. Too much brooding injures the spleen, and it can injure the blood of the heart by an indirect path. Long mental strain suppresses the secretions of digestion and the movement of the gut. Intake and absorption are both impaired. The quality of sleep falls. Sympathetic tone runs high. Emotion, digestion, and circulation meet again at the level of the system.
In Chinese medicine the spleen also keeps the blood within the vessels, and it governs the muscles and the four limbs. From a modern point of view, the function of platelets, the factors that clot the blood, the fragility of capillaries, and the role of skeletal muscle as an organ of metabolism are all related to parts of that clinical picture. Long sitting and little movement lower the sensitivity of muscle to insulin, increase the fat inside the abdomen, disorder lipids and glucose, and speed atherosclerosis. Reading “deficiency of the spleen with exuberant dampness” as a classical cousin of the metabolic syndrome is not a strict identity. It does help explain why care of the spleen and stomach is so often written on the same prescription as control of weight, of lipids, and of glucose. Eating and drinking to excess, dieting to excess, and taking meals on a schedule that turns day and night upside down all strike this hub. The relations among the microbes of the gut, the short-chain fatty acids they produce, and the setting of inflammation are still under study. The path from a diet that injures the spleen, to a low-grade inflammation of the whole body, and then to injury of the endothelium, is already enough to take seriously. Highly processed food, too many sweetened drinks, and alcohol taken chronically are sources of disturbance in the network.
Care of the relation between heart and spleen is therefore very much of this world. Meals come at fairly regular times. There is enough protein of good quality, and enough of the raw materials of blood, including iron, zinc, and folate. Chronic sources of blood loss, such as an ulcer of the stomach or duodenum and hemorrhoids, are treated. Drugs that injure the lining of the stomach are used with caution. Movement that is gentle and that can be kept up wakes the muscles of the limbs. A rhythm that reduces fruitless rumination, with sleep at a fixed hour, tasks written out of the head, and short periods of rest, protects the spleen’s work of transport from being exhausted by the mind. If palpitations come with obvious anemia or with a low level of protein in the blood, restoring those basic substances often comes closer to the root than an effort to settle the heart and calm the spirit alone. When qi and blood are sufficient, the vessels are full, and the spirit has something to rely on. When the spleen is sound, dampness does not encumber the body and phlegm does not arise, and the vessels have less extra stickiness to contend with. The direction agrees with what contemporary practice emphasizes: a pattern of eating that lowers inflammation, management of weight, and lipids brought to the range that has been set. When the spleen, the central earth of the classical scheme, transports well, the surrounding organs are nourished. When spleen and stomach are injured, the blood of the heart is hard to sustain. The heart in the living system often begins earlier at the table than in the catheterization laboratory, and the beginning there costs less.
7. The Autonomic Nerves: The Reins of Regulation
The sympathetic system and the parasympathetic system are like an accelerator and a brake. When the sympathetic system is active, the heart rate quickens, contraction of the heart muscle strengthens, some vessels narrow, the bronchi widen, and glucose is mobilized. That pattern suits a short period of fight or flight. When the parasympathetic system, carried in large part by the vagus nerve, is active, the heart rate slows, digestion and recovery are promoted, and the storage of energy is helped. That pattern suits rest and repair. Health is the ability to switch with the situation, and to show a reasonable rhythm between day and night. By day, a moderate sympathetic tone supports activity. By night, vagal tone predominates and supports sleep and repair. Newborn infants and athletes who are well trained often have a higher vagal tone. The heart rate at rest is slower, and it can still accelerate quickly when exercise begins. Flexibility, and a rate that is simply slow in every setting, are different things. Flexibility is the mark of adaptability.
The baroreflex adjusts heart rate and vascular tone to the pressure of the moment. Chemoreceptors adjust breathing and circulation to the oxygen and the carbon dioxide in the blood. Networks of emotion and cognition in the brain translate an anxious thought into real palpitations and real sweat. Heart-rate variability reflects the fluctuation in the interval between beats. It is often used as a window on the flexibility of autonomic regulation. Variability that is too low sometimes suggests a system that has grown stiff, a predominance of sympathetic tone, or a vagal function that has weakened. It is related to chronic strain, to a debt of sleep, and to certain states of disease. Heart-rate variability is a composite index. A single reading from a consumer device should not be over-read. A way of living that keeps the accelerator on the floor has, at the same time, a large body of evidence behind its risk. Atrial fibrillation, more frequent premature beats from the ventricles, and a lower threshold for angina can all be related to an imbalance of the autonomic nerves. A vagal tone that is too high at night can occasionally help to trigger some episodes of atrial fibrillation. A sympathetic storm by day more often keeps company with ischemia and with dangerous ventricular arrhythmia. Both ends of the reins have to be seen.
Chronic strain, too little sleep, long hours of sitting, too much caffeine and alcohol, pain that is not controlled, insomnia, and nightmares all push the autonomic system toward sympathetic predominance. The picture can include a fast heart rate at rest, wide swings of blood pressure, bloating with constipation or with diarrhea that alternates, sweating, a vigilance that will not stand down, and a tendency to startle. Over time, the function of the endothelium, the level of inflammation, the activity of platelets, and the threshold for arrhythmia are all affected in an unfavorable direction, and the risk of events in the heart and vessels rises. Overwork in a job, the exhaustion of someone who is caring for another person, and the insecurity of not knowing how the bills will be paid are social and psychological facts written into the autonomic and endocrine axes as well. The system does not stop at the organs inside the body. It includes the living world in which a person is set. In the other direction, regular aerobic exercise, enough sleep, training in relaxation, slow breathing, the support of other people, and a structure of life that can be managed help to restore vagal tone and the sensitivity of reflexes. These are repeatable effects of neural and hormonal regulation. Biofeedback, mindfulness, and cognitive-behavioral strategies can, in some people, lower the feeling of palpitations and the reactivity of blood pressure. They supplement medicines and the management of risk factors. They do not stand in for them.
Chinese medicine says that anger drives qi upward, joy slackens qi, grief consumes qi, fear drives qi downward, fright throws qi into disorder, and brooding binds qi. Emotion is written directly into the movement of qi and into the organs. The autonomic nerves are an important bridge by which emotion affects the circulation. In a panic attack the heart races. That is a sympathetic storm. In grief there is tightness in the chest, shortness of breath, and a loss of appetite. That is a low state shared by many systems. In rage, blood pressure rises abruptly, and the rise can precipitate an event at a plaque or a tear in the wall of an artery. Understanding these reins serves a double purpose. Bodily signals are taken seriously, and they are not allowed to take the person captive. When the heart races, disease of the organ is looked for first. At the same time, breathing, a sense of being on solid ground, and a fresh appraisal of the thought that set the alarm off can turn an excessive alarm down. Spirit and vessels truly meet at the autonomic layer. The next chapter will ask how awareness reads these signals from the viscera. This chapter first sets the physiological base of the reins in place.
8. The Whole View: Dynamic Balance in a Network
The holistic view of the Yellow Emperor’s Inner Canon stresses the mutual connection of the organs, the channels, qi, and blood, the correspondence of heaven and humankind, and the unity of bodily form and spirit. The cold and the heat of the four seasons affect the pulse and the onset of disease. The yin and yang of day and night affect sleep and the defensive qi that guards the surface of the body. Emotion, diet, exertion, and rest can all give rise to illness. In the vocabulary of our own time, these statements can be read as environmental exposure, circadian rhythm, behavioral risks, and the interaction of mind and body. Systems biology describes the same class of facts with the ideas of the network, of feedback, of homeostasis, and of emergence. No organ is an island. A local lesion can become a disorder of the whole. A disorder of the whole can show itself first in one place. Factors of inflammation, the community of microbes, the products of metabolism, the structure of sleep, social relations, and the pressure a person feels have all been shown to enter models of cardiovascular risk. At the level of the system, the claim that the heart governs the spirit can therefore be stated as four sentences that lock into one another.
First, the pump of the heart and the network of vessels maintain effective perfusion of the whole body, so that the limbs, the frame, and the organs have a material basis.
Second, neural and hormonal regulation keeps the internal environment steady, so that temperature, acid–base balance, volume, and glucose do not swing violently.
Third, a stable internal environment supports the clear working of the brain and of the organs, so that awareness, emotion, and decision have a physiological base.
Fourth, mental and emotional life, through the autonomic nerves, the endocrine system, and the choices of behavior, shapes circulation and metabolism in return.
These four sentences form a closed loop of their own. The vessels nourish the spirit, and the spirit also drives the vessels. The emphasis of preventive medicine, which is control of pressure, of lipids, and of glucose, together with quitting tobacco, movement, and sleep, is the ordinary maintenance of the heart in the living system. The six are like six pillars holding up the roof of the circulatory network. Take any one away, and wind and rain come in more easily.
Blood pressure. Shift the steady state of high blood pressure downward, and lighten the long wear on heart, brain, kidney, and eye. Watch for a fall in pressure on standing, and for pressure brought down too far. Measurement at home, management of salt and of weight, and adherence to medicine are three supports. Knowing one’s own target, and recognizing the clues to pressure that resists treatment or that has a secondary cause, matters more than an occasional single reading.
Lipids. Lower the raw material of atherosclerosis, and lower the inflammatory fuel that helps it burn. The pattern of eating, with less trans fat and less excess saturated fat, and with more fiber from food, together with attention to weight and, when they are needed, medicines such as the statins, leaves plaque more stable and events fewer. Abnormal lipids often produce no symptom, and they keep working quietly in the vessel wall. They call for a laboratory test.
Glucose. Reduce injury to the endothelium, disease of the small vessels, and disease of the autonomic nerves. Diabetes is a disease of the whole body. Heart, kidney, eye, and foot stand on the same report. A low blood glucose is dangerous as well, especially for older people and for people with coronary disease. A steady arrival at the chosen target is better than violent swings around it.
Tobacco. The state of the endothelium and of the platelets improves quickly after a person stops. The risk of spasm in the coronary arteries and of thrombosis falls, and the lung and the right heart are protected. An electronic cigarette is not a harmless substitute. The aim is still to leave nicotine dependence and exposure to smoke behind. Smoke inhaled from someone else’s cigarette injures vessels as well. A home and a workplace without smoke are a public intervention in the system.
Movement. Aerobic work and work against resistance, taken together, improve the reserve of cardiac output, the sensitivity to insulin, the function of the endothelium, and the regulation of mood. Begin with a walk that can actually be finished. Progress in order. A sudden violent load after a long period of sitting still asks more of the system than it can safely give. A week in which moderate activity accumulates fits the way the body adapts better than an occasional effort that spends everything at once. A person who already has heart disease should exercise in the manner of cardiac rehabilitation, after an assessment.
Sleep. Keep the hours of rest fixed. Look for sleep apnea when the clues are there. Reduce the screens that push bedtime later. Sleep is the window for repair under vagal tone, for the fall of blood pressure at night that makes a dipping pattern, and for the resetting of metabolism. Too little sleep is itself a cardiovascular risk. Extra sleep on the weekend cannot fully cancel the debt built up on workdays. A rhythm that stays fixed still helps.
Optimize one place, and many places benefit. Loss of weight may improve blood pressure, glucose, lipids, and sleep apnea together. Quitting tobacco benefits heart, lung, and vessels at once. Movement gains both mood and metabolism. Let one place collapse, and the pieces fall in a line. Sustained insomnia pushes sympathetic tone up. Blood pressure will not hold. Glucose swings. Eating becomes impulsive. Weight rises. By that costly feedback, the system shows that the whole view is a physiological fact.
The whole view also asks clinical decisions to stay clear of a fragmented habit of treating only the part that hurts. A person with heart failure needs to be asked about the kidney and the electrolytes. High blood pressure that will not come under control needs to be asked about sleep and about the arteries of the kidney. Palpitations need to be asked about the thyroid, about anemia, about caffeine, and about anxiety. Swelling needs to be sorted among the heart, the kidney, the liver, the veins, and the medicines in use. For a person’s own care, the whole view means adjusting life as a net. The intelligence of the sovereign lies in using the chancellor and the hundred officials well. The lung, the kidney, the spleen, the neural and hormonal signals, and the way of living are all officials of this court. A modern reading of the correspondence between heaven and humankind is plain. Respect the alternation of day and night. Add or reduce clothing and activity as the season changes. Reduce exposure to extreme environments and to pollution, so that the world outside adds less load to the steady state inside.
9. From the System Back to Daily Life: An Ordinary Lesson in Prevention
Gathering this knowledge into a rhythm that can be carried out may be worth more than memorizing a few more names. Rise slowly in the morning, and measure the blood pressure or look back over its trend. Keep the three meals at fairly regular times: vegetables and fruit, whole grains, protein of good quality, and a modest amount of nuts, with less processed meat and fewer sugary drinks. Stand and walk during the day, and let moderate activity add up. In the afternoon, avoid an excess of caffeine. Toward evening, reduce arguments and the kind of screen use that keeps the nervous system at a high pitch. At night, keep the light dim, the room cool, and the hours of sleep long enough. A person who already has a chronic disease takes medicine on schedule and has lipids, glucose, and renal function checked again at proper intervals. A person who snores and chokes asks for an evaluation. These actions look ordinary. On every loop of feedback they give a small push, and they tilt the steady state toward the side that can be sustained.
A person can also ask three questions in the course of a day. Is my breathing too shallow at this moment? Have I been sitting for more than an hour? Has emotion drawn my shoulders and my jaw into something as hard as stone? The questions are a place where the autonomic nerves can step down. They are a check, and they are a chance to change course. During travel, during overtime, and during the meals of a festival, the net loosens most easily. Having medicines ready beforehand, holding salt and alcohol within bounds, and protecting a minimum of sleep cost less than repair after the fact. Sharing a plan for measurement and for follow-up with the family turns care of the system from an act of private will into a habit of the household. The chance of keeping it up is often higher that way.
The heart in the living system also teaches a limit. Compensation does not go on forever. In youth, late nights are held up by sympathetic force. After middle age, the endothelium and the elasticity of the arteries decline, and the same overdraft more readily becomes high blood pressure, plaque that appears early, and disordered rhythm. The window for prevention is often widest while there are still no symptoms. An abnormal result on a checkup can be met without panic, and it can be met without the comfort of deciding that nothing is the matter. Translating the abnormality into behavior that can be changed, and into a plan that can be followed, is systems thinking brought down to the ground. In a family with early myocardial infarction, sudden death, high blood pressure that will not yield, or kidney disease, screening and a stronger way of living should begin sooner. Inheritance is a reason to start maintaining the network earlier.
The old saying is that the best physician treats what has not yet become disease. Prevent before illness appears. Once illness is present, prevent it from changing into something worse. After recovery, prevent it from returning. Mapped onto the circulation, that is the management of risk factors, the protection of the organs that pressure and disease would damage, and secondary prevention during rehabilitation. A stent or a bypass graft can rescue a heart in acute ischemia, and the procedure still leaves a lifelong need to control pressure, lipids, and glucose, and to exercise in the manner of cardiac rehabilitation. A diuretic can lighten swelling, and salt restriction and a clear understanding of volume remain necessary. A medicine that lowers blood pressure can work well, and sleep and loss of weight still contribute to pressure that has been hard to control. The more capable the technology becomes, the more the heart in the living system has to remind us of a division of labor. Instruments deal with nodes. A life shapes the network. A good life begins with the heart. At the level of the system, that means keeping the closed loop flowing, letting nourishment arrive where it is needed, holding blood pressure in a middle range, letting heart, lung, kidney, and spleen rest in relation with one another, letting the reins be tight and loose in due measure, and letting the six kinds of prevention become lessons used every day until they are hardly noticed.
The system gives a picture of the body as a whole: how the closed loop turns, where nourishment is accomplished, why blood pressure holds steady, how heart, lung, kidney, and spleen complete one another or drag one another down, how the autonomic nerves write emotion into the pulse, and how pressure, lipids, glucose, tobacco, movement, and sleep become the ordinary work of keeping order. In the next chapter we turn to a dimension that is harder to put into words, and that everyone has: the heart of awareness and spirit. When perfusion and the steady state are largely in place, how do awareness, feeling, and the self show themselves together with this heart?