Chapter 5: The Heart as an Organ

Zhang Jingyue, in the Illustrated Supplement to the Classified Classic (Leijing Tuyi), left a line that still opens this subject cleanly: 「心象尖圆，形如莲蕊。」 “The heart is pointed and rounded in form, like the bud of a lotus.” The old image does two kinds of work at once. It describes a shape: something pointed and rounded, seated in the center, wrapped in layers. It also describes a quality: something clear and unclouded, not meant to hold dirt for long. Modern anatomy gives the same organ a different sentence. It is a hollow muscular organ about the size of its owner’s fist, weighing roughly 250 to 350 grams, lying in the mediastinum between the lungs. The base points up and to the right. The apex points down, forward, and to the left. About two thirds of the heart sits to the left of the body’s midline.

An infant’s heart lies almost in the center. As the chest grows and the diaphragm descends, the adult apex shifts clearly leftward. An athlete’s heart may enlarge a little and work more strongly. A pathologically thickened heart often grows stiff and lives closer to the risk of poor blood supply. The same word, “large,” covers two different stories. Form and spirit meet here. Structure has to be exact if the heart is to govern the blood and the vessels. The blood and the vessels have to run steadily if the spirit is to be nourished. In the last chapter we watched cells sing together. This chapter pulls the camera back and looks at the organ that singing becomes: how it divides the stream and steers it, how it feeds itself, how each squeeze and each release sends life through the body, and how, under the eyes of physicians ancient and modern, it becomes the meeting place of chest impediment, true heart pain, and the unity of form and spirit.

At the scale of the organ, the heart is a thing that can be weighed and opened on an anatomy table. It is also a working whole that a stethoscope, an electrocardiograph, and an ultrasound probe can “see.” Understanding it does not require memorizing the Latin name of every muscle bundle. It does require a few main lines. Chambers and valves decide the direction of blood. The wall and the coronary arteries decide force and supply. The cardiac cycle and cardiac output decide how efficient the pump is. Heart sounds and images translate those events into something a person can hear and see. The old and new accounts of chest impediment and true heart pain, and the way form and spirit root each other at the level of the organ, put that scientific knowledge back into the life the book keeps naming: a good life begins with the heart. This chapter is the hinge on which the book turns from the very small to the larger view. Molecules and cells explain why a beat is possible. The organ explains what kind of precise pump that beat has become. The next chapter, the heart as a system, explains how that pump is set into the network of the whole body.

For an ordinary person the organ has a more familiar face. It is the knot of rhythm under the hand pressed to the left side of the chest. It is the drumming in the ears after a run. It is the knock against the ribs when fear or hurry arrives. The more exact the science becomes, the less it should steal that bodily sense. Exact knowledge should help a person notice trouble earlier, panic less when nothing serious is happening, and take better daily care of this “official who rules,” the monarch among the organs.

1. Four Chambers and the Valves: The Wisdom of One Direction

In the adult, the atrial septum and the ventricular septum divide the heart into a left atrium, a right atrium, a left ventricle, and a right ventricle. That is the four-chambered heart. The right side receives the venous blood returning from the body. Blood enters the right atrium, passes into the right ventricle, and is pumped into the pulmonary artery on its way to the air sacs of the lungs, where gas is exchanged. The left side receives the arterial blood brought back by the pulmonary veins. Blood enters the left atrium, passes into the left ventricle, and is pumped into the aorta to supply the whole body. One useful picture is to treat the right heart as the ferry to the lung station, and the left heart as the main pump for the body. The two sides are joined in series in a closed loop. Neither side can be spared.

Left and right do not ordinarily mix. When a sizable hole remains in the atrial septum or the ventricular septum, oxygenated blood and blood that has not yet been oxygenated cross and mingle. The body may then show a blue cast, a falling tolerance for effort, or a long burden of extra volume. Classical physicians had no name for a shunt. They could already tell, from complexion, breath, and pulse, that the blood had left its proper path. A patent foramen ovale, the small door between the atria that failed to seal after birth, is not rare in adults. Most tiny shunts cause no symptoms. In special circumstances, such as a venous clot crossing the wrong way into the body circulation, the finding still needs a clinician’s judgment. Complex congenital patterns, tetralogy of Fallot among them, can show clear lack of oxygen in infancy. Modern surgery and catheter treatment have rewritten many of those lives.

The valves are the living gates that keep flow moving one way. Four sets of valves, four jobs:

The atrioventricular valves, the tricuspid and the mitral, are tethered by chordae tendineae and papillary muscles. In contraction the leaflets meet and are kept from flipping up into the atrium, the way the ribs of an umbrella keep the canopy from turning inside out. The semilunar valves, the pulmonary and the aortic, rely on three crescent-shaped leaflets that fall together passively in diastole and seal. Opening and closing have to match the pressure difference in time. Pressure rises when it should rise and falls when it should fall, and only then do the leaflets move with the right measure. If a valve is narrowed, blood is held up as it tries to pass. The chamber upstream sees higher pressure, and it thickens or stretches. If a valve fails to close, and blood leaks backward, the heart does work that does not move life forward. Over time that wasted work wears the muscle down.

The late damage of rheumatic fever has become less common where antibiotics are widely used, and it is still seen in some communities. Degenerative calcification rises with age. Narrowing of the aortic valve has become one of the important causes of fainting, angina, and heart failure in older people. Myxomatous change in the valve tissue can lead to mitral valve prolapse and backward leak. Infective endocarditis can destroy a leaflet, and a severe leak can appear suddenly together with the signs of infection through the body. A congenital bicuspid aortic valve tends to calcify and narrow earlier than a valve with three leaflets. When ischemia disables a papillary muscle, or a chorda snaps, severe mitral regurgitation can appear all at once after a myocardial infarction. That complication needs urgent care.

The right heart and the left heart do not work at the same pressure. The lung circuit is a low-pressure system, and the right ventricular wall is relatively thin. The body circuit offers high resistance, and the left ventricular wall is plainly thicker. Thickness here is a reserve of muscle for overcoming peripheral resistance. It is a necessary build, and a swollen, clumsy wall is a different matter. On measurement, right ventricular systolic pressure is usually far below left ventricular systolic pressure. When a pulmonary embolus or chronic lung disease raises pressure in the pulmonary artery, the right ventricle is forced to lift a weight it was not built for. Its wall thickens, its chamber widens, and right-sided failure can follow: swelling of the legs, an enlarged liver, bulging neck veins, fluid in the abdomen. Left-sided failure more often shows itself as congestion in the lungs: shortness of breath, the need to sit up to breathe, a cough that brings frothy sputum. In the clinic the two failures often follow each other or sit together, because a side that stays decompensated for long will drag the other side down with it.

The atria are more like receiving stations and fine adjusters. From late in ventricular contraction into early relaxation they take in the venous return. Late in diastole they contract on purpose and push the last fifth to a third of the filling volume into the ventricles. In atrial fibrillation that atrial boost is lost. Ventricular filling then depends mainly on the passive phase. Cardiac output can fall by a tenth or more, and the drop is sharper when the heart is fast and the time for filling is short. That is why people with atrial fibrillation so often feel short of breath and weak. An uneven heartbeat is only the most obvious part of the story. An enlarged left atrium is also tied to the risk of stroke. Blood that stagnates in the left atrial appendage can form clot. If a piece breaks free and travels through the body circulation, it can block a vessel in the brain. Looking after atrial fibrillation therefore includes bringing the rate down, and it also includes judging whether anticoagulation is needed, whether the rhythm itself should be restored, and whether the upstream risks should be treated. Those are clinical judgments, made for a particular person. They are part of how the organ is understood.

Read again from the classical claim that the heart governs the blood and the vessels, the four chambers and the valves show why flow is prized when it is open, orderly, and measured in its rising, falling, entering, and leaving. The one-way wisdom of the valves is the anatomical footnote to “do not run backward into chaos.” The cooperation of the four chambers is “one qi circulating” written small inside a single organ. The ruling official does not have to do every task in person. The gates do have to be strict. A slack gate leaks like a theft. A gate shut too hard narrows like a choking. Care of these gates includes the prevention of rheumatic fever and infection, and the control of blood pressure so that the leaflets bear less stress. It also includes, as the years pass, listening and ultrasound follow-up, so that a small lesion does not grow into a large failure of compensation. The point of that care is to keep the architecture intelligible and intact. It is a stance toward the organ, and a qualified clinician still decides what any one person needs.

2. The Heart Wall and the Coronary Arteries: Force and Supply

From inside to outside, the heart wall falls roughly into three layers. Innermost is the endocardium, a smooth lining of the chambers that continues onto the surfaces of the valves and gives turbulence and clot fewer places to settle. In the middle is the myocardium, most of the thickness, and the source of contractile force. Outermost is the epicardium, which is also the visceral layer of the pericardium. Fat often lies beneath it, and branches of the coronary arteries run there. Around the heart is the pericardium, fibrous and serous. A small amount of fluid in the pericardial sac lubricates the movement, so that the beating heart does not grind hard against the tissues around it.

Too much fluid, or fluid that accumulates quickly, can press on the chambers and limit filling in diastole. In the severe form this is cardiac tamponade: the pulse pressure narrows, the veins stand out, the heart sounds grow distant. It is a true emergency, and the sac may need to be drained by pericardial puncture. Constrictive pericarditis is more like a hard shell fitted around the heart. Filling is limited in the same general way, and the picture may include abdominal fluid, swelling, and a high venous pressure. Some of what classical writers called water-qi overwhelming the heart, shui qi ling xin, finds a partial modern counterpart here. Viral or tuberculous pericarditis, uremia, tumor, trauma, and the period after surgery can all involve the pericardium. Chest pain that changes with posture, and a pericardial friction rub on listening, are important clinical clues.

The left ventricular wall is the thickest, because it must drive blood into the high-pressure aorta. The right ventricular wall is thinner, and it still has to meet the extra load when resistance in the lung circuit rises. Long-standing pulmonary hypertension can thicken and dilate the right ventricle and end in right-sided failure. The muscle fibers are arranged with a purpose. Bundles under the endocardium, in the middle of the wall, and under the epicardium run in different directions and produce something close to the twist of a wrung towel. Contraction shortens the chamber across its short axis and also twists. Untwisting afterward helps ejection and helps the heart suck venous blood back in during filling. Fibrosis, scar, or a patch of wall that moves badly breaks that geometry. The ejection fraction may still look acceptable as a number, while real efficiency and reserve have already fallen.

When high blood pressure goes uncontrolled for years, the left ventricle first thickens concentrically to overcome the afterload. Diastolic function then declines. In the end the chamber may dilate and contractile force fade. The path from “the muscle grew thick” to “the pump grew weak” is a chain that lifestyle and medicine can interrupt. Hypertrophic cardiomyopathy and related inherited diseases can produce asymmetric thickening even when blood pressure is normal. They can obstruct the outflow tract, invite malignant arrhythmia, and raise the risk of sudden death. They are among the important causes of exertion-related sudden death in the young, and they call for family screening and specialist care.

The heart muscle’s own blood comes from the coronary arteries. The left and right coronary arteries open from the aortic sinuses at the root of the aorta, just above the aortic valve. The left main trunk soon divides into the anterior descending artery and the circumflex artery. The anterior descending artery supplies mainly the front of the ventricular septum and the front wall of the left ventricle. The territory is large, and occlusion there is often grave, which is why the vessel picked up the grim nickname “widow-maker.” The circumflex artery supplies the side wall of the left ventricle and part of the back wall. In most people the right coronary artery supplies the right ventricle and the inferior wall, gives off the posterior descending artery, and also sends important branches to the sinus node and the atrioventricular node. Occlusion of the right coronary artery can therefore cause an inferior infarction and, along with it, a slow heart rate or a block in conduction. A minority of people are left-dominant, or balanced between the two patterns. Individual variation means that imaging should be read for the person in front of the screen, and a textbook map should not be assumed.

Coronary perfusion has one feature that matters every day. For the left ventricular muscle, blood supply is especially critical in diastole. During contraction, pressure inside the left ventricular wall is very high, and the vessels under the endocardium are nearly squeezed flat. In diastole the wall relaxes, and the coronary arteries can fill properly. A severe tachycardia shortens diastole. A diastolic pressure that is too low, or a severe leak backward through the aortic valve that lets diastolic pressure fall, can reduce effective coronary flow. The muscle just under the endocardium is the most sensitive to ischemia. That is why many ischemic changes appear there first, and why the electrocardiogram may show ST-segment and T-wave changes in the corresponding leads.

Atherosclerotic plaque grows slowly inside a coronary artery and can produce stable angina of effort. When demand for oxygen rises, on a fast walk, on the stairs, with strong emotion, after a heavy meal, or in the cold, supply and demand fall out of balance. Chest pain comes, and it eases with rest or with nitroglycerin under the tongue. The pain is often behind the breastbone. It may travel to the left arm, the neck, the jaw, or the upper abdomen. The quality is commonly pressure, tightness, or burning. A sharp stab is less typical. If a plaque ruptures or erodes, and platelets gather and thrombus forms on top of that injury, the lumen can close abruptly. The picture then becomes an acute coronary syndrome: unstable angina, non-ST-elevation myocardial infarction, or ST-elevation myocardial infarction.

Spasm, as in vasospastic angina that can strike at rest and even at night, along with embolism and spontaneous dissection, can also cause acute ischemia. Younger patients and women around the time of childbirth are among the groups in whom these less typical causes deserve a higher index of suspicion. Collateral vessels can compensate in part for chronic ischemia. They are often unequal to a sudden occlusion. Once myocardial ischemia lasts on the order of twenty to thirty minutes, cells begin to die in a way that cannot be reversed. The dead zone is later cleared by inflammation and repaired by fibrous scar. Scar does not contract, and it can become the substrate for re-entrant ventricular tachycardia. Time is muscle. Early reperfusion, by thrombolysis, by percutaneous coronary intervention, or by emergency bypass grafting, can limit the size of the infarct, preserve pump function, and reduce malignant arrhythmia and mechanical complications. Those are hospital decisions made against the clock. This chapter names them so the reader can see what the interval means. It does not teach anyone how to carry them out.

Narrowing of the large vessels on the surface of the heart is one story. Microvascular dysfunction and disordered endothelial function can cause angina-like symptoms while the angiogram “looks normal.” This pattern is relatively more common in women, and it is a reminder that ischemia in the organ of the heart cannot always be found as one plaque in a thick pipe. Smoking, diabetes, abnormal blood lipids, high blood pressure, obesity, long sitting, and a family history are the classic risks for atherosclerosis. Inflammation, sleep apnea, and chronic kidney disease take part as well. The levers of prevention are often set in youth and middle age: eating with a limit, moving the legs, leaving tobacco behind, sleeping properly, and keeping blood pressure, glucose, and lipids inside their targets. That work is cheaper and more effective than waiting for chest pain and then “opening a vessel.” It is a description of where risk is built, and of the direction in which ordinary life can lower it.

The wall and the coronary arteries say two plain things. A pump needs force, and force needs meat. Meat needs to stay alive, and staying alive needs blood. Classical medicine insists that qi and blood root each other: qi is the commander of blood, and blood is the mother of qi. At the scale of the organ that claim can be read almost directly. Contractile force depends on perfusion. Perfusion depends on diastole and on pressure. Pressure and rhythm are in turn tuned by nerves, by humoral signals, and by the way a person lives. To protect the wall is to protect a muscle, and it is also to protect the material base on which a clear spirit can rest.

3. The Cardiac Cycle: The Dance of Contraction and Filling

One complete heartbeat is one cardiac cycle. Take a sinus rhythm at about seventy beats a minute. Each cycle lasts about eight tenths of a second. Systole, the time of contraction, occupies about a third. Diastole, the time of relaxation and filling, occupies about two thirds. For most of its time the heart is “resting while it fills.” It is not straining without a pause. The cycle is the key to cardiac output, to heart sounds, and to many symptoms. It is also the reason rest is an active part of cardiac life. Diastole is filling, and it is the golden window for coronary perfusion.

A cycle can be walked through as a short sequence of scenes.

The first scene is atrial contraction. By then the ventricle has already received most of its diastolic filling. The atrium gives one more deliberate squeeze and adds the last twenty to thirty percent. In older age, in high blood pressure, in left ventricular hypertrophy, or when diastolic function is impaired, the ventricle has grown stiff and leans harder on this scene. When atrial fibrillation takes atrial contraction away, symptoms often worsen. Disease of the conduction system that leaves atrium and ventricle out of step weakens the same cooperation. One idea inside pacing therapy, cardiac resynchronization, is to rewrite the timetable of atrium and ventricle so that the squeeze lands when filling can use it.

The second scene is isovolumetric contraction. The ventricle begins to contract. Pressure inside it rises quickly and soon exceeds pressure in the atrium. The atrioventricular valves close. That closure is the main source of the first heart sound. Pressure inside the ventricle has not yet exceeded pressure in the aorta or the pulmonary artery, so the semilunar valves stay shut. For a brief moment the ventricular volume does not change. The phase is called isovolumetric for that reason. It is short, and it sets the “starting pressure” of the ejection that follows. The stronger the contractile force, and the more fitting the preload, the faster the pressure rises, and the better the conditions for a useful ejection.

The third scene is ejection. Pressure inside the ventricle exceeds pressure in the great artery. The semilunar valve opens, and blood is pumped out. Ejection is rapid at first, then slower. Left ventricular systolic pressure can reach well above one hundred millimeters of mercury. Right ventricular pressure is much lower. Ejection fraction, the stroke volume as a share of the volume at the end of diastole, is often used as a rough gauge of systolic function. In health it commonly sits between fifty and seventy percent. Below forty percent often means that systolic function is clearly impaired. A normal ejection fraction still leaves room for an unhealthy heart. Filling, the valves, the lung circuit, and the periphery can each go wrong on their own. Stroke volume itself also depends on the geometry of the ventricle. The same degree of shortening, acting on a larger end-diastolic volume, can produce a larger stroke volume. Early in dilated heart failure this is compensation by quantity standing in for quality. Later it is the setup for decompensation.

The fourth scene is isovolumetric relaxation. The ventricle begins to relax. Pressure inside it falls. When it drops below pressure in the great artery, the semilunar valve closes. That closure is the main source of the second heart sound. The atrioventricular valves have not yet opened, and volume is briefly unchanged again. If the aortic valve and the pulmonary valve close out of step, the second heart sound can split, physiologically or pathologically, and a trained ear hears the difference. Active relaxation spends energy. Ischemia, hypertrophy, and aging can all slow that letting-go, so that pressure inside the chamber falls more slowly and filling is delayed.

The fifth scene is filling. Pressure in the ventricle falls below pressure in the atrium. The atrioventricular valve opens. Blood fills the ventricle quickly, in the rapid filling phase, and then more slowly, until the next atrial contraction. The “suction” of early diastole depends on active muscular relaxation and on elastic recoil. If relaxation is impaired, or the wall is stiff, filling pressure is forced upward. Pressure in the pulmonary veins rises. The person feels short of breath, needs to sit upright to breathe, or wakes at night gasping. Many people with what used to be called diastolic heart failure, and what is now often called heart failure with preserved ejection fraction, are stuck in this scene. Their ejection fraction may “look decent.” Filling is obstructed, left ventricular filling pressure is high, and daily life shrinks. The emphasis of care often falls on blood pressure, weight, atrial fibrillation, and the diseases that travel with them. Chasing a single number for contractile strength misses where the trouble sits. Again, the emphasis is a map of the problem. The regimen belongs to the clinician who knows the person.

Stroke volume multiplied by heart rate equals cardiac output. At rest an adult’s cardiac output is about five liters a minute. In hard exercise it may rise to fifteen liters or more. Three classic factors set the stroke volume. Preload is how full the ventricle is at the end of diastole, roughly a matter of venous return and blood volume. Afterload is the resistance the ventricle must overcome to eject, tied to blood pressure, vessel stiffness, and the resistance of a narrowed valve. Contractility is the force the muscle can bring, shaped by sympathetic tone, by catecholamines, and by the state of the muscle itself. The Frank–Starling mechanism says that, within a range, a greater preload yields a greater stroke volume: what comes back in larger amount is pumped onward in larger amount. Past the fitting range the muscle is overstretched and efficiency falls. High blood pressure and aortic stenosis raise afterload, and the ventricle must push harder. Widening of the vessels and lowering of pressure, used in the right setting, can lighten afterload and improve ejection. A heart rate that is too fast leaves too little time to fill. A rate that is too slow means too few beats in the minute. The best band differs from person to person, and it always lies where filling is adequate and the number of beats is adequate together. Beta-blockers slow the heart in part so that diastole lasts longer and perfusion and filling can improve. That is a reason the drugs exist in cardiology. It is a reason a reader can understand a prescription. It is a prescription a physician writes.

Cardiac output also has to match what the body asks. Anemia, an overactive thyroid, fever, and pregnancy can raise demand, and the heart compensates by beating faster and harder. If valve disease or heart failure is already present, the room for compensation is narrow, and symptoms arrive earlier. In shock, cardiac output or the distribution of flow at the periphery is badly insufficient. Tissues lack oxygen. The spirit clouds, and the limbs grow cold. That is pump function collapsing at the scale of the whole system, and the next chapter will take it further.

What classical medicine calls heart qi can be heard, at the level of organ physiology, as effective pumping capacity together with reserve. When heart qi is ample, light activity does not bring panting, and the pulse arrives with composure. When heart qi is deficient, a little labor brings palpitation, shortness of breath, and weakness. On examination one may see a fall in cardiac-output reserve, trouble with ejection or with filling, or the many signs of chronic heart failure. Ideas such as qi stagnation and blood stasis can be set in conversation with an imbalance of preload and afterload, with venous congestion, and with disordered microcirculation. Each way of looking can sharpen the other. The older physicians watched a whole functional state. Modern measurement isolates links that can be quantified. The two can clarify each other. To nourish heart qi is to do more than take medicine. It includes refusing long overwork and sleeplessness, building aerobic training step by step, and keeping a fitting weight, so that every scene of the cardiac cycle still has something in reserve.

4. Heart Sounds: The Letter the Heart Writes to the Ear

Place a stethoscope on the right part of the chest wall and the “lub–dub” you hear is mainly the sound of valves closing, of blood moving, and of the wall vibrating. It is the acoustic signature of those events. The first heart sound, S1, is lower and duller. It marks the start of ventricular contraction and the closing of the atrioventricular valves. The second heart sound, S2, is crisper. It marks the start of ventricular relaxation and the closing of the semilunar valves. In a healthy person S1 is clearer at the apex, and S2 is clearer at the base. On inspiration, return to the right heart increases, the pulmonary valve closes a little later, and S2 may split physiologically. In mitral stenosis S1 can be loud. When contractile force is extremely weak, or regurgitation is severe, S1 can grow dull. These details are the dialect of auscultation. They take training, and they show that the heart is never silent.

Extra sounds and murmurs are the auditory signatures lesions leave behind. The third heart sound, S3, falls in early diastole during rapid filling. It can be heard in adolescents and in athletes, where it is physiological. It can also be heard when heart failure is overloaded with volume, where it is a pathological gallop. The fourth heart sound, S4, is tied to a strong atrial contraction pushing against a stiff ventricle. High blood pressure and hypertrophic cardiomyopathy are common settings. A systolic murmur may come from narrowing of the aortic or pulmonary valve, from mitral or tricuspid regurgitation, from a ventricular septal defect, or from an innocent speeding of flow. A diastolic murmur points much more strongly toward aortic or pulmonary regurgitation, or toward mitral or tricuspid stenosis, and it usually deserves closer attention. A click may go with mitral valve prolapse. A continuous murmur may be heard with a patent ductus arteriosus. Listening does not replace imaging. It is the fastest screen at the bedside. A well-trained clinician can often tell, from the timing of a murmur, its location, the direction in which it radiates, and the way it changes with breathing and posture, which set of valves is the likely problem, and can then decide how urgently ultrasound should come.

For a person who is not a clinician, the point of heart sounds is to understand that the heart has an acoustic language. The point is to know when that language has changed in a way that deserves a professional ear. A new murmur, palpitation with dimming of vision, marked shortness of breath after activity, swelling of the legs together with breathlessness at night: these are worth being taken seriously. “I’m just getting older” is a poor way to close the subject. When a doctor “listens to the heart” at a checkup, the gesture looks routine. It is one of the cheapest ways to guard the organ. Form can be seen in the face, and it can be heard in the chest. Inspection by listening, the classical wen zhen in its auditory sense, has not gone out of date on the organ of the heart. At home, noticing the rhythm and the strength of one’s own pulse, and seeking a professional assessment when an abnormality persists, is a way of turning the old spirit of pulse-taking into a modern habit of looking after oneself. It is attention. It is a decision to ask for skill when the signal stays.

5. The Electrocardiogram, Ultrasound, and the Other Ways of Seeing

If heart sounds are a letter to the ear, the electrocardiogram and the images are an instruction sheet for the eye and for reason. They are ordinary tools once you know which question each one is good at answering. An arrow on a report is a finding inside a method. A life is larger than any one arrow.

The surface electrocardiogram projects the heart’s three-dimensional electrical activity onto several leads and draws a family of waves. In plain language: the P wave roughly corresponds to atrial depolarization; the QRS complex corresponds to ventricular depolarization, with atrial repolarization buried inside it and usually impossible to see; the T wave corresponds to ventricular repolarization; a U wave is sometimes present and relates to late repolarization or to electrolytes. The PR interval reflects the time of conduction from atrium to ventricle. The width of the QRS reflects whether conduction inside the ventricles is synchronous. The QT interval relates to repolarization and to the risk of certain arrhythmias. From these a clinician judges whether the rhythm is led by the sinus node, whether there are early beats or a rate that is too fast or too slow, whether atrioventricular conduction is delayed or blocked, whether a bundle branch is blocked, whether the tracing shows acute or old ischemia and infarction, and whether there are traces of an electrolyte disorder, such as an abnormal potassium, or of a drug effect. Persistent ST-segment elevation in a person with chest pain often means that reperfusion has to be considered without delay. A pathological Q wave may mark an old infarct. Ambulatory electrocardiography stretches the recording to twenty-four hours or longer and catches the instants behind paroxysmal palpitation or syncope. Event recorders and implantable monitors can cover still longer stretches. A treadmill test watches whether effort provokes ischemic ST changes or arrhythmia, and it gauges exercise tolerance. When the treadmill is contraindicated, a drug can supply the load instead.

The limits of the electrocardiogram are equally plain. It reports electrical activity. It does not show the shape of a valve, and it is not itself an ejection fraction. One normal tracing at rest cannot promise that a coronary artery is free of severe narrowing, especially in a person whose supply and demand are still balanced while they sit still. The converse holds as well. Nonspecific ST-segment and T-wave changes do not automatically equal “coronary disease.” Age, symptoms, and risk have to be read with the tracing, so that anxiety and testing do not run ahead of the evidence.

Echocardiography is living anatomy in everyday speech. Transthoracic ultrasound uses the reflection of sound waves to show, in real time, the size of the chambers, the thickness and motion of the walls, the opening and closing of the valves, the speed and direction of blood flow by Doppler, an estimate of pulmonary artery pressure, the ejection fraction, and parameters of diastolic function. It is noninvasive, repeatable, and relatively available. It is the first-line instrument for valve disease, heart failure, cardiomyopathy, pericardial disease, and congenital structural abnormality. Color Doppler paints regurgitation and shunts in color. Spectral Doppler can estimate the pressure difference across a valve. Transesophageal ultrasound brings the probe closer to the heart, and the picture grows clearer. It is especially good at clot in the left atrial appendage, at certain valve details, at the function of a prosthetic valve, and at disease of the aorta. Stress echocardiography watches wall motion under a drug load or under exercise, and it helps judge ischemia and viable muscle.

For the person being examined, a transthoracic study means lying on the left side, gel on the skin, a probe sliding over the chest, and now and then a request to hold the breath. The process does not hurt, and the amount of information is large. Words in the report, “left atrium enlarged,” “regional wall-motion abnormality,” “moderate regurgitation,” “E/A ratio,” “e prime,” are answers to questions about filling pressure, about whether contraction is synchronous, and about how severe a valve lesion is. A clinician should explain them in light of symptoms. A table of “normal values” on the internet is a poor partner for a single line read in isolation.

Cardiac computed tomography, and coronary CT angiography in particular, suits people at low or intermediate risk when the question is whether the coronary arteries are narrowed and what the calcium score looks like. Its negative predictive value is high, and a clearly reassuring study can spare an unnecessary invasive angiogram. An irregular rhythm, heavy calcium, poor kidney function, and allergy to contrast limit its use. Coronary angiography threads a catheter through an artery to the coronary ostium and injects contrast. It is the reference path for the anatomy of the epicardial coronary arteries, and a stent can be placed in the same sitting when that is the right next step. What it shows is the outline of the lumen. Plaque inside the wall, and disease of the microvessels, are beyond its full reach.

Cardiac magnetic resonance can draw structure and function in fine detail, and it can show myocardial edema, fibrosis, and scar, the last of these by late gadolinium enhancement. It is especially valuable for myocarditis, for typing a cardiomyopathy, for the size of an infarct, and for judging living muscle. It uses no ionizing radiation. Claustrophobia, certain implanted devices, and simple access to the scanner set limits of their own. Nuclear myocardial perfusion imaging compares the distribution of blood flow under load and at rest, and it helps judge the extent of ischemia and the presence of viable muscle.

Among laboratory tests, a rise in high-sensitivity troponin points to myocardial injury. Injury is broader than infarction. Heart failure, myocarditis, and severe infection can raise it, and the number has to be read with the clinical picture. A rise in B-type natriuretic peptide, or in the N-terminal fragment of its precursor, is common when wall tension is high and when heart failure is present. The tests help with diagnosis and with sorting prognosis. Lipids, glucose, glycated hemoglobin, kidney function, thyroid function, and the blood count help look for risks and for diseases that travel alongside. D-dimer has a place when pulmonary embolism and similar alternatives need to be weighed.

These techniques make form highly visible. They still have to be read together with symptoms, signs, emotional state, and the history of a life. Assessment of the heart as an organ has never been the tyranny of a single number. A person with an ejection fraction of fifty-five percent can be in real danger from severe aortic stenosis. A person with an ejection fraction of forty percent, after disciplined treatment and cardiac rehabilitation, can regain a good quality of life. A mild rise in troponin can be an emergency, and it can be a fluctuation against a chronic background. A test is a map. The territory is the particular heart that is still beating, and the doctor and the patient walk that territory together. A sensible way to seek care is straightforward. Acute chest pain goes to emergency care first. It does not begin with teaching oneself how to order tests. Chronic symptoms go to a visit with a list of questions, so that the clinician can choose the test most able to answer those questions. Doing every expensive study in one afternoon is a poor substitute for a clear question.

6. Chest Impediment and True Heart Pain: The Classical Tradition Beside Modern Coronary Disease

The Yellow Emperor’s Inner Canon already describes the person with heart disease: 「心病者，胸中痛，胁支满，膺背肩胛间痛，两臂内痛。」 “When the heart is diseased, there is pain in the chest, fullness propping the flanks, pain between the breast, the back, and the shoulder blades, and pain along the inner sides of both arms.” The places where the pain travels are strikingly close to a modern description of angina. The same tradition also distinguishes heart pain from pain assigned to lung, liver, spleen, and kidney. Chest pain, the old physicians knew, has to be sorted by organ system. Pain in the chest does not by itself settle the diagnosis on the heart.

The Essentials from the Golden Cabinet gives chest impediment and heart pain a treatise of their own. It says, 「阳微阴弦，即胸痹而痛。」 “When yang is faint and the yin pulse is stringlike, there is chest impediment, and there is pain.” Yang qi in the upper burner is insufficient. Yin cold, phlegm, and turbidity from the lower burner ride upward and can block the center of the chest. The text offers formulas such as Gualou Xiebai Baijiu Tang and Gualou Xiebai Banxia Tang, under the method of freeing yang and flushing phlegm. Those names belong to a classical case literature. They are cited here as history and as a way of thinking. They are prepared and prescribed, when they are used at all, by people trained to do so, for a pattern they have identified. This chapter does not turn them into a recipe.

For the gravest degree the same literature has “true heart pain”: 「手足青至节，心痛甚，旦发夕死，夕发旦死。」 “The hands and feet turn blue-green as far as the joints, the heart pain is extreme; what begins at dawn is fatal by evening, and what begins at evening is fatal by dawn.” The picture is violent heart pain with cold limbs and a prognosis of the utmost danger. In its phenomenology it sits close to the danger of acute myocardial infarction complicated by shock or by malignant arrhythmia. Ancient physicians had no coronary angiogram. With pattern elements such as cold pathogen, phlegm turbidity, qi stagnation, blood stasis, qi deficiency, and yang deficiency, they drew a class of illness, dominated by chest pain, oppression, and short breath, out of a tangle of appearances. They treated it by warming and freeing, by flushing phlegm, by moving qi, by quickening blood, by boosting qi, and by warming yang. They left a large body of formula-and-pattern experience, and a large body of detail in pulse and symptom. The methods are named so the tradition can be recognized. Applying them is clinical work, outside the job of a chapter.

From a present-day point of view, the disease spectrum gathered under chest impediment and heart pain is wide. It includes stable and unstable angina, acute myocardial infarction, some microvascular angina and coronary spasm, and angina-like symptoms from severe aortic valve disease. Chest pain as a complaint also has to be distinguished from aortic dissection, pulmonary embolism, pneumothorax, esophageal spasm or reflux, costochondritis, the early phase of shingles, and panic attack. “Chest pain” is a chief complaint. It is a starting point for sorting, and the diagnosis comes after the sorting.

What sits closest to “true heart pain” is acute myocardial infarction, especially when cardiogenic shock, a mechanical complication, or primary ventricular fibrillation is added. The pain may be violent. It may show up in the wrong place, as upper abdominal pain or as pain in the throat. Cold sweat, cold limbs, and a pulse that is faint and on the point of vanishing belong to the same emergency. If reperfusion and life support do not arrive inside the time window, mortality is indeed very high. Women, people with diabetes, and older people may present in an atypical way, with shortness of breath, weakness, or nausea alone, and they need a higher vigilance. Setting the old account beside the new one is a comparison of what each tradition could see. “Blood stasis” is a classical image of flow that has lost its freedom, and thrombus is one modern mechanism inside a larger physiology. “Cold congealing” is a classical image of contraction and obstruction, and spasm is one modern mechanism that can look like it. “Phlegm turbidity” is a classical image of a heavy, clogging pathogen, and abnormal blood lipids are one modern risk that can be discussed alongside it. The useful meeting is this: the older physicians grasped a core picture of pathogenesis, qi and blood blocked in the chest, with an acute form that threatens life. Modern medicine parses that picture into plaque, thrombus, a mismatch of supply and demand, inflammation, the endothelium, and neural reflexes. From that parsing it has developed antithrombotic care, anti-ischemic care, lipid management, blood-pressure care, glucose management, revascularization, intensive care, and secondary prevention. Naming those fields shows what the modern image contains. It does not hand the reader a protocol.

Pattern-based treatment and modern treatment can proceed side by side. In the acute phase, reperfusion that races the clock, together with the medicines guidelines recommend, is the main axis for saving muscle. Delay can be paid for in the death of heart-muscle cells. In the stable phase and in rehabilitation, Chinese medicine still has a wide field of clinical practice in easing chest oppression, in adjusting a constitution that leans one way, in helping with risk-factor care, and in looking after the emotions. That work belongs under a properly trained physician, with an eye on harmful interactions with anticoagulant and antithrombotic drugs. The reader’s task in this chapter is to see why the two traditions are asked to respect each other’s timing. The acute hour is for emergency reperfusion. The longer work of constitution and mood is for a clinician who can see the whole person, and who will not let a formula delay a blocked artery.

Lifestyle is the real common denominator of the two eras: tobacco, alcohol, movement, sleep, food, weight, and mood. Zhang Zhongjing stressed yang shen, nourishing with caution. Cardiovascular prevention today writes behavior change at the same high priority. The “faint yang” of chest impediment in the Golden Cabinet can also turn our attention toward yang qi and warmth. In modern language that includes the way severe cold can provoke spasm and a surge of blood pressure, the way the sympathetic peak before dawn is a poor moment to ignore the body’s signals and strain violently, and the way a person with heart failure benefits from warmth and from the prevention of infection. These are observations about timing and vulnerability. They are the kind of caution the classical phrase already carried.

The lesson of chest impediment is double. The availability of a Chinese medicine is a poor reason to delay emergency care for acute chest pain. A stent already placed, or a bypass already done, is a poor reason to abandon the regulation of qi and blood as a whole, of a phlegm-damp constitution, and of the rhythm of daily life. When form has been opened, the spirit still needs to settle. When a vessel has been opened, it still needs protection against closing again. When lipids have been brought down, they still need protection against rising again. Adherence to the medicines of secondary prevention, and giving up tobacco, often decide the long future more than worry over any one tonic. That is an epidemiological and clinical observation. The choice of those medicines remains an individual prescription.

Culturally and psychologically, the three characters of zhen xin tong, true heart pain, already stack form and spirit. The pain is in the formed organ in the chest. It is also pain in what is “true,” the experience of a threat at the core of a life. Modern patients describing the prodrome and the attack of myocardial infarction often speak of a sense of impending death, extreme fear, drenching sweat, and helplessness. Phenomenologically this meets the old accounts of a savage prognosis. Disease of the heart as an organ is an engineering problem of a blocked pipe, and it is also a shaking of a person’s sense that existence is safe. Care should see the vessel, and it should see the hand gripping the edge of the bed. It should see the troponin curve, and it should see the alarm in a family member’s eyes. Cardiac rehabilitation trains walking and cardiopulmonary endurance. It also includes education, nutrition, psychological support, and the rebuilding of a rhythm for returning to life. That is “form and spirit nourished together,” given an institutional shape inside contemporary medicine.

7. Form and Spirit as One, at the Scale of the Organ

The Inner Canon says the heart is 「君主之官，神明出焉。」 “the official who is the monarch, and from whom spirit-brightness issues.” In the chapters on molecules and cells we already asked, through channels, energy, the pacemaker, and coupling, what physiological conditions the spirit requires. At the scale of the organ, the unity of form and spirit is more intuitive, and closer to daily experience. If the monarch’s storehouses are empty and the city gates are lost, orders are hard to carry out. If the heart’s chambers are in disorder, the valves have lost their measure, the wall is ischemic, and the cycle has lost its rhythm, the brain and the body lose the blood that sustains them, and the spirit is disturbed.

Injury to form can disturb spirit. A severe bradycardia or tachycardia, high-grade atrioventricular block, ventricular tachycardia, and ventricular fibrillation can change the brain’s perfusion in an instant. Vision dims, consciousness drops, and in Adams–Stokes attacks there may be convulsion. After waking, panic and a traumatic memory are common. The violent pain, the lack of oxygen, and the catecholamine storm of acute myocardial infarction can produce a sense of impending death and acute anxiety. Some people afterward develop symptoms in the family of post-traumatic stress. People with chronic heart failure live for a long time with a low cardiac output or with congested lungs. The brain and the organs of the body are under-nourished. Attention falls, mood sinks, sleep breaks into pieces, sexual function declines, and cognition may be impaired, along a spectrum sometimes discussed as heart-failure-related encephalopathy. Low sodium, failing kidneys, and many drugs at once can add confusion on top of that. When the old texts say that blood fails to nourish the spirit, and that the heart-spirit is unsettled, the organ-level meaning is direct. Once the pump, the valves, and the coronary arteries lose their competence, the material base of the spirit shakes. Talking only of “looking on the bright side,” while pump failure and ischemia go uncorrected, asks a change of mood to do the work that only a working pump can do. Handling only catheters and tablets, while fear and sleep are ignored, makes it hard for “spirit-brightness” to return to its place. Both corrections belong in the same care. One of them, pursued alone, leaves the person half seen.

Injury to spirit can burden form. Long anxiety, depression, hostility, social isolation, and chronic pressure, acting through sustained sympathetic activation, a fall in vagal tone, a rise in inflammatory mediators, damage to endothelial function, and a change in platelet reactivity, and acting also through the behavioral paths of smoking, sitting, binge eating, and insomnia, speed atherosclerosis and raise the risk of arrhythmia and of acute events. An acute and violent psychic trauma can induce stress cardiomyopathy, also called apical ballooning syndrome or broken-heart syndrome. There is chest pain, a changed electrocardiogram, a rise in cardiac markers, and on ultrasound a balloon-like weakening of motion at the apex, while the coronary arteries may show no fixed narrowing of importance. Function often recovers within weeks. The episode still proves that “injury to the spirit reaches form,” and that it can do so quickly and concretely. What is more common in ordinary life is quieter. “Matters of the heart,” year after year, rewrite heart-rate variability, the nighttime blood-pressure curve, and the structure of sleep, and at last show themselves at a checkup or in an episode of chest tightness as left ventricular hypertrophy, more early beats, or a heavier plaque burden. Classical medicine says that the seven emotions injure from within, that they injure the movement of qi first, and that over time they enter the blood and the network vessels. That narrative and the modern one can be read against each other.

Form and spirit also have outward signs: “the bloom is in the face,” and “the vessels are the mansion of blood.” When cardiac output is ample and the microcirculation is good, the complexion has a certain luster, the lips and nails are ruddy, the voice has force, and tolerance for activity is there. When heart yang is failing, or when blood stasis and water retention are present, the face is pallid or dusky, the lips and nails are blue-purple, the legs swell, and any movement brings severe panting. Chronic lack of oxygen can produce changes such as clubbed fingers. The slow, the rapid, the bound and intermittent, the thready and weak, the stringlike and forceful, the hasty and the irregularly intermittent pulses of classical examination have a surface on which they can converse with heart rate, rhythm, vessel tone, stroke volume, and the burden of early beats. Pulse reading is more whole and more qualitative. Instrumental measurement is more local and more quantitative. The two are best used together, and each keeps its own kind of information. Changes in complexion and in the tongue often hint at anemia, hypoxia, stasis, or phlegm-damp traveling along with the cardiac problem. The state of the heart as an organ is written on the visible surface of the body.

Protecting the organ of the heart is therefore a double track, and both tracks are ways of understanding a life. One track is medical. It is the control of risk factors. It is the disciplined use of medicines when they are indicated: antiplatelet agents, lipid-regulating drugs, beta-blockers, inhibitors of the angiotensin system, inhibitors of the sodium-glucose cotransporter, and others a clinician may choose for a specific person. It is revascularization and device therapy when they are needed: stents, bypass grafts, pacemakers, defibrillators, valve intervention or valve surgery. It is cardiac rehabilitation and regular follow-up. The list is a portrait of contemporary cardiology, so that a reader can recognize the landscape. Indication, dose, and combination are decided in a clinic, for one body, with one history. A chapter that tried to issue those decisions would be pretending to a knowledge it does not have of the person reading it.

The other track is the life around the medicines. Enough sleep lets diastole and the autonomic nerves repair. A weekly accumulation of moderate aerobic work, with some resistance training beside it, raises cardiac-output reserve and supports endothelial function. Leaving tobacco and limiting alcohol reduces the direct harm of those poisons to muscle and vessel. Learning to recognize and regulate emotion, and building relationships that can hold a person up, keeps the “accelerator pressed to the floor” from becoming a permanent posture. In food, less excess salt, sugar, and trans fat, and a balance that includes vegetables, fruit, whole grains, and adequate protein, is the language of modern guidelines, and it runs in the same direction as the old instruction to keep the diet measured. When form is established, the spirit can keep its post. When the spirit is settled, form grows firm. Between the four chambers and the valves, in every drop of perfusion during coronary diastole, and in each choice to climb the stairs or to stay up all night out of spite, that sentence has a concrete address in anatomy and in behavior.

The organ of the heart also teaches a boundary, and a certain humility. Chest pain has many sources besides infarction. Palpitation has many sources besides catastrophe. Pain along an intercostal nerve, caffeine, anxious palpitation, and early beats are harmless for most people, and sensation can magnify them. There are presentations that should go straight to emergency care: chest pain that persists and comes with cold sweat; pain that travels to the shoulder, the back, or the jaw; severe shortness of breath; pink frothy sputum; fainting; weakness on one side of the body; or speech that will not come clear. Those signs are a reason to ask for emergency help at once. They are a poor match for self-diagnosis on the internet, or for watching and resting alone. A good life begins with the heart, and in the critical hour it includes handing one’s life to the right professional sequence. That is the most practical respect one can pay the “spirit-brightness.” Learning to live with chronic disease is part of the same unity of form and spirit, practiced on ordinary days: reminders to take medicine, a record of blood pressure and heart rate, influenza vaccination, periodontal health because of its relation to the risk of infective endocarditis, a question asked before travel. None of these replaces the judgment of the clinician who knows the case. Each of them is a way the organ stays inside a life that is being looked after.

8. Closing: From the Shape of a Lotus Bud to the Work of a Pump

Look back over the chapter. The four chambers separate the clear from the turbid. The valves keep the stream one way. The wall supplies force, and the coronary arteries supply energy. The cardiac cycle dances between contraction and filling, and cardiac output translates that dance into so many liters of life per minute. Heart sounds, the electrocardiogram, ultrasound, and the other studies make this lotus-bud organ something that can be heard, measured, and followed over time. Setting chest impediment and true heart pain beside each other, classical and modern, lets us take the old books seriously and lets us use them with a modern eye. It lets us welcome the modern power of reperfusion, and it lets us keep the tradition of regulation as a whole and of nourishing with caution. At the scale of the organ, the unity of form and spirit weaves chest pain and fear, a failing pump and a weary spirit, complexion and pulse, stents and sleep, back into one net.

The heart of the cell answers who is beating. The heart of the organ answers what kind of structural and functional whole that beating has become. What looks like a master of the household is a strict cooperative art of fluid mechanics and electrophysiology. The ruler of spirit-brightness first requires chambers that are not in chaos, valves that do not run backward, a wall that has a blood supply, and a cycle that keeps its order. The heart never governs alone. Through the great arteries and the veins it joins the whole body. With the lungs it exchanges gas. With the kidneys it shares the long regulation of volume and blood pressure. With the brain it consults on rhythm and on mood. With the endocrine glands it writes the story of blood pressure, blood glucose, and water and salt. Only when the organ is set into the network do we see the full meaning of “the heart governs the blood and vessels of the body,” and only then do we understand why a wound in the heart can shake all five viscera.

The organ is the visible heart of flesh and blood. In the next chapter we set it into a larger network, the circulatory system and the steady state of the whole body. We watch how the heart answers the lungs, the kidneys, and the neural and humoral signals; how, at the scale of the system, it goes on with the work of governing spirit-brightness; and how blood pressure, the microcirculation, and the conversation among many organs decide whether we can truly settle into a life that begins with the heart.