The coronary arteries, which supply oxygenated blood to the heart, may become diseased. Cholesterol deposits may accumulate in the inner lining of the coronary arteries, a process called atherosclerosis. This results in narrowing the vessel channel and compromises blood flow to the heart muscle.

Various factors may cause a cholesterol plaque in the coronary artery to become unstable and rupture into the channel of the artery, exposing the fatty contents of the plaque to the circulating blood. When blood comes in contact with this fatty material, rapid clotting of the blood occurs. If the blood clot is large enough, it can completely occlude the channel of the coronary artery and prevent any blood from supplying the portion of heart muscle supplied by that particular artery. Since heart muscle cells can survive only minutes to hours without oxygen, occlusion of the coronary artery results in death of part of the heart muscle--a heart attack. It is important to understand that the likelihood that a cholesterol plaque will rupture does not depend on the degree of narrowing that plaque causes. A plaque forming a 20% narrowing, 50% narrowing, or 90% narrowing are all capable of rupturing and causing a heart attack. This explains how a "minor" plaque which does not cause any symptoms can cause a heart attack without warning.

The typical symptoms are chest pain or pressure ("angina"), sometimes with radiation to the arm or jaw, and shortness of breath. This may be accompanied by nausea, sweating, or dizziness. These symptoms typically are brought on with exertional or emotional stress. However, even when the coronary arteries become severely narrowed by cholesterol plaque, symptoms may be absent or subtle, especially in someone who leads a sedentary lifestyle. This is because the heart requires a relatively small amount of oxygen when someone is at rest. However, during the performance of physical work, the heart's oxygen requirements increase dramatically. Thus, a person with a coronary blockage can be symptom free at rest but have chest pain with a moderate exertion, such as walking on a treadmill, climbing stairs, or shoveling snow. This concept is the rationale behind provocative stress testing to elicit coronary insufficiency. Note that certain populations of individuals, such as diabetics and people over 70, do not exhibit the above classic angina symptoms, even with exertion.

Elevated cholesterol, smoking, diabetes, hypertension, male gender, and family history of coronary disease are all associated with a higher risk for developing coronary artery disease and myocardial infarction. These risk factors were identified by following a large population of "healthy" people over 20 - 30 years and coming up with a profile of those who ultimately went on to develop coronary artery disease. Recently, increased blood levels of homocysteine, an amino acid, has also been found to be a risk factor for coronary disease.

The gold standard for diagnosis of coronary artery disease is coronary angiography, also known as cardiac catheterization, which is described below. Although cardiac cath is the gold standard, it is an invasive test and not appropriate for all patients. For this reason, noninvasive stress testing has been developed for the diagnosis of coronary disease.

A stress test is a noninvasive exercise test used for the diagnosis of coronary artery disease. Stress testing involves placing the heart under physically stressful conditions--i.e., making it work--in order to elicit subjective (chest pain) and objective (EKG changes) findings of coronary insufficiency. Some stress tests involve the adjunctive use of various cardiac imaging modalities (echo, nuclear scanning) to increase the information gained from the test and improve the sensitivity. Some patients, such as people with severe arthritis, are unable to exercise on a treadmill. These patients can still have stress testing without physical exercise. In such patients, various drugs can be administered intravenously that "stress" the heart and simulate exercise.

Any person who is suspected of having coronary disease should have a diagnostic workup including a stress test. In some instances, if the degree of suspicion for coronary disease is extremely high, your doctor may decide to forego stress testing and proceed directly to a coronary angiogram. Stress testing is also frequently done to detect occult coronary disease in someone about to undergo major surgery, before one is allowed to embark on an exercise program, or in people whose occupation potentially affects public safety, such as a commercial airline pilot. Lastly, stress testing is performed in people who have had prior angioplasty or coronary bypass surgery, as part of their follow-up care. Typical profiles of people referred for a stress test include the following:

• A 50 year old male who complains of chest pain when he climbs up the stairs.
• A 65 year old male who is without any symptoms but who is overweight, smokes, has a positive family history or coronary disease, and who leads a sedentary lifestyle (i.e., a "couch potato").
• A 73 year old female with history of hypertension and high cholesterol who is about to undergo repair of an abdominal aortic aneurysm (a major surgery that places great stress on the heart).

Cardiac catheterization, also known as coronary angiogram, or "heart cath," is a procedure in which the coronary arteries and heart muscle are directly imaged under x-ray using iodine contrast dye. Cardiac cath is the "gold standard" for diagnosis of coronary disease. The procedure is usually performed through the femoral artery in your groin but is sometimes performed through the brachial artery on the inner aspect of your elbow. During a cardiac cath, your cardiologist administers local anesthesia to numb the groin, then inserts a thin, hollow catheter through the groin and advances it to the heart. Injection of contrast through the catheter under x-ray allows visualization of the coronary arteries. Blockages, or "stenoses" of the coronaries can be identified in this manner. Cardiac cath takes about one hour and can be done in an outpatient manner. However, if an angioplasty is performed at the same time as a heart cath, the patient is usually admitted to the hospital overnight for observation. All contrast dyes contain iodine. However, patients with a history of allergy to iodine can still undergo heart cath. These patients are usually pretreated with one or more days of oral steroids to suppress the body's allergic mechanisms.

Because atherosclerotic plaques almost always contain calcium deposits, they can be visualized by x-ray. In the last several years, specialized, high speed, CAT scanners have been developed that rapidly scan the heart "between" heartbeats and identify the presence of calcium in the coronary arteries. The resolution of these scanners is not quite sharp enough to detect the degree of narrowing of the coronary artery channel. However, the images are able to provide information about the quantity of calcium in the heart and calculate a "calcium score." Because the amount of calcium in the heart correlates with the amount of cholesterol plaque, a conclusion can be drawn regarding how much plaque one has in his/her coronaries. This gives an idea of the likelihood of a future cardiac event, such as a heart attack.

Thus, a calcium scan cannot identify a specific lesion, or narrowing in a coronary artery that may lead to symptoms or to a heart attack, but it can identify which patient may be at risk. A calcium scan is not appropriate for everyone, particularly if someone has already had coronary angiography. Physicians sometimes use a calcium scan if a patient has undergone a stress test which has shown equivocal results.

The treatment of coronary disease is geared toward relief of symptoms of angina and reduction of the risk of future heart attack or death from cardiac cause. Several medications have been shown to reduce mortality from coronary disease. Aspirin, which is a weak blood thinner, reduces the risk of a first heart attack or of a future heart attack in a patient who has already suffered one. Aspirin exerts its protective effect by weakly blocking the action of platelets, the blood cells that bring about clotting.

The classes of blood pressure drugs known as beta blockers and ACE-inhibitors similarly reduce mortality (by a mechanism that is independent of their effects on blood pressure).

The cholesterol-lowering agents known as statin drugs (because they end in a suffix - "statin") also lower the risk of heart attack and mortality. These drugs seem to act by "stabilizing" existing plaques and preventing plaque progression, rather than by "shrinking" plaque.

The class if drugs known as "nitrates," such as nitroglycerine, are very effective in relieving symptoms of chest pain. These drugs do not have any effect on the natural course of the disease atherosclerosis and do not change mortality.

Coronary angioplasty and coronary bypass surgery, described below, are very effective in treating the symptoms of angina. In addition, in cases where the heart muscle is severely weakened by the presence of coronary disease, coronary bypass also prolongs life.

Coronary angiography is a diagnostic procedure during which the coronary arteries are imaged in order to define their anatomy and identify stenoses, or blockages, within the arteries. Coronary angioplasty, or percutaneous transluminal coronary angioplasty (PTCA), is a therapeutic procedure geared toward treating coronary stenosis or occlusion. During this procedure, the cardiologist advances an angioplasty balloon into the coronary artery and, under x-ray guidance, positions the balloon over the site of the blockage, or stenosis. Inflation of the balloon stretches the artery, compressing the plaque against the artery wall, thereby enlarging the artery channel. While the balloon is inflated, it occludes the artery channel and blood cannot pass. During this time, the patient may experience chest discomfort, until the balloon is deflated. Following angioplasty, the artery channel is enlarged. However, since the artery contains elastic tissue, there is always some degree of "recoil" after the balloon is deflated. Over the ensuing weeks, as the artery heals, the recoil process may continue. In some cases (30-40%), severe recoil can cause "restenosis," or renarrowing of the arterial channel. This is a drawback to angioplasty. Fortunately, a device known as a "stent" has been developed that overcomes the recoil phenomenon.

A stent is a tubular mesh of metal (usually stainless steel) that is deployed in the coronary artery after an angioplasty. A stent is mounted on an angioplasty balloon in its collapsed state. The stent/balloon assembly is then advanced into the coronary artery and positioned over the site of the coronary lesion. When the balloon is inflated, the stent becomes fully expanded and apposed against the coronary artery wall, "tacking up" the atherosclerotic lesion and buttressing the artery wall. The balloon is then removed but the stent remains in the coronary artery (forever). Following stenting, the patient is treated with aspirin in addition to another blood thinner (clopidogrel or ticlopidine) in order to prevent blood clotting at the site of the bare metal stent. These drugs must be continued for 3 - 4 weeks, until the stent becomes lined with a layer of tissue, making it less likely to induce blood clotting.

A balloon-mounted coronary stent being deployed

The use of stents has dramatically reduced the restenosis rate to 20%, or about half of that observed after angioplasty alone. This is because a fully expanded stent virtually abolishes the arterial recoil phenomenon seen after angioplasty. However, restenosis can occur within a stent. In this process, the stent does not collapse, but, rather, an aggressive scar tissue reaction occurs inside the stent, narrowing the channel. Some degree of scarring occurs after every stent, but differs in degree from patient to patient. Restenosis usually occurs within 6 to 12 months after a stent. Beyond that time period, the scarring process essentially stops. The restenosis rate seems to be more common in diabetics and in smaller sized coronary arteries. When restenosis occurs, it can usually be treated with repeat angioplasty. Recently, intracoronary radiation has been used to abate the scarring process. This is reserved for cases of recurrent and aggressive restenosis. Research and clinical trials are currently ongoing with drug-coated stents that have been reported to elicit virtually no scarring reaction. However, these drug-coated stents are still under investigation not yet available.

A coronary blockage can be angioplastied or stented. Some patients, however, are not good candidates for angioplasty. These include patients that have blockages in all three coronary arteries or who have anatomy that is not amenable to angioplasty, such as a completely (100%) occluded artery. In these patients, coronary bypass, or "open heart surgery," is considered. Coronary bypass involves taking a vein or artery (from the chest wall, leg, or arm) and using it as a bypass conduit by sewing one end to the aorta and the other end to the coronary artery distal to the place of blockage. Coronary bypass surgery is an excellent procedure that generally provides good long term relief of angina and, in patients with a weakened heart or disease of the "left main artery," prolongs life span.

Large clinical trials have been done comparing coronary bypass surgery and angioplasty. These trials have shown no difference in long term survival between patients who undergo bypass surgery versus those who undergo angioplasty. Patients undergoing angioplasty tend to have a higher incidence of recurrent angina due to restenosis, necessitating repeat angioplasty procedures, whereas coronary bypass patients have a lower incidence of recurrent chest pain. However, coronary bypass surgery is a much more invasive procedure involving a longer hospitalization and higher short term incidence of complications.

An arrhythmia is any disturbance in the regular, rhythmic beating of the heart. Bradycardia is an inappropriately slow heartbeat (< 60 beats/min), whereas tachycardia is an inappropriately fast heartbeat (> 100 beats/min). Tachycardias are subdivided into supraventricular, which originate in the atria, and ventricular, which originate in the ventricles. The presence of an arrhythmia indicates a problem in the electrical conduction system of the heart. Sometimes, however, coronary artery disease and heart attack may lead to arrhythmias.

Typical symptoms of bradycardia include weakness, dizziness, or fainting spells. Tachycardias may cause palpitations, lightheadedness, anxiety, or fainting. In some cases, an arrhythmia may be asymptomatic and a patient may be unaware that he/she is having an irregular heartbeat.

One diagnostic test used to identify arrhythmias is a Holter monitor, which is a small cassette recorder that is worn by the patient for a period of 24 hrs, during which a continuous EKG recording is made. During this time, the patient writes down any symptoms he/she experiences in a diary, which is reviewed by the cardiologist when the rhythm recordings are analyzed.

One syndrome that may cause fainting spells is called neurocardiogenic syncope. In this disorder, an overactivity of one part of the nervous system (sympathetic nervous system, which is responsible for the "fight-flight" response), leads to a rebound lowering of the pulse and blood pressure, with a pooling of blood in the leg veins, leading to dizziness and passing out. A tilt table exam is a provocative test that, in a controlled setting, brings out the typical characteristics of this syndrome in a patient who has neurocardiogenic syncope. During a tilt study, the patient is lays flat on a cushioned table with seat belts. The table is then tilted head upward for a period of time, usually twenty minutes. A patient with neurocardiogenic syncope will manifest the typical symptoms of slow heart rate and lowering of blood pressure in response to this measure.

A study of the heart's electrical system is known as an electrophysiology test. During this test, wire electrode catheters are advanced through a vein in the groin to various positions in the heart. The electrical activity of the heart is then examined and the conduction properties of the nerves in the heart are measured. The second part of this test involves electrical stimulation of various parts of the heart in an attempt to induce an abnormal heart rhythm. Identification of this abnormal rhythm allows specific treatment to be tailored towards it. Electrophysiology testing is usually performed on patients with symptoms of dizziness or fainting. In some instances, a Holter monitor may pick up an abnormal and potentially dangerous heart rhythm that is further investigated by electrophysiology study.

A study of the heart's electrical system is known as an electrophysiology test. During this test, wire electrode catheters are advanced through a vein in the groin to various positions in the heart. The electrical activity of the heart is then examined and the conduction properties of the nerves in the heart are measured. The second part of this test involves electrical stimulation of various parts of the heart in an attempt to induce an abnormal heart rhythm. Identification of this abnormal rhythm allows specific treatment to be tailored towards it. Electrophysiology testing is usually performed on patients with symptoms of dizziness or fainting. In some instances, a Holter monitor may pick up an abnormal and potentially dangerous heart rhythm that is further investigated by electrophysiology study.

A slow heart rhythm, or bradycardia, can be treated with a permanent pacemaker. This sophisticated device is only about the size of a silver dollar coin and is implanted beneath the skin in the upper chest. The procedure is done under local anesthesia. The pacemaker lies dormant as long as the heart is beating normally. However, if the heart should beat inappropriately slowly, the pacemaker "kicks in" and paces the heart.

An automatic implantable cardiac defibrillator is a device capable of detecting a dangerous heart rhythm and applying an electrical shock to the heart in order to convert the rhythm back to normal. This device is implanted under the skin, much like a pacemaker, in patients who have a predisposition to dangerous arrhythmias that could cause loss of consciousness.

The heart is a muscle that vigorously contracts and pumps blood through the body. Some disease processes can weaken the heart muscle and diminish its ability to contract. This failure of the heart's forward pumping action results in the backup of blood in various tissues. When the right ventricle fails, blood backs up in the extremeties (usually the legs). This is referred to as "right heart failure." Left ventricular failure results in blood "backing up" in the lungs, causing shortness of breath and left-sided "congestive heart failure."

The proper function of the heart depends both on normal heart muscle contraction in systole and normal muscle relaxation in diastole. Improper relaxation of the left ventricle in diastole may impede the normal easy flow of blood returning from the lungs into the left ventricle. This is known as diastolic dysfunction, and results in the lungs becoming congested with blood (left-sided congestive heart failure). Congestive heart failure due to diastolic dysfunction frequently is associated with chronic hypertension but also occurs in the absence of hypertension as the normal heart ages.

In a healthy heart, the forward flow of blood through the heart chambers is controlled by four valves: mitral, tricuspid, aortic, and pulmonic. The mitral and tricuspid (atrioventricular) valves are situated between the atria and ventricles. The aortic and pulmonic (semilunar) valves are situated between the ventricles and their respective great vessels (aorta and pulmonary artery). The atrioventricular valves control the flow of relatively low velocity blood between the atria and ventricles and thus are "floppier" and seated around a much larger sized orifice than are the semilunar valves, which are smaller and stiffer and designed to control high velocity blood ejected out of the ventricles. The opening and closing of the valves through the cardiac cycle is passive and results from differences in hydraulic pressure between the chambers on either side of the valve. The atrioventricular valves open in diastole, allowing blood to pass from blood-filled right and left atria into the empty right and left ventricles, which are at rest. When the blood-filled ventricles contract, pressure within the ventricles rapidly increases, slamming shut the atrioventricular valves (preventing "backward" flow of blood into the atria) and forcing open the semilunar valves, resulting in forward ejection of blood into the great vessels.

Two disease processes can affect the heart valves: stenosis and regurgitation. In valvular stenosis, a valve may become stiffened and immobile. Such a stiffened valve does not open properly and actually impedes the forward flow of blood. One example of this pathology is rheumatic mitral valve stenosis. In this disease, the mitral valve becomes damaged by an immunologic reaction resultant from a childhood episode of rheumatic fever. The mitral valve becomes stiff, calcified, and unable to open properly. Thus, blood cannot easily pass from left atrium to left ventricle. This leads to enlargement of the left atrial chamber and backup of blood into the lungs. As the disease progresses, the lungs become increasingly engorged with blood and lung scarring occurs. This causes symptoms of shortness of breath, weakness, and dizziness.

Valvular stenosis may also be congenital, such as congenital tricuspid stenosis, or congenital bicuspid aortic valve leading to aortic stenosis in the adult.

Mild valvular stenosis is treated medically. Severe valvular stenosis must be treated surgically, with valve repair or replacement. In some cases where the valve has not become severely calcified, valvuloplasty may be performed percutaneously with a balloon catheter inserted through the groin. The balloon is placed across the valve and inflated, stretching the valve open.

A valve may also become regurgitant (leaky). When a normal, healthy valve closes, the leaflets do not come together in a perfect, seamless fashion and a trivial amount of "leakage" does occur. However, a valve that becomes diseased can leak, or regurgitate, severely. One example of this occurs in bacterial endocarditis, when a heart valve becomes infected by bacteria. Bacterial organisms grow on and destroy valve tissue such that the valve leaflets do not close properly, resulting in leakage of blood through the closed valve. Another example is severe mitral valve prolapse with regurgitation.

Valvular regurgitation may be treated medically when it is "mild" or "moderate." Severe regurgitation must be treated with surgical valve replacement.

The closing of heart valves can be heard using a stethoscope. Actually, the sound heard is that of blood moving at a high velocity as it slams against a valve that has just closed. In a healthy heart, there are two heart sounds, known as S1 and S2. S1 is due to the simultaneous closure of the mitral and tricuspid valves and S2 is due to closure of the aortic and pulmonic valves.

In the same way that rocks in a rapidly flowing stream can interrupt the smooth flow of current and create a "swooshing" sound, blood flowing turbulently across a stiff, stenotic valve or leaking backwards through a regurgitant valve causes sounds that can be heard through a stethoscope. These sounds are called murmurs. Although a heart murmur may be indicative of a valve problem, not all murmurs are "pathologic," or indicative of a disease state. For example, pregnant women or athletes frequently have murmurs because they have a high volume flow of blood through the heart and across the heart valves.

The mitral valve sits in the left side of the heart between the left atrium and left ventricle and is composed of two leaflets: anterior and posterior. The mitral valve opens in diastole, when the heart is resting, and allows blood to fill the left ventricle, then closes in systole when the left ventricle contracts. The closed mitral valve prevents blood from flowing backwards into the left atrium. The blood is thus pumped out of the left ventricle through the aortic valve and on to the body.

In some people, the mitral valve closes in a slightly improper way. Instead of the two leaflets coming together seamlessly, the leaflets come together in an awkward fashion and flop, or prolapse, into the left atrium during the forceful ventricular contraction. The prolapse may involve one or both the leaflets. This prolapse of the mitral valve causes a "click" sound that can be heard through a stethoscope. If the leaflets prolapse severely, then the mitral valve will leak, or regurgitate, blood back into the left atrium during systole. In severe cases of mitral valve prolapse, the valve leaflets can also become thickened over time. Patients with severe mitral valve prolapse with significant regurgitation are usually instructed by their cardiologist to take prophylactic antibiotics before having dental work.

Mitral valve prolapse is more common in women than in men. Patients with mitral valve prolapse frequently have symptoms of chest pain, the reasons for which are not well known. Mitral valve prolapse is also associated with heart rhythm abnormalities that cause symptoms of palpitations. These rhythm abnormalities are usually benign.

Normal heart valves have relatively "non-stick" surfaces. However, a diseased leaky or stenotic valve loses this property. In addition, turbulence of blood flow across the diseased valve allows any particles that may be present in the blood to settle on the valve and infect it. Bacteria can enter the bloodstream during infection anywhere in the body. They can also enter the bloodstream from the oral cavity, during tooth cleaning or other dental work. People with heart murmurs are felt to be at a somewhat increased risk of valve infection and should therefore take antibiotics before having dental work. The usual antibiotics used for this purpose are amoxicillin, erythromycin, and clindamycin.

A stenotic valve can sometimes be "stretched" open by inflating a balloon across it. This is known as valvuloplasty and is done nonsurgically, through a catheter placed in the femoral artery in the groin. This procedure is done in only certain centers, and not all patients are candidates for this. For example, significant scarring or calcification of the valve, or severe regurgitation of the valve, preclude a successful valvuloplasty result.

Atherosclerosis is a systemic disease that affects all the arteries, and patients who have coronary artery disease also have a higher likelihood of having peripheral vascular disease. Just as the coronary arteries can become diseased with cholesterol plaque that affects the inner lining of the artery and causes narrowing of the channel, the arteries of the lower (and more rarely, upper) extremities can become laden with cholesterol plaque. This causes arterial insufficiency, or "poor circulation" to the legs. The classic symptoms of peripheral vascular disease include pain in the calves, thigh, or buttocks during walking (claudication), which subsides after ceasing walking. As the disease progresses, there is gradual loss of muscle tissue, thickening of the toe nail beds, and thickening and brownish pigmentation of the skin overlying the shins. In advanced cases, there may be pain in the feet even at rest. This is typically noticed more at night, when the feet are at a horizontal position in bed. The pain is sometimes relieved by "dangling" the feet, allowing gravity to help blood flow to the feet. Ulcers may develop in the feet or shins and are very slow to heal. In very severe cases, gangrene may develop, requiring amputation.

Mild or moderate peripheral vascular disease is treated conservatively. Aggressive cholesterol control and cessation of smoking are critical. Patients with mild/moderate claudication are urged to "walk through" the pain. This creates stimulus for the body to form "collateral" arteries to help supply the legs with blood. In cases of severe claudication, rest pain, or presence of non-healing foot ulcers, arterial revascularization is required. This may be surgical or percutaneous (with angioplasty), depending on the severity of anatomic disease.