Atherosclerosis:  The Basic Cause of Heart Disease

Atherosclerosis is a long-term disease process in which cholesterol and other substances slowly build up in the inner lining of artery walls.  This buildup is called plaque.  When plaque builds up in an artery to the heart, the artery begins to narrow, reducing the heart's blood supply.  Eventually the artery may become completely closed off, either by the plaque itself or by a blood clot that lodges in the narrowed area.  When the blood supply can't reach a part of the heart muscle, that part begins to die.  This is called a heart attack.  Similarly, if an artery to the brain becomes clogged, a stroke results.

"Heart Disease" is a vague term.  Many different types of problems can be called heart disease.  All heart disease can be classified within one of four categories:
 

     1. Diseases of the Arteries
     2. Problems With Heart Valves
     3. Diseases of the Muscle
     4. Problems of the Electrical System

Diseases of the arteries, specifically the coronary arteries, generally refer to the buildup of cholesterol in the inside layers of the arteries.  Like any muscle, the heart needs a constant supply of oxygen and nutrients that are carried to it by the blood in the coronary arteries.  When the coronary arteries become narrowed or clogged and cannot supply enough blood to the heart, the result is coronary artery disease.  If not enough oxygen-carrying blood reaches the heart, the heart may respond with pain called angina.  The pain is usually felt in the chest or sometimes in the left arm and shoulder.  (However, the same inadequate blood supply may cause no symptoms, a condition called silent angina.)  When the blood supply is cut off completely, the result is a heart attack.  The part of the heart that does not receive oxygen begins to die, and some of the heart muscle may be permanently damaged.  Forms of treatment for heart disease of the arteries are percutaneous transluminal coronary angioplasty, also known as PTCA, and coronary artery balloon dilation or balloon angioplasty.  About 70-90 percent of these procedures also involve the placement of a stent, a wire mesh tube used to prop open an artery that stays in the artery permanently, holds it open, and improves blood flow to the heart muscle.  Blockage could possibly grow through the wire mesh over time.  Bypass surgery ö also known as coronary bypass ö is another form of treatment. Top of page

The heart valves are also susceptible to problems.  Each valve has a set of flaps (also called leaflets or cusps).  When working properly, the heart valves open and close fully.  Two major problems occur with valves ö stenosis and regurgitation.  Stenotic valves are those that close down, making the flow of blood between chambers difficult.  Aortic stenosis, for example, is a condition in which the valve regulating the blood flow as it leaves the heart and enters the aorta will not open fully.  Valve regurgitation is a condition in which the valve leaks.  Leaking valves cause blood to move backward in the heart, limiting the effectiveness of the pump.  A person can be born with an abnormal heart valve, a type of congenital heart defect.  Or a valve can become damaged by infections such as infective endocarditis, rheumatic fever, or changes in valve structure in the elderly.  People with congenital heart valve defects may need medical treatment with drugs.  Some valve defects may be repaired with surgery. Top of page

Disease involving the heart muscle is called "cardiomyopathy."  Cardiomyopathy is a serious disease in which the heart muscle becomes inflamed and doesn't work as well as it should, resulting in a decreased ability of the heart to pump efficiently.  Cardiomyopathies have a wide variety of causes including viral infections and excessive alcohol intake.  Research suggests that strenuous exercise during a viral infection such as a cold should be avoided because the risk of cardiomyopathy increases in this situation.  The major treatments for congestive heart failure caused by cardiomyopathy include medications and heart transplantation. Top of page

Diseases of the heart's electrical or conduction system occur in many people.  The conduction system of the heart stimulates the heart to beat, which in turn pumps blood into the body.  Many different types of malfunctions occur in this system, most of which are not serious.  In fact, most people experience "extra beats" intermittently.  This can be caused by excess caffeine intake or, for women, fluid shifts during the menstrual cycle.

Diseases of the hearts conduction system are worrisome when a person loses consciousness or if dangerous beats or rhythms are seen during tests such as an EKG.  Disturbances of the heart rhythm are typically treated with medication.  Some patients need a pacemaker if the natural mechanisms for regulating the heart beat wear out or are damaged in some way.  Radiofrequency ablation, a non-surgical procedure in the cath lab, is used to treat some types of rapid heart beating, especially Wolff-Parkinson-White syndrome or supraventricular tachyarrhythmias.  Radiofrequency ablation has a success rate of over 90%, a low risk of complications and the patient can resume normal activities in a few days.

Sometimes, patients with dangerous rhythms require an automatic implantable cardioverter-defibrillator (AICD).  This device is placed surgically like a pacemaker.  However, instead of stimulating the heart to pump rhythmically as a pacemaker does, the ACID revives patients who lose consciousness because of a heart emergency.

In summary, a wide variety of diseases fall under the heading of "heart disease."  These diseases can be diagnosed and treated today in ways that would have been considered miraculous a generation ago.  Today, people are regularly beating heart disease, and the outlook for even more effective treatments is bright. Top of page
 

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