Cardiomegaly and Cardiomyopathy

Description

There are three basic types of cardiomyopathy:

1. Dilated cardiomyopathy. The heart muscle becomes weak and the heart chambers subsequently enlarge (dilate).

2. Hypertrophic cardiomyopathy. The heart muscle itself is much thicker than normal.

3. Restrictive cardiomyopathy. The heart becomes stiff and cannot fill efficiently during distal, the period of the heartbeat when the chambers fill with blood.

Dilated Cardiomyopathy

Dilated cardiomyopathy refers to overall enlargement (dilatation) of the heart chambers, especially the ventricles. Although this enlargement is a key part of dilated cardiomyopathy, it is not the initial problem, but rather the heart's own response to a weakness of heart muscle and poor pumping ability. The weakness of the heart muscle in this condition is generalized, "global" - all parts of the myocardium are affected about equally. Enlargement of the heart is the heart's way of trying to compensate for the weakness of its muscle. This is called a compensatory mechanism.

If the heart muscle is weak, it is unable to pump out the same portion of blood that it could at normal strength. Rather than simply "accepting" the limitations of decreased pumping ability, the heart and other organs of the body undergo compensatory changes to try to maximize their efforts.

Dilated cardiomyopathy causes heart failure - an inability of the heart to provide an adequate supply of blood to the body's organs and tissues - which if left untreated is always associated with excess fluid retention, congestion in the lungs and liver, and swelling of the legs.

Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy is an overgrowth of heart muscle that can impair blood flow both into and out of the heart. The disease is characterized by a disorderly growth of heart muscle fibers, causing the heart chambers to become thick-walled and bulky. All the chambers are affected, but the thickening is generally most striking in the walls of the left ventricle. Most commonly, one of the walls, the septum, which separates the right and left ventricles, is asymmetrically enlarged. The distorted left ventricle contracts, but the supply of blood to the brain and other vital organs may be inadequate because blood is trapped within the heart during contractions.

Hypertrophic cardiomyopathy is sometimes called idiopathic hypertrophic subaortic (beneath the aorta) stenosis, abbreviated IHSS. This overgrowth creates a bulge that protrudes into the ventricular chamber and impedes the flow of blood from the heart to the aorta and the rest of the body.

When this obstruction is present, the cardiomyopathy is also called hypertrophic obstructive cardiomyopathy (HOCUM, often pronounced "hokum"). In this condition, the problem is not that the heart muscle is weak but that the overgrown heart muscle impedes the flow of blood through and out of the heart.

Restrictive Cardiomyopathy

Restrictive cardiomyopathy is less common than the other two forms. It can stem from infiltration of the heart muscle with abnormal material (for example in amyloidosis) or with any other type of chronic fibrosing process. The result is a heart that cannot expand sufficiently to fill with blood, and cannot contract efficiently such that adequate amounts of blood perfuse either the lungs for oxygenation, or the tissues for normal blood supply.

Causes and Risk Factors

Possible causes of dilated congestive cardiomyopathy include: inflammation of the heart muscle (myocarditis) either infectious or non-infectious, excessive alcohol consumption, nutritional deficiencies, complications arising shortly before or after childbirth (postpartum), and genetic disorders. Causes of the hypertrophic and restrictive forms are usually unknown.

Symptoms

Symptoms associated with all forms of cardiomyopathy can range from minor to moderate feelings of fatigue, shortness of breath with exertion, irregular heartbeat, to frank symptoms and signs of congestive heart failure where the heart no longer functions adequately to circulate blood.

Diagnosis

The diagnosis of cardiomyopathy is made by a physician via a thorough history and physical exam. Definitive diagnosis usually depends upon cardic catheterization with measurement of heart function and flow characteristics, and sometimes heart muscle biopsy.

Treatment

Management of dilated cardiomyopathy involves treating the underlying disorder such as a curable infection or nutritional deficiency. For example, in the case of heart muscle disease caused by alcohol consumption, treatment entails total abstinence. But in most cases the cause is unknown, so treatment focuses on relieving symptoms and improving the function of the injured heart chambers.

Patients receive medications that enhance the capacity of the heart muscle. The few drugs that produce this effect work indirectly by increasing the level of calcium inside the heart cells. (Calcium initiates heart muscle contractions). Digitalis and its derivatives such as digoxin, the oldest and best known of such drugs, are usually administered orally but may be given by an intravenous injection. More potent cardiac stimulants such as dobutamine (Dobutex), dopamine (Intropin), and amrinone (Inocor) are reserved for hospital use.

Management of hypertrophic cardiomyopathy involves limiting stressful physical activity and the use of drugs to relieve symptoms. Traditionally, drugs called beta blockers have been used to prevent a rapid heartbeat and decrease the excessive force of contractions. Antiarrhythmic drugs are often prescribed to treat abnormal heart rhythms.

In the past decade, calcium channel blockers, particularly verapamil (Calan), have been shown to be especially effective for relief of symptoms. Like beta blockers, calcium antagonists reduce the force of the heart's contractions, but they also increase the flexibility of the bulky heart chambers. These combined effects increase the efficiency of pumping and reduce congestion.

Questions to Ask Your Doctor

Do any tests need to be done for diagnosis?

What type of cardiomyopathy is involved?

What are the complications of the condition?

What is the underlying cause of the heart enlargement?

How serious is the condition?

What type of treatment will you be recommending?

How successful is this treatment?

Will you be prescribing any medications? What are the side effects?

How long will the medications need to be taken?

What is the prognosis of the condition?