Cardiac Enlargement: A Patient Guide

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What is cardiac enlargement?

Cardiac enlargement refers to an increase in the size of the heart. There are two types of cardiac enlargement: hypertrophy and dilation. (Though usually occurring separately, they may occur at the same time.) Hypertrophy involves an increase in the thickness of the heart muscle. Dilation involves an increase in the size of the inside cavity of a chamber of the heart. Hypertrophy usually occurs in only one chamber while dilation may occur in one, two, three, or all of the chambers, based on its cause. In most cases, cardiac enlargement is abnormal and accompanied by additional cardiovascular problems. The one exception is regular aerobic exercise, which produces a beneficial enlargement involving both hypertrophy and dilation of the heart.

What causes cardiac hypertrophy?

Hypertrophy, or thickening, of the heart muscle occurs in response to increased stress on the heart. It typically involves one of the bottom chambers of the heart, which are known as the ventricles. The right ventricle pumps blood to the lungs and the left ventricle pumps blood to the body. The most common causes of hypertrophy are related to increased blood pressure in either the lungs or the body. The extra work of pumping blood against the increased pressure causes the ventricle to thicken over time, the same way a body muscle increases in mass in response to weightlifting.

High blood pressure, or hypertension, is the most frequent cause of left ventricular hypertrophy (LVH). Stenosis of the aortic valve - a condition in which, for a variety of reasons, this heart valve cannot open fully - is another common cause of LVH. Hypertrophic cardiomyopathy (a disease previously known as idiopathic hypertrophic subaortic stenosis or IHSS), and the ongoing use of cocaine round out the list of most common causes of LVH. Hypertrophic cardiomyopathy is a genetic disease related to weakness of the individual muscle fibers of the heart. These fibers need to work harder to pump blood and become thickened over time. Hypertrophic cardiomyopathy occurs in 1 in 500 people and is the most common cardiac cause of sudden death in young athletes.

The most common causes of right ventricle hypertrophy (RVH) are diseases that damage the lung like emphysema and cystic fibrosis. These diseases destroy blood vessels in the lung, causing increased pressure in the remaining vessels. Conditions that decrease oxygen levels, such as chronic bronchitis and sleep apnea, also lead to RVH. Stenosis of the pulmonic heart valve, repeated blood clots to the lungs (chronic pulmonary embolism), and primary pulmonary hypertension are a few of the remaining causes of RVH.

What causes cardiac dilation?

The most common causes of dilation are conditions that directly damage the heart muscle. The heart's healing response is a thinning and stretching-out of the muscle. Types of damage include prior heart attack, long-term alcohol abuse, and heart muscle inflammation. Heart muscle inflammation, or myocarditis, is sometimes of unknown cause and is often associated with a viral infection or interaction between the immune system and the heart muscle. This immune reaction can be seen with inflammatory diseases like lupus or toward the end of pregnancy (approximately 1 in 4000 chance). Other sources of damage to the heart muscle, which can lead to dilatation, include:

  • Some types of cancer chemotherapy
  • Excess iron accumulation in the body from the disease hemochromatosis
  • Cocaine use
  • Several of the anti-viral medications used to treat HIV
  • Some of the older medications to treat schizophrenia
  • Exposure to metals like cobalt, lead, and mercury (an important consideration for those who work in manufacturing processes that includes exposure to these metals)

Cardiac dilation may also be associated with thyroid disease. There is a genetic form of dilated cardiomyopathy, related to many of the several forms of muscular dystrophy; in these, the disease process which affects and weakens body muscle does the same to the heart muscle. Finally, problems with the heart valves can cause abnormal cardiac dilation. In situations where the heart valves cannot fully close, a condition called valvular regurgitation, a backflow of blood with each heartbeat stretches out a chamber of the heart (typically the left atrium or left ventricle), causing it to dilate over time.

What health problems are associated with cardiac enlargement?

With the exception of exercise-induced enlargement, all forms of cardiac enlargement are abnormal and associated with further problems, including heart failure, irregular heart rhythms , and an increased risk of angina and heart attack. Heart failure results because thickened or dilated heart muscle cannot function effectively as a pump. The diseased muscle cells in both types of enlargement are also capable of causing irregular heart rhythms that can lead to passing-out or sudden death. Because the processes which cause hypertrophy typically do not increase the amount of heart blood vessels to match the thickened heart muscle, the consequences of decreased blood flow to the heart, angina and heart attack, are more common. All of this contributes to an increased risk of death and decreased quality of life for most of those with cardiac enlargement. Treatments are available to help most of these problems.

What are the symptoms of cardiac enlargement?

Some people can have varying degrees of cardiac enlargement and have no symptoms. Once dilation or hypertrophy begins to place undue demands on heart function, however, symptoms do result. These can include:

  • Shortness of breath
  • Chest pressure or pain
  • Palpitations (a sense that the heart is beating rapidly or forcefully or "skipping beats")
  • Swelling of the feet, ankles, or legs
  • Dizziness or lightheadedness
  • Loss of consciousness

In milder forms of cardiac enlargement, the symptoms may occur only with exercise or exertion. In more severe forms, they can occur at any time, even while resting. Other heart and lung problems and other diseases can cause these symptoms as well, so they are not specific to cardiac enlargement.

How is cardiac enlargement diagnosed?

Cardiac enlargement can sometimes be diagnosed based on a physical examination by a physician or other health care provider. A patient's symptoms or family medical history, high blood pressure, characteristic heart murmur, forceful heart beat, swelling of the legs, or the sound of fluid in the lungs can be clues to the diagnosis. A chest x-ray can show an enlarged heart size or fluid in the lungs and an ECG will often show increased waveforms, indicating LVH or RVH. In fact, it has been suggested that ECG be used to screen young athletes for hypertrophic cardiomyopathy. Unfortunately, cost issues are likely to prevent this from being done on a large-scale basis.

The best way for a physician to evaluate cardiac enlargement is with an echocardiogram. This test uses a form of ultrasound similar to that used to look at gallbladders, kidneys, and pregnant women's babies. Using a sophisticated computer and monitor and a small plastic probe and some gel placed on the chest, the echocardiogram can directly show the size and thickness of the heart muscle in each chamber. It can also gauge heart function, an important piece on information when deciding how to treat the enlargement.

Is treatment for cardiac enlargement necessary? Is the condition permanent?

Because any of the forms of cardiac enlargement will result in an increased risk of death and decreased quality of life for most patients, treatment is strongly recommended. Treatment may slow or reverse the disease process and help symptoms, if they are present. When cardiac enlargement is diagnosed early, treatment is recommended even before symptoms start.

Unfortunately, in cases of cardiac dilation, whatever damage has been done is usually permanent; treatment will focus on improving heart function, in spite of the damage. In some cases of hypertrophy, however, at least some of the muscular thickening can be reversed by the use of beta-blocker medication. In addition, the calcium channel blocker verapamil has been shown to improve prognosis for those with hypertrophy by directly relaxing the heart muscle.

What is the treatment for cardiac enlargement?

For patients with cardiac enlargement, all underlying causes - such as high blood pressure, hemochromatosis, thyroid problems, pulmonary blood clots, sleep apnea, emphysema, chronic bronchitis, lupus or other inflammatory disease - should be treated as completely as possible. This will decrease the chance of ongoing damage to the heart. Metal exposure or alcohol or cocaine use should be controlled or eliminated, when applicable. If medications for HIV or schizophrenia are a factor, risks and benefits of continuing or changing medications should be considered. Luckily, there are alternative medications in many cases. Those with valvular heart disease should have their condition treated with medication. Depending on a variety of factors, heart valve replacement or repair - either through "open heart" surgery or with a catheter entering the heart through a blood vessel at the groin, in a procedure similar to that used for a coronary angiogram - may be recommended.

Cardiovascular or coronary artery disease (CVD or CAD) can cause dilated cardiomyopathy and can severely complicate either form of cardiac enlargement and should be aggressively treated. Treatment for CVD/CAD and its risk factors - smoking, high dietary and blood cholesterol levels, diabetes, high blood pressure, being overweight and sedentary - includes the use of medications, lifestyle changes, angioplasty with or without coronary artery stenting, or bypass surgery.

In situations of either dilation or hypertrophy, heart failure can be treated with medications like beta blockers (to relax the heart), ACE inhibitors or the newer angiotensin receptor blockers (to decrease the pressure against which the heart has to pump), diuretics (to ease breathing and help decrease excess fluid in the lungs and body), and digoxin and other medications ("inotropes") which improve the heart's pumping strength. In severe cases, salt and fluid intake may be controlled.

Based on a number of factors, the chance of irregular heart rhythms can be reduced by using a variety of medications. For patients at highest risk, an implantable cardioverter-defibrillator can be life saving. For slow or blocked heart rhythms, a pacemaker may be needed.

Due to the risk of blood clot formation in a weak, dilated heart, blood thinners like warfarin (brand name Coumadin) are recommended for those with very poor heart function or those who have already had an episode of clotting.

Cardiac rehabilitation in the form of a structured exercise program can help reduce symptoms and improve exercise tolerance for those with cardiac enlargement.

For some of those with hypertrophic cardiomyopathy, where the thickened heart muscle blocks blood flow from the ventricle, there are procedures to reduce sections of heart muscle and improve heart function. One of these, a septal myomectomy, requires open heart surgery. A non-invasive option, called an alcohol septal ablation, involves a procedure and catheter similar to an angiogram. Instead of using contrast dye, however, alcohol is injected. This causes muscle cells in the thickened septum to die, reducing blood flow blockage. Heart transplantation is a last-resort option for selected patients with either type of cardiac enlargement and severely decreased heart function.

When should I seek treatment for cardiac enlargement?

If you have any symptoms of heart disease, either with exertion or at rest, you should see a doctor promptly. Symptoms include:

  • Shortness of breath
  • Chest pressure or pain
  • Palpitations
  • Swelling of the feet, ankles, or legs
  • Dizziness or lightheadedness
  • Loss of consciousness

These may indicate cardiac enlargement or may be due to other heart or lung problems or other conditions that may require treatment.

You should also seek treatment if a family member has hypertrophic cardiomyopathy. In this situation, a physical exam and a screening ECG are usually performed. This may be followed by an echocardiogram, if abnormalities are found or if suspicion continues.

Where can I learn more about cardiac enlargement?

The following organizations offer additional information about cardiac enlargement:

The Cardiomyopathy Association is a private charitable organization based in the United Kingdom which provides educational information and networking for those with cardiac enlargement and their families. Their Web site, address, and phone number can be found at www.cardiomyopathy.org.

The National Heart Lung and Blood Institute of the National Institutes of Health has information on its Web site.

The American Hearth Association has information on the topic on its Web site.

Sources

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Franz WM, Muller OJ, Katus HA. Cardiomyopathies: from genetics to the prospect of treatment. Lancet 2001; 358(9293):1627-37.

Brown CA, O'Connell JB. Myocarditis and idiopathic dilated cardiomyopathy. Am J Med 1995;99(3):309-14.

Maron BJ, Shirani J, Poliac LC, et al. Sudden death in young competitive athletes. Clinical, demographic, and pathological profiles. JAMA 1996;276(3):199-204.

Maron BJ, Shen WK, Link MS, et al. Efficacy of implantable cardioverter-defibrillators for the prevention of sudden death in patients with hypertrophic cardiomyopathy. NEJM 2000;342(6):365-73.

Maron BJ. 1997. Hypertrophic Cardiomyopathy. Lancet 1997;350(9071):127-33.

Shamim W, Yousufuddin M, Wang D, et al. Nonsurgical reduction of the interventricular septum in patients with hypertrophic cardiomyopathy. NEJM 2002:347(17):1326-33.

"Cardiomyopathy" Outlines in Clinical Medicine on Physicians on Line, accessed January 29, 2003.