Cocaine Use Leads to Enlarged Heart

Enlarged heart is a term that doctors use to describe a heart muscle that grows beyond its expected size, either on the whole or in part. Some forms of heart enlargement, such as those frequently found in habitual exercisers, can support improved cardiac health. However, other forms of heart enlargement make the heart increasingly dysfunctional and set the stage for life-threatening problems such as a heart attack and cardiac arrest. Cocaine use can lead to a form of heart enlargement that seriously increases risks for cardiac arrest and sudden, unpredictable death.

Background

The muscle content of the heart, called the myocardium or myocardial tissue, gives the organ the power it needs to contract and pump blood. The primary pumping chamber—known as the left ventricle—forms the lower left segment of the heart, while the secondary pumping chamber, known as the right ventricle, forms the lower right segment of the organ. The left ventricle moves oxygen-rich blood to the body’s arteries; the right ventricle moves oxygen-depleted blood to the lungs, where new supplies of oxygen enter the bloodstream. The upper left chamber of the heart—known as the left atrium—carries oxygen-rich blood to the heart from the lungs, while the upper right chamber, known as the right atrium, carries oxygen-depleted blood to the heart from the rest of the body.

Enlarged Heart Basics

The medical term for heart enlargement is cardiac hypertrophy. This phenomenon occurs when the muscular walls of the heart (i.e., the myocardium) grow unusually thick. When unusual thickness appears in either of the ventricles, the affected individual has a condition called ventricular hypertrophy; when unusual thickness appears in either of the atria (plural of atrium), the affected individual has a condition called atrial hypertrophy. As noted previously, some forms of hypertrophy can make the heart work better. For instance, athletes and regular exercisers can develop a form of ventricular hypertrophy that makes it easier for the heart to pump blood to the lungs or other parts of the body. However, as also noted previously, some forms of hypertrophy reduce the heart’s effectiveness. This typically occurs when enlargement scars and stiffens the walls of the ventricles, and thereby decreases their ability to contract and pump blood.

Damaging forms of heart enlargement are known collectively as pathological cardiac hypertrophy. Apart from cocaine use, potential underlying causes of damaging enlargement include chronic high blood pressure, a heart attack, disease in any of the valves that sit between the heart’s chambers, and heart failure. Typically, unhealthy heart enlargement develops gradually over time; however, in certain circumstances, it can also develop relatively rapidly. In many cases, dangerous cardiac hypertrophy produces no symptoms until its effects are relatively advanced. For this reason, people with the condition can die suddenly from a heart attack or from an abrupt stoppage of heart.

The Role of Cocaine

Cocaine use causes heart enlargement through a unique series of health changes, according to the results of a study published in 2006 in the Journal of Cardiovascular Pharmacology. First, the presence of the drug in the bloodstream activates a specialized type of protein (enzyme) called CaMK; in turn, activation of this enzyme encourages an abnormal buildup of the mineral calcium in the heart’s tissues. When calcium builds up in the heart, it promotes the accumulation of other proteins that normally only appear in the hearts of developing fetuses. When they first appear, these immature proteins increase the size of individual cells inside the myocardium. Eventually, enlargement spreads to larger areas of tissue and triggers the onset of cardiac hypertrophy. Typically, this process occurs in the heart’s primary pumping chamber, the left ventricle.

People who habitually use cocaine can develop degrees of hypertrophy that enlarge their left ventricles by up to 70 percent, the authors of a study published in 2003 in the Journal of Cardiovascular Pharmacology and Therapeutics report. The amount of enlargement associated with long-term cocaine use can weaken the left ventricle to the point where this chamber can no longer meet the strict timing requirements necessary to coordinate heart activity and efficiently pump blood. In turn, lack of proper heart beat timing can lead to serious forms of a condition called a heartbeat irregularity, or arrhythmia.

The degree of arrhythmia associated with long-term cocaine use can lead to unsustainable changes in heart rhythm and the unpredictable, frequently fatal appearance of cardiac arrest. Unlike people with chronic heart disease, cocaine users can easily develop enlargement-related cardiac arrest without developing symptoms—such as high blood pressure or an increase in resting heart rate—that cue doctors to the possible presence of dangerous changes in normal heart function. According to the authors of the study published in 2006 in the Journal of Cardiovascular Pharmacology, as many as half of all habitual cocaine users with normal blood pressure may have some degree of heart enlargement.