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Structural heart disease

Examples of structural heart diseases include: cardiomyopathies (hypertrophic, dilated, or arrhythmogenic), cardiac rhythm disturbances, myocarditis, and congestive heart failure.

Left ventricular hypertrophy is a leading cause of sudden cardiac deaths in the adult population. This is most commonly the result of longstanding high blood pressure, or hypertension, which has led to maladaptive overgrowth of muscular tissue of the left ventricle, the heart's main pumping chamber. This is because elevated blood pressure over the course of several years requires the heart to adapt to the requirement of pumping harder to adequately circulate blood throughout the body. If the heart does this for a prolonged period of time, the left ventricle can experience hypertrophy (grow larger) in a way that decreases the heart's effectiveness. Left ventricular hypertrophy can be demonstrated on an echocardiogram and electrocardiogram (EKG).

Abnormalities of the cardiac conduction system (notably the Atrioventricular Node and His-Purkinje system) may predispose an individual to arrhythmias with a risk of progressing to sudden cardiac arrest, albeit this risk remains low. Many of these conduction blocks can be treated with internal cardiac defibrillators for those determined to be at high risk due to severity of fibrosis or severe electrophysiologic disturbances.

Structural heart diseases unrelated to coronary artery disease account for 10% of all sudden cardiac deaths. A 1999 review of sudden cardiac deaths in the United States found that structural heart diseases accounted for over 30% of sudden cardiac arrests for those under 30 years.