Cardiomegaly is the term for an enlarged heart. Rather than being a diagnosis in itself, it is a sign of an underlying cardiac or systemic condition. Cardiomegaly is typically identified on a chest X-ray, where the cardiac silhouette is wider than normal relative to the width of the chest (cardiothoracic ratio above 0.5), or on echocardiography, which can characterise the chambers more precisely.
Common causes include: dilated cardiomyopathy, in which the left ventricle is enlarged and its walls thinned due to primary muscle disease, causing reduced ejection fraction; hypertension, where chronically elevated blood pressure forces the left ventricle to work harder, causing it to thicken and eventually dilate; significant valve disease such as mitral valve regurgitation or aortic regurgitation, causing volume overload and left heart enlargement; heart failure, where the heart enlarges as it compensates for reduced function; poorly controlled atrial fibrillation, which can lead to a tachycardia-induced cardiomyopathy; and a large pericardial effusion, which can create apparent cardiomegaly on chest X-ray.
Cardiomegaly in the context of reduced ejection fraction is associated with increased risk of ventricular arrhythmia and sudden cardiac arrest. ICD implantation may be indicated depending on the degree of functional impairment.
Identifying and treating the underlying cause is the primary goal of management. In some cases, successfully treating the cause (for example, controlling AF rate or relieving hypertension) can result in partial or full reversal of cardiomegaly over time.
« Back to Glossary Index