From the Guidelines
An enlarged cardiac silhouette is a clinically significant finding that warrants further evaluation to determine the underlying cause and severity of the condition. This is because it often indicates cardiomegaly, which is associated with underlying heart disease, as noted in the 2009 focused update incorporated into the ACC/AHA 2005 guidelines for the diagnosis and management of heart failure in adults 1. When detected, further evaluation with echocardiography is recommended to determine the specific cause and severity. Common causes of an enlarged cardiac silhouette include:
- Heart failure
- Valvular heart disease
- Cardiomyopathy
- Pericardial effusion
- Congenital heart defects
The clinical approach should include a thorough history and physical examination focusing on symptoms like:
- Shortness of breath
- Fatigue
- Chest pain
- Edema As patients may be found to have evidence of cardiac enlargement or dysfunction during their evaluation for a disorder other than heart failure, such as abnormal heart sounds or abnormal electrocardiogram or chest x-ray, hypertension or hypotension, diabetes mellitus, an acute myocardial infarction (MI), an arrhythmia, or a pulmonary or systemic thromboembolic event 1. Management depends on the underlying cause but may include medications such as ACE inhibitors, beta-blockers, diuretics, or antiarrhythmics. Lifestyle modifications including sodium restriction, regular exercise, and smoking cessation are also important. The significance of an enlarged cardiac silhouette varies with the degree of enlargement and associated findings, and cardiomegaly occurs when the heart takes up more than 50% of the thoracic width on a PA chest X-ray, which warrants attention because increased heart size often correlates with decreased cardiac function and can predict adverse outcomes in many cardiovascular conditions.
From the Research
Clinical Significance of Enlarged Cardiac Silhouette
- An enlarged cardiac silhouette on chest radiography can be caused by various factors, including dilated cardiomyopathy 2, cardiac adiposity 3, and radiation-induced pericardial effusion 4.
- The clinical significance of an enlarged cardiac silhouette can vary depending on the underlying cause, with some studies suggesting that it may be associated with coronary risk factors and coronary calcification and stenosis 3.
- The accuracy of chest radiography in detecting true cardiomegaly has been questioned, with one study finding that the true positive rate of cardiomegaly identified on chest radiograph was only 56% and the false positive rate was 44% 5.
- Risk factors for enlargement of cardiac silhouette on chest radiography after radiotherapy for esophageal cancer include the area of the cardiac silhouette in the initial radiation field 4.
- The use of echocardiography as a gold standard tool for determining true cardiomegaly has been recommended, with one study suggesting that all patients with cardiomegaly on chest radiograph should undergo echocardiography to confirm the diagnosis 5.
- The substantially enlarged cardiac silhouette can be an impressive manifestation of various diagnoses, highlighting the importance of further investigation to determine the underlying cause 6.