Muffled heart sounds are most characteristic of which condition?

• A. Pneumothorax
• B. Myocardial infarction
• C. Pulmonary edema
• D. Cardiac tamponade

Answer: (D)

Muffled heart sounds occur when sound transmission from the heart is dampened by fluid or pressure around the heart. In cardiac tamponade, fluid accumulates in the pericardial sac, raising intrapericardial pressure and compressing the heart so its sounds are faint or distant. This is often accompanied by hypotension and jugular venous distension (Beck’s triad) and may include pulsus paradoxus. Other conditions affect the lungs or heart in different ways and do not typically produce muffled cardiac sounds. Pneumothorax changes lung sounds; myocardial infarction and pulmonary edema present with chest pain or crackles and other signs, rather than muffled heart sounds. So muffled heart sounds point most strongly to tamponade from pericardial effusion.