mill wheel murmur

mill wheel mur·mur

churning cardiac murmur produced by air embolism to the heart; also heard in pneumohydropericardium. Synonym(s): waterwheel murmur
A temporary loud, machinery-like, churning or splashing sound due to blood mixing with air in the right ventricle, best heard over the precordium, which is a late sign of significant—i.e., > 200 mL—venous air embolism, accompanied by increased pressure, cyanosis, tachycardia, syncope. It may be of pleural, pericardial, or cardiac origin