A diastolic murmur heard in patients with severe coronary artery disease (CAD), especially left anterior descending (LAD) artery stenosis.
Timing
Early diastolic murmur.
Location
Best heard at the left sternal border (similar area to where aortic regurgitation is heard).
Mechanism
Due to relative ischemic insufficiency of the aortic valve from severe LAD disease; thought to be related to ischemia-induced dysfunction of the aortic root/valve cusp support.
Clinical importance
Mimics aortic regurgitation murmur, but in the absence of valvular disease. Indicates critical coronary artery disease.
Differentiation
Unlike true aortic regurgitation, Dock’s murmur occurs without actual valve pathology; disappears after successful coronary revascularization.
Dock’s murmur
Dock’s murmur is
a rare type of diastolic heart murmur caused by severe stenosis (narrowing) of the left anterior descending (LAD) coronary artery. The murmur, caused by turbulent blood flow, is named after Dr. William Dock, who first described it in 1967.
Characteristics
Timing: Diastolic, because the coronary arteries fill with blood during diastole (the relaxation phase of the cardiac cycle). It is often described as early diastolic and can have both an early and a late accentuation.
Sound: A high-pitched sound similar to the murmur of aortic regurgitation.
Location: Best heard over a very localized area at the third intercostal space, just left of the sternum.
Maneuver: The murmur may be audible only when the patient is sitting upright.
Association with other conditions
Dock’s murmur can occur in patients with critical LAD stenosis who also present with Wellens syndrome, a condition that involves characteristic T-wave abnormalities on an electrocardiogram (ECG) and often precedes a large anterior wall myocardial infarction.
Distinction from other murmurs
Since it resembles the murmur of aortic regurgitation, it is important for a physician to consider the patient’s other clinical signs to make the correct diagnosis. For instance, a patient with Dock’s murmur may have atypical chest pain and show T-wave abnormalities but lack a history of aortic regurgitation.
Clinical significance
Because it signals severe coronary artery disease, the discovery of Dock’s murmur should prompt immediate and further investigation, such as coronary flow imaging, to confirm the diagnosis. The murmur typically resolves following coronary artery bypass surgery to treat the stenosis.
👉 So, Dock’s murmur is essentially an ischemic functional diastolic murmur, first described by W. Dock, and is a valuable clinical clue for severe CAD.
Comparison table between Dock’s murmur and Aortic Regurgitation murmur:
