How do you elicit a water hammer pulse in a patient with suspected severe aortic (Aortic Valve) regurgitation?

How to Elicit Water Hammer Pulse

The water hammer pulse (also called collapsing pulse) is best elicited by palpating the radial artery with your palm while the patient's arm is elevated above heart level, feeling for a characteristic bounding upstroke followed by a rapid collapse during diastole. 1

Technique

Standard Method

• Grasp the patient's wrist or forearm with your palm over the radial artery (not just fingertips), then elevate the arm above the level of the heart 1
• The characteristic finding is a forceful, slapping upstroke followed by a sudden collapse as blood regurgitates back into the left ventricle during diastole 1
• The elevation accentuates the collapsing component by increasing the gravitational effect on arterial pressure 1

Alternative Approach

• The bounding, slapping upstroke can often be appreciated during routine radial pulse examination without arm elevation 1
• This may be more practical and avoids confusion, as normal pulses can feel stronger with arm elevation due to physiological changes 1
• Focus on detecting the sharp, forceful upstroke rather than relying solely on the collapsing phase 1

Clinical Context

Associated Findings in Severe Aortic Regurgitation

• Wide pulse pressure with elevated systolic and reduced diastolic blood pressure 2
• Displaced, hyperdynamic left ventricular impulse on precordial palpation 2
• High-pitched diastolic murmur best heard at the left sternal border (or right sternal border if due to aortic root dilatation) 2
• Austin-Flint rumble (low-pitched mid-diastolic murmur at apex), which is specific for severe AR 2

Important Caveat

In acute severe aortic regurgitation, the water hammer pulse and wide pulse pressure may be absent or diminished because systolic pressure is reduced and diastolic pressure equilibrates rapidly with the elevated left ventricular diastolic pressure 2. The sudden volume overload on a non-compliant ventricle prevents the typical hemodynamic changes seen in chronic AR 2.

Pathophysiology

The water hammer pulse reflects the hemodynamic consequences of severe chronic aortic regurgitation 3, 4:

• The left ventricle ejects a large total stroke volume to compensate for regurgitant volume, elevating systolic arterial pressure 3
• Blood regurgitates back into the left ventricle throughout diastole, causing rapid decline in aortic diastolic pressure 3
• This creates the characteristic bounding upstroke (from high stroke volume) and rapid collapse (from diastolic runoff) 1