Water Hammer Pulse: Examination, Causes, Aortic Regurgitation, vs. Collapsing Pulse, AV Fistula, Sound, Neck Sign

Content:

• What is Water Hammer Pulse?
• Examination
• Causes
• Aortic Regurgitation
• Water Hammer Pulse vs. Collapsing Pulse 
• AV Fistula
• Sound
• Neck Sign

What is Water Hammer Pulse?

Water hammer pulse, also known as Corrigan pulse, is a clinical sign characterized by a bounding pulse with a rapid rise and sudden collapse. It is best felt in the radial or brachial artery and becomes more prominent when the patient’s arm is elevated. The name “water hammer” comes from its resemblance to the sudden forceful surge and collapse seen in old plumbing systems when water flow is abruptly stopped.

This pulse reflects a large pulse pressure, meaning a high systolic blood pressure with a low diastolic pressure. The rapid upstroke occurs due to increased stroke volume, while the quick collapse happens because blood flows back rapidly or into dilated peripheral vessels. Water hammer pulse is not a disease by itself but an important physical finding that often points toward underlying cardiovascular conditions.

Examination

Examination of a water hammer pulse is simple and done during routine cardiovascular assessment. The examiner gently palpates the patient’s radial artery while raising the patient’s arm above heart level. A classic water hammer pulse feels strong and forceful initially, followed by a rapid collapse under the fingers. This maneuver exaggerates the collapsing nature of the pulse, making it easier to detect.

In addition to radial artery palpation, clinicians may also assess the brachial or carotid pulse. Care should be taken while examining the carotid artery to avoid excessive pressure. Observing associated signs such as visible arterial pulsations or head bobbing can further support the finding. Proper examination technique is essential because mild forms can be missed if the arm is not elevated.

Causes

The most common cause of a water hammer pulse is aortic regurgitation, but several other conditions can produce this sign. Any disorder that increases stroke volume or decreases peripheral vascular resistance may result in a bounding, collapsing pulse. These conditions create a wide pulse pressure, which is the key hemodynamic feature behind this pulse pattern.

Other causes include patent ductus arteriosus (PDA), hyperthyroidism, anemia, fever, pregnancy, and arteriovenous malformations. In these states, increased cardiac output or rapid runoff of blood from the arterial system leads to the characteristic pulse. Identifying the cause is crucial because management focuses on treating the underlying condition rather than the pulse itself.

Aortic Regurgitation

Water hammer pulse is classically associated with aortic regurgitation, a condition in which the aortic valve fails to close properly during diastole. This allows blood to flow back from the aorta into the left ventricle, lowering diastolic pressure while systolic pressure remains high due to increased stroke volume.

In chronic aortic regurgitation, the pulse becomes more prominent over time as the left ventricle adapts by dilating and pumping larger volumes of blood. Patients may also have other signs such as wide pulse pressure, bounding carotid pulses, and peripheral vascular signs. Detection of a water hammer pulse can therefore be an early clue prompting further evaluation with echocardiography.

Water Hammer Pulse vs. Collapsing Pulse

The terms water hammer pulse and collapsing pulse are often used interchangeably in clinical practice. Both describe the same phenomenon of a rapid rise and fall of the arterial pulse due to wide pulse pressure. However, “water hammer pulse” emphasizes the forceful upstroke, while “collapsing pulse” highlights the sudden drop.

Functionally, there is no true clinical difference between the two terms. Some clinicians prefer “collapsing pulse” because it directly describes what is felt during palpation. Regardless of terminology, the underlying mechanisms and associated conditions remain the same, and both terms point toward similar cardiovascular pathologies.

AV Fistula

An arteriovenous (AV) fistula can also produce a water hammer pulse due to rapid runoff of blood from the arterial system into the venous circulation. This leads to reduced diastolic pressure and increased pulse pressure, mimicking the hemodynamic changes seen in aortic regurgitation.

Patients with large AV fistulas, whether congenital or created for hemodialysis access, may show bounding pulses and visible arterial pulsations. Recognizing this cause is important, especially in dialysis patients, as the pulse finding may be related to fistula size or high-output cardiac states rather than primary valvular disease.

Sound

Although water hammer pulse is primarily a palpable sign, it may also be associated with audible vascular sounds. In conditions like aortic regurgitation or AV fistula, turbulent blood flow can produce murmurs or bruits heard during auscultation.

For example, a diastolic murmur may accompany aortic regurgitation, while a continuous bruit may be heard over an AV fistula. These sounds, when combined with a bounding, collapsing pulse, strengthen clinical suspicion and guide further diagnostic testing.

Neck Sign

A prominent neck-related sign associated with water hammer pulse is Corrigan’s sign, which refers to visible pulsations of the carotid arteries in the neck. These pulsations are exaggerated due to the high stroke volume and rapid arterial filling.

Other related neck and peripheral signs may include head bobbing (de Musset sign) and capillary pulsations. Observing these signs during physical examination provides valuable clues about underlying cardiovascular conditions and highlights the importance of careful bedside assessment.