Causes of Pulsus Bisferiens
Pulsus bisferiens is primarily caused by hypertrophic cardiomyopathy (HCM), but can also occur in severe aortic regurgitation, thoracoabdominal aortic aneurysms, and aortic dissection. 1
Hypertrophic Cardiomyopathy (HCM)
Pulsus bisferiens (meaning "twice beating") is a characteristic physical finding in patients with HCM, particularly those with left ventricular outflow tract obstruction (LVOTO). This distinctive carotid pulse pattern presents as a double systolic peak with a mid-systolic dip 1, 2.
Key features in HCM:
- Associated with dynamic left ventricular outflow tract obstruction
- Often accompanied by a harsh crescendo-decrescendo systolic murmur
- May be accompanied by an S4 heart sound from a noncompliant left ventricle
- Becomes more pronounced with provocative maneuvers like standing or Valsalva
- Diminishes with squatting (unlike most other murmurs which intensify)
The pathophysiological mechanism involves:
- Rapid early systolic ejection
- Mid-systolic obstruction due to systolic anterior motion (SAM) of the mitral valve
- Late systolic ejection after partial relief of obstruction
Aortic Regurgitation
Severe aortic regurgitation can also cause pulsus bisferiens 3, 4. In this condition:
- The first peak results from rapid ejection of a large stroke volume
- The second peak is created by reflected waves from the periphery
- Often accompanied by a diastolic murmur and wide pulse pressure
- May show diastolic flow reversal in carotid arteries on Doppler studies
- The bisferious pattern may resolve after aortic valve replacement
Thoracoabdominal Aortic Aneurysms
Thoracoabdominal aortic aneurysms can produce pulsus bisferiens through a different mechanism 5:
- Early systolic forward-traveling compression wave
- Prominent late systolic forward-traveling expansion wave
- Abnormal prominent late systolic/early diastolic backward-traveling compression wave
- This creates a sharp rise in diastolic pressure responsible for the bisferious pattern
Aortic Dissection
Aortic dissection can cause pulsus bisferiens through dynamic compression of the aorta by the dissection flap 6:
- The flap creates alternating obstruction and relief during the cardiac cycle
- Results in abnormal flow patterns detectable on Doppler studies
- May be accompanied by pulse deficits in various arterial distributions
Differential Diagnosis
When evaluating pulsus bisferiens, it's important to distinguish between causes through additional findings:
- In HCM: Systolic murmur increases with standing and Valsalva, decreases with squatting
- In aortic regurgitation: Early diastolic murmur, wide pulse pressure, water-hammer pulse
- In aortic pathologies: May have associated bruits, pulse deficits, or signs of aortic insufficiency
Clinical Significance
Recognition of pulsus bisferiens is clinically important as:
- It may be the first clue to underlying cardiovascular disease
- Up to one-third of patients with aortic regurgitation may not have a detectable murmur 3
- In HCM, it helps identify patients with dynamic obstruction who might benefit from specific treatments
- The presence of this finding should prompt further cardiac evaluation with echocardiography
Careful palpation of the carotid pulse remains an important part of the cardiovascular examination, as this distinctive pulse pattern can provide valuable diagnostic information about underlying cardiac pathology.