What causes a dicrotic pulse?

Causes of Dicrotic Pulse

A dicrotic pulse is primarily caused by exaggerated visibility of the dicrotic notch due to low cardiac output states, severe aortic regurgitation, or altered vascular compliance. 1

Pathophysiological Mechanisms

The dicrotic pulse is characterized by two distinct palpable pulsations during a single cardiac cycle:

• The first pulsation occurs during systole
• The second pulsation occurs in early diastole, immediately following the second heart sound

Primary Mechanisms

1. Low Cardiac Output States

   • When cardiac output is reduced, the systolic upstroke of the aortic pressure pulse becomes significantly diminished 1
   • The incisural notch (dicrotic notch) maintains its normal amplitude even in weak beats
   • This creates a relative exaggeration of the dicrotic notch compared to the systolic component, resulting in the characteristic M-shaped waveform 1

2. Valvular Heart Disease

   • Aortic Regurgitation: A common cause of dicrotic pulse, especially in chronic severe cases 2

     • The wide pulse pressure and altered vascular compliance from chronic AR create conditions favorable for dicrotic pulse formation
     • Studies show that 95% of patients with moderate to severe preoperative aortic insufficiency developed dicrotic pulses after Ross procedure 3

   • Aortic Valve Prolapse: Can cause dicrotic pulse even without regurgitation due to altered flow dynamics 4

     • Deep reversal flow confined to early diastole has been observed in the abdominal aorta

3. Post-Cardiac Surgery

   • Particularly common after valve replacement for regurgitant lesions 5
   • Occurs in patients with:
     • Larger preoperative end-diastolic and end-systolic volumes
     • Lower ejection fractions
     • Larger left ventricular dimensions
     • Reduced fractional shortening of left ventricular cavity
     • Poor thickening properties of the left ventricular posterior wall

Clinical Significance

The clinical significance of a dicrotic pulse varies based on context:

1. Post-Valve Replacement

   • May indicate poor prognosis when persistent after valve surgery 5
   • Correlates with continued left ventricular dysfunction and poor clinical outcomes

2. Post-Ross Procedure

   • Common finding (61% of patients) that does not necessarily indicate poor prognosis 3
   • Not associated with increased use of vasoactive medications or longer hospitalization

3. Acute Aortic Regurgitation

   • May be part of the clinical presentation in acute severe AR, which is a surgical emergency 2
   • Associated with pulmonary edema and hypotension

Diagnostic Considerations

When evaluating a dicrotic pulse:

• Perform echocardiography to assess:

  • Valvular function, particularly aortic valve
  • Left ventricular size and function
  • Presence of regurgitant lesions

• Consider hemodynamic monitoring in critically ill patients to evaluate:

  • Cardiac output
  • Vascular resistance
  • Pressure waveforms

Management Implications

The management should target the underlying cause:

• For low cardiac output states: Address the primary cause and optimize cardiac function
• For valvular disease: Consider appropriate timing for surgical intervention based on symptoms and ventricular function 6, 2
• For post-surgical patients: Monitor closely for signs of persistent left ventricular dysfunction 5

Remember that while a dicrotic pulse has traditionally been considered an ominous finding in many contexts, its significance varies by clinical scenario and may be a benign finding in certain post-surgical states like the Ross procedure 3.