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Explain in HCM

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2024 AHA ACC hypertrophic cardiomyopathy guideline physical examination bisferiens pulse

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In hypertrophic obstructive cardiomyopathy (HOCM), the carotid pulse may be jerky and bifid, called pulsus bisferiens.

What the note means

  • Jerky pulse
    • The carotid upstroke is brisk because the hypertrophied LV contracts forcefully in early systole.
    • This gives a sharp, rapid initial rise.
  • Pulsus bisferiens
    • Literally means a pulse with two systolic peaks felt in one cardiac cycle.
    • It is best appreciated in the carotid artery.
  • First peak = percussion wave
    • Caused by rapid early systolic ejection from the strongly contracting LV.
    • It is usually the larger, sharper peak in HOCM.
  • Midsystolic dip
    • As systole progresses, the anterior mitral leaflet moves toward the hypertrophied septum, termed systolic anterior motion (SAM).
    • This dynamically narrows the LV outflow tract (LVOT), briefly reducing forward aortic flow.
  • Second peak = tidal wave
    • After the transient fall, there is a later systolic pulse peak.
    • Thus, the arterial tracing/palpated pulse appears bifid: peak - dip - second peak.
Sequence to remember:
Forceful early ejection → large percussion wave → SAM/LVOT obstruction causes midsystolic dip → smaller late systolic tidal wave

Important correction to the handwritten line

“2nd peak due to obstruction by SAM” is a useful simplified explanation, but more precisely, SAM causes the midsystolic interruption/dip in flow that produces the bifid contour. The second late systolic component is seen after this dynamic change in the arterial waveform.

Other bedside findings in HOCM

  • Sustained, hyperdynamic apex beat, sometimes with a presystolic lift
  • Harsh systolic ejection murmur at the left lower sternal border/apex
  • Murmur becomes louder with standing or Valsalva because reduced LV filling worsens dynamic LVOT obstruction
  • Murmur becomes softer with squatting because increased preload and afterload reduce obstruction
This pulse is most associated with obstructive HCM, so it is not necessarily present in non-obstructive HCM. Dynamic LVOT obstruction is linked to SAM and is provoked by maneuvers such as Valsalva and exercise. The 2024 ACC HCM guideline summary likewise recommends provocative maneuvers when a resting LVOT gradient is not demonstrated.

Doesn't in normal pulse waveform percussion wave and tidal occur

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normal arterial pulse waveform percussion wave tidal wave pulsus bisferiens clinical examination

Yes. A normal central arterial pulse waveform also has:
  1. Percussion wave: the early systolic wave caused by LV ejection.
  2. Tidal wave: a smaller late systolic augmentation, partly related to reflection of the pressure wave from peripheral arteries.
But normally they occur so close together that you feel one smooth pulse peak, not two separate palpable peaks.
In pulsus bisferiens, the two components are exaggerated and separated by a noticeable midsystolic dip, so two distinct systolic peaks can be felt, particularly in the carotid pulse.

In HOCM

  • Strong early LV contraction produces a prominent percussion wave.
  • SAM of the mitral valve creates dynamic LVOT obstruction in mid-to-late systole.
  • This produces or deepens the midsystolic dip, making the late tidal component distinct.
So, the correction is:
SAM does not create the tidal wave itself. It causes the systolic interruption/dip that separates the normally fused percussion and tidal waves.
This is the “spike-and-dome” carotid contour of obstructive HCM. Textbook descriptions identify the normal central pulse as having a larger percussion wave and smaller tidal wave that are ordinarily difficult to distinguish clinically; two clearly palpable systolic peaks define pulsus bisferiens, as explained in this NCBI clinical review.
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