Monday, October 1, 2012

The Pulse Sometimes Strikes Twice

"Bis" + "feriens" = "twice strikes"

A waveform with two systolic phases is said to be pulsus bisferiens, and joins that small infamous group of Latin pulses, including alternans, and paradoxicus. So what causes pulsus bisferiens, and what causes the waveform?

It may be easier to think of it as a normal pulse with "mid systolic retraction" rather than a pulse with "two strikes"... pulsus vacuumus, if you will.  But despite the fact that pulsus bisferiens has been recognized for at least five hundred years, its mechanism is still not fully understood.

First, an example of a normal CCA waveform as a baseline:

Then, the pulsus bisferiens

The arrow points to the "mid systolic retraction." The wedge points to the normal dicrotic notch. The dicrotic notch is a normal finding and is due to closure of the aortic valve, temporary cessation of forward flow, followed by resumption of forward flow driven by elastic rebound of aortic wall.(1)

The three entities most closely with a pulsus bisferiens are aortic regurgitation, combined aortic regurgitation and aortic stenosis (with regurgitation dominant), and HOCM (hypertrophic obstructive cardiomyopathy).

Aortic regurgitation

Since carotid ultrasound is not usually performed simultaneously with ECG, the diagnosis can only be made with certainty when a dicrotic notch is clearly present.  Pulsus bisferiens may exist without a dicrotic notch visible on the spectral ultrasound waveform, but this finding is technically indeterminate.

Pulsus bisferiens is most often encountered on vascular ultrasound of the common carotid arteries, and may be the first finding of valvular disease... oddly enough it is palpated more effectively in the peripheral arteries.

1. Rohen EM, Kliewer MA, Carroll BA, Hertzberg BS. "A Spectrum of Doppler Waveforms in the Carotid and Vertebral Arteries." AJR December 2003 vol. 181 no. 6 1695-1704
2.Kallman CE, Gosink BB, Gardner DJ. Carotid Duplex Sonography: Bisferious Pulse Contour in Patients with Aortic Valvular Disease." AJR August 1991 vol. 157 no. 2 403-407