Pulsus alternans

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Pulsus alternans is a physical finding with arterial pulse waveform showing alternating strong and weak beats. It is almost always indicative of left ventricular systolic impairment, and carries a poor prognosis.

Pulse pressure waveform displaying the variation in pressure between beats in pulsus alternans.

[edit] Pathophysiology

In left ventricular dysfunction, the ejection fraction will decrease significantly, causing reduction in stroke volume, hence causing an increase in end-diastolic volume. There may initially be a tachycardia as a compensatory mechanism to try and keep the cardiac output constant. As a result, during the next cycle of systolic phase, the myocardial muscle will stretch harder than usual and as a result cause an increase in myocardial contraction and hence a stronger pulse is felt.

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