|Pulse pressure waveform displaying the variation in pressure between beats in pulsus alternans.|
|Classification and external resources|
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.
In left ventricular dysfunction, the ejection fraction will decrease significantly, causing reduction in stroke volume, hence causing an increase in end-diastolic volume. As a result, during the next cycle of systolic phase, the myocardial muscle will be stretched more than usual and as a result there will be an increase in myocardial contraction, related to the Frank–Starling physiology of the heart. This results, in turn, in a stronger systolic pulse. There may initially be a tachycardia as a compensatory mechanism to try to keep the cardiac output constant.
Palpate radial or femoral arteries, feel for regular rhythm but alternating strong and weak pulses Use blood pressure cuff to confirm: Raise blood pressure cuff to over systolic level then, lower slowly towards the systolic level, if hearing alternating loud & soft korotkoff sounds, pulses alternans is indicated.
Indicative of severe Left-sided heart failure 
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Then he felt her pulse. There was a strong stroke and a weak one, like a sound and its echo. That was supposed to betoken the end....
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