Phasic aortic flow velocity in patients with pulsus alternans.

Phasic aortic flow velocity was recorded in two patients with pulsus alternans using a flow velocity probe connected to a Doppler ultrasonic flowmeter system. The variations in beat-to-beat peak velocity paralleled the variations in arterial and ventricular systolic pressures. This study provides direct evidence that stroke volume varies during this abnormal haemodynamic status. It is conceivable, though not proved in this study, that this phenomenon may be secondary to alternation between large and small end-diastolic fibre length.