Mechanisms of Pulsus Alternans

The mechanisms of pulsus alternans were studied in three patients by cineangiographic determinations of left ventricular volume. In two patients with left ventricular disease, pulsus alternans occurred without detectable variation in left ventricular enddiastolic pressure (LVEDP) or end-diastolic volume (EDV), although in the second case these values did alternate in the initial postextrasystolic beats. Another patient with normal left ventricular function had brief postextrasystolic pulsus alternans associated with LVEDV alternations. Twenty-nine patients with valvular aortic stenosis who showed pulsus alternans during left heart catheterization were also studied. Persistent alternation in LVEDP occurred in eight, with transient LVEDP alternation appearing after extrasystoles in 22 cases. Cardiac cycle length and diastolic interval alternation occurred inconsistently.