Pressure-flow studies in man. An evaluation of the duration of the phases of systole

Abstract

A B S TR A C T This study was designed to assess the independent effects of stroke volume and heart rate on the phases of systole and other selected hemodynamic parameters. By means of the pressure gradient technique instantaneous blood pressure and flow were recorded in the ascending aorta at fixed ventricular rates in five patients with complete heart block and in four patients with atrio-ventricular dissociation induced by ventricular pacing. Because of the variable contribution of atrial systole to ventricular filling, a wide range of stroke volumes were observed at each heart rate. The results indicate that the duration of ejection bears a close direct linear relationship to stroke volume while heart rate has only a weak but independent relation. On the other hand, the duration of total systole is related chiefly to the heart rate but stroke volume exerts an important independent effect. In a given patient, both duration of ejection and pulse pressure reflect changes of stroke volume and the product of the duration of ejection and the pulse pressure shows a good correlation with the stroke volume. INTRODUCTIONPrevious studies in man of the relationships between heart rate, stroke volume, and other hemodynamic parameters such as the phases of systole, have been limited by the methodological difficulties encountered in measuring phasic blood flow. The recent development of the pres-

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“…LVET reflects the duration that the aortic valve remains opened; thus, it is directly related to stroke volume (SV) [32][33][34] obtained with treatment of OvxE was 0.07 ± 0.003, 0.074 ± 0.01, 0.077 ± 0.01, 0.07 ± 0.01, and 0.074 ± 0.01 on 7 th , 15 th , 30 th , 60 th , and 90 th day of treatment, respectively, whereas baseline with OvxV was 0.095 ± 0.06 s.…”

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“…The slope of their regression line differed from that of Weissler et al (1968), possibly because of their use of exercise to vary heart rate. Harley, Starmer & Greenfield (1969), studying patients with complete heart block in whom heart rate could be varied by a ventricular pacemaker found yet another relation with ejection time, and also that the effects of rate were, in these circumstances, less than those of stroke volume. In patients with atrial fibrillation, the relation between RR interval and ejection time also differs from that in normal subjects with sinus rhythm (Tavel, Baugh, Feigenbaum & Nasser, 1972;Kligfield, 1974).…”