Left Ventricular Internal Resistance and Unloaded Ejection Flow Assessed From Pressure‐Flow RelationsA Flow‐Clamp Study on Isolated Rabbit Hearts
作者:
Simon Vaartjes,
Herman Boom,
期刊:
Circulation Research
(OVID Available online 1987)
卷期:
Volume 60,
issue 5
页码: 727-737
ISSN:0009-7330
年代: 1987
出版商: OVID
关键词: ventricular mechanics;rabbit isolated heart;flow-clamp technique;pressure-flow relations;ventricular internal resistance;3-component mechanical model;Qmax
数据来源: OVID
摘要:
Left ventricular pressure-flow relations were studied, using excised working rabbit hearts and imposing constant flow ejections (flow-clamps) to separate the effects of flow on pressure from those of time, flow duration, starting volume, ejected volume, and volume at specified time. Pressure-flow data at given volume and time were independent of flow duration, starting volume, and ejected volume for flow-clamp durations exceeding 30 msec. Flow history independent of pressure-flow relations was linear for flow values larger than ± 5 ml/sec. The time-varying elastance model, E(t), of the ventricle was extended with a resistive component. Transient effects of flow can be explained by including a second elastance. The resulting verified 3-component model is consistent with recent reported experimental findings. The properties of internal resistance correspond to a constant unloaded ejection flow Qmax which was tested by extrapolating the linear pressure-flow relations to zero pressure. Qmax reached a plateau value of approximately 25 ml/sec within 50 msec after the start of contration. In relaxation, Qmax is only slightly smaller. Qmax did not depend on volume; therefore, the following equation was adequate for the relation between pressure, p(t); volume, V(t); and flow Q(t), during the flow-clamped ejections from 30 minutes after the start of the flow: (t) = E(t)±(V(t) - Vd)±(l - QW/Qmax)
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