Key Points
- To determine the left ventricular-arterial coupling conditions that maximize stroke work and evaluate the conversion efficiency of pressure-volume area to stroke work.
- Studied 8 instrumented conscious dogs measuring left ventricular pressure and dimensions via ultrasonic crystals during transient caval occlusion.
- Modulated the ratio of end-systolic elastance to arterial elastance across a range of 0.18 to 2.59 using phenylephrine, nitroprusside, and dobutamine infusions.
- Baseline resting ratio of end-systolic elastance to arterial elastance was 0.96 ± 0.20, and maximal left ventricular stroke work occurred at a ratio of 0.99 ± 0.15 under constant inotropic state and end-diastolic volume.
- Stroke work stayed within 20% of its maximum value over a wide elastance ratio range of 0.56 to 2.29, declining markedly only when arterial elastance substantially exceeded ventricular elastance.
- Conversion efficiency of left ventricular pressure-volume area to stroke work increased monotonically as the ventricular-to-arterial elastance ratio increased.
Structured PICO
PPopulation8 conscious dogs instrumented to measure left ventricular (LV) pressure and determine LV volume from three ultrasonically determined dimensions
IInterventionInfusion of graded doses of phenylephrine and nitroprusside before and during administration of dobutamine to vary the ratio of end-systolic elastance to arterial elastance (EES/EA)
CComparatorBaseline (rest, with intact reflexes)
OOutcomeLeft ventricular stroke work (SW) and the transformation of LV pressure-volume area (PVA) to SWsurrogate
In conscious dogs, the left ventricle and arterial system produce maximum stroke work when ventricular and arterial elastance are equal, supporting the utility of analyzing LV-arterial coupling in the pressure-volume plane.