Quantitative comparison of canine right and left ventricular isovolumic pressure waves

The mechanical properties of the right and left ventricles (RV and LV) have previously been studied separately. However, because of differences in RV and LV architecture, geometry, and muscle mass, it is not obvious how the properties of the two chambers would relate to each other. This study compared the time courses of RV and LV isovolumic pressure waves (LVP, RVP, respectively) meaured simultaneously in the same heart. We compared RVP and LVP in each of five isolated, supported canine hearts after pentobarbital anesthesia. RV and LV volumes were varied independently so that on various beats peak LVP exceed, equaled, or was less than peak RVP. There was a delay of ~35 ms between the onset of LV and RV pressure waves with atrial pacing, but only 5 ms with ventricular pacing. LVP and RVP were measured and digitized at a sampling rate of 200 Hz. Pressure waves were offset and rescaled by their respective amplitudes so that for each beat the pressure wave had a minimum value of 0% at end diastolic and a maximum value of 100% at end systole. RVP was then shifted in time so that its upstroke was synchronous with that of the LVP at the point of 50% of maximal developed pressure. The rescaled, time-shifted RVP was plotted as a function of the rescaled LVP for each point of the cardiac cycle, and the relation between the two was quantified by their root mean square difference (D(rms)). D(rms) averaged 2.3 ± 1.5% (SD) for the first half of contraction, 1.5 ± 0.4% for the second half of contraction, and 4.6 ± 1.6% during relaxation. This analysis indicates that the time courses of RVP and LVP generation are nearly identical throughout the cardiac cycle. This near identity implies significant similarities in right and left ventricular chamber properties despite marked anatomic and geometric differences.