Application of a time varying elastance model to right ventricular performance in man

Area of Science:

• Cardiology
• Physiology
• Biomedical Engineering

Background:

• Assessing instantaneous right ventricular (RV) pressure-volume (P-V) relations is crucial for understanding RV systolic function.
• Existing methods may not fully capture the dynamic nature of RV performance under varying conditions.

Purpose of the Study:

• To evaluate instantaneous right ventricular pressure-volume relations using a time-varying elastance model.
• To determine the accuracy of different pressure-volume parameters in estimating maximal time-varying elastance (Emax).

Main Methods:

• Simultaneous high-fidelity pressure, flow-velocity, and biplane cineventriculographic volumes were acquired in nine healthy subjects.
• Data were collected during atrial pacing, partial autonomic blockade, and altered ventricular loading.
• Maximal time-varying elastance (Emax) was determined as the maximum slope of isochronal P-V data points.

Main Results:

• The mean Emax slope was 1.30(0.84) mm Hg/mL with a volume axis intercept (Vo) of 46(21) mL.
• Emax was characterized by parallel shifts in P-V loops with significant changes in Vo.
• Only maximum pressure/volume ratio and peak RV pressure/minimum volume correlated significantly with Emax (r=0.82 and 0.84, p=0.05).

Conclusions:

• Right ventricular systolic function can be approximated by a time-varying elastance model with a time-dependent volume intercept (Vo).
• Maximum pressure/volume ratio and peak RV pressure/minimum volume are reliable estimators of Emax.
• Other end-systolic P-V relations near end-ejection do not accurately reflect Emax due to temporal differences.