Abstract
End-systolic left ventricular (LV) elastance (Ees) has been previously calculated and validated invasively using LV pressure-volume (P-V) loops. Noninvasive methods have been proposed, but clinical application remains complex. The aims of the present study were to 1) estimate Ees according to modeling of the LV P-V curve during ejection (“ejection P-V curve” method) and validate our method with existing published LV P-V loop data and 2) test the clinical applicability of noninvasively detecting a difference in Ees between normotensive and hypertensive subjects. On the basis of the ejection P-V curve and a linear relationship between elastance and time during ejection, we used a nonlinear least-squares method to fit the pressure waveform. We then computed the slope and intercept of time-varying elastance as well as the volume intercept (V0). As a validation, 22 P-V loops obtained from previous invasive studies were digitized and analyzed using the ejection P-V curve method. To test clinical applicability, ejection P-V curves were obtained from 33 hypertensive subjects and 32 normotensive subjects with carotid tonometry and real-time three-dimensional echocardiography during the same procedure. A good univariate relationship (r2 = 0.92, P < 0.005) and good limits of agreement were found between the invasive calculation of Ees and our new proposed ejection P-V curve method. In hypertensive patients, an increase in arterial elastance (Ea) was compensated by a parallel increase in Ees without change in Ea/Ees. In addition, the clinical reproducibility of our method was similar to that of another noninvasive method. In conclusion, Ees and V0 can be estimated noninvasively from modeling of the P-V curve during ejection. This approach was found to be reproducible and sensitive enough to detect an expected increase in LV contractility in hypertensive patients. Because of its noninvasive nature, this methodology may have clinical implications in various disease states.