Validation by Cardiac Catheterization of Noninvasive Estimation of Time Constant of Left Ventricular Pressure Decline as an Index of Relaxation by Speckle Tracking Echocardiography

Abstract

There has been no established echocardiographic parameter to accurately assess left ventricular (LV) relaxation. Impaired LV relaxation assessed by the time constant of LV pressure decline (Tau) is one of the major components of diastolic dysfunction. We sought to noninvasively estimate Tau (eTau) by speckle tracking echocardiography (STE) and to validate the eTau against Tau by catheterization. Tau was reported to be calculated using the isovolumic relaxation time (IVRT), LV end-systolic pressure, and left atrial (LA) pressure. We reported that pulmonary capillary wedge pressure (ePCWP) can be noninvasively and accurately estimated as 10.8 - 12.4 × Log (LA active emptying function/minimum LA volume index). Therefore, the eTau by STE is noninvasively calculated using the formula: eTau = IVRT / (ln 0.9 × systolic blood pressure-ln ePCWP). Echocardiographic parameters were measured just before catheterization in 110 patients with cardiac disease (age 72 ± 8). There was a good correlation between the eTau and Tau by catheterization (r = 0.69, p <0.001), whereas IVRT and the e' had a poor correlation with Tau (r = 0.33 and -0.33, respectively). The sensitivity and specificity of the eTau to predict prolonged Tau (>48 ms) was 77% and 91%, respectively, with area under curve of 0.87 using an optimal cutoff of 48 ms. Bland-Altman analysis revealed a good agreement between the eTau and Tau. In conclusion, this study demonstrated that the eTau by our noninvasive method has a good correlation with Tau obtained by cardiac catheterization. LV relaxation may be noninvasively and accurately estimated by STE.