Noninvasive single-beat determination of left ventricular end-systolic elastance in humans

OBJECTIVES: The goal of this study was to develop and validate a method to estimate left ventricular end-systolic elastance (E(es)) in humans from noninvasive single-beat parameters. BACKGROUND: Left ventricular end-systolic elastance is a major determinant of cardiac systolic function and ventricular-arterial interaction. However, its use in heart failure assessment and management is limited by lack of a simple means to measure it noninvasively. This study presents a new noninvasive method and validates it against invasively measured E(es). METHODS: Left ventricular end-systolic elastance was calculated by a modified single-beat method employing systolic (P(s)) and diastolic (P(d)) arm-cuff pressures, echo-Doppler stroke volume (SV), echo-derived ejection fraction (EF) and an estimated normalized ventricular elastance at arterial end-diastole (E(Nd)): E(es(sb)) = [P(d) - (E(Nd(est)) x P(s) x 0.9)[/(E(Nd(est)) x SV). The E(Nd) was estimated from a group-averaged value adjusted for individual contractile/loading effects; E(es(sb)) estimates were compared with invasively measured values in 43 patients with varying cardiovascular disorders, with additional data recorded after inotropic stimulation (n = 18, dobutamine 5 to 10 microg/kg per min). Investigators performing noninvasive analysis were blinded to the invasive results. RESULTS: Combined baseline and dobutamine-stimulated E(es) ranged 0.4 to 8.4 mm Hg/ml and was well predicted by E(es(sb)) over the full range: E(es) = 0.86 x E(es(sb)) + 0.40 (r = 0.91, SEE = 0.64, p < 0.00001, n = 72). Absolute change in E(es(sb)) before and after dobutamine also correlated well with invasive measures: E(es(sb)): DeltaE(es) = 0.86 x DeltaE(es(sb)) + 0.67 (r = 0.88, p < 0.00001). Repeated measures of E(es(sb)) over two months in a separate group of patients (n = 7) yielded a coefficient of variation of 20.3 +/- 6%. CONCLUSIONS: The E(es) can be reliably estimated from simple noninvasive measurements. This approach should broaden the clinical applicability of this useful parameter for assessing systolic function, therapeutic response and ventricular-arterial interaction.