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 (Ees) 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 Ees. Methods Left ventricular end-systolic elastance was calculated by a modified single-beat method employing systolic (Ps) and diastolic (Pd) arm-cuff pressures, echo-Doppler stroke volume (SV), echo-derived ejection fraction (EF) and an estimated normalized ventricular elastance at arterial end-diastole (ENd): Ees(sb) = [Pd − (ENd(est) × Ps × 0.9)[/(ENd(est) × SV). The ENd was estimated from a group-averaged value adjusted for individual contractile/loading effects; Ees(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 μg/kg per min). Investigators performing noninvasive analysis were blinded to the invasive results. Results Combined baseline and dobutamine-stimulated Ees ranged 0.4 to 8.4 mm Hg/ml and was well predicted by Ees(sb) over the full range: Ees = 0.86 × Ees(sb) + 0.40 (r = 0.91, SEE = 0.64, p < 0.00001, N = 72). Absolute change in Ees(sb) before and after dobutamine also correlated well with invasive measures: Ees(sb): ΔEes = 0.86 × ΔEes(sb) + 0.67 (r = 0.88, p < 0.00001). Repeated measures of Ees(sb) over two months in a separate group of patients (n = 7) yielded a coefficient of variation of 20.3 ± 6%. Conclusions The Ees 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.