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 and an estimated normalized ventricular elastance at arterial end-diastole (E-Nd): E-es(sb) = [Pd - (E-Nd(test) x P-s x 0.9)]/(E-Nd(test) 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 mug/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): E-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. (J Am Coll Cardiol 2001;38:2028-34) (C) 2001 by the American College of Cardiology.