Validation of Myocardial Acceleration During Isovolumic Contraction as a Novel Noninvasive Index of Right Ventricular Contractility: Comparison With Ventricular Pressure-Volume Relations in an Animal Model

Background—We have demonstrated that myocardial acceleration during isovolumic contraction (IVA) is a sensitive index of left ventricular contractile function. In this study, we assessed the utility of IVA to measure right ventricular (RV) contractile function. Methods and Results—We examined 8 pigs by using tissue Doppler imaging of the RV free wall and simultaneous measurements of intraventricular pressure, volume, maximal elastance (emax), preload recruitable stroke work, and dP/dtmax by conductance catheterization. Animals were paced in the right atrium at a rate of 130 beats per minute (bpm). IVA was compared with elastance during contractility modulation by esmolol and dobutamine and during preload reduction and afterload increase by transient balloon occlusion of the inferior vena cava and pulmonary artery, respectively. Data were also obtained during incremental atrial pacing from 110 to 210 bpm. Esmolol led to a decrease in IVA and dP/dtmax. During dobutamine infusion, IVA, dP/dtmax, preload recruitable stroke work, and emax all increased significantly. During preload reduction and afterload increase, IVA remained constant up to a reduction of RV volume by 54% and an RV systolic pressure increase of 58%. Pacing up to a rate of 190 bpm led to a stepwise increase in IVA and dP/dtmax, with a subsequent fall at a pacing rate of 210 bpm. Conclusions—IVA is a measurement of RV contractile function that is unaffected by preload and afterload changes in a physiological range and is able to measure the force-frequency relation. This novel index may be ideally suited to the assessment of acute changes of RV function in clinical studies.