Noninvasive serial evaluation of myocardial mechanics in pressure overload hypertrophy of rabbit myocardium

Background: The determination of progression from afterload mismatch to myocardial failure in small animals requires invasive monitoring to assess ventricular pressure. Objective: We sought to (1) validate the noninvasive determination of blood pressure using optical plethysmography, and (2) determine the time course and progression from afterload mismatch to myocyte failure in neonatal rabbits with coarctation (aortic banding at 7-10 days of life) compared to normal rabbits. Methods and Results: Comparison of continuous arterial pressure determined by optical plethysmography with high-fidelity intraarterial recording was performed in nine animals. An accuracy of 5.9 +/- 4.7 and 9.2 +/- 6.9 mm Hg for systolic and diastolic blood pressure was noted. Fourier analysis confirmed similar frequency components. Simultaneous transthoracic echocardiography and optical plethysmography were serially performed in 33 banded and 13 control animals. Load-dependent and -independent measures of myocardial function were obtained. Midwall contractility, initially normal, showed a gradual significant deterioration (0.22 +/- 1.68 [week 3] to -1-36 +/- 1.24 [week 6]; Z-scores). Conclusions: This novel noninvasive method for determination of myocardial mechanics allows for serial evaluation of cardiac function and the determination of the time course from compensated hypertrophy to myocyte failure.