Doppler evaluation of the descending aorta in patients with hypertrophic cardiomyopathy: Potential for assessing the functional significance of outflow tract gradients and for optimizing pacemaker function

Abstract

We evaluated whether analysis of aortic flow could be useful for determining the functional significance of left ventricular outflow gradients and for optimizing pacing therapy in patients with hypertrophic cardiomyopathy (HOCM). Methods: Doppler echocardiography was performed in 32 patients with HOCM. Eleven patients with pacemakers (PPM) also underwent treadmill and quality-of-life (QOL) testing in a randomized crossover trial (1 month of backup pacing (AAI at 30 beats per minute), 1 month with an atrioventricular interval (AVI) of 30 ms (DDD30), and 1 month with an "optimized" AVI (DDDop) that maximized the descending aortic Doppler velocity time integral. Results: Patients with HOCM displayed a notch in the aortic Doppler flow profile. The location of the notch in systole corresponded with the development of the peak left ventricular outflow gradient. Aortic flow after the notch was variable ranging from 6-48% of the total flow. In patients with pacemakers, improved response to pacing was noted in those patients that developed the notch early in systole and had subsequent attenuation of aortic flow. Optimizing the AVI was associated with improved exercise tolerance (AAI: 4.6 ± 2.3 min., DDD30: 5.5 ± 2.2 min., and DDDop: 7.7 ± 2.5 min.; p < 0.05) and improved QOL. Conclusions: Patients with HOCM have a notch in their aortic Doppler flow profile. The location of the notch correlates with the development of the peak left ventricular outflow gradient and flow after the notch is variable. Patients with an early notch and attenuated flow after the notch appear to have the greatest response to pacing therapy.