Effect of Pacing Mode and Pacing Site on Torsional and Strain Parameters and on Coronary Flow

Abstract

Right ventricular apical pacing may induce detrimental effects on left ventricular function and coronary flow. In this study, the effects of pacing site and mode on cardiac mechanics and coronary blood flow were evaluated. This prospective study included 25 patients who received dual-chamber pacemakers with the ventricular lead placed in the right ventricular apex and presented in sinus rhythm (SR) at their regularly scheduled visits at the pacemaker clinic. Patients underwent complete transthoracic echocardiographic examinations while in SR, followed by noninvasive Doppler assessment of coronary flow in the left anterior descending coronary artery (LAD) and speckle-tracking echocardiography of short-axis planes in SR, atrial pacing (AAI-P), atrioventricular (dual-chamber) pacing (DDD-P), and ventricular pacing (VVI-P). Rotation of the base was significantly decreased with VVI-P compared with AAI-P. Left ventricular twist decreased significantly with DDD-P compared with AAI-P. Circumferential strain of the base significantly decreased with DDD-P and VVI-P compared with SR. The velocity-time integral of diastolic flow in the LAD decreased significantly with DDD-P compared with SR (10.7±2.2 vs 10.2±2.2 vs 8.9±1.6 vs 8.7±2.6cm in SR and with AAI-P, DDD-P, and VVI-P, respectively, P=.003). Basal rotation and time from onset of the QRS complex to peak basal rotation as a percentage of systole were independently associated with the velocity-time integral of diastolic flow in the LAD during SR and the three pacing modes. Acute right ventricular apical pacing showed a detrimental effect on left ventricular twist and basal mechanics, with the latter being independently associated with decreased LAD diastolic flow velocity parameters.