Background: Pacing from the right ventricular apex (RVA) is associated with cardiac dysfunction and shows electrophysiological features similar to left bundle branch block in which left ventricular (LV) mechanical dyssynchrony impairs septal coronary artery perfusion.
Methods: A total of 62 non-ischemic patients with an implanted pacemaker at the RVA with a pacing rate of >95% were studied. LV septal coronary perfusion as indicated by the LV septal perfusion index was measured by electrocardiography (ECG)-gated single-photon emission computed tomography for all patients at baseline and for patients who were upgraded to CRT at 6months after CRT. Relationships among LV septal perfusion index, QRS duration, and LV ejection fraction were analyzed.
Results: Among the patients with permanent RVA pacing, 28 of 62 (45%) had impaired septal perfusion (i.e., septal perfusion index <0.9). The LV septal perfusion index was significantly correlated with both QRS duration (r=-0.763, p<0.001) and LV ejection fraction (r=0.462, p=0.001). Eleven patients were upgraded to CRT. CRT significantly improved the LV septal perfusion index from 0.63 (SD=0.13) to 0.89 (SD=0.19) (p<0.001)and cardiac function: LV end-systolic volume from 102.3mL (SD=70.0) to 179.7mL (SD=118.4) (p=0.002) and LV ejection fraction from 22.5 (SD=8.9%) to 38.4% (SD=13.9%) (p=0.001).
Conclusions: Nearly half of the non-ischemic patients with permanent RVA pacing presenting with prolonged QRS duration and LV dysfunction developed LV septal hypoperfusion. Both septal perfusion and LV function improved in patients who were upgraded to CRT.
Keywords: Cardiac resynchronization therapy; Emission computed tomography; Heart failure; Redistribution; Right ventricular apical pacing.
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