Evaluation of cardiac function by pacing at different right ventricular sites in patients with third-degree atrioventricular block using Doppler ultrasound.

OBJECTIVE: This study utilized Doppler ultrasonography cardiograms in patients with third-degree atrioventricular (III-AV) block to compare right ventricular apex (RVA) pacing and right ventricular outflow tract (RVOT) pacing with respect to their effects on synchronization of contraction between the two ventricles, as well as on timing of specific left-ventricular electrical and mechanical events and their impact on left ventricular function.

METHODS: Thirty-eight patients with (III-AV) block were implanted with dual-chamber pacemakers, in 20 cases, implantation occurring in the RVOT (RVOT group), while in 18 cases implantation occurred in the RVA (RVA group). Patients underwent Doppler echocardiography and electrocardiography (ECG) one month pre- and one month post-surgery, as well as 12 months post-surgical implantation of the pacemaker.

RESULTS: Prior to pacemaker implantation, no significant differences were found between the two groups with respect to the following parameters: left ventricular end-diastolic diameter (LVEDD), left ventricular end systolic diameter (LVESD), left ventricular ejection fraction (LVEF), E/A value (ratio of early [E] to late [A] ventricular filling velocities), inter-ventricular mechanical delay (IVMD)and septal-to-posterior wall motion delay (SPWMD). One month after implantation, no significant differences were found between the two groups for LVEDD, LVESD, LVEF, and E/A. However, compared with the RVOT group, the RVA group exhibited prolonged IVMD and SPWMD. Twelve months after pacemaker implantation, there was no significant difference for E/A between the two groups; however, compared with the ROVT group, the RVA group exhibited prolonged LVEDD, LVESD, IVMD, and SPWMD and significantly lower LVEF.

CONCLUSION: Relative to RVA pacing, RVOT pacing mitigated impairment of systolic function and systolic dys-synchronization.