96-34: Importance and Difference of Variability of Paced QRS Duration Caused by Right Ventricular Apex Pacing and Septal Pacing in Patients with Atrioventricular Block

Abstract

Purpose: The variability of paced QRS duration (pQRSd) is sometimes recognized in the clinical situation. The aim of this study was to evaluate the importance of pQRSd and to assess effects of right ventricular septal (RVS) pacing compared with right ventricular apex (RVA) pacing in patients with atrioventricular block (AVB). Method: 181 consecutive new patients with a RV electrode due to high-degree AVB during the period from January 2004 to December 2013 were studied retrospectively. They were observed regularly at pacemaker (PM) clinic during at least 1 year. The sites of RVS were decided by chest X-ray and QRS morphology in II lead of the 12-lead electrocardiogram (ECG) as high septum (HS), mid septum (MS), and low septum (LS). Result: Mean age was 75.1 years and 99 were men. Mean follow-up was 5.2 years and 130 patients had a complete AVB. 77 patients received RVA pacing and 104 received RVS pacing. 153 patients had more than 50% as the percentage of ventricular pacing (%VP). In all patients, the mean pQRSd at PM implanting was 151ms and the mean pQRSd during follow-up period was 155ms. Although there was no significant difference between the intrinsic QRS duration in patients with RVA pacing and that in patients with RVS pacing, the mean pQRSd caused by RVS pacing was significantly narrower than that caused by RVA pacing and the difference had been recognized through an observation period (153ms vs. 159ms, p = 0.029). It needed 4.4 years to get the longest pQRSd on the average (8–4088 days). In patients with more than 50% as %VP, although there was no significant difference of pQRSd among sites in RVS, the rate of change of pQRSd (%pQRSd) caused by HS pacing was higher than that caused by MS and LS pacing (5.06% vs. 2.38%, p = 0.02). Similarly, %pQRSd caused by HS pacing tended to be higher than that caused by RVA pacing, MS and LS pacing (p = 0.059). In patients with ≧50% as %VP, there was no difference in probability of heart failure (HF) hospitalization between patients with RVS pacing and patients with RVA pacing. Furthermore there was no significant difference of the prognosis between patients with ≧150ms as pQRSd and with <150ms, but in patients with left ventricular (LV) dysfunction with LV ejection fraction (EF) less than 40% the probability of HF hospitalization in patients with ≧150ms as pQRSd was significantly worse than that in patients with <150ms (p = 0.04). Moreover, patients with LV dysfunction and prolonged pQRSd, that means %pQRSd was more than 0%, had significantly high provability of HF hospitalization (p = 0.03). On the other hand, each of LV dysfunction and PH affected HF hospitalization regardless of pacing site (p = 0.03 and p = 0.02), although antiarrhythmic agents did not bring any influence prognosis. Conclusion: Each of pacing sites in RV or pQRSd did not any affect on prognosis in patients with AVB. The pQRSd and %pQRSd are important in patients with LV dysfunction, so HS should not be selected in patients with LV dysfunction because HS pacing brings high %pQRSd. And pQRSd changes for a long term, so that it should be observed carefully.