Evaluation of the Effects of DDDR and VVIR Pacemakers on Cardiac Functions with Exercise Test and Echocardiography

Studies on the effects of cardiac pacing on the hemodynamics of circulation, have been disparate due to combination of many factors such as methodology, protocols, different patient populations, atrioventricular (AV) synchrony, ra te response, AV delay and associated cardiac disease. This study was planned to compare the hemodynamic effects of AV synchrony, rate response and AV de lay, which was programmed according to velocity time integral (VTI) measured by echocardiography, between DDDR and VVIR pacing modes. ı5 patients (mean age 55 years old; 10 women) with activity sensor and rate responsive dua! chamber pacemakers were included to this study. Pacemaker indications were complete AV block (n=ı2), sick sinus syndrome (n=2) and 2: ı AV b lock w ith varying degrees of block (n=l). The study design was randomized and crossover. Before changing the program, echocardiography and exercise test were performed. In exercise test, the difference was not significant between these two modes when considering total exercise duration (DDDR: 5.36±1.70 min, VVIR: 4.72±2.50 min), period to reach maximal heart rates (DDDR: 3.37±2.ı9 min, VVIR: 3.94±2.46 min) and recovery period (DDDR: 3.76±2.09 min, VVIR:3.002±21 min) but maximal heart rate values (DDDR: 121±13, VVIR: 1 07±13, p<0.005) and blood pressure-heart rate product (DDDR: 22.36±4.30, VVIR: 18.32±5 .40 (x ı 000), p<0.005) w ere significant different. According to echocardiography, ejection fraction (EF) (DDDR: %56±1 1, VVIR: 50± 12, p<0.005); stroke volume index (SVI), (DDDR: 47±11 ml/m2, Türk Kardiyol Dem Arş 1999; 27: 658-661 VVIR: 39±12 ml/m2, p<0.005); velocity time integral (VTI) (DDDR: 0.29, VVIR: 0.24, p<0.05) were better with DDDR pacemaker mode as compared to those obtained with VVIR mode. There were no significant differences in exercise parameters between two pacemaker modes except maximal heart rate and double product, because rate response was preserved. Cardiac output during exereise was related primarily to heart rate, but not AV synchrony. Echocardiographically, DDDR pacemakcr was significantly bcttcr and it is concludcd that this good left ventricular performance obtained by DDDR pacemaker mode may be helpful in the daily life of the patients.