Preservation of native atrioventricular conduction by automatic pacing mode conversion

Himmrich E. et al. Preservation of native atrioventricular conduction by au tomatic pacing mode conversion. Fixed dual chamber pacing in patients with preserved atrioventricular (AV) conduction or intermittent AV block is powe r-wasting and hemodynamically undesirable. The purpose of this study was to assess the benefit of DDD Automatic Mode Conversion (DDD AMC) mode, which allows automatic conversion from DDD to AAI mode in the presence of intrins ic conduction, versus standard DDD(R) mode in patients implanted with Choru m(TM) pacemakers CELA Medical). Data were analyzed from 48 patients implant ed for sinus node dysfunction (49%), bradycardia-tachycardia syndrome (4%), paroxysmal AV block (10%), combination of these disorders (31%) or other ( 6%). DDD(R) or DDD AMC(R) mode was programmed according to a randomized pro tocol with cross-over between 2 periods of I month. At the end of each peri od, pacemakers were fully interrogated, including retrieval of number of at rial and ventricular paced events, and of arrhythmic events validated with respective marker chains. A functional evaluation of the study participants was also performed. Results: The percentage of ventricular paced events during DDD(R) pacing wa s 47.9+/-37.2%, versus 15,1+/-17.3 during DDD AMC(R) mode (p=0.0001). Signi ficantly fewer mode switch episodes occurred during DDD AMC(R) mode (12.8+/ -30.4, range 1-103) than during DDD(R) pacing (16.1+/-32.4, range 1-95, p<0 .02). No other significant difference was found between the 2 modes in the mean values of several other pacing characteristics, neither in the inciden ce of arrhythmic events. Finally, no statistically significant difference w as found in patients' functional status between the 2 pacing modes. Conclusions: DDD AMC(R) pacing significantly reduces the frequency of ventr icular paced events as compared to DDD(R) mode. This resulted in an estimat ed mean increase in pacemaker longevity of 5.5 months. Although no signific ant effect of DDD AMC(R) on functional status was found, longer-term observ ations are warranted to examine the potential benefits of DDD AMC(R) pacing on atrial and ventricular mechanical function.