Evaluation of Ventricular Pacing Suppression Algorithms in Dual Chamber Pacemaker

The adverse cardiac outcomes due to right ventricular apical pacing with dual chamber pacemakers have been widely observed such as ventricular dyssynchrony resulting in reduced left ventricular function, increased risk of heart failure and atrial fibrillation. To minimize the ventricular pacing, manufacturers of pacemaker have made an effort to develop special algorithms designed to deliver right ventricular pacing only in case of demonstrated persistent long PR interval or repetitively lacking intrinsic ventricular activation. Currently, there are three methods and algorithms are available with a pacemaker from the Biotronik SE \& Co. KG to minimize right ventricular pacing as follows; DDD mode with fixed longer atrioventricular (AV) delay than intrinsic conduction time; Intrinsic rhythm support (IRSplus); Ventricular pacing suppression (VpS). In the real world, it is the most common practice to program the DDD(R) mode with fixed long AV delay because of physician's concerns about the possible failure of an algorithm or long pause being resulted from 2 consecutive loss of AV conduction by the algorithm. However, the main disadvantage of a fixed with long AV delay is that the prolonged total atrial refractory period (TARP) results in changes of the upper rate behavior (i.e., pseudo-Wenckebach AV block and subsequently 2:1 block at lower atrial tracking rates). The possibility of pacemaker-mediated tachycardia is getting high if the post-ventricular atrial refractory period (PVARP) is shortened to compensate. Furthermore, there is a high chance to have fusion/pseudo-fusion of ventricular pacing in a fixed long AV delay because the AV conduction is dynamic according to the heart rate. The recent systematic review showed that there are no significant differences between the pacing modes for mortality, heart failure, stroke, and atrial fibrillation (AF) in patients with sinus node dysfunction (SND) without AV block. However, the dual chamber pacemaker is still recommended in patients with SND due to lack of tools to identify patients at high risk of developing the complete AV block. The meta-analysis about the effect of the reduction in unnecessary ventricular pacing using a sophisticated algorithm in patients with SND showed there are no benefits in clinical outcomes compared with conventional DDD mode. But the percentage of ventricular pacing in ventricular pacing reduction modality group was not negligible between 1\~11.5%. The result might be changed if we have data with a more significant reduction in ventricular pacing using difference algorithm. The recent study using IRSplus and VpS algorithm from Biotronik pacemaker showed the significant reduction in ventricular pacing to less than 3%. The purpose of this study is to evaluate the efficacy of IRSplus and VpS algorithm compared with conventional DDD pacing with a fixed AV delay.