Aims: Increasing evidence from randomized trials and experimental studies indicates that right ventricular (RV) pacing may induce congestive heart failure. We studied regional left ventricular (LV) dyssynchrony and global LV function in 50 consecutive patients with sick sinus syndrome (SSS) randomized to either atrial pacing [AAI(R)] or dual chamber RV-pacing [DDD(R)].
Methods and results: Fifty consecutive patients were randomized to AAI(R) or DDD(R)-pacing. Tissue-Doppler imaging was used to quantify LV dyssynchrony in terms of number of segments with delayed longitudinal contraction (DLC). Left ventricular ejection fraction (LVEF) was measured using three-dimensional echocardiography. Dyssynchrony was more pronounced in the DDD(R)-group than in the AAI(R)-group at the 12 months follow-up (P < 0.05). This reflected a significant increase of dyssynchrony in the DDD(R)-group from baseline to the 12 months follow-up (1.3 +/- 1 to 2.1 +/- 1 segments displaying DLC per patient), P < 0.05. No change was observed in the AAI(R)-group (1.6 +/- 2 to 1.3 +/- 2 segments displaying DLC per patient, NS). No difference in LVEF, NYHA or NT-proBNP was observed between AAI(R)- and DDD(R)-mode after 12 months of pacing although LVEF decreased significantly in the DDD(R)-group from baseline (63.1 +/- 8%) to the 12 months follow-up (59.3 +/- 8%, P < 0.05), while LVEF remained unchanged in the AAI(R)-group (61.5 +/- 11% at baseline vs. 62.3 +/- 7% after 12 months, NS.
Conclusion: In patients with SSS, DDD(R)-pacing but not AAI(R)-pacing induces significant LV desynchronization and reduction of LVEF.