Adverse effects of continuous ventricular pacing in patients with slower atrial fibrillation and normal left ventricular systolic function.

BACKGROUND: Both heart rate irregularity during chronic atrial fibrillation (AF) and ventricular desynchronization imposed by ventricular pacing may compromise ventricular function. We investigated whether heart rhythm regularization achieved through ventricular overdrive pacing (VP) gives additional benefit over rate control alone in patients with AF.

METHODS: We studied 27 patients (mean age 72 +/- 7 years) with AF and normal left ventricular (LV) systolic function who were implanted with a common VVIR pacemaker. Cardiac function was assessed by using serial echocardiographic conventional, tissue Doppler imaging (TDI) and color M-Mode (CMM) examinations, together with B-type natriuretic peptide (BNP) measurements. Baseline data were obtained during AF (mean heart rate 58 +/- 5 beats/minute) with the pacemakers programmed to ventricular mere back-up pacing. These data were compared to the corresponding measurements following a 2-week VP period after the devises had been programmed to a lower rate of 70 beats/min, ensuring most of the time continuing VP.

RESULTS: Continuous VP compared to AF, reduced the LV cardiac index (2.28 +/- 0.44 l/min/m(2) vs 2.33 +/- 0.39 l/min/m(2), P < 0.05), increased the LV end-systolic volume (38 +/- 14 mL vs 35 +/- 11 mL, P < 0.05), and decreased the TDI-derived systolic and diastolic mitral velocity (8.1 +/- 1.8 cm/s vs 8.3 +/- 1.6 cm/s, and 8.1 +/- 1.8 cm/s vs 8.3 +/- 1.6 cm/s, respectively, both P < 0.05) and the CMM-derived transmitral early diastolic flow propagation velocity (37.6 +/- 9.2 vs 41.5 +/- 9.7, P < 0.05). Following VP, both ratios E/Ea and E/Vp showed a trend toward increase (P = NS), whereas BNP rose up to 25.5% (median value, from 111 pg/mL to 165 pg/mL, P < 0.01).

CONCLUSION: VP may be considered disadvantageous compared to slower AF.