Stimulation rate and the optimal interventricular interval during cardiac resynchronization therapy in patients with chronic atrial fibrillation

Background: Optimization of cardiac resynchronization therapy (CRT) with respect to the interventricular (V‐V) interval is mainly limited to pacing at a resting heart rate. We studied the effect of higher stimulation rates with univentricular and biventricular (BiV) pacing modes including the effect of the V‐V interval optimization. Methods: In 36 patients with heart failure and chronic atrial fibrillation (AF), the effects of right ventricular (RV), left ventricular (LV), simultaneous BiV, and optimized sequential BiV (BiVopt) pacing were measured. The effect of the pacing mode and the optimal V‐V interval was determined at stimulation rates of 70, 90, and 110 ppm using invasive measurement of the maximum rate of left ventricular pressure rise (LV dP/dt_max). Results: The average LV dP/dt _max for all pacing modalities at stimulation rates of 70, 90, and 110 ppm was 781 ± 176, 833 ± 197, and 884 ± 223 mmHg/s for RV pacing; 893 ± 178, 942 ± 186, and 981 ± 194 mmHg/s for LV pacing; 904 ± 179, 973 ± 187, and 1052 ± 206 mmHg/s for simultaneous BiV pacing; and 941 ± 186, 1010 ± 198, and 1081 ± 206 mmHg/s for BiVopt pacing, respectively. In BiVopt pacing, the corresponding optimal V‐V interval decreased from 34 ± 29, 28 ± 28, and 21 ± 27 ms at stimulation rates of 70, 90, and 110 ppm, respectively . In two individuals, LV dP/dt_max decreased when the pacing rate was increased from 90 to 110 ppm. Conclusion: In patients with AF and heart failure, LV dP/dt_max increases for all pacing modalities at increasing stimulation rates in most, but not all, patients. The rise in LV dP/dt_max with increasing stimulation rates is higher in biventricular (BiV and BiVopt) than in univentricular (LV and RV) pacing. The optimal V‐V interval at sequential biventricular pacing decreases with increasing stimulation rates.