Prolongation of the ventricular cycle length during atrial fibrillation reduces the sensitivity of left ventricular performance parameters to cycle length irregularity.
Does prolongation of ventricular cycle length improve left ventricular performance by reducing sensitivity to cycle length irregularity during atrial fibrillation in an animal model?
Slowing the ventricular rate during atrial fibrillation improves left ventricular performance by reducing its sensitivity to cycle length irregularity.
Atrial fibrillation (AF) is characterized by short and irregular ventricular cycle lengths (VCL). While the beneficial effects of heart rate slowing (i.e., the prolongation of VCL) in AF are well recognized, little is known about the impact of irregularity. In 10 anesthetized dogs, R-R intervals, left ventricular (LV) pressure, and aortic flow were collected for >500 beats during fast AF and when the average VCL was prolonged to 75%, 100%, and 125% of the intrinsic sinus cycle length by selective atrioventricular (AV) nodal vagal stimulation. We used the ratio of the preceding and prepreceding R-R intervals (RR(p)/RR(pp)) as an index of cycle length irregularity and assessed its effects on the maximum LV power, the minimum of the first derivative of LV pressure, and the time constant of relaxation by using nonlinear fitting with monoexponential functions. During prolongation of VCL, there was a pronounced decrease in curvature with the formation of a plateau, indicating a lesser dependence on RR(p)/RR(pp). We conclude that prolongation of the VCL during AF reduces the sensitivity of the LV performance parameters to irregularity.
Popović et al. (Sun,) conducted a other in Atrial fibrillation (n=10). Prolongation of ventricular cycle length by selective AV nodal vagal stimulation vs. Fast AF was evaluated on Sensitivity of LV performance parameters to cycle length irregularity. Prolongation of the ventricular cycle length during atrial fibrillation reduces the sensitivity of left ventricular performance parameters to cycle length irregularity.