The hemodynamic effect of simulated atrial fibrillationon left ventricular function

ntroduction:Atrial fibrillation (AF) is the most common sustained arrhythmia inhumans. The onset of the arrhythmia can significantly impair cardiac function. Thishemodynamic deterioration has been explained by several mechanisms such as theloss of atrial contraction, shortening of ventricular filling, or heart rhythm irregularity.This study sought to evaluate the relative hemodynamic contribution of each ofthese components during in vivo simulated human AF.Methods:Twelve patients undergoing catheter ablation for paroxysmal AF werepaced simultaneously from the proximal coronary sinus and the His bundleregion according to prescribed sequences of irregular R−Rintervalswiththeaverage rate of 90 and 130 bpm, which were extracted from the database ofdigital ECG recordings of AF from other patients. The simulated AF wascompared to regular atrial pacing with spontaneous atrioventricular conductionand regular simultaneous atrioventricular pacing at the same heart rate. Beat‐by‐beat left atrial and left ventricular pressures, including LV dP/dT and Tauindex were assessed by direct invasive measurement; beat‐by‐beat strokevolume and cardiac output (index) were assessed by simultaneous pulse‐wavedoppler intracardiac echocardiography.Results:Simulated AF led to significant impairment of left ventricular systolic anddiastolic function. Both loss of atrial contraction and heart rate irregularitysignificantly contributed to hemodynamic impairment. This effect was pronouncedwith increasing heart rate.Conclusion:Our findings strengthen the rationale for therapeutic strategies aimingat rhythm control and heart rate regularization in patients with AF.