Understanding the effects of heartbeat irregularity on ventricular function in human atrial fibrillation: simulation models may help to untie the knot

We read with great interest the study by Lyon et al.,1 who investigated the link between beat-to-beat ventricular interval (RR) dynamics and left ventricular (LV) function in atrial fibrillation (AF) patients. By combining speckle-tracking echocardiography with simulation models of the heart and circulation, the authors showed that LV peak strain was affected by both RR interval history (i.e. mean ventricular rate) and RR sudden changes. Through shortening of the diastolic filling time and alterations in preload, the variability of RR intervals had detrimental effects on LV peak strain, especially at higher ventricular rates. These findings draw attention on the crucial role of ventricular beat rate and variability in determining LV function during AF. In a previous set of studies,2–4 we showed the existence of a wide spectrum of ventricular responses with distinct rate, variability, and irregularity features, during different atrial arrhythmia types. Combining clinical data with computer...