Numerous clinical evidences as well as experimental studies show an increased vulnerability to atrial arrhythmias by acute stretch of the atrial walls. However, the mechanism by which atrial dilatation favours the development of sustained atrial tachyarrhythmias, such as atrial fibrillation (AF), is not fully understood. The effects of acute atrial dilatation on the substrate of atrial fibrillation were investigated in Langendorff-perfused rabbit heart. Increased atrial pressure resulted in a significant increase in vulnerability to AF, while release of the atrial stretch resulted in prompt cardioversion of AF. Atrial stretch has been shown to modulate the atrial vulnerable parameters. Stretch-induced shortening in atrial refractoriness and impairment of atrial conduction have been demonstrated. Atrial stretch through the modulation of the electrophysiological properties may not only favour the onset of arrhythmias but may also modulate the rate of reentrant arrhythmias. Cyclic variations in atrial volume following ventricular contraction modulate the atrial flutter cycle length and account for the spontaneous variability of the arrhythmia.
Copyright © 2005, Academia Publishing House Ltd.