[Atrial fibrillation and flutter: experimental and clinical electrophysiology]

Several early publications already provided indirect evidence that atrial fibrillation is due to multiple, simultaneously activated reentrant wavelets. However, direct proof of this "multiple wavelet hypothesis" could only be obtained by means of activation mapping, which was conducted more recently in experimental as well as clinical atrial fibrillation. The surgical techniques for the treatment of atrial fibrillation are based on the knowledge on the pathophysiology of the arrhythmia. Similarly, early studies already suggested single, large reentrant circuits as the mechanism underlying atrial flutter. It could be demonstrated that a surgical lesion between the superior and inferior vena cava provided the basis for stable reentry around this large anatomical obstacle. But not only anatomical, but also functional obstacles, may be found in the center of a reentrant circuit. In typical atrial flutter, a long arc of functional conduction block extends from the inferior to the superior vena cava. In atypical atrial flutter, the central obstacle may be found anywhere in the right or, less frequently, in the left atrium. These experimental findings are supported by the clinical observation that a lesion in the area between the inferior vena cava and the nearby AV ring reproducibly terminates typical atrial flutter.