REENTRY AND ATRIAL-FIBRILLATION

In patients undergoing cardiac surgery for paroxysmal tachycardia related to the WPW syndrome, atrial fibrillation was induced by programmed electrical stimulation. The electrical activation of the free wall of the right and left atrium was mapped with an epicardial multiple recording electrode (diameter 5 cm) containing 256 individual leads. Multiple reentering wavelets both in the right and left atrium were found to be responsible for the arrhythmia. In 19 chronically instrumented conscious dogs atrial fibrillation was induced by single early premature beats. The vulnerability to atrial fibrillation was correlated with measurements of the refractory period, conduction velocity and wavelength of the early impulse. A variety of drugs were administered intravenously (acetylcholine, propafenone, lidocaine, ouabain, quinidine, d-sotalol). It turned out that the wavelength (product of refractory period and conduction velocity) was the major determinant for the inducibility of atrial fibrillation. Drugs that shorten the wavelength (acetylcholine) facilitate atrial fibrillation, whereas the antifibrillatory action of drugs like quinidine and d-sotalol was based on a clear prolongation of the atrial wavelength.