Nearly half a century has passed since quinidine was first used to convert atrial fibrillation to regular sinus rhythm in man (Frey, 1918). There is general agreement nowadays that the cardiorespiratory benefits resulting from the successful reversion of long-standing atrial fibrillation to sinus rhythm are worth the risk of quinidine therapy (Hay, 1924; Stroud, LaPlace, and Reisinger, 1932; Ko...