Electrocardiographic changes during the first few seconds after cardioversion of atrial fibrillation and flutter.

Electrocardiograms were registered with a special technique during attempts at cardioversion in 22 patients with atrial fibrillation or flutter. The registrations permitted analysis of the electrocardiogram 0.1-0.5 s after the electrical discharge. Mean values indicate that there is no compensatory pause after the d.c. shock. After 29 of the 42 synchronized d.c. shocks the first QRS complex was aberrant.