Prediction of the onset of atrial fibrillation after cardiac surgery using the monophasic action potential

Objective—To show that the monophasic action potential (MAP) recorded continuously from human epicardium may be used to predict the imminent onset of atrial fibrillation or flutter (AF) following surgery, thus allowing prophylactic treatment to be started. Patients—22 patients (14 male, 8 female; mean (SD) age 64 (12) years) undergoing aortic valve replacement. Setting—Tertiary referral centre. Methods—Over a mean observation period of 8 (2.7) days (range 4 to 14), nine episodes of AF were seen in six patients. Before AF, specific and significant alterations of the MAP morphology were observed. In seven of nine episodes the MAP shortened (25 (4)% 60 minutes before AF), developed a triangular shape, and the plateau amplitude decreased from 5.3 (1.2) to 2 (0.2) mV. In the two remaining episodes the beat to beat variability of cycle length and MAP duration at 90% repolarisation (MAPd90) increased significantly from 24 (7) ms and 12 (8) ms (24 hours before AF) to 137 (27) ms and 56 (11) ms (30 minutes before AF) respectively. AF was successfully treated by the administration of sotalol in three cases and by a combination of verapamil and digoxin in a further four. Previously observed changes of MAPd90 and MAP morphology regressed after conversion to sinus rhythm. Conclusions—The continuous and intermediate term recording of the MAP from atrial epicardium appears to be a valid tool for detecting imminent AF after cardiac surgery with a high sensitivity (99%) and specificity (88%). Optimised antiarrhythmic treatment may thus be given selectively for prophylaxis. Keywords: postoperative atrial fibrillation;  monophasic action potential;  postoperative management;  prophylactic antiarrhythmic treatment;  arrhythmias