Cardiac rhythm and conduction before and after Mustard's operation for complete transposition of the great arteries.

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Abstract
From 1973-1978, 120 patients with transposition of the great arteries had a modification of Mustard''s operation designed to avoid damage to the sinus and atrioventricular nodes. Of these, 88 had an atrial baffle alone from which 9 hospital and 4 late deaths occurred (total mortality 14.8%); 32 had additional closure of ventricular septal defect and/or relief of left ventricular outflow tract obstruction from which 6 hospital and 3 late deaths occurred (28%). On the standard ECG, 101 of 105 patients (96%) discharged from hospital were in sinus rhythm, but of the 4 patients with arrhythmias two had conduction abnormalities before operation. A further 2 patients with complex procedures had acquired bifascicular block. ECG [24 h] in 19 patients who had pre- and postoperative recordings showed acquired arrhythmias in 1 of 13 who had simple Mustard''s operation and in 2 of 6 who had additional procedures. Of a further 39 patients who had only postoperative 24 h recordings, 3 of 30 with a simple operation and 3 of 9 with additional surgical procedures had arrhythmias that were thought to be acquired. Rhythm patterns and rates previously considered to be surgically acquired were found before operation on 24 h ECG in patients with complete transposition and occur in normal infants and children. There is no evidence to support the view that such episodes with the ECG patterns of Wenckebach, 2:1 or complete sinoatrial block, atrial premature beats of less than 12/h or intermittent junctional escape rhythms represent acquired cardiac arrhythmias. Of the 22 deaths, 7 occurred after leaving hospital including five which were sudden and unexpected, no adequate cause being found at necropsy. Four of these had conduction disorders or arrhythmias on standard and 24 h ECG, including 3 with complex procedures. A modified Mustard''s operation evidently may reduce the frequency of surgically acquired arrhythmias.