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Late complete heart block may occur after correction of tetralogy of Fallot. Whether postoperative electrophysiologic studies can identify patients at risk of developing this conduction disturbance is unknown. In this study, 57 children who underwent electrophysiologic investigation after correction of tetralogy of Fallot were followed up for 1 to 13 (mean 6.5) years after the investigation. One late death and two cases of late complete heart block occurred. The late death was due to ventricular arrhythmia and not to a conduction disturbance. The cases of late heart block occurred 2 and 5 years, respectively, after electrophysiologic study, and in both cases the patient had a prolonged HV interval; in one patient progressive lengthening of the HV interval could be demonstrated at two subsequent studies 1 year apart. Another five patients with a prolonged HV interval had normally conducted sinus rhythm up to 11 years after study. Atrial pacing at increasing rates (up to the occurrence of second degree atrioventricular block) during electrophysiologic study was the best means of predicting late heart block: of three patients with block below the bundle of His occurring at pacing rates less than 180/min, two developed late complete heart block. Thus, electrophysiologic testing of the conduction system after correction of tetralogy of Fallot is useful in predicting late complete heart block and should be performed in patients with a history of transient heart block after surgery and in those with a prolonged PR interval.

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A case of progressive trifascicular block late after correction of Fallot’s tetralogy is reported. Progressive damage to the His bundle and/or its branches over 18 months after surgery was suggested by sequential ECGs and confirmed by repeat electrophysiological studies done 3 and 18 months postoperatively: the H-V interval increased from 55 to 80 ms over this period. With atrial pacing at increasing rates, supra-His 2:1 atrioventricular (AV) block occurred at a rate of 158/min at the first study; at the second study, infra-His block occurred at an atrial pacing rate of only 128/min. A permanent pacemaker was implanted prophylactically. 5 years after surgery, complete heart block occurred without symptoms, the pacemaker having taken over ventricular stimulation.

Despite the high prevalence of sickle cell disease and trait in the black population and its serious potential for microinfarction, there are only a few reports on acute myocardial damage during vasoocclusive crisis. We report a unique case of transient second degree atrioventricular (A-V) block of Mobitz I and II type during a severe sickle cell crisis. Localized high ventricular septum hypoperfusion demonstrated by a 99mTc-MIBI radionuclide study and reversible echocardiographic wall motion abnormalities in the same area were strong indicators for a local ischemic event in the A-V node and His bundle area, explaining the observed transient conduction abnormalities. The present report draws attention to a potentially lethal complication of sickle cell crisis.