Palliation of patients with concordant atrioventricular and discordant ventriculo-arterial connections, or transposition, using an intra-atrial baffle has provided excellent short-term clinical results, and improved long-term survival. Although quality of life is good in young adults after the Mustard repair, adult survivors continue to be at risk of arrhythmias, cardiac failure, and premature death. Should it occur, the cause of sudden death is often unclear, but has been considered to be due to rapid ventricular activation during atrial flutter, or a primary ventricular tachyarrhythmia. To our knowledge, primary ventricular fibrillation has yet to be unequivocally documented as a terminal arrhythmia in a patient following the Mustard operation. We now describe such a case.
Case report
A 30-year-old male presented with episodes of recurrent collapse associated with mild exercise. He had undergone the Mustard procedure for definitive palliation of transposition at the age of 3 years. An inhibitory mode pacemaker, sensed and paced from the ventricle, was implanted because of complete heart block 14 years later. Because of failure of the leads, revision using the femoral approach was required since he had developed baffle occlusion, and refused placement of an epicardial system or further surgery. The patient also had severe stenosis of the baffle for the inferior caval vein, for which he had undergone balloon angioplasty. At presentation, the patient was in atrial fibrillation, and there was significant systemic ventricular dysfunction. He was treated with lisinopril, carvedilol, spironolactone, and amiodarone, but continued to have occasional palpitations and dizzy spells. No cause could be found despite multiple Holter recordings, but he developed a brief run of non-sustained broad complex tachycardia on exercise stress testing (Fig. 1).
Figure 1. The broad complex tachycardia noted on exercise stress testing.
In view of his recurrent symptoms, a Reveal Plus™ loop recorder was implanted. Within a few weeks, he had an episode of collapse. Pacemaker-sensing dysfunction was detected, leading to change of the pacemaker system. Three weeks later, he suffered a further collapse from which he could not be resuscitated. The arrhythmia recorded on this occasion was ventricular fibrillation (Fig. 2).
Figure 2. The terminal arrhythmia, seen to be ventricular fibrillation.
Discussion
Atrial re-direction procedures for patients born with transposition have provided excellent short-term clinical results, and improved long-term survival. Indeed, most young adults continue to have excellent palliation and a good quality of life.1–4 Despite this, adults surviving either the Mustard or the Senning procedures are at risk of premature death, cardiac failure, and arrhythmias.5 The most important complication is the ongoing risk of late and unexpected death, this being reported to occur in up to one-tenth of patients.4
The presence of symptoms, and documented atrial flutter or fibrillation, are known to predict sudden death in this group of patients.6 Risk factors for the development of atrial flutter include perioperative bradycardia, re-operation, and loss of sinus rhythm during follow-up. Sudden death has also been associated with earlier date of operation, postoperative arrhythmias, and an associated ventricular septal defect.1
The exact mechanism of sudden death in patients definitively palliated with an atrial redirection procedure is not fully understood. It has been postulated that one-to-one atrioventricular conduction during atrial flutter may result in ventricular tachycardia and subsequent fibrillation. This was not possible in our patient due to the presence of complete heart block, and the cause of death was primary ventricular fibrillation. Other proposed mechanisms of sudden death include prolonged asystole due to overdrive suppression of subsidiary pacemakers following spontaneous termination of atrial flutter. This was also untenable in our patient, since the patient was being artificially paced. Primary ventricular arrhythmias have also been suggested to be the cause of sudden death.5 This may be due to the development of myocardial scars, which have been documented in adult survivors.7
To our knowledge, ours is the first report of ventricular fibrillation documented as a terminal arrhythmia in a patient subsequent to the Mustard operation. The occurrence of primary ventricular fibrillation in our patient with systemic ventricular dysfunction following the atrial switch implies that primary implantation of a defibrillator should be considered, particularly if there is pre-existing heart block. Although atrial flutter is a risk factor for sudden death, this may reflect underlying ventricular dysfunction and the tendency to ventricular arrhythmias.
