• tetralogy of Fallot
• pacemakers
• implanted cardiac defibrillators

Because of the successes of paediatric cardiac care, there is a burgeoning population of adults with congenital heart disease with an ever-increasing complexity of underlying cardiac disease necessitating interventions to stave off mortality and morbidity.1 This is typified in patients with tetralogy of Fallot (TOF), the most common form of cyanotic congenital heart disease. While surgical palliation is usually completed in infancy, patients with TOF exhibit significant mortality and morbidity as they age, including incident myocardial dysfunction, need for pulmonary valve replacement and an elevated risk of arrhythmia and sudden cardiac death.2 These events are usually heralded by ventricular pressure and volume loading from significant pulmonary valve incompetence, a common haemodynamic derangement after pulmonary transannular patching used as a part of complete palliation for TOF.

The arrhythmia burden in adult patients with repaired TOF is substantial. In a large multicentre study, 43.3% of 556 patients aged 36.8±12.0 years had either a sustained arrhythmia or required intervention for arrhythmia.3 Ventricular arrhythmias occurred in 14.6%, usually associated with multiple surgeries, a widening QRS duration and left ventricular dysfunction. It was noted that there was an uptick in incident atrial fibrillation and ventricular arrhythmia after age 45. Risk stratification therefore is paramount in patients with repaired TOF, particularly because it may not be that establishing pulmonary valve competency attenuates the risk of malignant arrhythmia.4 Another large multicentre cohort study detailed death or sustained ventricular arrhythmia at a median age of 38 years in 32 out of 873 young (median age 24.4 years) patients with repaired TOF.5 Right ventricular hypertrophy, right or left ventricular dysfunction and atrial arrhythmias predicted these events in this young cohort. Given these data, it follows that cardiac implantable electronic devices, particularly internal cardioverter-defibrillators (ICD), have a role in patients with repaired TOF, even after pulmonary valve replacement. In fact, the recent American Heart Association/American College of Cardiology Guideline for the Management of Adults with Congenital Heart Disease gives a IIa recommendation for a primary prevention ICD in those patients with multiple risk factors for sudden cardiac death (left ventricular systolic or diastolic dysfunction, non-sustained ventricular tachycardia, QRS duration >180 ms or extensive myocardial fibrosis on cardiac MRI).6

Egbe et al provide a contemporary set of data about implanted cardiac device complications in adult patients with repaired TOF.7 They report a single-centre retrospective cohort study of 99 relatively older patients (age 46±14 years at initial device implantation) with repaired TOF and an implanted cardiac device and describe indications, use and device-related complications. Most were men (66%) and had ICDs (59%) versus pacemakers.

Of those with ICDs, 38% were implanted for primary prevention. The total number of device-related complications was 20 (20%) during a follow-up period of 8.2±7.5 years. During that time there were 33 appropriate shocks (5.7% per year) in 30 patients, most for monomorphic ventricular tachycardia, and 37 inappropriate shocks (6.2% per year) in 34 patients. The device discharge rate was similar for both primary and secondary prevention indications. The use of class III antiarrhythmic medications protected against both appropriate and inappropriate shocks.

Importantly, other endpoints detailed a 79% freedom from lead failure in 10 years. Incident device-related infection occurred in 11%, with most (33%) occurring within 30 days of generator placement. Most of these patients had bacteraemia without a vegetation. Given that five of the 12 patients were successfully treated with antibiotics, further information regarding blood cultures or other imaging would be helpful to definitively say whether these was a device infection. Three patients (3%) had thrombus noted on the right atrial lead via transthoracic echocardiogram; embolism in these patients was not mentioned and presumably did not occur. Interestingly, inducible ventricular tachycardia before device placement may predict those who experience appropriate device discharge later and may be useful in preprocedural patient counselling. The authors conclude that all patients met the guidelines for device implantation and that the prevalence of lead failure and appropriate and inappropriate shocks were similar to previous reports of patients with repaired TOF.

The high prevalence of pacemaker placement is striking, because, historically, incident late heart block is rare after TOF repair and the data on pacemakers in patients with ToF are sparse.8 The authors note high-grade atrioventricular block as the most common indication in most of these patients, but did not mention whether these were postoperative complications or if they were late incident events. A Dutch study included 33 patients with ToF and a pacemaker, 27% of which had acquired heart block and 18% had surgical heart block.9 Over 12 years of follow-up, 15% had periprocedural complications and 24% had late pacemaker complications, which was most commonly lead failure. Regardless, the data from Egbe et al would represent one of the most robust data set on pacemakers in patients with TOF, which might be an interesting study to detail in a subsequent publication.

The primary finding of the report by Egbe et al, which quantifies device-related complications in a relatively older cohort of patients with repaired TOF, is important. This is particularly salient for those who will undergo ICD placement because patients with those devices often report a decline in quality of life as well as impairment of psychological function with depression, anxiety disorder and post-traumatic stress disorder after defibrillator discharges.10 Young or hesitant patients may be presented with the option of ongoing treatment with a class III antiarrhythmic medication in the hopes of reducing defibrillator shocks. Given that many patients with repaired TOF will experience late complications from an arrhythmia, Egbe and colleagues’ work is helpful for ongoing patient counselling and informs shared decision-making between congenital heart providers and their patients.