Long-Term Efficacy of Implantable Cardioverter Defibrillator in Repaired Tetralogy of Fallot - Role of Anti-tachycardia Pacing

Evaluation and Management of Sudden Death Risk in Repaired Tetralogy of Fallot

Although substantial progress has been made to prevent sudden cardiac death in repaired tetralogy of Fallot patients, ventricular arrhythmia and sudden death continue to be major causes of morbidity and mortality in these patients. Greater survival in contemporary cohorts has been attributed to enhanced surgical techniques, more effective management of heart failure, and increased efforts in risk stratification and management of ventricular arrhythmias. More recently, our understanding of predictive risk factors has evolved into personalized risk prediction tools that rely on comprehensive demographic, imaging, functional, and electrophysiological data. However, the universal applicability of these different scoring systems is limited due to differences between study cohorts, types of anatomic repair, imaging modalities, and disease complexity. Noninvasive risk stratification is critical to identify those who may derive benefit from catheter ablation or cardioverter defibrillator implantation for primary prevention. Ultimately, assessment and risk stratification by a multidisciplinary team is crucial to analyze the various complex factors for every individual patient and discuss further options with patients and their families.

Risk Stratification for Sudden Cardiac Death in Repaired Tetralogy of Fallot

There has been significant progress in the prevention of sudden cardiac death in repaired tetralogy of Fallot. Contemporary cohorts report greater survival attributable to improved surgical techniques, heart failure management, and proactive strategies for risk stratification and management of ventricular arrhythmias including defibrillator implantation and ablation technology. Over the last 25 years, our understanding of predictive risk factors has also improved from invasive and more limited measures to individualized risk prediction scores based on extensive demographic, imaging, electrophysiological, and functional data. Although each of these contemporary scoring systems improves prediction, there are important differences between the study cohorts, included risk factors, and imaging modalities that can significantly affect interpretation and implementation for the individual patient. In addition, accurate phenotyping of disease complexity and anatomic repair substantially modulates this risk and the mechanism of sudden death. Routine implementation of risk stratification within repaired tetralogy of Fallot management is important and directly informs primary prevention defibrillator implantation as well as consideration for proactive invasive strategies including ventricular tachycardia ablation and pulmonary valve replacement. Assessment and risk stratification by a multidisciplinary team of experts in adult congenital heart disease are crucial and critical. Although we have increased understanding, reconciliation of these complex factors for the individual patient remains challenging and often requires careful consideration and discussion with multidisciplinary teams, patients, and their families.

Inappropriate implantable cardioverter-defibrillator shocks in repaired tetralogy of fallot patients: Prevalence and electrophysiological mechanisms

Background

Patients with Tetralogy of Fallot (TOF) are at increased risk for sudden cardiac death, often undergo implantable cardioverter defibrillator (ICD) implantation at younger ages, and are at greater risk of experiencing inappropriate shocks. We investigated occurrences of ICD shocks in TOF patients to identify prevalence, characteristics associated with inappropriate shocks, and therapeutic interventions after inappropriate shocks.

Methods

Records of patients with repaired TOF and ICD implantation who were followed at Columbia University Irving Medical Center between 1/1/2000 and 5/1/2019 were analyzed.

Results

44 patients with repaired TOF and ICD implantation were reviewed. Mean age at implantation was 39 ± 13 years. Eight (18%) patients received both appropriate and inappropriate shocks, 6 (14%) received only appropriate shocks, and 3 (7%) received only inappropriate shocks. Three patients received inappropriate shocks for sinus tachycardia, 7 for atrial arrhythmias, and 1 for noise artifact. Inappropriately shocked patients had lower beat per minute (bpm) cutoff values for ICD therapy (mean = 162 ± 24 bpm vs. 182 ± 16 bpm, p = 0.007). After inappropriate shocks, 1 patient underwent lead replacement, 1 had the VT cutoff increased, and 6 were treated with medications.

Conclusions

One quarter of TOF patients with ICDs experienced inappropriate shock therapy, the timing of which was most often clustered within the first two years after implant or years later. Lower shock therapy zones were associated with increased risk for inappropriate shocks, and the majority of inappropriate shocks resulted from atrial arrhythmias with rapid ventricular response. Treatments for inappropriate shocks included increasing VT therapy bpm and rhythm and/or rate control medications.

Cardiac Implantable Electronic Devices in Adults with Tetralogy of Fallot

Patient with repaired tetralogy of Fallot (TOF) sometimes require cardiac implantable electronic devices (CIED) for tachy/bradyarrhythmias. There are no population-based studies of CIED-related outcomes in the adult TOF population. We reviewed the Nationwide/National Inpatient Sample to determine trends in CIED-related admissions in adults with TOF repair. This is a retrospective review of the Nationwide/National Inpatient Sample database from January 1, 2000 to December 31, 2014. There were 18,353 admissions in adults with TOF diagnosis, and of these, CIED were implanted in 792 (4.3%) admissions (CIED-related admissions). Of these 792 CIED-related admissions, pacemakers were implanted in 242 (30.7%) yielding an incidence of 1.3% and implantable cardioverter-defibrillators were implanted in 550 (69.4%) yielding an incidence of 3.0%. In-hospital mortality occurred in 14 (1.8%) of the CIED-related admissions. The mean hospital length of stay was 7.7 ± 1.3 days and inflation-adjusted hospitalization cost was $141,860 ± $127,516. In 5-year intervals (2000 to 2004, 2005 to 2009, and 2010 to 2014), there was a temporal increase in the incidence of CIED-related admissions (3.7% vs 4.4% vs 4.9%, p = 0.006). There was a similar trend in the age at the time of implantation (37.7 ± 14.2 vs 38.2 ± 13.1 vs 39.0 ± 14.5 years, p < 0.001) and Charlson Comorbidity Index (1.1 ± 1.4 vs 1.4 ± 1.8 vs 1.3 ± 1.7, p < 0.001). In conclusion, the incidence of CIED-related admissions was 4.3% and increased over time. Further studies are required to determine if the observed temporal increase in incidence of CIED implantations (particularly implantable cardioverter-defibrillators) is associated with a concomitant increase in incidence of aborted sudden cardiac death.

ISL1 loss-of-function mutation contributes to congenital heart defects

Congenital heart defect (CHD) is the most common form of birth deformity and is responsible for substantial morbidity and mortality in humans. Increasing evidence has convincingly demonstrated that genetic defects play a pivotal role in the pathogenesis of CHD. However, CHD is a genetically heterogeneous disorder and the genetic basis underpinning CHD in the vast majority of cases remains elusive. This study was sought to identify the pathogenic mutation in the ISL1 gene contributing to CHD. A cohort of 210 unrelated patients with CHD and a total of 256 unrelated healthy individuals used as controls were registered. The coding exons and splicing boundaries of ISL1 were sequenced in all study subjects. The functional effect of an identified ISL1 mutation was evaluated using a dual-luciferase reporter assay system. A novel heterozygous ISL1 mutation, c.409G > T or p.E137X, was identified in an index patient with congenital patent ductus arteriosus and ventricular septal defect. Analysis of the proband's pedigree revealed that the mutation co-segregated with CHD, which was transmitted in the family in an autosomal dominant pattern with complete penetrance. The nonsense mutation was absent in 512 control chromosomes. Functional analysis unveiled that the mutant ISL1 protein failed to transactivate the promoter of MEF2C, alone or in synergy with TBX20. This study firstly implicates ISL1 loss-of-function mutation with CHD in humans, which provides novel insight into the molecular mechanism of CHD, implying potential implications for genetic counseling and individually tailored treatment of CHD patients.

Cardiac implantable electronic devices in adults with tetralogy of Fallot

BACKGROUND

Tachyarrhythmias and bradyarrhythmias affect 20%-50% of adult patients with tetralogy of Fallot (TOF) and some of these patients will require cardiac implantable electronic devices (CIED) such as pacemaker and/or internal cardioverter defibrillator.

METHODS

The Mayo Adult Congenital Heart Disease database was queried for patients with repaired TOF and history of CIED implantation, 1990-2017. The study objectives were: (1) determine the occurrence of device-related complications defined as lead failure, lead recall, device infection and lead thrombus; and (2) determine the occurrence and risk factors for defibrillator shock.

RESULTS

There were 99 patients (age 46±14 years and 66 (66%) men) with CIED, and the CIEDs were 41 (41%) pacemakers and 73 (73%) defibrillators. Indication for defibrillator implantation was for primary prevention in 28 (38%) and secondary prevention in 45 (62%). Device-related complications occurred in 20 (20%) patients (lead failure 17, lead recall 4, device infection 12 and thrombus 3). Twenty-five per cent of all device infections occurred within 30 days from the time of device generator change. Annualised rates of appropriate and inappropriate shocks were 5.7% and 6.2%, respectively. The use of class III antiarrhythmic drug was protective against defibrillator shock.

CONCLUSION

The current study provides useful outcome data to aid patient counselling and clinical decision-making. Further studies are required to explore ways to decrease the risk of postprocedural infection after device generator change, and to determine which patients will benefit from empirical antiarrhythmic therapy as a strategy to decrease incidence of inappropriate defibrillator shock.