This patient had multiple risk factors for sudden cardiac death (SCD), including initial palliation with a Blalock-Taussig-Thomas shunt, LV systolic dysfunction, prolonged QRSd, NSVT, and a recent episode of unexplained syncope.¹ He is therefore at higher risk of SCD ICD placement.

Implantable loop recorder placement would provide long-term arrhythmia monitoring and switching from lisinopril to sacubitril/valsartan might optimize guideline-directed medical therapy for treatment of ventricular dysfunction. However, these should not take precedence over steps to mitigate this patient's SCD risk. Similarly, a plan limited to placing an ambulatory heart rhythm monitor with an outpatient visit in 6 months would not expeditiously address the primary SCD concern.

Ventricular arrhythmia (VA) serves as the primary mechanism leading to SCD in the setting of repaired tetralogy of Fallot (rTOF).² Reports indicate that approximately 15% of patients with rTOF develop sustained VA.^3,4 The most common form is monomorphic ventricular tachycardia (VT),¹ which can often be fast and poorly tolerated.^5,6

Although this patient met the criteria for pulmonary valve replacement, this approach alone would not decrease the SCD risk. Noninvasive risk stratification plays a crucial role in identifying patients who could benefit from ablation or primary-prevention ICD placement.

The PREVENTION-ACHD (PRospEctiVE study on implaNTable cardIOverter defibrillator therapy and suddeN cardiac death in Adults with Congenital Heart Disease) risk score was developed to identify high-risk features for SCD in patients with congenital heart disease (CHD), incorporating data from 138 patients with rTOF. The seven identified risk factors are as follows:

1. Coronary artery disease
2. New York Heart Association (NYHA) class II/III heart failure (HF)
3. Supraventricular tachycardia (SVT)
4. Impaired systemic ventricular function (EF <40%)
5. Impaired pulmonary ventricular function (EF <40%)
6. QRSd ≥120 msec
7. QT dispersion ≥70 msec.

In patients with rTOF who had four risk factors, the annual SCD risk was 3%; in those with six risk factors, the annual SCD risk was 14%.⁷ This patient had four of these criteria: NYHA class III HF, SVT, LVEF <40%, and QRSd >120 msec.

For patients with multiple noninvasive risk factors, a frequently employed strategy involves referring patients for an invasive EP study for further risk stratification.⁸ The 2018 American Heart Association/American College of Cardiology (AHA/ACC) Guideline for the Management of Adults With CHD recommends an invasive EP study with programmed ventricular stimulation for patients with rTOF who exhibit additional risk factors for SCD.⁹ Additionally, primary-prevention ICD in rTOF is a Class 2a recommendation with Level of Evidence B-NR for patients with multiple risk factors for SCD. The guidelines identify five risk factors:

1. LV dysfunction
2. NSVT
3. QRSd ≥180 msec
4. Extensive RV scarring
5. Inducible sustained VT observed during an invasive EP study.

This patient had the first three of these risk factors.

References

1. Khairy P, Harris L, Landzberg MJ, et al. Implantable cardioverter-defibrillators in tetralogy of Fallot. Circulation 2008;117:363-70.
2. Krieger EV, Zeppenfeld K, DeWitt ES, et al.; American Heart Association Adults With Congenital Heart Disease Committee of the Council on Lifelong Congenital Heart Disease and Heart Health in the Young and Council on Clinical Cardiology. Arrhythmias in repaired tetralogy of Fallot: a scientific statement from the American Heart Association. Circ Arrhythm Electrophysiol 2022;15:[ePub ahead of print].
3. Khairy P, Aboulhosn J, Gurvitz MZ, et al.; Alliance for Adult Research in Congenital Cardiology (AARCC). Arrhythmia burden in adults with surgically repaired tetralogy of Fallot: a multi-institutional study. Circulation 2010;122:868-75.
4. Pinsker BL, Serfas JD, Krasuski RA. Burden and impact of arrhythmias in repaired tetralogy of Fallot. Curr Cardiol Rep 2022;24:225-34.
5. Kapel GF, Reichlin T, Wijnmaalen AP, et al. Re-entry using anatomically determined isthmuses: a curable ventricular tachycardia in repaired congenital heart disease. Circ Arrhythm Electrophysiol 2015;8:102-9.
6. Waldmann V, Bouzeman A, Duthoit G, et al.; DAI-T4F Investigators. Long-term follow-up of patients with tetralogy of Fallot and implantable cardioverter defibrillator: the DAI-T4F Nationwide Registry. Circulation 2020;142:1612-22.
7. Vehmeijer JT, Koyak Z, Leerink JM, et al. Identification of patients at risk of sudden cardiac death in congenital heart disease: the PRospEctiVE study on implaNTable cardIOverter defibrillator therapy and suddeN cardiac death in Adults with Congenital Heart Disease (PREVENTION-ACHD). Heart Rhythm 2021;18:785-92.
8. Khairy P. Programmed ventricular stimulation for risk stratification in patients with tetralogy of Fallot: a Bayesian perspective. Nat Clin Pract Cardiovasc Med 2007;4:292-3.
9. Stout KK, Daniels CJ, Aboulhosn JA, et al. 2018 AHA/ACC guideline for the management of adults with congenital heart disease: a report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines. J Am Coll Cardiol 2019;73:e81-e192.