More than 1.4 million adults are living with congenital heart defects (CHD) in the United States, according to the American Heart Association, and thanks to modern medical techniques, more children with CHD are surviving to adulthood.1 On a global scale, an estimated 12 million people—of all ages—were living with CHD in 2017.2
Twelve-lead ECG is an invaluable tool for clinical assessment in these diverse and complex patient cases, as it contains important prognostic and diagnostic information. Anatomic changes from a primary CHD or surgery intended to correct a CHD can influence QRS duration, P waves, T waves, and other aspects of an ECG, and having these figures in hand is critical to ensuring that any changes that could put the patient at greater risk are identified and addressed in due time.
QRS Patterns Associated with Congenital Heart Defects
The QRS complex, which represents electrical activation of the right and left ventricles, carries a wealth of information that is particularly useful to cardiologists taking care of CHD patients with issues ranging from simple atrial septal defects (ASDs) to complex atrium, ventricle, or atrioventricular valve defects.
Atrial Septal Defects
It has been established in medical research that many, if not most, patients with significant ASDs have an rsr' or rSR' pattern in leads V1 and V2, which is thought to be related to right ventricular volume overload rather than a true disturbance in conduction, according to a recent study in the Annals of Pediatric Cardiology.3
That study of 141 children with secundum ASD—which was asymptomatic in the majority of cases—found a prevalent rSR' pattern in 26%, which increased to 54% in the large ASD group. In patients with moderate to large ASDs, the rSR' pattern was predictive of the need for surgical closure.
A so-called "crochetage" pattern of QRS, which is a notch near the apex of the R wave in the inferior ECG leads, is strongly associated with a diagnosis of ostium secundum ASD, according to a study in the Indian Journal of Critical Care Medicine.4 Specificity increases to more than 90% when the crochetage sign is found in all inferior leads.
Moreover, the authors note, the crochetage sign may correlate positively with both left-to-right shunt severity and larger shunt size.
D-Transposition of the Great Arteries
Almost 5% of CHD is due to D-transposition of the great arteries (D-TGA), wherein the aorta originates from the right ventricle (RV) and the pulmonary arteries from the left ventricle.5 This defect is incompatible with life unless there is some communication between the systemic and pulmonary circuits.
The current surgery to treat this condition consists of an arterial switch in the first days of life, but prior to the mid-1980s, the condition was treated by surgically creating an interatrial baffle or through atrial switch surgical procedures (Senning or Mustard procedures), which corrected the circulation to physiologic but left the RV facing a systemic load.
Thus, the ECG QRS after atrial switch for D-TGA manifests evidence of RV hypertrophy, including right axis deviation and right bundle branch block (RBBB). RV overload manifests in right precordial leads with high voltage small R waves and in left precordial leads with a deep S wave due to an underdeveloped left ventricle (LV) facing the lower pressure pulmonary circuit.
Congenitally Corrected Transposition of the Great Arteries
Congenitally corrected transposition of the great arteries (CCTGA or L-transposition) is rare. In such cases, both the LV and RV and their respective atrioventricular valves are reversed. The RV therefore faces a systemic arterial circulation and becomes hypertrophied as the patient ages.
As the right and left bundle branches are reversed, septal activation occurs from right to left, according to the JAMA Cardiology review. A pathognomonic CCTGA ECG pattern is the result: Q waves are noted in the right precordial leads, whereas no Q waves are noted in the left precordial leads. The duration of the QRS is typically normal until advanced systemic RV dilatation and dysfunction develop.
Tetralogy of Fallot
Tetralogy of Fallot (TOF) is the most common cyanotic heart defect.6 It consists of right ventricular outflow tract obstruction, a ventricular septal defect, an overriding aortic root, and RV hypertrophy.
Various surgical approaches are utilized for TOF, typically within the first year of life. The ECG changes seen with TOF reflect both the initial pathology and the results of surgical intervention.
The JAMA Cardiology review notes that with TOF, RBBB is near-universal and may reflect RV hypertrophy and dilatation as well as surgical injury to the right bundle branch. An atypical appearance is common with variable QRS duration, depending on specific leads. Often the maximal QRS duration is in right-sided precordial leads, reflecting interference from RV surgical incisions or patches.
Given that ECG diagnosis of RV hypertrophy in the presence of RBBB is problematic in cases of TOF, multimodality cardiac imaging should be considered for precise estimation of RV size and function in these patients.
Patients with TOF have a heightened risk of ventricular arrhythmias and sudden cardiac death (SCD), even after surgical repair, according to a review in the Journal of the American College of Cardiology.7 And although the risk of SCD is much less in patients with TOF than among patients with primary prevention implantable cardioverter-defibrillators (ICDs) for ischemic or dilated cardiomyopathy, for example, many such deaths occur many years after surgery.
Several factors have been associated with both mortality and ventricular arrhythmias in the setting of TOF, including older age at repair, a prior palliative shunt, RV dysfunction of at least moderate severity, and a longer QRS duration.
Guidelines from the European Society of Cardiology state that ICD implantation should be considered for select patients with TOF who have arrhythmia symptoms and a positive programmed electrical stimulation (PES) study, or a combination of other risk factors and a positive PES.8 Those risk factors include:
- Moderate RV or LV dysfunction
- Extensive RV scarring on cardiac magnetic resonance imaging
- Severe QRS fragmentation
- QRS duration ≥ 180 ms
Ebstein Anomaly
Ebstein anomaly (EA) is characterized by an apically displaced and malformed tricuspid valve (TV). With EA, there is a wide range of TV displacement/malformation, resulting in a wide range of tricuspid regurgitation. Milder forms tend to be without any signs or symptoms and can remain undiagnosed late into adulthood.9 These cases are often diagnosed by an incidentally performed ECG.
The major ECG manifestations in EA are related to the right atrial enlargement caused by variable amounts of tricuspid regurgitation, as noted in the JAMA Cardiology review. The QRS axis reflects abnormal activation of the atrialized RV, resulting in an incomplete or complete but atypical RBBB.
Atrioventricular Septal Defect
Atrioventricular septal defect (AVSD) is strongly associated with Down's syndrome (DS), and all infants with DS should be evaluated for CHD with an echocardiogram, according to the Centers for Disease Control and Prevention.10 Partial AVSD is characterized by the presence of an ostium primum ASD and a cleft mitral valve.
A characteristic ECG pattern with AVSD consists of a superior QRS axis with R waves in leads AVL and AVR, an rSR or rSr pattern in the right precordial leads stemming from RV volume and/or pressure overload, predominant S waves in the inferior leads, and prolongation of the PR interval, as the JAMA Cardiology review explains. This is thought to represent early impulse propagation to posterior aspects of the LV due to hypoplasia of the left anterior fascicle and the posterior displacement of the AV node.
The Role of 12-Lead ECG
The 12-lead ECG remains a crucial tool for cardiologists in their clinical evaluation of adult patients with CHD. Distinctive and sometimes unique ECG patterns of ventricular activation can often be found in the QRS of these patients. Knowledge of these QRS changes may allow diagnosis of heretofore unknown CHD, and it could also provide additional prognostic information in patients with known CHD before and after surgical intervention.
Resources:
1. John AS, Jackson JL, Moons P, et al. Advances in managing transition to adulthood for adolescents with congenital heart disease: a practical approach to transition program design: a scientific statement from the American Heart Association. Journal of the American Heart Association. April 2022;11(7):e025278. https://www.ahajournals.org/doi/10.1161/JAHA.122.025278
2. GBD 2017 Congenital Heart Disease Collaborators. Global, regional, and national burden of congenital heart disease, 1990-2017: a systematic analysis for the Global Burden of Disease Study 2017. Lancet Child & Adolescent Health. March 2020;4(3):185-200. https://www.thelancet.com/journals/lanchi/article/PIIS2352-4642(19)30402-X/fulltext
3. Refaei M, Islam S, Mackie AS, Atallah J. Correlation of electrocardiogram parameters and hemodynamic outcomes in patients with isolated secundum atrial septal defects. Annals of Pediatric Cardiology. May-August 2017;10(2):152-157. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5431027/
4. Sarma A. Crochetage sign: an invaluable independent ECG sign in detecting ASD. Indian Journal of Critical Care Medicine. February 2021;25(2):234-235. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7922464/
5. Waldmann V, Combes N, Ladouceur M, et al. Understanding electrocardiography in adult patients with congenital heart disease: a review. JAMA Cardiology. December 2020;5(12):1435-1444. https://jamanetwork.com/journals/jamacardiology/fullarticle/2769556
6. Ossa Galvis MM, Bhakta RT, Tarmahomed A, et al. 2023 Jan 31. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan–. https://www.ncbi.nlm.nih.gov/books/NBK500001/
7. Cohen MI, Khairy P, Zeppenfeld K, et al. Preventing arrhythmic death in patients with tetralogy of Fallot: JACC review topic of the week. Journal of the American College of Cardiology. February 2021;77(6):761-771. https://www.sciencedirect.com/science/article/pii/S0735109720381079
8. Zeppenfeld K, Tfelt-Hansen J, de Riva M, et al. 2022 ESC guidelines for the management of patients with ventricular arrhythmias and the prevention of sudden cardiac death. European Heart Journal. October 2022;43(40):3997-4126. https://academic.oup.com/eurheartj/article/43/40/3997/6675633
9. Singh DP, Hussain K, Mahajan K. 2023 May 25. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan–. https://www.ncbi.nlm.nih.gov/books/NBK534824/
10. Centers for Disease Control and Prevention. Facts about atrioventricular septal defect (AVSD). CDC.gov. https://www.cdc.gov/ncbddd/heartdefects/avsd.html. Accessed July 21, 2023.
