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PubMed This is a summary of 15 peer-reviewed journal articles Updated
Cardiology

The Electrical System: Heart Block and Pacing Strategies

At a Glance

People with ccTGA have an abnormally positioned electrical system that is prone to scarring, often leading to complete heart block. If a pacemaker is needed, specialized devices like biventricular or conduction system pacemakers must be used to protect the heart muscle from weakening.

In a typical heart, the electrical system acts like a built-in spark plug, sending signals through “wires” to tell the heart when to squeeze. In ccTGA, because the heart chambers are swapped, these electrical wires are located in unusual places and follow abnormal paths [1][2]. Understanding this “wiring” is crucial, as many people with ccTGA will eventually need support to keep their heart rhythm steady.

Fragile Wiring: The Risk of Heart Block

The main control center for the heart’s rhythm is the atrioventricular (AV) node. In ccTGA, this node and the bundle of wires it connects to (the His bundle) are located in an abnormal, anterior (forward) position in the heart [1][3].

  • The “Stretched” Path: Because these wires sit in an abnormal spot, they have to travel a longer, more winding route to reach the bottom pumping chambers, putting them under physical stress [1].
  • Fibrosis (Scarring): Over time, this unusual positioning makes the wires prone to fibrosis, a process where the electrical tissue slowly wears out and is replaced by stiff scar tissue [1].
  • Complete Heart Block: If the wires scar over completely, the electrical signal from the top of the heart can no longer reach the bottom. This is called complete heart block [4]. It causes the heart to beat too slowly, leading to dizziness, fainting, or severe fatigue [5].

Why “Standard” Pacing Can Be Problematic

If complete heart block occurs, a pacemaker is required to keep the heart beating. However, for a heart with ccTGA, a traditional “single-wire” pacemaker can actually cause harm.

  • Dyssynchrony: Standard pacemakers only signal one part of the heart to squeeze at a time. This causes the heart to beat in an uncoordinated, “wobbling” motion called dyssynchrony [6][7].
  • Systemic RV Failure: In ccTGA, the morphologic right ventricle is already doing the heavy lifting of pumping to the body. If a standard pacemaker forces it to beat uncoordinatedly, the muscle can weaken rapidly, leading to heart failure [8][9].

Modern Pacing: Protecting the Pump

To avoid the damage caused by dyssynchrony, doctors now prefer more advanced pacing strategies that mimic the heart’s natural, synchronized rhythm:

  1. Biventricular Pacing (CRT): Also called Cardiac Resynchronization Therapy, this uses leads on both sides of the heart to make them squeeze at exactly the same time [10][11]. This coordination helps support the systemic right ventricle and can even reduce leaking in the tricuspid valve [12].
  2. Conduction System Pacing (CSP): This newer approach involves placing the pacemaker lead directly into the heart’s remaining natural “wiring” (like the bundle branches). By tapping into the natural electrical highway, the heart beats much more efficiently [13][14].

Because these strategies are so effective at protecting the heart muscle, biventricular or conduction system pacing is considered the “standard of care” for ccTGA patients who need electrical help [10][15].

Common questions in this guide

Why do people with ccTGA often develop heart block?
In ccTGA, the heart's electrical wiring is located in an abnormal position and has to stretch further than usual. Over time, this unusual path can cause the electrical tissue to wear out and form scar tissue, eventually blocking the signals that tell the heart to beat.
What are the symptoms of complete heart block?
When the heart's electrical signals are blocked, the heart beats much slower than normal. This lack of proper blood flow can cause you to feel dizzy, unusually tired, or even faint.
Why is a standard pacemaker dangerous for someone with ccTGA?
Standard pacemakers only stimulate one part of the heart, causing it to beat in an uncoordinated way. Because the right ventricle in a ccTGA heart is already working extra hard to pump blood to the entire body, this uncoordinated beating can rapidly weaken the muscle and lead to heart failure.
What is the best type of pacemaker for ccTGA?
Cardiologists generally recommend advanced pacemakers that use Biventricular Pacing (CRT) or Conduction System Pacing (CSP). These specialized devices synchronize the heart's squeeze, which protects the right ventricle and helps it pump blood more efficiently.
How often should my heart's electrical system be checked?
Because the risk of heart block increases as you age with ccTGA, regular monitoring is essential. Your doctor will likely use EKGs or Holter monitors periodically to catch early signs of electrical wear and tear before severe symptoms develop.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.Has an EKG or Holter monitor shown any signs of early-stage heart block or conduction delays?
  2. 2.If heart block occurs, would you recommend biventricular pacing (CRT) or conduction system pacing (CSP) over traditional right-ventricular pacing?
  3. 3.How does my/my child's unique anterior node anatomy affect the placement of pacemaker leads?
  4. 4.If surgery is being planned for other reasons, should we discuss preemptive pacing leads?
  5. 5.How often do we need to screen for electrical 'wear and tear' as I/my child ages?

Questions For You

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References

References (15)
  1. 1

    Incessant bundle branch reentrant ventricular tachycardia in a patient with corrected transposition of the great arteries.

    Kato K, Yagishita D, Ejima K, et al.

    HeartRhythm case reports 2015; (1(6)):434-438 doi:10.1016/j.hrcr.2015.05.009.

    PMID: 28491600
  2. 2

    Advances in conduction system pacing and implications for congenital heart disease.

    Fuentes Rojas S, Mondésert B, Raymond-Paquin A, et al.

    Expert review of cardiovascular therapy 2025; (23(12)):831-839 doi:10.1080/14779072.2025.2586700.

    PMID: 41195644
  3. 3

    Management of congenitally corrected transposition from fetal diagnosis to adulthood.

    Kowalik E

    Expert review of cardiovascular therapy 2023; (21(6)):389-396 doi:10.1080/14779072.2023.2211264.

    PMID: 37143366
  4. 4

    Cardiac Conduction System in Congenitally Corrected Transposition of the Great Arteries and Its Clinical Relevance.

    Baruteau AE, Abrams DJ, Ho SY, et al.

    Journal of the American Heart Association 2017; (6(12)) doi:10.1161/JAHA.117.007759.

    PMID: 29269355
  5. 5

    Complete heart block in a young adult with non-isolated congenitally corrected transposition of the great arteries: Case report.

    Faraj R, Bachar A, Sidaty O, et al.

    Annals of medicine and surgery (2012) 2022; (76()):103500 doi:10.1016/j.amsu.2022.103500.

    PMID: 35340322
  6. 6

    Right Ventricular Apical Pacing in Patients With Preserved LVEF: Adverse Effects and Mechanisms.

    Naqvi TZ, Liu S, Waldo O, et al.

    JACC. Advances 2025; (4(8)):102007 doi:10.1016/j.jacadv.2025.102007.

    PMID: 40883053
  7. 7

    Prior Pacemaker Implantation and Clinical Outcomes in Patients With Heart Failure and Preserved Ejection Fraction.

    Shen L, Jhund PS, Docherty KF, et al.

    JACC. Heart failure 2019; (7(5)):418-427 doi:10.1016/j.jchf.2018.12.006.

    PMID: 30981744
  8. 8

    Failing systemic right ventricle in a patient with dextrocardia and complex congenitally corrected transposition of the great arteries: a case report of successful transvenous cardiac resynchronization therapy.

    Nederend M, van Erven L, Zeppenfeld K, et al.

    European heart journal. Case reports 2021; (5(4)):ytab068 doi:10.1093/ehjcr/ytab068.

    PMID: 34124542
  9. 9

    Prognostic Implications of Progressive Systemic Ventricular Dysfunction in Congenitally Corrected Transposition of Great Arteries.

    Egbe AC, Miranda WR, Jain CC, Connolly HM

    JACC. Cardiovascular imaging 2022; (15(4)):566-574 doi:10.1016/j.jcmg.2021.09.016.

    PMID: 34801447
  10. 10

    Impact of pacing on systemic ventricular function in L-transposition of the great arteries.

    Hofferberth SC, Alexander ME, Mah DY, et al.

    The Journal of thoracic and cardiovascular surgery 2016; (151(1)):131-8.

    PMID: 26410005
  11. 11

    Adverse impact of univentricular pacing for the patient with functional single ventricle: successful conversion to cardiac resynchronization therapy.

    Sugimoto A, Takigiku K, Shiraishi S, et al.

    Surgical case reports 2020; (6(1)):101 doi:10.1186/s40792-020-00863-4.

    PMID: 32405970
  12. 12

    Cardiac resynchronization therapy by pacing the right ventricular dorsal site of inflow and anterior outflow for congenitally corrected transposition of the great arteries: a case report.

    Baba S, Miyazaki A, Watanabe T, et al.

    European heart journal. Case reports 2024; (8(12)):ytae607 doi:10.1093/ehjcr/ytae607.

    PMID: 39659464
  13. 13

    Indications for Cardiac Resynchronization Therapy in Patients with Congenital Heart Disease.

    Karpawich PP, Chubb H

    Cardiac electrophysiology clinics 2023; (15(4)):433-445 doi:10.1016/j.ccep.2023.07.005.

    PMID: 37865517
  14. 14

    Conduction System Pacing for Cardiac Resynchronization Therapy.

    Cano Ó, Navarrete-Navarro J, Jover P, et al.

    Journal of cardiovascular development and disease 2023; (10(11)) doi:10.3390/jcdd10110448.

    PMID: 37998506
  15. 15

    Conduction System Pacing for Cardiac Resynchronization Therapy in Heart Failure with Reduced Ejection Fraction.

    Karki S, Lakra P, Kumar K, Rao SJ

    Journal of clinical medicine 2025; (14(3)) doi:10.3390/jcm14030917.

    PMID: 39941589

This page provides educational information about heart rhythms and pacing strategies in ccTGA. Always consult your cardiologist or electrophysiologist for medical advice specific to your heart's unique anatomy.

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