Thyroid hormones (THs) profoundly influence cardiac electrophysiology, cellular architecture, and hemodynamic performance. Dysregulation of triiodothyronine (T3) and thyroxine (T4)—whether overt or subclinical—produces multilayer remodeling ranging from ion-channel transcription to autonomic imbalance, creating an arrhythmogenic substrate. Hyperthyroidism accelerates depolarization kinetics, shortens action potential duration (APD), enhances β-adrenergic responsiveness, and increases intracellular Ca²⁺ cycling, predisposing to atrial fibrillation (AF) and supraventricular tachyarrhythmias. Conversely, hypothyroidism prolongs repolarization, disrupts Ca²⁺ reuptake, induces myocardial stiffness, and increases susceptibility to bradyarrhythmias and torsadogenic ventricular arrhythmias. This article integrates genomic, non-genomic, electrophysiological, structural, and hemodynamic pathways linking TH dysregulation to cardiac arrhythmogenesis, bridging molecular physiology with clinical electrophysiology.

cardiac arrhythmia, atrial excitability, sinus tachycardia, hyperthyroidism, hypothyroidism

Corona G, Croce L, Sparano C, Petrone L, Sforza A, Maggi M, et al. Thyroid and heart, a clinically relevant relationship. J Endocrinol Invest (2021) 44(12):2535–44. doi: 10.1007/s40618-021-01590-9

Stojkovic M, Zarkovic M. Subclinical thyroid dysfunction and the risk of cardiovascular disease. Curr Pharm Des (2020) 26(43):5617–27. doi: 10.2174/1381612826666201118094747

Biondi B, Palmieri EA, Lombardi G, Fazio S. Effects of subclinical thyroid dysfunction on the heart. Ann Intern Med (2002) 137(11):904–14. doi: 10.7326/0003-4819-137-11-200212030-00011

Razvi S, Jabbar A, Pingitore A, Danzi S, Biondi B, Klein I, et al. Thyroid hormones and cardiovascular function and diseases. J Am Coll Cardiol (2018) 71(16):1781–96. doi: 10.1016/j.jacc.2018.02.045

Dietrich JW. Thyreotoxische krise und myxödemkoma. Der Nuklearmediziner (2016) 39(02):124–31. doi: 10.1055/s-0042-105786

Akamizu T, Satoh T, Isozaki O, Suzuki A, Wakino S, Iburi T, et al. Diagnostic criteria, clinical features, and incidence of thyroid storm based on nationwide surveys. Thyroid (2012) 22(7):661–79. doi: 10.1089/thy.2011.0334

Komatsu R, Karimi N, Zimmerman NM, Sessler DI, Bashour CA, Soltesz EG, et al. Biochemically diagnosed hypothyroidism and postoperative complications after cardiac surgery: a retrospective cohort analysis. J Anesth (2018) 32(5):663–72. doi: 10.1007/s00540-018-2533-5

Selmer C, Faber J. Mild thyroid dysfunction: A potential target in prevention of atrial fibrillation? Circulation (2017) 136(22):2117–8. doi: 10.1161/CIRCULATIONAHA.117.031283

Baumgartner C, da Costa BR, Collet TH, Feller M, Floriani C, Bauer DC, et al. Thyroid function within the normal range, subclinical hypothyroidism, and the risk of atrial fibrillation. Circulation (2017) 136(22):2100–16. doi: 10.1161/CIRCULATIONAHA.117.028753

Abbey EJ, McGready J, Ferrucci L, Simonsick EM, Mammen JSR. Thyroid hormone supplementation and all-cause mortality in community-dwelling older adults: Results from the Baltimore longitudinal study of aging. J Am Geriatr Soc (2021) 69(5):1283–90. doi: 10.1111/jgs.17015