Bradycardia‐Mediated Ventricular Electrical Remodeling

Abstract

Bradycardic states are associated with myocardial electrical remodeling predisposing to potentially lethal ventricular tachydysrhythmias. We used a novel model of complete heart block (CHB) in the rabbit to test the hypothesis that ventricular activation rate is the primary determinant of early bradycardic electrical remodeling. Chronic endocardial right ventricular demand (VVI) pacing was applied at either the near-physiologic rate of 280 beats/min or at the bradycardic rate of 140 beats/min, beginning immediately after transcatheter radiofrequency AV node ablation. A third group of animals underwent sham ablation and served as non-paced, normal sinus rhythm controls. The major finding of this study was that electrical remodeling was established within 8 days of CHB induction in the bradycardic animals, but was not observed in either of the other 2 groups. Bradycardic animals had significant QT interval prolongation and biventricular downregulation of the delayed rectifier K+ currents, IKr and IKs. The Ca2+-independent transient outward K+ current, I(to), and the inwardly rectifying K+ current, I(K1), were unaffected. This paper highlights these findings in the context of a literature-based review of heart rate-dependent remodeling of the mammalian myocardium, summarizing the current state of knowledge and describing future challenges.

From Bradycardia to Tachycardia: Complete Heart Block

“…3 QT interval prolongation in patients with heart block can be due to medications or acquired repolarization abnormalities. 4,5 In patients with concurrent torsades de points and heart block, the ECG usually shows exaggerated lengthening of the QT interval. 6 Importantly, the QT interval is dynamic and may only be extended just prior to the initiation of torsades de pointes.…”

Atrial Fibrillation-The Final Frontier

“…Studies have shown that chronic bradycardia due to sinoatrial node disease can predispose patients to developing atrial and ventricular tachyarrhythmias. 87 Bradycardia causes ventricular electrical remodeling, manifest on the electrocardiogram by QT interval prolongation. This is due to repolarization abnormalities resulting from reduced expression of the rapidly (I Kr ) and slowly (I Ks ) activating delayed-rectifier currents.…”

A case of successful catheter ablation of blocked atrial bigeminy and bradycardia with the recovery of normal sinus rhythm and myocardial reverse remodeling

“…3 , 4 However, there are few reports of myocardial remodeling and cardiomyopathy due to bradycardia with blocked atrial bigeminy. 5 , 6 …”

“…Similar to abnormal persistent tachyarrhythmia, severe bradycardia can also induce cardiomyopathy and heart failure 3,4 . However, there are few reports of myocardial remodeling and cardiomyopathy due to bradycardia with blocked atrial bigeminy 5,6 …”

“…3,4 However, there are few reports of myocardial remodeling and cardiomyopathy due to bradycardia with blocked atrial bigeminy. 5,6 Herein, we studied a case of bradycardia with blocked atrial bigeminy and ectopic atrial rhythm, resulting in cardiac remodeling and heart failure. Successful catheter ablation of blocked PACs resulted in recovery to normal sinus rhythm with myocardial reverse remodeling.…”