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Connexin43 gene transfer reduces ventricular tachycardia susceptibility after myocardial infarction.

ABSTRACT: The aim of this study was to evaluate the links between connexin43 (Cx43) expression, myocardial conduction velocity, and ventricular tachycardia in a model of healed myocardial infarction.Post-infarction ventricular arrhythmias frequently cause sudden death. Impaired myocardial conduction has previously been linked to ventricular arrhythmias. Altered connexin expression is a potential source of conduction slowing identified in healed scar border tissues. The functional effect of increasing border-zone Cx43 has not been previously evaluated.Twenty-five Yorkshire pigs underwent anterior infarction by transient left anterior descending coronary artery occlusion, followed by weekly testing for arrhythmia inducibility. Twenty animals with reproducibly inducible sustained monomorphic ventricular tachycardia were randomized 2:1:1 to receive AdCx43, Ad?gal, or no gene transfer. One week later, animals underwent follow-up electrophysiologic study and tissue assessment for several functional and molecular measures.Animals receiving AdCx43 had less electrogram fractionation and faster conduction velocity in the anterior-septal border zone. Only 40% of AdCx43 animals remained inducible for ventricular tachycardia, while 100% of controls were inducible after gene transfer. AdCx43 animals had 2-fold higher Cx43 protein levels in the anterior-septal infarct border, with similar percents of phosphorylated and intercalated disk-localized Cx43 compared with controls.These data mechanistically link Cx43 expression to slow conduction and arrhythmia susceptibility in the healed scar border zone. Targeted manipulation of Cx43 levels improved conduction velocity and reduced ventricular tachycardia susceptibility. Cx43 gene transfer represents a novel treatment strategy for post-infarction arrhythmias.

SUBMITTER: Greener ID

PROVIDER: S-EPMC3578694 | biostudies-literature | 2012 Sep

REPOSITORIES: biostudies-literature

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Connexin43 gene transfer reduces ventricular tachycardia susceptibility after myocardial infarction.

Greener Ian D ID Sasano Tetsuo T Wan Xiaoping X Igarashi Tomonori T Strom Maria M Rosenbaum David S DS Donahue J Kevin JK

Journal of the American College of Cardiology 20120808 12

<h4>Objectives</h4>The aim of this study was to evaluate the links between connexin43 (Cx43) expression, myocardial conduction velocity, and ventricular tachycardia in a model of healed myocardial infarction.<h4>Background</h4>Post-infarction ventricular arrhythmias frequently cause sudden death. Impaired myocardial conduction has previously been linked to ventricular arrhythmias. Altered connexin expression is a potential source of conduction slowing identified in healed scar border tissues. Th ...[more]

PMID: 22883636

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Project description:ObjectiveSympathetic predominance and ventricular repolarization abnormalities represent epilepsy-associated cardiac alterations and may underlie seizure-induced ventricular arrhythmias. Myocardial ion channel and electrical remodeling have been described early in epilepsy development and may contribute to ventricular repolarization abnormalities and excitability. Using the pilocarpine-induced acquired epilepsy model we sought to examine whether altered myocardial ion channel levels and electrophysiological changes also occur in animals with long-standing epilepsy.MethodsWe examined myocardial adrenergic receptor and ion channel protein levels of epileptic and age-matched sham rats (9-20 months old) using western blotting. Cardiac electrical properties were examined using optical mapping ex vivo and electrophysiology in vivo. We investigated the propensity for ventricular tachycardia (VT) and the effects of β-adrenergic blockade on ventricular electrical properties and excitability in vivo.ResultsIn animals with long-standing epilepsy, we observed decreased myocardial voltage-gated K+ channels Kv4.2 and Kv4.3, which are known to underlie early ventricular repolarization in rodents. Decreased β1 and increased α1A adrenergic receptor protein levels occurred in the myocardium of chronically epileptic animals consistent with elevated sympathetic tone. These animals exhibited many cardiac electrophysiological abnormalities, represented by longer QRS and corrected QT (QTc) intervals in vivo, slower conduction velocity ex vivo, and stimulation-induced VT. Administration of a β-adrenergic antagonist late in epilepsy was beneficial, as the therapy shortened the QTc interval and decreased stimulation-induced VT.SignificanceOur findings demonstrate that myocardial ion channel remodeling and sympathetic predominance, risk factors for increased ventricular excitability and arrhythmias, persist in chronic epilepsy. The beneficial effects of β-adrenergic antagonist treatment late in the course of epilepsy suggest that attenuating elevated sympathetic tone may represent a therapeutic target for ameliorating epilepsy-associated cardiac morbidity.

Dataset Information

Connexin43 gene transfer reduces ventricular tachycardia susceptibility after myocardial infarction.

Publications

Connexin43 gene transfer reduces ventricular tachycardia susceptibility after myocardial infarction.

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