Genotype-phenotype correlation in tissue models of Brugada syndrome simulating patients with sodium and calcium channelopathies

Morita, Hiroshi; Zipes, Douglas P.; Morita, Shiho T.; Wu, Jiashin

doi:10.1016/j.hrthm.2010.01.039

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Volume 7, Issue 6 , Pages 820-827, June 2010

Genotype-phenotype correlation in tissue models of Brugada syndrome simulating patients with sodium and calcium channelopathies

Hiroshi Morita, MD
- Krannert Institute of Cardiology, Indiana University School of Medicine, Indianapolis, Indiana
- Department of Cardiovascular Medicine, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan
Douglas P. Zipes, MD, FHRS
- Krannert Institute of Cardiology, Indiana University School of Medicine, Indianapolis, Indiana
Shiho T. Morita, MD
- Krannert Institute of Cardiology, Indiana University School of Medicine, Indianapolis, Indiana
- Department of Cardiovascular Medicine, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan
Jiashin Wu, PhD
- Department of Molecular Pharmacology and Physiology, University of South Florida, Tampa, Florida
- Address reprint requests and correspondence: Jiashin Wu, Department of Molecular Pharmacology and Physiology, University of South Florida, 4001 East Fletcher Avenue, Tampa, Florida 33612

Received 24 August 2009; accepted 25 January 2010. published online 01 February 2010.

Background

Genetic defects in the sodium channel or in the calcium channel have been identified in patients with Brugada syndrome (BS). However, the differences in their genotype-phenotype correlations are still unclear.

Objective

We evaluated the phenotypic differences and therapeutic effects between the sodium channel and calcium channel abnormalities in in vitro models of BS.

Methods

We created two models of BS in 18 isolated and arterially perfused canine right ventricular preparations: (1) sodium channel dysfunction model (Na model, n = 11) by pilsicainide and pinacidil and (2) calcium channel dysfunction model (Ca model, n = 7) by verapamil; optically mapped action potentials (APs) on their transmural surface; and evaluated APs and electrocardiograms (ECGs) at pacing cycle lengths (CLs) of 2,000 and 1,000 ms.

Results

CL = 1,000 ms: Both models had coved-type ST elevation in the ECG, longer AP duration (APD) in the epicardium than in the endocardium, and a similar incidence of spontaneous ventricular arrhythmias. However, the Ca model had a higher incidence of T wave alternans (TWA) than the Na-model. CL = 2,000 ms: ECGs of the Ca model converted to saddleback-type ST elevation with shorter APDs in the epicardium than in the endocardium, whereas the Na model still had coved-type ST elevation and longer APDs in the epicardium. None of the Ca model preparations had ventricular arrhythmias or TWA, although the Na model had frequent ventricular arrhythmias and TWA.

Conclusion

Although both sodium channel and calcium channel dysfunction produced similar BS ECGs and arrhythmogenesis at 60 bpm, calcium channel dysfunction was associated with a higher incidence of TWA at 60 bpm, less ST elevation, and fewer arrhythmias at 30 bpm compared with sodium channel dysfunction.

Keywords: Brugada syndrome, Phase 2 reentry, Epicardium, Premature ventricular complex, Ventricular fibrillation

Abbreviations: AP, action potential, APD, action potential duration, BS, Brugada syndrome, CL, cycle length, ECG, electrocardiogram, PVC, premature ventricular contraction, TWA, T wave alternans, VT, ventricular tachyarrhythmias