The Role of Mechanical-Electrical Interaction in Ventricular Arrhythmia: Evidence From a Novel Animal Model for Repaired Tetralogy of Fallot

Department of Pediatrics, National Taiwan University Hospital and Medical College, National Taiwan University, Taipei 100, Taiwan, Republic of China.
Pediatric Research (Impact Factor: 2.31). 05/2011; 70(3):247-52. DOI: 10.1203/PDR.0b013e318225fd8b
Source: PubMed


Pulmonary regurgitation and prolonged QRS duration of right bundle branch (RBB) block are common in repaired tetralogy of Fallot (TOF) and increase the risk of sudden death. We sought to establish an animal model to reflect both abnormalities. Twenty-one canines: group I (n = 7) received a surgical right ventricular outflow tract (RVOT) transannular patch plus pulmonary valve destruction; group II (n = 5) received RBB ablation and sham operation; and group III (n = 9) received combined interventions. Serial electrophysiological data were obtained up to 1 y. Procedure mortality was 27.6%. At 1 y, although severe pulmonary regurgitation was documented in most dogs in groups I (71%) and III (100%), progressive RVOT dilatation was noted in group III. RBB block was present in all dogs in groups II and III. However, the increments of QRS duration, QTc, JTc, and QT dispersion progression between 1 mo and 1 y were all greatest in group III. Ventricular arrhythmia events were frequent in group III (median 3.3/mo) but uncommon in groups I and II (median 1/mo). We have created a novel animal model that adequately reflects both the hemodynamic and electrophysiological characteristics of repaired TOF patients and can be applied to examine the risk of ventricular arrhythmias.

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Available from: Chun-An Chen, Oct 28, 2015
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    ABSTRACT: Tetralogy of Fallot (TOF) is the most common cyanotic congenital heart disease in Taiwan. This study investigates the long-term survival and risks of TOF in an Asian cohort. This study enrolled 819 consecutive patients with TOF (61.1% male), who received total correction between 1970 and 2002, as participants. Patient medical records were reviewed, and the survival status of those out of contact was confirmed by death records retrieved from the National Health database. The mean (±SD) patient age at cardiac repair was 6.5±7.6 years, and a prior shunt operation was performed in 119 (14.5%) of the patients. At cardiac repair, a transannular patch for right ventricle outlet reconstruction was required in 444 (54.2%) of the patients. After 13,808 patient-years of follow-up, the 30-year survival rate was 90.5%. The annual mortality rate increased from 0.123% in the initial 15 years after repair to 0.395% thereafter (P<0.05). The presence of major aortopulmonary collateral arteries, older operative age, and previous shunt operation are independent risks of late cardiac deaths. Secondary to cardiac mortality, unnatural deaths (accident and suicide) accounted for 27.6% of late deaths, significantly higher compared with that of the general population (odds ratio, 2.18; P=0.028). In this Asian TOF cohort, except for a late decrease after 15 years, long-term survival after cardiac repair was satisfactory. Although cardiac death was the most common cause of late death, accidents or suicide may also be associated with late mortality, suggesting a potential role for psychosocial support.
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    ABSTRACT: Coexisting long QT gene mutations/polymorphisms in Tetralogy of Fallot (TOF) patients may aggravate the repolarization abnormality from cardiac repair. We investigated the impact of these genes on the risk of life-threatening events. Genetic variants of the three common long QT genes were identified from patients with repaired TOF. Life-threatening events were defined as sudden cardiac death and hemodynamic unstable ventricular arrhythmia. Biophysical characterization of the alleles of the genetic variants was performed using a whole-cell voltage clamp with expression in Xenopus oocytes. A total of 84 patients (56.0 % male with 1,215 patients-year follow-up) were enrolled. Six rare variants and six non-synonymous single nucleotide polymorphisms (SNPs) were found in 40 (47.6 %) patients. Life-threatening events occurred in five patients; four received implantable cardioverter defibrillator and one died of sudden cardiac death. Life-threatening events occurred more often in those with genetic variants than those without (5/40 vs. 0/44, P = 0.021); particularly, the hERG or SCN5A gene mutations/polymorphisms (2/5 vs. 3/79, P = 0.027 and 5/27 vs. 0/57, P = 0.003, respectively). Among the five patients with life-threatening events, three had compound variants (hERG p.M645R/SCN5A p.R1193Q, hERG p.K897T/SCN5A p.H558R, and KVLQT1 p.G645S/SCN5A p.P1090L), that also increased the risk of events. Their QTc and JTc were all prolonged. Functional study of the novel variant (hERG gene p.M645R) from patients with life-threatening events revealed a dominant negative effect. In conclusion, in repaired TOF patients, coexisting long QT mutations/polymorphisms might have additive effects on the repolarization abnormality from surgery and thereby increase the risks of life-threatening events.
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