[Relationship between new-onset atrial fibrillation and sympathetic neural remodeling in a canine acute myocardial infarction model].

OBJECTIVE: To establish the canine model of new-onset atrial fibrillation (AF) after acute myocardial infarction (AMI), and explore the relationship between new-onset AF and sympathetic neural remodeling in this model. METHODS: Twenty four adult mongrel dogs were randomly divided into 4 groups by applying random number table. Group A (n=6): ligate the left circumflex artery (LCX). Group B (n=6): ligate the LCX and right atrial anterior artery and right atrial middle artery. Group C (n=6): ligate left anterior descending artery.Group D (n=6): sham operation.Sequential electrophysiology study was performed in all dogs to determine the AF induction rate, AF duration, effective refractory period (ERP), the density of tyrosine hydroxylase (TH) and norepinephrine transporter (NET) before AMI or sham operation, and at 30 min, 2 hours and 4 hours after AMI or sham operation. RESULTS: (1) The highest AF induction rate of right atrium and left auricle was 96.7%(58/60) and 95.0%(57/60) in group B, 81.7%(49/60) and 38.3%(23/60) in group A, 28.3%(17/60) and 35.0%(21/60) in group C, 20.0%(12/60) and 33.3%(20/60) in group D. (2) At 4 hours after AMI, AF duration was significantly prolonged in group B(193.50±54.67) s, compared with group A(53.83±9.37) s, group C(45.00±19.50) s, and group D(16.67±4.50) s (all P<0.05). (3) In group B, the ERP of AF was prolonged at 30 minutes after AMI and shortened at 2 hours and 4 hours after AMI compared with baseline level(all P<0.05). (4) The TH density of left atrium ((3 485±694) µm2/mm2) and left auricle((2 645±454) µm2/mm2) in group A and the TH density of left atrium ((7 873±1159) µm2/mm2) and left auricle((3 070±605) µm2/mm2) in group B were significantly higher than those in group C ((1 474±475) µm2/mm2, (1 177±277) µm2/mm2) and group D ((678±206) µm2/mm2, (489±125) µm2/mm2) (all P<0.05), and the TH density of right atrium and right auricle in group B were higher than group A (all P<0.05). The NET density of left atrium((476±75) µm2/mm2) and left auricle ((414±52) µm2/mm2) in group A and the NET density of left atrium((527±81) µm2/mm2) and left auricle((429±85) µm2/mm2) in group B were lower than that in group C ((1 044±105) µm2/mm2, (867±67) µm2/mm2) and group D ((1 438±60) µm2/mm2, (1 027±119) µm2/mm2) (all P<0.05). CONCLUSIONS: Ligating the LCX, right atrial anterior artery and right atrial middle artery at the same time can significantly increase the success rate in establishing the canine model of new-onset atrial fibrillation after acute myocardial infarction and can also increase the AF duration.Cardiac sympathetic remodeling after acute myocardial infarction is associated with induction and duration of AF.

In Vitro Drug Screening Using iPSC-Derived Cardiomyocytes of a Long QT-Syndrome Patient Carrying KCNQ1 & TRPM4 Dual Mutation: An Experimental Personalized Treatment.

Congenital long QT syndrome is a type of inherited cardiovascular disorder characterized by prolonged QT interval. Patient often suffer from syncopal episodes, electrocardiographic abnormalities and life-threatening arrhythmia. Given the complexity of the root cause of the disease, a combination of clinical diagnosis and drug screening using patient-derived cardiomyocytes represents a more effective way to identify potential cures. We identified a long QT syndrome patient carrying a heterozygous KCNQ1 c.656G>A mutation and a heterozygous TRPM4 c.479C>T mutation. Implantation of implantable cardioverter defibrillator in combination with conventional medication demonstrated limited success in ameliorating long-QT-syndrome-related symptoms. Frequent defibrillator discharge also caused deterioration of patient quality of life. Aiming to identify better therapeutic agents and treatment strategy, we established a patient-specific iPSC line carrying the dual mutations and differentiated these patient-specific iPSCs into cardiomyocytes. We discovered that both verapamil and lidocaine substantially shortened the QT interval of the long QT syndrome patient-specific cardiomyocytes. Verapamil treatment was successful in reducing defibrillator discharge frequency of the KCNQ1/TRPM4 dual mutation patient. These results suggested that verapamil and lidocaine could be alternative therapeutic agents for long QT syndrome patients that do not respond well to conventional treatments. In conclusion, our approach indicated the usefulness of the in vitro disease model based on patient-specific iPSCs in identifying pharmacological mechanisms and drug screening. The long QT patient-specific iPSC line carrying KCNQ1/TRPM4 dual mutations also represents a tool for further understanding long QT syndrome pathogenesis.