Modeling polymorphic ventricular tachycardia at rest using patient-specific induced pluripotent stem cell-derived cardiomyocytes

Background

While mutations in the cardiac type 2 ryanodine receptor (RyR2) have been linked to exercise-induced or catecholaminergic polymorphic ventricular tachycardia (CPVT), its association with polymorphic ventricular tachycardia (PMVT) occurring at rest is unclear. We aimed at constructing a patient-specific human-induced pluripotent stem cell (hiPSC) model of PMVT occurring at rest linked to a single point mutation in RyR2.

Methods

Blood samples were obtained from a patient with PMVT at rest due to a heterozygous RyR2-H29D mutation. Patient-specific hiPSCs were generated from the blood samples, and the hiPSC-derived cardiomyocytes (CMs) were generated via directed differentiation. Using CRIPSR/Cas9 technology, isogenic controls were generated by correcting the RyR2-H29D mutation. Using patch-clamp, fluorescent confocal microscopy and video-image-based analysis, the molecular and functional properties of RyR2-H29D hiPSC—CMs and control hiPSC—CMs were compared.

Findings

RyR2-H29D hiPSC—CMs exhibit intracellular sarcoplasmic reticulum (SR) Ca²⁺ leak through RyR2 under physiological pacing. RyR2-H29D enhances the contribution of inositol 1,4,5-trisphosphate receptors to excitation-contraction coupling (ECC) that exacerbates abnormal Ca²⁺ release in RyR2-H29D hiPSC—CMs. RyR2-H29D hiPSC—CMs exhibit shorter action potentials, delayed afterdepolarizations, arrhythmias and aberrant contractile properties compared to isogenic controls. The RyR2-H29D mutation causes post-translational remodeling that is fully reversed with isogenic controls.

Interpretation

To conclude, in a model based on a RyR2 point mutation that is associated with short-coupled PMVT at rest, RyR2-H29D hiPSC—CMs exhibited aberrant intracellular Ca²⁺ homeostasis, shortened action potentials, arrhythmias and abnormal contractile properties.

Funding

French Muscular Dystrophy Association (AFM; project 16,073, MNM2 2012 and 20,225), “Fondation de la Recherche Médicale” (FRM; SPF20130526710), “Institut National pour la Santé et la Recherche Médicale” (INSERM), National Institutes of Health (ARM; R01 HL145473) and New York State Department of Health (NYSTEM C029156).

Portomesenteric Vein Thrombosis after Laparoscopic Sleeve Gastrectomy: A Case Report

Portomesenteric vein thrombosis is an uncommon but potentially life-threatening complication associated with laparoscopic sleeve gastrectomy. We present the case of a 26-year-old male who underwent an uneventful laparoscopic sleeve gastrectomy and presented on postoperative day 14 with portomesenteric vein thrombosis. The patient was treated conservatively with IV heparinization, followed by an oral anticoagulant agent. He was discharged in stable condition without further problems. A high index of suspicion for the disease is required not to miss or delay the diagnosis of portomesenteric vein thrombosis which could lead to a fatal outcome. All patients should be screened beforehand for underlying hypercoagulability before surgery.

Portomesenteric venous thrombosis after laparoscopic sleeve gastrectomy: A case report and a call for prevention

Postoperative portomesenteric venous thrombosis (PMVT) is being increasingly reported after bariatric surgery. It is variable and often a nonspecific presentation along with its potential for life-threatening and life-altering outcomes makes it imperative that it is prevented, detected early and treated optimally. We report the case of a 50-year-old morbidly obese man undergoing a laparoscopic sleeve gastrectomy who developed symptomatic PMVT two weeks postsurgery, which was successfully treated by anticoagulant therapy. We provide postulates to the etiopathological mechanism for this thrombotic entity. The growing recognition that obesity and bariatric surgery create a procoagulant state regionally and systemically provides impetus for designing the ideal protocol for PMVT prophylaxis, which could be more common than currently believed. We support the early screening for PMVT in the postbariatric surgical patient with unexplainable or intractable abdominal symptoms. The role of routine surveillance and the ideal duration of post-PMVT anticoagulation is yet to be elucidated.

Wearable cardioverter-defibrillator use in patients perceived to be at high risk early post-myocardial infarction

OBJECTIVES

The aim of this study was to describe usage of the wearable cardioverter-defibrillator (WCD) during mandated waiting periods following myocardial infarction (MI) for patients perceived to be at high risk for sudden cardiac arrest (SCA).

BACKGROUND

Current device guidelines and insurance coverage require waiting periods of either 40 days or 3 months before implanting a cardioverter-defibrillator post-myocardial infarction (MI), depending on whether or not acute revascularization was undertaken.

METHODS

We assessed characteristics of and outcomes for patients who had a WCD prescribed in the first 3 months post-MI. The WCD medical order registry was searched for patients who were coded as having had a "recent MI with ejection fraction ≤35%" or given an International Classification of Diseases, Ninth Revision 410.xx diagnostic code (acute MI), and then matched to device-recorded data.

RESULTS

Between September 2005 and July 2011, 8,453 unique patients (age 62.7 ± 12.7 years, 73% male) matched study criteria. A total of 133 patients (1.6%) received 309 appropriate shocks. Of these patients, 91% were resuscitated from a ventricular arrhythmia. For shocked patients, the left ventricular ejection fraction (LVEF) was ≤30% in 106, 30% to 35% in 17, >36% in 8, and not reported in 2 patients. Of the 38% of patients not revascularized, 84% had a LVEF ≤30%; of the 62% of patients revascularized, 77% had a LVEF ≤30%. The median time from the index MI to WCD therapy was 16 days. Of the treated patients, 75% received treatment in the first month, and 96% within the first 3 months of use. Shock success resulting in survival was 84% in nonrevascularized and 95% in revascularized patients.

CONCLUSIONS

During the 40-day and 3-month waiting periods in patients post-MI, the WCD successfully treated SCA in 1.4%, and the risk was highest in the first month of WCD use. The WCD may benefit individual patients selected for high risk of SCA early post-MI.

Survival after shock therapy in implantable cardioverter-defibrillator and cardiac resynchronization therapy-defibrillator recipients according to rhythm shocked. The ALTITUDE survival by rhythm study

OBJECTIVES

This study sought to determine if the risk of mortality associated with inappropriate implantable cardioverter-defibrillator (ICD) shocks is due to the underlying arrhythmia or the shock itself.

BACKGROUND

Shocks delivered from ICDs are associated with an increased risk of mortality. It is unknown if all patients who experience inappropriate ICD shocks have an increased risk of death.

METHODS

We evaluated survival outcomes in patients with an ICD and a cardiac resynchronization therapy defibrillator enrolled in the LATITUDE remote monitoring system (Boston Scientific Corp., Natick, Massachusetts) through January 1, 2010. First shock episode rhythms from 3,809 patients who acutely survived the initial shock were adjudicated by 7 electrophysiologists. Patients with a shock were matched to patients without a shock (n = 3,630) by age at implant, implant year, sex, and device type.

RESULTS

The mean age of the study group was 64 ± 13 years, and 78% were male. Compared with no shock, there was an increased rate of mortality in those who received their first shock for monomorphic ventricular tachycardia (hazard ratio [HR]: 1.65, p < 0.0001), ventricular fibrillation/polymorphic ventricular tachycardia (HR: 2.10, p < 0.0001), and atrial fibrillation/flutter (HR: 1.61, p = 0.003). In contrast, mortality after first shocks due to sinus tachycardia and supraventricular tachycardia (HR: 0.97, p = 0.86) and noise/artifact/oversensing (HR: 0.91, p = 0.76) was comparable to that in patients without a shock.

CONCLUSIONS

Compared with no shock, those who received their first shock for ventricular rhythms and atrial fibrillation had an increased risk of death. There was no significant difference in survival after inappropriate shocks for sinus tachycardia or noise/artifact/oversensing. In this study, the adverse prognosis after first shock appears to be more related to the underlying arrhythmia than to an adverse effect from the shock itself.