Katherine Fan

Amiodarone-Induced Thyrotoxicosis Is a Predictor of Adverse Cardiovascular Outcome

BACKGROUND Amiodarone-induced thyrotoxicosis (AIT) is a clinical condition that is notoriously difficult to manage; the relative risk of adverse cardiovascular events in these patients compared with euthyroid patients is largely unknown. OBJECTIVE We compared the clinical characteristics and major adverse cardiovascular events (MACE) in AIT and euthyroid patients. METHOD Patients at a tertiary referral center who had been prescribed amiodarone for at least 3 months were retrospectively analyzed. Baseline clinical characteristics, laboratory parameters, and outcome events were evaluated. MACE was defined as cardiovascular mortality, myocardial infarction, stroke and heart failure, or ventricular arrhythmias that required hospitalization. RESULTS A total of 354 patients (61.8 +/- 14.1 yr; 64.7% male) with a mean follow-up of 48.6 +/- 26.7 months were studied. AIT, euthyroid status, and amiodarone-induced hypothyroidism were identified in 57 (16.1%), 224 (63.3%), and 73 (20.6%) patients, respectively. No differences in baseline clinical characteristics were observed between AIT and euthyroid patients. Nonetheless AIT patients demonstrated a higher MACE rate (31.6 vs. 10.7%, P < 0.01), mostly driven by a higher rate of ventricular arrhythmias that required admission (7.0 vs. 1.3%, P = 0.03). Cox-regression multivariate analysis revealed that AIT (hazard ratio 2.68; confidence interval 1.53-4.68; P < 0.01) and left ventricular ejection fraction less than 45% (hazard ratio 2.52; confidence interval 1.43-4.42; P < 0.01) were independent predictors of MACE. CONCLUSION In patients prescribed long-term amiodarone therapy, occurrence of AIT is associated with a 2.7-fold increased risk of MACE. Regular and close biochemical surveillance is thus advisable to identify and treat this high-risk group of patients.

Nonfluoroscopic magnetic electroanatomic mapping to facilitate focal pulmonary veins ablation for paroxysmal atrial fibrillation

TSE, H.‐F., et al.: Nonfluoroscopic Magnetic Electroanatomic Mapping to Facilitate Focal Pulmonary Veins Ablation for Paroxysmal Atrial Fibrillation. RF ablation of ectopic foci in the pulmonary veins (PVs) is a promising treatment for patients with paroxysmal AF. The aim of this study was to evaluate the feasibility of using nonfluoroscopic magnetic electroanatomic mapping of PV during spontaneous or induced ectopy to facilitate focal ablation procedure. The study included 35 patients with drug refractory paroxysmal AF who underwent focal RF ablation of the PV. In 10 (29%) patients, mapping and RF ablation procedures were performed using the nonfluoroscopic magnetic electroanatomic mapping system to enable automatic capture of the location and the timing of the ectopy. As a control, 25 patients underwent conventional endocardial activation mapping technique. There were no significant differences in the clinical characteristics between the two groups. Overall procedural duration was similar between them (199 ± 52 vs 221 ± 82 minutes, P > 0.05). However, the mean fluoroscopy time (25 ± 6 vs 52 ± 12 minutes, P = 0.01) and the mean number of RF applications (5 ± 3 vs 12 ± 9, P = 0.02) were significantly less in patients who underwent electroanatomic mapping. There were no significant differences between the two groups in the acute (90 vs 84%) and long‐term success rate (60 vs 56%) after a mean follow‐up of 12 ± 9 months. In conclusion, RF ablation of ectopic foci using nonfluoroscopic magnetic electroanatomic mapping of PVs during spontaneous or induced ectopy is useful even in patients with a limited number of ectopy, and is associated with a similar success rate, but less fluoroscopy time and RF application compared to the conventional approach.

Mechanisms of biatrial pacing for prevention of postoperative atrial fibrillation--insights from a clinical trial.

Atrial fibrillation (AF) occurs in a high proportion of patients after cardiac surgery and is associated with increased morbidity and longer hospital stay. Beta-blockers and amiodarone have been shown to reduce the incidence, but AF still occurs in up to 25% despite pre-treatment. The mechanisms of AF after cardiac surgery are presumably multifactorial. The transient nature of postoperative AF suggests a reversible trigger in patients with susceptible underlying electrophysiological substrates such as abnormal automaticity and conduction delay due to atrial incisions, ischemia and preexisting disease). These could result in atrial premature beats (APBs) and prolonged atrial activation causing lengthening of the P wave. Prophylactic atrial pacing (single- or multi-site) is reported to be effective in patients at high risk for postoperative AF. The mechanisms are probably a combination of preventing bradycardia-induced arrhythmias, overdrive suppression of APBs, eliminating compensatory pauses after APBs and reduction of dispersion of refractoriness. By reducing non-uniform and asynchronous activation resulting from anatomic or functional block, multi-site pacing could improve local excitability and reduce the window of opportunity for AF initiation. We found that the incidence of AF after coronary bypass surgery (CABG) was significantly reduced in patients who received prophylactic biatrial overdrive pacing (BiA) compared with single site left atrial (LA) or right atrial (RA) pacing or no pacing. (BiA 12.5% versus LA 36.4%; RA 33.3% or control 41.9%; P < 0.05). BiA pacing was associated with the greatest reduction of P wave dispersion compared with single site pacing or control (BiA 42 +/- 8%; LA 13 +/- 6%; RA 10 +/- 9%; P < 0.05). Prophylactic postoperative BiA pacing is thus a reasonable and attractive strategy for reducing the risk for postoperative AF.

Dual Chamber Implantable Cardioverter Defibrillator Benefits and Limitations

Dual chamber ICD capable of providing dual chamber pacing (DDD) and ventricular arrhythmia therapy is now available. We report our experience of clinical performance of dual chamber ICDs amongst Chinese population.Methods: 9 patients (6 men and 3 women) received dual chamber ICDs, mean age 50 ± 18.8 years. The indications were ventricular fibrillation (VF) [5], hemodynamic intolerant ventricular tachycardia (VT) [3] and unexplained syncope plus positive induction of VF [1]. The underlying cardiac pathology were congenital LQT syndrome(1), hypertrophic cardiomyopathy [2], coronary artery disease [2], rheumatic valvular disease [1], Brugada syndrome [1], arrhythmogenic right ventricular dysplasia [1] and idiopathic VF [1]. Four patients have documented paroxysmal atrial fibrillation (AF). All patients have defibrillation thresholds (DFT) determined with a binary search protocol starting at 12 joules (J) at implantation.Results: A total of 34 episodes of VF were induced at implantation with mean DFT 13.8 ± 7 J. The average shocking impedance was 40 ± 3.6 Ω. The mean acute P wave measured 3.3 ± 1.3 mV and R wave measured 13.2 ± 3.2 mV. Atrial and ventricular thresholds, at pulse width 0.5 ms, averaged 0.8 ± 0.4 V and 0.4 ± 0.2 V. During follow-up period, 16 episodes of VF were documented and were successfully treated with the first programmed shock. In the patient with LQT syndrome, DDD was initiated to prevent pause-dependant VF. Three episodes of inappropriate therapy (15.8%) were delivered. One patient experienced 2 shocks after exercise. Stored electrograms showed sinus tachycardia with first degree heart block which was misdiagnosed as VT with retrograde 1:1 conduction. Another inappropriate therapy occurred with AF with fast ventricular response within the VF zone and VT therapy inhibitor was disabled.Conclusion: Dual chamber ICD allows combined benefits of DDD and VT/VF therapy. Storage of both atrial and ventricular electrograms provide more information in elucidation of nature of dysarrhythmias. Inappropriate shocks, though reduced, are still possible and the rigid algorithms of SVT discrimination from VT will need further published.

Relation of Tricuspid Regurgitation to Liver Stiffness Measured by Transient Elastography in Patients With Left-Sided Cardiac Valve Disease

The aim of the study was to evaluate the relation between tricuspid regurgitation (TR) severity and liver stiffness (LS) in patients with TR. A total of 131 patients with various degrees of TR secondary to left-sided heart valve disease were enrolled. Severity of TR was quantitatively assessed by proximal isovelocity surface area-derived effective regurgitant orifice (ERO). Patients were divided into 2 groups: 48 with mild-moderate TR (ERO <0.4 cm(2)) and 83 with severe TR (ERO ≥0.4 cm(2)). Transient elastography was used to measure the level of LS, an established marker of liver fibrosis, with the threshold of significant LS set at ≥12.5 kPa. Patients with severe TR had a higher LS and prevalence of significant LS than those with mild-moderate TR. Furthermore, LS and significant LS independently correlated with TR-ERO, right atrial pressure and inferior vena cava (IVC) diameter. The presence of a large TR-ERO (≥0.4 cm(2)) and IVC diameter (>2.15 cm(2)) provided a high specificity of 78% for significant LS. In conclusion, the present study demonstrates that TR-ERO, right atrial pressure, and IVC diameter are important parameters associated with LS in patients with TR.

Permanent ventricular pacing from coronary sinus after Fontan operation using newly designed left ventricular lead

The functional single ventricles in Fontan procedures are isolated from the systemic return and thereby precluding conventional endocardial ventricular pacing. We reported a young patient who underwent Fontan operation at the age of 8 years old. He presented with significant bradyarrhythmias 13 years later requiring pacing therapy. A specially designed self-retained left ventricular (LV) pacing lead was implanted successfully through the coronary sinus and its anterolateral branch with satisfactory and stable chronic thresholds by one years follow-up.

Use of low molecular weight heparin in postangioplasty management

The results of using low molecular weight heparin (LMWH) in postangioplasty management are examined. In comparison to intravenous unfractionated heparin, subcutaneous LMWH caused less groin complications and was simpler and cheaper to be administered by the medical personnel. The incidence of ischaemic complications after angioplasty including acute closure and myocardial infarction, however, remained similar and was not excessive. Subcutaneous administration of LMWH provides and alternative simple and cost-effective strategy for postangioplasty management.

Long term survival and prevalence of cardiac allograft vasculopathy in Chinese adults after heart transplantation — A retrospective study in Hong Kong

Article history: Received 12 May 2016 Accepted 28 June 2016 Available online 29 June 2016 Among heart transplant donors, 86 (65%) were male. The age at donation ranged from 14 to 61, with a mean of 39.8 years. The commonest cause of death for donors was traumatic or spontaneous intracranial hemorrhage (70%), followed by ischemic stroke (12%), and hypoxic brain injury (7%). The overall survival rates (which are equivalent to graft survival

Lysosomal membrane permeabilization is involved in oxidative stress-induced apoptotic cell death in LAMP2-deficient iPSCs-derived cerebral cortical neurons

Patients with Danon disease may suffer from severe cardiomyopathy, skeletal muscle dysfunction as well as varying degrees of mental retardation, in which the primary deficiency of lysosomal membrane-associated protein-2 (LAMP2) is considerably associated. Owing to the scarcity of human neurons, the pathological role of LAMP2 deficiency in neural injury of humans remains largely elusive. However, the application of induced pluripotent stem cells (iPSCs) may shed light on overcoming such scarcity. In this study, we obtained iPSCs derived from a patient carrying a mutated LAMP2 gene that is associated with Danon disease. By differentiating such LAMP2-deficient iPSCs into cerebral cortical neurons and with the aid of various biochemical assays, we demonstrated that the LAMP2-deficient neurons are more susceptible to mild oxidative stress-induced injury. The data from MTT assay and apoptotic analysis demonstrated that there was no notable difference in cellular viability between the normal and LAMP2-deficient neurons under non-stressed condition. When exposed to mild oxidative stress (10 μM H2O2), the LAMP2-deficient neurons exhibited a significant increase in apoptosis. Surprisingly, we did not observe any aberrant accumulation of autophagic materials in the LAMP2-deficient neurons under such stress condition. Our results from cellular fractionation and inhibitor blockade experiments further revealed that oxidative stress-induced apoptosis in the LAMP2-deficient cortical neurons was caused by increased abundance of cytosolic cathepsin L. These results suggest the involvement of lysosomal membrane permeabilization in the LAMP2 deficiency associated neural injury.

Pseudo–Pre-Excitation Unraveled Down to Its Core

A 17-year-old, previously healthy boy was incidentally noted to have persistently raised serum levels of creatinine kinase (2221 U/L [reference range, <355 U/L]), troponin I (0.36 ng/mL [reference range, <0.04 ng/mL]), and transaminases after a sports injury. He had normal exercise tolerance and never experienced any episodes of palpitation or syncope. His ECG showed sinus rhythm with a very short PR interval with prominent delta waves over every lead (Figure 1). In addition, there was left ventricular hypertrophic pattern and diffuse deep symmetrical T inversion. Echocardiogram showed concentric left ventricular hypertrophy (septal wall, 16 mm; posterior wall, 18 mm) with preserved left ventricular ejection fraction. There was no left ventricular outflow tract obstruction or any significant valvular lesion (Figure 2). Likewise, cardiac magnetic resonance imaging exhibited concentric left ventricular hypertrophy with delayed myocardial enhancement over the left ventricle …