SciCombinator

Discover the most talked about and latest scientific content & concepts.

Concept: Supraventricular tachycardia

45

Background Antiarrhythmic drugs are used commonly in out-of-hospital cardiac arrest for shock-refractory ventricular fibrillation or pulseless ventricular tachycardia, but without proven survival benefit. Methods In this randomized, double-blind trial, we compared parenteral amiodarone, lidocaine, and saline placebo, along with standard care, in adults who had nontraumatic out-of-hospital cardiac arrest, shock-refractory ventricular fibrillation or pulseless ventricular tachycardia after at least one shock, and vascular access. Paramedics enrolled patients at 10 North American sites. The primary outcome was survival to hospital discharge; the secondary outcome was favorable neurologic function at discharge. The per-protocol (primary analysis) population included all randomly assigned participants who met eligibility criteria and received any dose of a trial drug and whose initial cardiac-arrest rhythm of ventricular fibrillation or pulseless ventricular tachycardia was refractory to shock. Results In the per-protocol population, 3026 patients were randomly assigned to amiodarone (974), lidocaine (993), or placebo (1059); of those, 24.4%, 23.7%, and 21.0%, respectively, survived to hospital discharge. The difference in survival rate for amiodarone versus placebo was 3.2 percentage points (95% confidence interval [CI], -0.4 to 7.0; P=0.08); for lidocaine versus placebo, 2.6 percentage points (95% CI, -1.0 to 6.3; P=0.16); and for amiodarone versus lidocaine, 0.7 percentage points (95% CI, -3.2 to 4.7; P=0.70). Neurologic outcome at discharge was similar in the three groups. There was heterogeneity of treatment effect with respect to whether the arrest was witnessed (P=0.05); active drugs were associated with a survival rate that was significantly higher than the rate with placebo among patients with bystander-witnessed arrest but not among those with unwitnessed arrest. More amiodarone recipients required temporary cardiac pacing than did recipients of lidocaine or placebo. Conclusions Overall, neither amiodarone nor lidocaine resulted in a significantly higher rate of survival or favorable neurologic outcome than the rate with placebo among patients with out-of-hospital cardiac arrest due to initial shock-refractory ventricular fibrillation or pulseless ventricular tachycardia. (Funded by the National Heart, Lung, and Blood Institute and others; ClinicalTrials.gov number, NCT01401647 .).

Concepts: Myocardial infarction, Cardiology, Cardiac arrest, Ventricular tachycardia, Supraventricular tachycardia, Amiodarone, Ventricular fibrillation, Defibrillation

28

Rationale: Catecholaminergic Polymorphic Ventricular Tachycardia (CPVT) is caused by mutations in cardiac ryanodine receptor (RyR2) or calsequestrin (Casq2) genes. Sinoatrial node dysfunction associated with CPVT may increase the risk for ventricular arrhythmia. Objective: To test the hypothesis that CPVT is suppressed by supraventricular overdrive stimulation. Methods and Results: Using CPVT mouse models (Casq2-/- and RyR2(R4496C)+/- mice), the effect of increasing sinus heart rate was tested by pretreatment with atropine and by atrial overdrive pacing. Increasing intrinsic sinus rate with atropine before catecholamine challenge suppressed ventricular tachycardia (VT) in 86% of Casq2-/- mice (6/7) and significantly reduced the ventricular arrhythmia (VA) score (atropine: 0.6±0.2 vs. vehicle: 1.7±0.3, p<0.05). Atrial overdrive pacing completely prevented VA in 16/19 (84%) Casq2-/- and in 7/8 (88%) RyR2(R4496C)+/- mice and significantly reduced ventricular premature beats in both CPVT models (p<0.05). Rapid pacing also prevented spontaneous calcium waves and triggered beats in isolated CPVT myocytes. In humans, heart-rate dependence of CPVT was evaluated by screening a CPVT patient registry for antiarrhythmic drug-naïve individuals that reached >85% of their maximum predicted heart rate during exercise testing. All 18 CPVT patients who fulfilled the inclusion criteria exhibited VA before reaching 87% of maximum heart rate. In six CPVT patients (33%), VA were paradoxically suppressed as sinus heart rates increased further with continued exercise. Conclusions: Accelerated supraventricular rates suppress VAs in two CPVT mouse models and in a subset of CPVT patients. Hypothetically, atrial overdrive pacing may be a therapy for preventing exercise-induced VT in treatment-refractory CPVT patients.

Concepts: Cardiology, Heart, Ventricular tachycardia, Supraventricular tachycardia, Heart rate, Sinoatrial node, Tachycardia, Bradycardia

28

BACKGROUND: Atrial fibrillation (AF) recurrence after ablation is difficult to predict. The development of AF is associated with inflammation, and inflammatory markers such as big endothelin-1 (big ET-1) reflect inflammatory status. It is unknown, however, whether big ET-1 can be used as a predictor for AF recurrence. The aim of this study was to investigate the relationship between plasma levels of big ET-1 and AF recurrence. METHODS: A total of 158 patients who had undergone primary ablation for symptomatic and/or drug-refractory AF, including 103 with paroxysmal and 55 with persistent AF, were included in this study. Left atrial diameter was measured with echocardiography and plasma big ET-1 levels with ELISA. All patients were followed up for at least 12 months and AF recurrence defined as an episode of AF lasting ≥ 30 s, with or without atrial flutter or atrial tachycardia. RESULTS: The AF recurrence rate was 44.9% (71/158) during the median follow-up period of 22 (13, 40) months. Plasma levels of big ET-1 in the recurrence group were higher than those in the non-recurrence group in all patients [0.80 (0.54, 1.30) vs. 0.57 (0.48, 0.72) fmol·L(-) (1), p  = 0.001], in patients with paroxysmal AF [0.81 (0.46, 1.30) vs. 0.57 (0.48, 0.70) fmol·L(-) (1), p  = 0.009] as well as in patients with persistent AF [0.77 (0.57, 1.28) vs. 0.57 (0.49, 0.89) fmol·L(-) (1), p = 0.034]. Multiple logistic regression analyses showed that plasma levels of big ET-1 were associated with AF recurrence in patients with paroxysmal AF (p  = 0.037). Kaplan-Meier analysis demonstrated that the sinus rhythm maintenance rate was lower in patients with higher big ET-1 levels than those with lower levels (p  < 0.05). CONCLUSIONS: Baseline plasma big ET-1 levels are associated with AF recurrence after primary ablation procedure in patients with paroxysmal AF, and may be used in the prediction of AF recurrence in these patients.

Concepts: Regression analysis, Logistic regression, Atrial fibrillation, Cardiac electrophysiology, Supraventricular tachycardia, Atrial flutter, Tachycardia, Left atrial appendage

28

OBJECTIVE: Describe the electrophysiological characteristics in subjects with asymptomatic Wolff-Parkinson-White with sports activities or high professional responsibility. METHODS: Nineteen subjects, mean age 33±13 years (group A). The electrophysiological characteristics were compared with a matched group with symptomatic WPW (group B). RESULTS: At baseline the anterograde refractory period and the anterograde conduction 1:1 over the accessory pathway were longer in group A (300±48ms vs 262±32ms, p<0.05 and 355±108ms vs 307±86ms, p<0.05), respectively. None of group A had a anterograde refractory period<250ms and 58% showed absence of retrograde conduction over the accessory pathway vs 4% of group B (p<0.001). Induction of tachycardia was significantly less in group A (5%) than in group B (92%) (p<0.001). Atrial fibrillation was induced in only one of group A vs 32% of group B (p<0.001). CONCLUSION: We confirm the benign electrophysiological characteristics in asymptomatic compared to symptomatic subjects. Poor anterograde conduction along with absence of retrograde conduction explains the low frequency of tachyarrhythmias and would not support the routine investigation of all asymptomatic subjects. But, due to possible consequences, remains the systematic indication for preventive ablation in the subgroup of asymptomatic subjects with sporting activities or high professional responsibility.

Concepts: Atrial fibrillation, Cardiac electrophysiology, Supraventricular tachycardia, Atrial flutter, Orgasm, Asymptomatic, Tachycardia, Wolff-Parkinson-White syndrome

28

AIMS: Orthodromic atrioventricular reentrant tachycardia (ORT) is the most common arrhythmia at electrophysiological study (EPS) in patients with pre-excitation. The purpose of the study was to determine the clinical significance and the electrophysiological characteristics of patients with inducible antidromic tachycardia (ADT).METHODS AND RESULTS: Electrophysiological study was performed in 807 patients with a pre-excitation syndrome in control state and after isoproterenol. Antidromic tachycardia was induced in 63 patients (8%). Clinical and electrophysiological data were compared with those of 744 patients without ADT. Patients with and without ADT were similar in term of age (33 ± 18 vs. 34 ± 17), male gender (68 vs. 61%), clinical presentation with spontaneous atrioventricular reentrant tachycardia (AVRT) (35 vs. 42%), atrial fibrillation (AF) (3 vs. 3%), syncope (16 vs. 12%). In patients with induced ADT, asymptomatic patients were less frequent (24 vs. 37%; <0.04), spontaneous ADT and spontaneous malignant form more frequent (8 vs. 0.5%; <0.001) (16 vs. 6%; <0.002). Left lateral accessory pathway (AP) location was more frequent (51 vs. 36%; P < 0.022), septal location less frequent (40 vs. 56%; P < 0.01). And 1/1 conduction through AP was more rapid. Orthodromic AVRT induction was as frequent (55.5 vs. 55%), but AF induction (41 vs. 24%; P < 0.002) and electrophysiological malignant form were more frequent (22 vs. 12%; P < 0.02). The follow-up was similar; four deaths and three spontaneous malignant forms occurred in patients without ADT. When population was divided based on age (<20/≥20 years), the older group was less likely to have criteria for malignant form.CONCLUSION: Antidromic tachycardia induction is rare in pre-excitation syndrome and generally is associated with spontaneous or electrophysiological malignant form, but clinical outcome does not differ.

Concepts: Atrial fibrillation, Supraventricular tachycardia, Atrial flutter, Neurophysiology, Asymptomatic, Tachycardia, Wolff-Parkinson-White syndrome, AV nodal reentrant tachycardia

28

BACKGROUND: -Supraventricular tachycardia (SVT) is one of the most common conditions requiring emergent cardiac care in children yet its management has never been subjected to a randomized controlled clinical trial. The purpose of this study was to compare the efficacy and safety of the 2 most commonly used medications for antiarrhythmic prophylaxis of SVT in infants: digoxin and propranolol. METHODS AND RESULTS: -This was a randomized, double-blind, multi-center study of infants <4 months with SVT (AVRT or AVNRT), excluding Wolff-Parkinson-White, comparing digoxin to propranolol. The primary end-point was recurrence of SVT requiring medical intervention. Time to recurrence and adverse events were secondary outcomes. Sixty-one patients completed the study, 27 randomized to digoxin and 34 to propranolol. SVT recurred in 19% of patients on digoxin and 31% of patients on propranolol. (P=0.25). No recurrence occurred after 110 days of treatment. The 6-month recurrence-free status was 79% for patients on digoxin and 67% for patients on propranolol (P=0.34, and there were no first recurrences in either group between 6 and 12 months. There were no deaths and no serious adverse events related to study medication. CONCLUSIONS: -There was no difference in SVT recurrence in infants treated with digoxin versus propranolol. The current standard practice may be treating infants longer than required and indicates the need for a placebo-controlled trial. Clinical Trial Registration Information-http://clinicaltrials.gov; NCT-00390546.

Concepts: Pharmacology, Clinical trial, Randomized controlled trial, Pharmaceutical industry, Clinical research, Supraventricular tachycardia, Antiarrhythmic agent, Tachycardia

27

27

Catheter cryoablation of supraventricular tachycardias involving the perinodal regions is considered to be a safer alternative compared to radiofrequency ablation. Limited information is available for efficacy, midterm outcomes, and complications regarding the ablation of parahissian accessory pathways (APs) in pediatric patients.

Concepts: Medical terms, Physician, Supraventricular tachycardia, Radiofrequency ablation

27

Differentiation between atrioventricular nodal reentry tachycardia (AVNRT) and atrioventricular reentrant tachycardia (AVRT) can be sometimes challenging. Apical right ventricular (RV) entrainment can help in differentiation; however, it has some fallacies. We thought to compare the accuracy of anteroseptal basal RV entrainment to RV apical entrainment in identifying the mechanism of supraventricular tachycardia (SVT).

Concepts: Supraventricular tachycardia, Adenosine, Tachycardia, AV nodal reentrant tachycardia

27

OBJECTIVE: This study aimed to reveal individual variations in Koch’s triangle using NavX and to evaluate the efficacy of the NavX-guided slow pathway ablation. METHODS: A regional geometry around Koch’s triangle was constructed in 42 consecutive patients with atrioventricular nodal reentrant tachycardia (AVNRT), and a bipolar electrogram map was created with 72 ± 30 sampling points during sinus rhythm to identify sites with Haissaguerre’s slow potentials (SPs) and His bundle electrograms (HBEs) to examine the anatomical and electrical variations. Radiofrequency ablation was performed at the most prominent SP recording site. The acute results and long-term outcome were examined in comparison to another 42 consecutive patients who underwent a conventional fluoroscopy-guided slow pathway ablation in the previous months. RESULTS: The size of Koch’s triangle and the coronary sinus ostium varied over a wide range of 132 to 490 and 69 to 346 mm(2), respectively. HBEs were recorded linearly along the antero-septal right atrium (n = 29) or deviated downward toward the midseptum (n = 13, 31 %). The SPs were always distributed below the lowest HBE recording site. The NavX-guided ablation eliminated AVNRT with a median of 1 radiofrequency pulse, 9.1 ± 4.6 min of fluoroscopy, and 49 ± 14 min of procedure time, all of which were significantly smaller than those in fluoroscopy-guided ablation. No procedure-related complications or long-term recurrence was noted in either group. CONCLUSION: Koch’s triangle varies in terms of the size and electrogram distribution, and the NavX-guided slow pathway ablation overcomes the diversity and seems more effective than fluoroscopy-guided ablation.

Concepts: Cardiology, Heart, Atrial fibrillation, Cardiac electrophysiology, Supraventricular tachycardia, Sinus venosus, AV nodal reentrant tachycardia, Coronary sinus