SciCombinator

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

Concept: Tachycardia

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

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

6

-Catheter ablation for ventricular tachycardia (VT) and premature ventricular complexes (PVCs) is common. Catheter ablation of atrial fibrillation is associated with a risk of cerebral emboli attributed to cardioversions and numerous ablation lesions in the low-flow left atrium, but cerebral embolic risk in ventricular ablation has not been evaluated.

Concepts: Heart, Atrial fibrillation, Cardiac anatomy, Tachycardia, Embolism, Premature ventricular contraction

6

Intravenous procainamide and amiodarone are drugs of choice for well-tolerated ventricular tachycardia. However, the choice between them, even according to Guidelines, is unclear. We performed a multicentre randomized open-labelled study to determine the safety and efficacy of intravenous procainamide and amiodarone for the acute treatment of tolerated wide QRS complex (probably ventricular) tachycardia.

Concepts: Cardiology, Atrial fibrillation, Ventricular tachycardia, Amiodarone, Ventricular fibrillation, Acute accent, Tachycardia, QRS complex

5

Supraventricular tachycardias (SVTs) are a common cause of acute hospital presentations. Adenosine is an effective treatment. To date, no studies have directly compared paramedic-with hospital-delivered treatment of acute SVT with adenosine.

Concepts: Cardiology, Randomized controlled trial, Effectiveness, Efficacy, Supraventricular tachycardia, Tachycardia, Wolff-Parkinson-White syndrome, AV nodal reentrant tachycardia

4

Distinguishing genetic variants that cause disease from variants that are rare but benign is one of the principal challenges in contemporary clinical genetics, particularly as variants are identified at a pace exceeding the capacity of researchers to characterise them functionally.

Concepts: Genetics, Cardiology, Ventricular tachycardia, Tachycardia, Brugada syndrome