Susumu Tao

Adenosine triphosphate-induced atrial fibrillation: the clinical significance and relevance to spontaneous atrial fibrillation

PurposeAdenosine triphosphate (ATP) frequently triggers atrial fibrillation (AF), but the clinical significance of this phenomenon is unknown. The purpose of this study was to reveal the relevance between spontaneous AF and ATP-induced AF.MethodsIn 81 AF patients undergoing pulmonary vein isolation (PVI), we injected 20 mg of ATP before PVI, and recorded triggering sites of the AF induced. We also injected 20 mg of ATP in 44 patients receiving ablation for atrioventricular reciprocating tachycardia (AVRT).ResultsATP provoked AF in 24 (29.6 %) of the 81 PVI patients and atrial ectopic beats in a further 48 (59.3 %). The trigger site of the AF was in the PV and the right atrium in 22 (91.7 %) and 2 patients, respectively. In 14 of those 24 patients, spontaneous AF arose from the same triggering site as the ATP-induced AF. In the 48 patients with ATP-provoked ectopic beats, spontaneous AF arose from the same site in 13. Conversely, among the 34 patients demonstrating spontaneous AF initiation, AF or ectopic beats were provoked by ATP from the same site in 14 (41.2 %) and 13 patients (38.2 %), respectively. ATP provoked AF in only 2 (4.5 %) of the AVRT patients. In summary, ATP provoked AF or atrial ectopic beats in 88.9 % of PVI patients, 36.1 % of whose triggering sites matched that of the spontaneous AF, while 79.4 % of spontaneous AF trigger sites matched ATP-provoked AF or ectopic beat sites. ConclusionsATP-induced AF was strongly associated with clinical AF, and ATP is useful for identifying arrhythmogenic sites.

Severe iatrogenic bradycardia related to the combined use of beta-blocking agents and sodium channel blockers

Purpose Drug-induced bradycardia is common during antiarrhythmic therapy; the major culprits are beta-blockers. However, whether other antiarrhythmic drugs are also a significant cause of this, alone or in combination with beta-blockers, is not well known. Methods We retrospectively investigated the records of all patients hospitalized at our institution for drug-related bradycardia from the years 2004 to 2012. Patients with cardiac disease and electrolytic or hormonal abnormalities that could cause bradyarrhythmias were excluded. Results Eight patients were identified (mean age, 79±5 years; range, 71–85 years; 6 women). Three patients were taking only beta-blockers (hereafter referred to as the BB group), while five patients were on both beta-blockers and Na channel blockers (hereafter referred to as the BB + Na group). Heart rates ranged from 20∼49 beats/minute on arrival. The initial electrocardiogram showed sinus bradycardia (n=6) or sinus arrest with escape beats (n=2). QRS duration was 80–100 ms. The clinical presentation of the BB + Na group was considerably worse than that of the BB group, and included cardiogenic shock and heart failure. Four of the BB + Na patients had been on their medications for over 300 days. The BB group recovered solely with drug discontinuation, while 4 of the 5 patients in the BB + Na group needed additional treatments, such as intravenous administration of atropine or adrenergic agonist and temporary pacing. Bradycardia did not recur during follow-up (median, 687 days). Conclusion Although wide QRS ventricular tachyarrhythmia is a better known proarrhythmic effect of Na channel blockers, life-threatening bradycardia may also occur in combination with beta-blockers in the elderly, even months after the start of medication, and at plasma concentrations that do not prolong QRS width.

High Atrial Defibrillation Threshold With Internal Cardioversion Indicates Arrhythmogenicity of Superior Vena Cava in Non-Long-Standing Persistent Atrial Fibrillation.

BACKGROUND The purpose of this study was to clarify the relation between atrial defibrillation threshold (ADFT) for internal cardioversion (IC) and arrhythmogenicity of the superior vena cava (SVC). METHODS AND RESULTS A total of 159 consecutive patients (139 male, age 59.9±10.3 years) who underwent radiofrequency catheter ablation of atrial fibrillation (AF) were assessed. IC was performed in 50 patients with non-long-standing persistent AF (non-LSAF) with a purpose-built cardioversion catheter in which direct current is delivered between the right atrium and the coronary sinus. SVC arrhythmogenicity was defined as SVC firing initiating AF, SVC associated with maintenance of AF, or frequent ectopy in the SVC. In all 50 non-LSAF patients, AF termination was obtained on IC during the procedure except in 1 patient with SVC AF. In the patients with ADFT >10 J (n=10), SVC arrhythmogenicity was observed more often than in those with ADFT ≤10 J (n=40; 60% vs. 13%; P=0.004). There were no significant differences between the 2 groups in left atrial diameter (40.8±7.6 vs. 40.6±6.3 mm; P=0.92), persistent AF (33% vs. 50%; P=0.46), or other clinical parameters. The patients who underwent SVC isolation, however, had higher ADFT before SVC isolation than those who did not (15.5±8.8 vs. 9.2±4.4 J; P=0.01). CONCLUSIONS High IC ADFT is associated with SVC arrhythmogenicity in non-LSAF patients.

Usefulness of Implantable Cardioverter-Defibrillators in Patients with Coronary Spasm and Inducible Ventricular Arrhythmia

Background: Coronary artery spasm is one of causes of life-threatening ventricular arrhythmia and sudden cardiac death, but indication of implantable cardioverter-defibrillators (ICDs) is controversial. Our aim is to reveal the clinical features and long term prognosis of vasospastic angina patients with ventricular arrhythmia. Methods: We investigated retrospectively 31 survivors of cardiac arrest with implantation of ICDs. All patients underwent coronary angiography, and without ischemic findings we performed acetylcholine provocation test and electrophysiological study. Results: In 5 patients (56.6±15.7 years old, 5 males) multi-vessel spasm was induced by acetylcholine injection, and in 4 patients of them ventricular fibrillation were inducted by right ventricular 3 extrastimuli, and in 1 patient ventricular tachycardia was inducted by right ventricular 2 extrastimuli. All patients were treated with calcium channel blocking agents, isosorbide and antiarrhythmic drug. During mean follow up of 37±16.9 months (between 25 to 66 months), 2 patients received appropriate ICD shocks to ventricular fibrillation respectively in 10 and 14 months after implantation. One patient had a saddle-back-type ECG abnormality, and in another patient ventricular tachycardia was easily induced by right ventricular 2 extrastimuli. Conclusion: In patients with coronary spasm and inducible ventricular arrhythmia ICDs is useful to prevent sudden cardiac death.