Yoshifumi Okano

Comparison of late potentials for 24 hours between Brugada syndrome and arrhythmogenic right ventricular cardiomyopathy using a novel signal-averaging system based on Holter ECG.

Background— Late potentials (LP) detected with signal-averaged ECGs are known to be useful in identifying patients at risk of Brugada syndrome (BS) and arrhythmogenic right ventricular cardiomyopathy (ARVC). Because the pathophysiology is clearly different between these disorders, we clarified the LP characteristics of these disorders. Methods and Results— This study included 15 BS and 12 ARVC patients and 20 healthy controls. All BS patients had characteristic ECG changes and symptomatic episodes. All ARVC patients had findings that were consistent with recent criteria. Three LP parameters (filtered QRS duration, root mean square voltage of the terminal 40 ms of the filtered QRS complex, and duration of low-amplitude signals [<40 µV] in the terminal, filtered QRS complex) were continuously measured for 24 hours using a novel Holter-based signal-averaged ECG system. The incidences of LP determination in BS (80%) and ARVC (91%) patients were higher than in healthy controls (5%; P<0.0001 in both) but did not differ between BS and ARVC patients. In BS patients, the dynamic changes of all LP parameters were observed, and they were pronounced at nighttime. On the contrary, these findings were not observed in ARVC patients. When the SD values of the 3 LP parameters (filtered QRS duration, root mean square voltage of the terminal 40 ms of the filtered QRS complex, and duration of low-amplitude signals [<40 µV] in the terminal, filtered QRS complex) over 24 hours were compared for the 2 patient groups, those values in BS patients were significantly greater than those in ARVC patients (P<0.0001 in all). Conclusions— LP characteristics detected by the Holter-based signal-averaged ECG system over 24 hours differ between BS and ARVC patients. Dynamic daily variations of LPs were seen only in BS patients. This may imply that mechanisms of lethal ventricular arrhythmia in BS may be more correlated with autonomic abnormality than that of ARVC.

Defibrillation Effects of Intravenous Nifekalant in Patients with Out‐of‐Hospital Ventricular Fibrillation

Nifekalant (NF), a pure K+ channel blocker developed in Japan, has been reported to be effective in the treatment of life‐threatening ventricular arrhythmias. We studied its efficacy in 18 men and 4 women with out‐of‐hospital ventricular fibrillation (VF) admitted to our emergency department between August 2001 and March 2004. The number of DC shocks delivered for out‐of‐hospital VF, serum Na+ and K+, arterial blood pH, and base excess were compared in 8 patients treated with NF, 0.3 mg/kg i.v. followed by a continuous intravenous (group N) versus 14 patients treated with lidocaine, 2 mg/kg, i.v. (group C). The two groups were similar with respect to their baseline characteristics. Sinus rhythm returned in 5 of 8 patients in group N versus 2 of 14 patients in group C (P < 0.05). These seven patients were admitted to the intensive care unit, though all died within 1 month. The results of this study suggest that NF may be effective in defibrillation of out‐of‐hospital VF, though controlled studies are needed to confirm our observations.

The radio frequency catheter ablation of inter-fascicular reentrant tachycardia: new insights into the electrophysiological and anatomical characteristics.

IntroductionMacro-reentrant ventricular tachycardias (VT) utilizing the bundle branches and Purkinje fibers have been reported as verapamil sensitive VT (idiopathic left VT), bundle branch reentrant VT (BBRT) and inter-fascicular reentrant tachycardia (inter-fascicular VT). However, diagnostic confusion exists with these VTs due to the difficulty in differentiating between them with conventional electrophysiological (EP) studies. The aim of this study was to clarify the EP and anatomical entity of inter-fascicular VT, and provide successful methods for the radio frequency catheter ablation (RFCA) of inter-fascicular VT.Methods and resultsA total of nine patients were included in this study. All patients were diagnosed with idiopathic left VT in the first session, and underwent a second session after a failed RFCA. Detailed EP studies guided by a three-dimensional (3D) mapping system were performed to further analyze the VTs.All VTs were finally diagnosed as inter-fascicular VT. They were successfully cured with RFCA targeting the left anterior or posterior fascicle, which was regarded as a requisite part of the reentrant circuit of the inter-fascicular VT, using 3D and fluoroscopic images combined with a detailed EP investigation instead of the conventional RFCA method targeting Purkinje potentials for the RFCA of idiopathic left VT.ConclusionsInter-fascicular VT could be misdiagnosed as idiopathic left VT due to the limitations of the conventional EP study. Failed RFCA in presumptive idiopathic left VT cases has to be carefully investigated by further analysis, and a tailored RFCA strategy targeting the requisite portions of the left fascicles in the inter-fascicular VT reentrant circuit will be required for the successful elimination of the inter-fascicular VT.

Successful Radiofrequency Catheter Ablation of Nonreentrant Supraventricular Tachycardia Due to Simultaneous Conduction Through Dual Atrioventricular Nodal Pathways

Objectives We evaluated whether pacing algorithms (PA) triggered by onset mechanism (OM) of atrial fibrillation (AF) were actually effective. Methods Ten patients (5males, mean age 67.5+/−7.3years) who received Vitatrons Selection pacemaker with >1 AF during 3months after implantation were included. PA were turned off (phase OFF), selectively turned on based on OM of AF (phase ON), and turned on based on all 4 PA (phase ALL-ON) for 3months by crossover method. We compared atrial pacing dependency (%pacing), number of AF, cumulative AF duration, and number of PAC between each setting. The effect of %pacing on AF was evaluated. Result %pacing was greater during phases ON and ALL-ON (phases OFF: 55.6+/−34.7%, ON: 84.2+/−19.7%, ALL-ON: 90.1+/−14.7%, p=0.0004). Number of AF (229.6+/−381.1, 152.8+/−226.5, 318.3+/−577.7, NS), cumulative AF duration (8240+/−12308min, 4013.1+/−8290.5min, 8656.4+/−18071.2min, NS) and number of PAC (88705.6+/−150316.5, 41525.4+/−48130, 139285.1+/−215336.9, NS) were minimized during phase ON. Number of AF negatively correlated with %pacing (r=−0.457, p=0.01). Conclusions PA decreased AF when those were selectively turned on. Higher %pacing was effective to decrease AF regardless of PA. Carefully chosen PA maximizing %pacing will be effective for AF suppression.

Evaluation of defibrillation safety and shock reduction in implantable cardioverter-defibrillator patients with increased time to detection: A randomized SANKS study

The need for ways to minimize the number of implantable cardioverter‐defibrillator (ICD) shocks is increasing owing to the risk of its adverse effects on life expectancy. Studies have shown that a longer detection time for ventricular tachyarrhythmia reduces the safety of therapies, in terms of syncope and mortality, but not substantially in terms of the success rate. We aimed to evaluate the effects of increased number of intervals to detect (NID) VF on the safety of ICD shock therapy and on the reduction of inappropriate shocks.

Fontan conversion with novel direct ablation after childbirth: Report of a case

A 38-year-old woman underwent atriopulmonary Fontan surgery at age 18 years and subsequently successfully delivered a girl by cesarean section at age 34. Her condition later deteriorated due to atrial tachyarrhythmia and progressed to New York Heart Association (NYHA) class IV heart failure. Her treatment, at age 36, comprised total cavopulmonary connection conversion, direct right atrial ablation with bipolar radiofrequency devices, the creation of an atrial septal defect, and placement of a dual-chamber permanent pacemaker. Three years after the conversion, her condition has improved to NYHA class I.

3-D mapping of Left Atrial Conduction Pattern

The purpose of this study is to examine a normal conduction pathway of the left atrium. During pulmonary vein isolation using a three‐dimensional mapping system, we observed the characteristics of the conduction pattern. Subjects consisted of 15 patients with paroxysmal atrial fibrillation (mean age, 62.8 ± 8.4 years). Left atrial activation conduction begins in the interatrial septum, and moves toward the peak of the ridge between the left atrial appendage and left pulmonary vein. In coronary sinus or appendage pacing, conduction was in the opposite direction at the same location. The mean conduction velocity in this area was 2.03 ± 0.43 m/s. Features of decrement conduction were not present. Anatomical position of the appendage differed greatly between patients. A detailed observation using the inner‐cavity view of a three‐dimensional mapping system also showed that the peak of the ridge reached the center of the roof.

Prevalence and prognosis of patients with lone and paroxysmal atrial tachyarrhythmias showing Brugada-type electrocardiograms after class IC antiarrhythmic drug administration but no risk-stratifying factors

Class IC antiarrhythmic drugs, used to prevent paroxysmal atrial tachyarrhythmias (ATs), are well known to effectively unmask the electrocardiogram (ECG) pattern of Brugada syndrome. We used these drugs to investigate the prevalence and prognosis of patients with lone and paroxysmal ATs and Brugada‐type ECGs.

16. ICD: Defibrillation Threshold Testing & Other Issues

Purpose Electrical cardioversion for ventricular arrhythmias (VAs) contained of ventricular tachycardia (VT), ventricular fibrillation (VF) and torsades de pointes (TdP), was established to be effective for VAs. Little is known about which case should have an effect on chest thump version (TV) in patients with VAs. Method Subjects were 18 patients (Male: Female = 9:9, mean age 61±20 years old). TV was done for 28 episodes in VT, 8 episodes in VF, and 5 episodes in TdP. TV was performed after onset of symptoms within one minutes, and electrocardiogram (ECG) monitor was analyzed. Heart beats were averaged with 10 beats of VF and TdP. The time from Q wave to TV was measured from ECG monitoring in VT patients. Result TV successfully terminated VT in 12 of 28 episodes, VF in 1 of 8 episodes, and 1 of 5 episodes. TV terminated VT in the range between -20ms and +60ms. The mean cycle length of VT was 284±30ms, VF was 238±21ms, and TdP was 270±25ms, respectively. The mean cycle length of successful TV was significantly longer than that of failed TV in VT (358±57ms vs 289±59ms, p<0.01). There was no acceleration of VT in this study. Conclusion TV was available for slower VT at the timing in the range between -20ms and +60ms, and not for TdP and VF.

Efficacy of Chest Thump Version for Ventricular Arrhythmias

Purpose Electrical cardioversion for ventricular arrhythmias (VAs) contained of ventricular tachycardia (VT), ventricular fibrillation (VF) and torsades de pointes (TdP), was established to be effective for VAs. Little is known about which case should have an effect on chest thump version (TV) in patients with VAs. Method Subjects were 18 patients (Male: Female = 9:9, mean age 61±20 years old). TV was done for 28 episodes in VT, 8 episodes in VF, and 5 episodes in TdP. TV was performed after onset of symptoms within one minutes, and electrocardiogram (ECG) monitor was analyzed. Heart beats were averaged with 10 beats of VF and TdP. The time from Q wave to TV was measured from ECG monitoring in VT patients. Result TV successfully terminated VT in 12 of 28 episodes, VF in 1 of 8 episodes, and 1 of 5 episodes. TV terminated VT in the range between -20ms and +60ms. The mean cycle length of VT was 284±30ms, VF was 238±21ms, and TdP was 270±25ms, respectively. The mean cycle length of successful TV was significantly longer than that of failed TV in VT (358±57ms vs 289±59ms, p<0.01). There was no acceleration of VT in this study. Conclusion TV was available for slower VT at the timing in the range between -20ms and +60ms, and not for TdP and VF.