Mahito Noro

Assessment of Noninvasive Markers in Identifying Patients at Risk in the Brugada Syndrome: Insight Into Risk Stratification

OBJECTIVES The aim of this study was to compare the use of various noninvasive markers for detecting risk of life-threatening arrhythmic events in patients with Brugada syndrome. BACKGROUND The role of conduction disturbance in arrhythmogenesis of the syndrome is controversial, whereas it is well established that repolarization abnormalities are responsible for arrhythmias. The value of noninvasive markers reflecting conduction or repolarization abnormalities in identifying patients at risk for significant arrhythmias has not been shown. METHODS We assessed late potentials (LP) using signal-averaged electrocardiography (ECG), microvolt T-wave alternans (TWA), and corrected QT-interval dispersion (QTD) in 44 consecutive patients who had ECGs showing a pattern of right bundle branch block and ST-segment elevation in leads V1 to V3 but structurally normal hearts. The patients were compared with 30 normal individuals. RESULTS Eleven patients were excluded from data analysis because of an absence of ECG manifestations of Brugada syndrome at the time of the tests. A history of life-threatening events defined as syncope and aborted sudden death was present in 19 of 33 patients (58%); in 15 of the 19 patients, stimulation induced ventricular fibrillation or polymorphic ventricular tachycardia. The LP were present in 24 of 33 patients (73%); TWA were present in 5 of 31 patients (16%); and a QTD >50 ms was present in 9 of 33 patients (27%). The incidence of LP in Brugada patients was significantly (p < 0.0001) higher than in the controls, whereas incidences of TWA and QTD were not significantly different. Multivariate logistic regression analysis revealed that the presence of LP had the most significant correlation to the occurrence of life-threatening events (p = 0.006). CONCLUSIONS Late potentials are a noninvasive risk stratifier in patients with Brugada syndrome. These results may support the idea that conduction disturbance per se is arrhythmogenic.

Combined assessment of T-wave alternans and late potentials used to predict arrhythmic events after myocardial infarction ☆: A prospective study

OBJECTIVES The aim of the present study was to determine whether the combination of two markers that reflect depolarization and repolarization abnormalities can predict future arrhythmic events after acute myocardial infarction (MI). BACKGROUND Although various noninvasive markers have been used to predict arrhythmic events after MI, the positive predictive value of the markers remains low. METHODS We prospectively assessed T-wave alternans (TWA) and late potentials (LP) by signal-averaged electrocardiogram (ECG) and ejection fraction (EF) in 102 patients with successful determination results after acute MI. The TWA was analyzed using the power-spectral method during supine bicycle exercise testing. No antiarrhythmic drugs were used during the follow-up period. The study end point was the documentation of ventricular arrhythmias. RESULTS The TWA was present in 50 patients (49%), LP present in 21 patients (21%), and an EF <40% in 28 patients (27%). During a follow-up period of 13 +/- 6 months, symptomatic, sustained ventricular tachycardia or ventricular fibrillation occurred in 15 patients (15%). The event rates were significantly higher in patients with TWA, LP, or an abnormal EF. The sensitivity and the negative predictive value of TWA in predicting arrhythmic events were very high (93% and 98%, respectively), whereas its positive predictive value (28%) was lower than those for LP and EF. The highest positive predictive value (50%) was obtained when TWA and LP were combined. CONCLUSIONS The combined assessment of TWA and LP was associated with a high positive predictive value for an arrhythmic event after acute MI. Therefore, it could be a useful index to identify patients at high risk of arrhythmic events.

Predicting the recurrence of ventricular tachyarrhythmias from T-wave alternans assessed on antiarrhythmic pharmacotherapy : A prospective study in patients with dilated cardiomyopathy

Background: Microvolt T‐wave alternans (TWA) has been proposed as a useful index to identify patients at risk of ventricular tachyarrhythmias. Recent studies have demonstrated that antiarrhythmic drugs, such as amiodarone and procainamide, decrease the prevalence of TWA. In this study, we tested whether TWA in patients on antiarrhythmic pharmacotherapy significantly predicts the recurrence of ventricular tachyarrhythmias in patients with dilated cardiomyopathy.

Left Axillary Pacemaker Generator Implantation with a Direct Puncture of the Left Axillary Vein

Pacemaker generators are routinely implanted in the anterior chest. However, where to place the generator may need to be considered from the mental, functional, and cosmetic standpoints.

Efficacy and Myocardial Injury With Subcutaneous Implantable Cardioverter Defibrillators – Computer Simulation of Defibrillation Shock Conduction –

BACKGROUND Subcutaneous implantable cardiac defibrillator (S-ICD) systems have a lower invasiveness than traditional ICD systems, and expand the indications of ICD implantations. The S-ICD standard defibrillation shock output energy, however, is approximately 4 times that of the traditional ICD system. This raises concern about the efficacy of the defibrillation and myocardial injury. In this study, we investigated the defibrillation efficacy and myocardial injury with S-ICD systems based on computer simulations. METHODS AND RESULTS First, computer simulations were performed based on the S-ICD system configurations proposed in a previous study. Furthermore, simulations were performed by placing the lead at the left or right parasternal margin and the pulse generator in the superior and inferior positions (0-10 cm) of the recommended site. The simulated defibrillation threshold (DFT) for the 4 S-ICD system configurations were 30.1, 41.6, 40.6, and 32.8 J, which were generally similar to the corresponding clinical results of 33.5, 40.4, 40.1, and 34.3 J. CONCLUSIONS The simulated DFT were generally similar to their clinical counterparts. In the simulation, the S-ICD system had a higher DFT but relatively less severe myocardial injury compared with the traditional ICD system. Further, the lead at the right parasternal margin may correspond to a lower DFT and cause less myocardial injury.

Outcomes of Brugada Syndrome Patients with Coronary Artery Vasospasm

Objective To evaluate the outcomes of patients with concomitant Brugada syndrome and coronary artery vasospasm. Methods Patients diagnosed with Brugada syndrome with an implantable cardiac defibrillator were retrospectively investigated, and the coexistence of vasospasm was evaluated. The clinical features and outcomes were evaluated, especially in patients with coexistent vasospasm. A provocation test using acetylcholine was performed in patients confirmed to have no organic stenosis on percutaneous coronary angiography to confirm the presence of vasospasm. Implantable cardiac defibrillator shock status was checked every three months. Statistical comparisons of the groups with and without vasospasm were performed. A univariate analysis was also performed, and the odds ratio for the risk of implantable cardiac defibrillator shock was calculated. Patients Thirty-five patients with Brugada syndrome, of whom six had coexistent vasospasm. Results There were no significant differences in the laboratory data, echocardiogram findings, disease, or the history of taking any drugs between patients with and without vasospasm. There were significant differences in the clinical features of Brugada syndrome, i.e. cardiac events such as resuscitation from ventricular fibrillation or appropriate implantable cardiac defibrillator shock. Four patients with vasospasm had cardiac events such as resuscitation from ventricular fibrillation and/or appropriate defibrillator shock; three of them had no cardiac events with calcium channel blocker therapy to prevent vasospasm. The coexistence of vasospasm was a potential risk factor for an appropriate implantable cardiac defibrillator shock (odds ratio: 13.5, confidence interval: 1.572-115.940, p value: 0.035) on a univariate analysis. Conclusion Coronary artery vasospasm could be a risk factor for cardiac events in patients with Brugada syndrome.

The Efficacy and Safety of Oral Rivaroxaban in Patients with Non-Valvular Atrial Fibrillation Scheduled for Electrical Cardioversion.

Objective Electrical cardioversion (EC) is associated with an increased risk of thrombotic events in patients with non-valvular atrial fibrillation (NVAF). Patients who experience AF for a period of >48 hours therefore require adequate anticoagulation therapy for at least 3 weeks before and 4 weeks after EC. While the guidelines address the management of vitamin K antagonists (VKAs), there are limited data on the use of novel oral anticoagulants (NOAC). One NOAC, rivaroxaban, has a rapid onset of action and might therefore shorten the time for which anti-coagulant treatment is required before a patient undergoes EC. Methods This study included 91 patients with NVAF of >48 hours in duration or in whom the time of onset was unknown who were undergoing EC after pretreatment with rivaroxaban. All of the patients were pretreated with rivaroxaban for at least 2 hours before EC and the same dose of rivaroxaban was prescribed for 4 weeks after EC. The primary endpoint was a successful EC without any thrombotic events or bleeding complications within 30 days after EC. The secondary endpoint was the time to EC. Results The mean age was 63±12 years and 70 of the 91 patients were male. The CHADS2 and HAS-BLED scores were 1.0±1.0 and 1.7±1.3, respectively. Although there were no thrombotic events, minor bleeding (gingival hemorrhage) occurred 20 days after the initiation of rivaroxaban treatment in one patient. The average time to EC was 11.9±11.1 days. Conclusion Rivaroxaban is safe and effective drug for NVAF patients who are scheduled for an EC. Furthermore, since VKAs take a substantial amount of time to establish adequate anticoagulation, pretreatment with rivaroxaban could shorten the time to the EC.

Decreased Defibrillation Threshold and Minimized Myocardial Damage With Left Axilla Implantable Cardioverter Defibrillator Implantation

BACKGROUND To reduce myocardial damage caused by implantable cardioverter defibrillator (ICD) shock, the left axilla was studied as an alternative pulse generator implantation site, and compared with the traditional implantation site, the left anterior chest. METHODSANDRESULTS Computer simulation was used to study the defibrillation conduction pattern and estimate the simulated defibrillation threshold (DFT) and myocardial damage when pulse generators were placed in the left axilla and left anterior chest, respectively; pulse generators were also newly implanted in the left axilla (n=30) and anterior chest (n=40) to compare the corresponding DFT. On simulation, when ICD generators were implanted in the left axilla, compared with the left anterior chest, the whole heart may be defibrillated with a lower defibrillation energy (left axilla 6.4 J vs. left anterior chest 12.0 J) and thus the proportion of cardiac myocardial damage may be reduced (2.1 vs. 4.2%). Clinically, ventricular fibrillation was successfully terminated with a defibrillation output ≤5 J in 86.7% (26/30) of the left axillary group, and in 27.5% (11/40) of the left anterior group (P<0.001). CONCLUSIONS Clinically and theoretically, the left axilla was shown to be an improved ICD implantation site that may reduce DFT and lessen myocardial damage due to shock. Lower DFT also facilitates less myocardial damage, as a result of the lower shock required.

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.

The clinical course of symptomatic deep vein thrombosis after 3 months of anticoagulant therapy using fondaparinux/edoxaban or fondaparinux/vitamin K antagonist

Background For the management of venous thromboembolism (VTE), providing anticoagulant therapy within the therapeutic range has been a major challenge, as conventional therapy with unfractionated heparin (UFH) and vitamin K antagonist (VKA) requires frequent laboratory monitoring and dose adjustment. Recently, fondaparinux and edoxaban are being used as beneficial alternatives to UFH and VKA. Methods We evaluated the clinical course of symptomatic deep vein thrombosis (DVT) in patients who received the 3-month anticoagulation therapy with fondaparinux/edoxaban (Group A; n=40) in comparison with the findings from our previous experience of patients who received the fondaparinux/VKA combination (Group B; n=33). Results In both Groups A and B, serum D-dimer was significantly improved after treatment (p<0.001). The thrombus volume assessed by quantitative ultrasound thrombosis (QUT) score was significantly reduced in both groups (p<0.001). There was no difference in the proportion of patients who were normalized (ie, disappearance of DVT) between the groups, although Group A had significantly more patients who were normalized or improved (ie, disappearance and reduction of DVT) (p<0.001). No bleeding event was observed in either group. However, in one patient in Group B, worsening of DVT and development of symptomatic PE were observed. Conclusion Fondaparinux/edoxaban therapy is as effective as fondaparinux/VKA. This treatment has the possible advantage in thrombus regression. This would be a beneficial therapeutic option for both patients and physicians.