Safety and Efficacy of Subcutaneous Cardioverter Defibrillator in Patients at High Risk of Sudden Cardiac Death　- Primary Japanese Experience.

BACKGROUND: The entirely subcutaneous implantable cardioverter defibrillator (S-ICD) was introduced as a new alternative to conventional transvenous ICD (TV-ICD) in Japan in February 2016, but its safety and efficacy are unclear.Methods and Results:A total of 60 patients (48 men, median age, 60 years; IQR, 44-67 years; primary prevention, n=24) underwent S-ICD implantation between February 2016 and August 2017. The device pocket was formed in the intermuscular space between the serratus anterior muscle and the latissimus dorsi muscle, and the parasternal S-ICD lead was placed according to pre-implant screening. Defibrillation test was performed in 56 patients (93%). Ventricular fibrillation (VF) was induced in 55 patients and terminated by a single 65-J shock in all patients. The median time to shock therapy was 13.4 s (IQR, 12.1-14.9 s) and the median post-shock impedance of the S-ICD lead was 64 Ω (IQR, 58-77 Ω). There were no operation-related complications or subsequent infectious complications. During follow-up (median, 275 days; IQR, 107-421 days), 1 patient (1.7%) had appropriate shock for VF with successful termination, whereas 5 patients (8.3%) had inappropriate shock due to oversensing of myopotential (n=3) or T-wave (n=1), and detection of supraventricular tachycardia (n=1). CONCLUSIONS: S-ICD is a safe and effective alternative to conventional TV-ICD. The long-term safety and efficacy of the S-ICD need further investigation.

Long Postpacing Interval After Entrainment of Tachycardia Including a Slow Conduction Zone Within the Circuit.

BACKGROUNDS: Postpacing interval (PPI) measured after entrainment pacing describes the distance between pacing site and reentrant circuit. However, the influential features to PPI remain to be elucidated. METHODS AND RESULTS: This study included 22 cases with slow/fast atrioventricular (AV) nodal reentrant tachycardia (AVNRT), 14 orthodromic AV reciprocating tachycardia (AVRT) using an accessary pathway, 22 typical atrial flutter (AFL), and 18 other macroreentrant atrial tachycardia (atypical AFL). Rapid pacing at a pacing cycle length (PCL) 5% shorter than tachycardia cycle length (TCL) was done from a site on or close to the reentry circuit. Pacing sites included the coronary sinus ostium in AVNRT, earliest atrial activation site in AVRT, and cavotricuspid isthmus in typical AFL. In atypical AFL, tachycardia circuit was determined on the basis of CARTO mapping, and then the pacing site was. TCL was significantly longer in AVNRT and AVRT than in typical AFL and atypical AFL (both P < 0.05). PCL minus TCL value was similar among the 4 groups. PPI minus TCL value (milliseconds) was significantly longer in AVNRT (median, 40 [IQR, 29-60.8]) and AVRT (34 [20-47]) than in typical AFL (0 [0-4]) and atypical AFL (3.5 [0-8]) (both P < 0.05). Furthermore, PPI minus TCL was prolonged with shortening of PCL in AVNRT and AVRT (both P < 0.05), whereas it was unchanged in typical AFL (P = 0.50). CONCLUSION: PPI after concealed entrainment is prolonged compared with TCL when the reentry circuit involves a slow conduction zone with a decremental conduction property such as the AV node.

Impact of Sex Difference on Severity and Functional Outcome in Patients with Cardioembolic Stroke.

INTRODUCTION: Female sex is a risk factor for thromboembolic events in Caucasian, but not in Japanese, patients with nonvalvular atrial fibrillation. However, it remains unclear whether the female sex is also a risk factor for severe stroke and unfavorable functional outcome in patients with cardioembolic (CE) stroke. METHODS: Three hundred fifty-five consecutive patients with CE stroke within 48 hours after onset and with a modified Rankin Scale (mRS) score of 1 or lower before onset were studied. We compared basic characteristics, stroke severity, and functional outcome between female (n = 157) and male (n = 198) patients. RESULTS: The mean age was higher in female than in male patients (80 ± 8 versus 75 ± 9 years, P < .00001). The congestive heart failure, hypertension, age [≥ 75 years], diabetes, stroke/transient ischemic attack [TIA] (CHADS2) score before onset was similar between the two groups (median, 3 [2-4] in both groups). Stroke severity on admission, assessed by the National Institutes of Health Stroke Scale (NIHSS), was higher in female than in male patients (13 [5-20] versus 8 [3-16], P = .0009). Functional outcome at discharge, assessed by mRS, was unfavorable in female than in male patients (3 [1-5] versus 2 [1-4], P = .005). An mRS score of 3 or higher at discharge was found more in female than in male patients (59% versus 39%, P = .0001). Multivariate analyses confirmed that female sex was a significant determinant of severe stroke (NIHSS ≥ 8) on admission (odds ratio [OR] to male = 1.97; 95% confidence interval [CI]; 1.24-3.15, P = .004) and for the mRS score of 3 or higher at discharge (OR = 1.83; 95% CI, 1.16-2.89; P = .01). Similar results were obtained by propensity-score matching analysis. CONCLUSIONS: Female sex is a risk factor for severe stroke on admission and unfavorable functional outcome at discharge in Japanese patients with CE stroke.

A novel screening test for inappropriate shocks due to myopotentials from the subcutaneous implantable cardioverter-defibrillator.

BACKGROUND: The subcutaneous implantable cardioverter-defibrillator (S-ICD) is effective in preventing sudden cardiac death. Compared with transvenous ICDs, S-ICDs have a lower rate of inappropriate shocks (IASs) for supraventricular arrhythmias, but such shocks for T-wave oversensing (TWO) and extracardiac myopotentials are more common. No screening tests to identify patients at risk for IAS due to myopotential interference (MPI) currently are available. OBJECTIVE: The purpose of this study was to assess the efficacy of a tube exercise test (TET) developed to detect MPI post S-ICD implantation. METHODS: TET includes 3 different maneuvers using an exercise tube. S-ICD electrograms were recorded to assess MPI while patients performed each of the maneuvers. RESULTS: TET was performed in 43 patients, and MPI was observed in 12 patients (28%). In 10 of the 12 TET-positive patients, the positive vector corresponded with a vector that did not show TWO on standard S-ICD preoperative screening. During median follow-up of 672 days (interquartile range 465-805 days), 3 patients (7%) experienced IAS due to MPI. Importantly, the vector at the time of IAS in all 3 patients passed standard preoperative screening for TWO but was positive with TET. Sensitivity and specificity of TET were 100% and 78%, respectively, and positive and negative predictive values were 25% and 100%, respectively. CONCLUSION: Postimplant screening for MPI identified patients at increased risk for IAS. TET may be helpful for guiding optimal programming to prevent IAS.

Study of flow fractionation characteristics of magnetic chromatography utilizing high-temperature superconducting bulk magnet.

We present numerical simulation of separating magnetic particles with different magnetic susceptibilities by magnetic chromatography using a high-temperature superconducting bulk magnet. The transient transport is numerically simulated for two kinds of particles having different magnetic susceptibilities. The time evolutions were calculated for the particle concentration in the narrow channel of the spiral arrangement placed in the magnetic field. The field is produced by the highly magnetized high-temperature superconducting bulk magnet. The numerical results show the flow velocity difference of the particle transport corresponding to the difference in the magnetic susceptibility, as well as the possible separation of paramagnetic particles of 20 nm diameter.

Safety and efficacy of contemporary catheter ablation for atrial fibrillation patients with a history of cardioembolic stroke in the era of direct oral anticoagulants.

BACKGROUND: The safety and efficacy of the contemporary atrial fibrillation (AF) ablation in patients with a recent or previous history of cardioembolic stroke (CS) or transient ischemic attack (TIA) remain to be established. METHODS: A total of 447 patients who underwent first-ever contact force (CF)-guided AF ablation with circumferential pulmonary vein isolation were included. Of these, 17 had CS or TIA within 6 months before ablation (Group 1), 30 more than 6 months before ablation (Group 2), and the other 400 without CS or TIA (Group 3). Procedural complications and recurrence of AF and atrial tachyarrhythmias were compared among the 3 groups. RESULTS: The mean age was 71±7, 66±9, and 61±11 years in Groups 1, 2, and 3, respectively (p<0.05, Group 1 versus Group 3). The oral anticoagulants were warfarin (n=108, 24.1%), dabigatran (n=101, 22.6%), rivaroxaban (n=147, 32.9%), apixaban (n=87, 19.5%), and edoxaban (n=4, 0.9%), and did not differ among the 3 groups. Median follow-up period was 14 [IQR 12-22], 13 [12-14], and 12 [10-16] months, respectively. One episode of cardiac tamponade, 2 episodes of arteriovenous fistula, and some minor complications occurred in Group 3, but no complications occurred in Groups 1 and 2 in the periprocedural period. Although one episode of CS occurred 11 days after the procedure in Group 3, there were no periprocedural CS, TIA, or major bleedings in Groups 1 and 2. AF recurrence-free rate after the procedure was 76.5%, 86.7%, and 79.1% in Groups 1, 2, and 3, respectively, and there was no difference in Kaplan-Meier curves among the 3 groups. CONCLUSION: The safety and efficacy of CF-guided AF ablation in the era of direct oral anticoagulants in patients with a recent or previous history of CS or TIA are similar to those in patients without it.

Potential roles of the wearable cardioverter-defibrillator in acute phase care of patients at high risk of sudden cardiac death: A single-center Japanese experience.

BACKGROUND: The wearable cardioverter-defibrillator (WCD) has been expected to play a role as an effective bridge therapy to implantable cardioverter-defibrillator (ICD) implantation in patients at high risk of ventricular tachyarrhythmias (VA). Although WCD has been available since April 2014 in Japan, its usefulness remains unclear. METHODS AND RESULTS: During the early period after hospitalization, patients at high risk of VA after excluding some elderly patients were prescribed WCD. The consecutive 50 patients with WCD use (median age 56 years, 38 for secondary prevention) were studied. We analyzed clinical efficacy and safety of WCD, and examined its potential roles. Of the 50 patients, 38 used WCD only during hospitalization. During WCD use [median 16 (IQR 8-33) days], all patients wore WCD for 98% of a day regardless of in or out-of-hospital use. Sustained VA was detected in 4 patients (8%; for primary prevention in 1) with 7 episodes, and 6 of 7 episodes required shock therapy. Of the 6 shock therapies, 4 were for sustained ventricular tachycardia with the median rate of 236beats/min (IQR 203-250), and the other 2 for ventricular fibrillation. Subsequently, only 27 patients (54%) of all underwent ICD implantation following the WCD use, because of reduced risk of VA after optimal pharmacological therapy or improvement in the left ventricular function. CONCLUSIONS: The WCD use for the acute phase care of patients at high risk of VA can be safe and effective, and may be useful for evaluating indication of ICD implantation.