Background: Implanting a ventricular demand leadless pacemaker (VVI-LPM) for patients with non-atrial fibrillation (AF) bradyarrhythmias such as sick sinus syndrome (SSS) or high-grade (i.e., second-or third-degree) atrioventricular (AV) block is not recommended unless they have limited vascular access or a high infection risk; nevertheless, an unexpectedly high number of VVI-LPM implantations have been performed. This study investigated the clinical outcomes of these unusual uses. Methods and Results:This study retrospectively analyzed 193 patients who were newly implanted with a VVI-LPM or an atrioventricular synchronous transvenous pacemaker (DDD-TPM) for non-AF bradyarrhythmias at a high-volume center in Japan from September 2017 to September 2020. Propensity score-matching produced 2 comparable cohorts treated with a VVI-LPM or DDD-TPM (n=58 each). Each group had 20 (34%) patients with SSS and 38 (66%) patients with high-grade AV block. During a median follow up of 733 (interquartile range 395−997) days, there were no significant differences between the VVI-LPM and DDD-TPM groups regarding late device-related adverse events (0% vs. 4%, log-rank P=0.155), but the VVI-LPM group had a significantly increased readmission rate for heart failure (HF) (29% vs. 2%, log-rank P=0.001) and a tendency to have higher all-cause mortality (28% vs. 4%, log-rank P=0.059). Conclusions:The implantation of a VVI-LPM for non-AF bradyarrhythmias increased the incidence of HF-related rehospitalization at the mid-term follow up compared to the use of a DDD-TPM.

Background:The optimum cut-off value of premature atrial contraction (PAC) burden (CV-PACb) in 24-h Holter electrocardiography (24-h ECG) for predicting atrial fibrillation (AF) is debatable, with few validation data. Methods and Results:We retrospectively analyzed 61 patients already diagnosed with AF (AD-AF) and 147 patients never diagnosed with AF (ND-AF), aged ≥50 years, free of heart disease, and who had undergone 24-h ECG and transthoracic echocardiography (TTE). Receiver operating characteristic analysis demonstrated that 0.4% was the optimal CV-PACb differentiating AD-AF from ND-AF, with 69% sensitivity and 72% specificity (area under the curve [AUC] 0.72; 95% confidence interval [CI] 0.65-0.79); however, the left atrial volume index was not significant (AUC 0.60; 95% CI 0.51-0.68). To verify the CV-PACb, new propensity-matched cohorts (i.e., subjects with a PAC burden ≥0.4% and <0.4%; n=69 in each group) were compared based on new detection of AF at a median follow-up of 50 months (interquartile range 12-60 months) Multivariable Cox regression analysis revealed that among 24-h ECG and TTE findings, only PAC burden ≥0.4% was independently associated with incident AF (hazard ratio 5.28; 95% CI 1.28-26.11; P=0.023). Conclusions:A high PAC burden (≥0.4%) in 24-h ECG was a reliable indicator to identify undiagnosed AF, whereas TTE parameters did not show any predictive value.

Introduction: High shock impedance is associated with conversion failure among patients with subcutaneous implantable cardioverter defibrillators (S-ICD). Currently, there is no preoperative assessment method for predicting high shock impedance. This study aimed to examine the efficacy of chest computed tomography (CT) as a preoperative evaluation tool to assess the shock impedance of S-ICDs. Methods and Results: The amount of adipose tissue adjacent to the device and the anteroposterior diameter at the basal heart region were measured preoperatively using a chest CT. We examined the correlation between these measurements and shock impedance at the conversion test. We enrolled 43 patients with S-ICDs (age: 54±15 years, body mass index: 23±4 kg/m , PRAETORIAN score: 30–270 points, amount of adipose tissue 1250±716 cc), who underwent intraoperative conversion tests by inducing ventricular fibrillation, which was terminated with a 65 J shock. A strong concordance correlation coefficient was observed between the shock impedance and the amount of adipose tissue (r=0.616, p < 0.01) and anteroposterior diameter (r=0.645, p < 0.01). Moreover, these were identified as independent predictive factors of shock impedance (amount of adipose tissue: β=0.439, p = 0.009; anteroposterior diameter: β=0.344, p = 0.038) in the stepwise multiple regression analysis. Conclusions: Preoperative CT-measured amount of adipose tissue and basal heart anteroposterior diameter are independent predictors of shock impedance. These may provide better accuracy in identifying high shock impedance in patients with S-ICDs.

Ventricular-demand leadless pacemakers (VVI-LPMs) have often been used as an alternative to atrioventricular (AV) synchronous transvenous pacemakers (DDD-TPMs) in patients with high-grade AV block following transcatheter aortic valve replacement (TAVR). However, the clinical outcomes of this unusual usage are not elucidated. Patients who received permanent pacemakers (PPMs) owing to new-onset high-grade AV block after TAVR from September 2017 to August 2020 at a high-volume center in Japan were included in the analysis, and the clinical courses of VVI-LPM and DDD-TPM implants through 2 years of follow-up were compared retrospectively. Out of 413 consecutive patients who underwent TAVR, 51 (12%) patients received a PPM. After excluding 8 patients with chronic atrial fibrillation (AF), 3 with sick sinus syndrome, and 1 with incomplete data, 17 VVI-LPMs and 22 DDD-TPMs were included in our final cohort. The VVI-LPM group had lower serum albumin levels (3.2 ± 0.5 vs. 3.9 ± 0.4 g/dL, P < .01) than the DDD-TPM group. Follow-up revealed no significant differences between the 2 groups in terms of the incidence of late device-related adverse events (0% vs. 5%, log-rank P = .38) and new-onset AF (6% vs. 9%, log-rank P = .75); however, there were increases in the rates of all-cause death (41% vs. 5%, log-rank P < .01) and heart failure rehospitalization (24% vs. 0%, log-rank P = .01) in the VVI-LPM group. This small retrospective study reveals favorable post-procedural complication rates but higher all-cause mortality with VVI-LPM compared to DDD-TPM therapy for high-grade AV block after TAVR at 2 years of follow-up.

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