Hirad Yarmohammadi

Background: Accurate identification of macro-reentrant atrial tachycardia (AT) circuits is critical for successful ablation but remains challenging with conventional mapping techniques. The aim of this study was to automatically detect macro-reentrant AT loops from high-density local activation time (LAT) maps. Methods: We developed an algorithm for automated detection of macro-reentrant AT circuits using LAT-derived directed graphs. Compared to previous graph-based approaches, the algorithm is designed to identify the fastest-conducting reentrant pathways and cluster them by rotational orientation (clockwise vs. counterclockwise) to distinguish single- from dual-loop circuits. The algorithm was applied retrospectively to 60 macro-reentrant scar-related AT cases mapped with CARTO or Ensite from two institutions. The results were compared with blinded expert electrophysiologist annotations of loop location and single- vs. dual-loop classification. Results: The 60 cases included 16 right atrial and 44 left atrial ATs from 51 patients. Expert review identified 57% single-loop and 43% dual-loop circuits. Compared with expert annotation, the algorithm correctly identified anatomical loop locations with 88% accuracy and correctly distinguished single- vs. dual-loop ATs in 93% of cases. Conclusion: Our LAT graph-based algorithm automatically identified single- and dual-loop macro-reentrant AT circuits. Localizing these pathways may provide insight into circuit mechanisms and help guide ablation. CLINICAL PERSPECTIVE: What is Known: Accurate characterization of macro-reentrant atrial tachycardias (ATs) is essential for effective catheter ablation, yet identifying these circuits from local activation time (LAT) maps remains challenging and operator dependent. What the Study Adds: We developed and validated a graph-based algorithm that automatically identifies macro-reentrant AT circuits from LAT maps with high agreement compared to expert electrophysiologist annotation. The algorithm localizes reentrant loop pathways and distinguishes single- from dual-loop circuits. Localizing these pathways may provide insight into circuit mechanisms and help guide ablation.

Background: Conventional transvenous dual-chamber pacemakers may have deleterious effects on the left ventricle, such as pacing-induced cardiomyopathy for those with a high pacing burden. Although the effect of right ventricular (RV) pacing on left ventricular function has been well studied, its impact on RV remodelling and function is not well established. Methods: This systematic review and meta-analysis were constructed according to PRISMA guidelines. We searched Embase, PubMed and SCOPUS using MeSH terms, associated keywords and Boolean operators from inception to March 2024. Relevant studies reported on at least one component of RV function following RV pacing, including: change in RV ejection fraction (RVEF), pulmonary artery systolic pressure (sPAP), tricuspid annular plane systolic excursion (TAPSE), RV volume, tissue Doppler-derived tricuspid lateral annular systolic velocity (S′), 2D fractional area change (FAC), RV index of myocardial performance (RIMP) and tricuspid regurgitation. Results: In all, 18 studies, enrolling 1,220 patients, were examined to analyse the effect of RV pacing on RV echocardiographic parameters. The meta-analysis revealed that RV pacing influenced several echocardiographic parameters. RVEF showed a pooled mean difference of 2.28% (95% CI [−1.2818, 5.8385]; p=0.21), whereas TAPSE (−0.0444 cm; 95% CI [−0.1976, 0.1089]; p=0.57) and RIMP (−0.0714; 95% CI [−0.2888, 0.1459]; p=0.52) exhibited small, non-significant reductions in pooled mean difference. In contrast, S′ pooled mean difference decreased significantly (−1.3522 cm/s; 95% CI [−2.3647, −0.3396]; p=0.0089), but there were no significant changes in FAC% (−0.1208 %; 95% CI [−3.6630, 3.4215]; p=0.95) or sPAP (3.7282 mmHg; 95% CI [−6.0651, 13.5216]; p=0.46) pooled mean difference. Heterogeneity was high across all RV function parameters examined, with I² values exceeding 89%. Length of treatment was not significantly associated with changes in RVEF (p=0.21), TAPSE (p=0.53), S′ (p=0.22), or FAC% (p=0.68), but significantly influenced RIMP (p=0.01). Site of pacing significantly affected TAPSE (p=0.0198), S′ (p=0.0124), FAC% (p=0.0014) and sPAP (p=0.0006). Apical pacing was consistently associated with the worst outcomes across parameters, including the greatest negative impact on TAPSE, S′ and sPAP, whereas left bundle branch area pacing (LBBAP) generally showed better outcomes, including the least impact on sPAP. Conclusion: RV pacing is associated with significant reductions in S′ and notable effects on other echocardiographic parameters, with heterogeneity largely driven by the site of pacing. Apical pacing had the most detrimental effects across multiple parameters, whereas LBBAP was generally associated with better outcomes. Further studies are needed to address residual heterogeneity and examine additional covariates.