Background: Reliable reference annotation is critical for accurate activation mapping. Currently used referencing algorithms can be limited by suboptimal detection and stability performance. The advanced reference annotation (ARA) algorithm, a novel algorithm using a weighted reference across multiple electrodes, has been developed to optimize reference annotation. Materials and Methods: To evaluate ARA, recordings using CARTO from 26 clinical cases with complex cardiac arrhythmias, representing mapping of various rhythms, were segmented into test vectors consisting of roughly 62,000 annotation events. These were annotated by an expert clinician (gold standard [GS]) and compared with the legacy/ARA algorithms on detection rate and stability and positive predictive value (PPV). Results: The ARA algorithm detection rate uniformly outperformed legacy, when compared with GS (97 ± 4% vs. 81 ± 19%, respectively; P = 0.001). ARA was performed with high fidelity with an average stability metric (the percentage of true positive ARA annotations within 10 ms of the GS annotation) of 98 ± 3% with most test vectors achieving perfect (100%) stability. Overall, the PPV of ARA annotations was 98 ± 4%; nearly all ARA-annotated activation corresponded to clinically observed events; ARA was superior to legacy across all analyzed test vectors (98 ± 4% vs. 88 ± 23%, P = 0.004); all ARA test vector groups had PPV >90%. Conclusion: The ARA algorithm outperformed the clinical standard, compared to an expert clinician GS. These improvements may translate into greater mapping accuracy/efficiency and procedural outcomes in diagnosis of complex cardiac arrhythmias.

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Background: We aimed to explore the electrophysiological and left atrial anatomical characteristics of pulmonary vein isolation with the “crosstalk” technique during second-generation cryoballoon ablation and figure out a better practice of this technique. Subjects and Methods: A total of 504 patients (311 males and 193 females) with atrial fibrillation were included. All of these patients underwent initial ablation with second-generation cryoballoon. Among these patients, 89 patients (17.7%) did not achieve left/right superior pulmonary vein (LSPV/RSPV) isolation during first cryoablation. In the crosstalk group, there were 35 (39.3%) patients had “crosstalk” phenomenon. The remaining 54 patients (60.7%) without “crosstalk” were included in the control group. The baseline data, electrophysiological and anatomic characteristics of the left atrium were compared between crosstalk group and control group. The study was approved by the Ethics Committee of Fuwai Hospital, China. Results: In the crosstalk group, 33 patients (94.3%) had “crosstalk” phenomenon in the LSPV. The percentage of pulmonary vein potential (PVP) delay during first cryoablation was significantly increased in the crosstalk group compared with the control group (100% vs. 72.2%, P < 0.05). The total ablation time and frequency were significantly decreased in the crosstalk group compared with the control group (P < 0.05). As for the anatomic characteristics, the average distance from LSPV to inferior pulmonary vein, average distance of RSPV and inferior pulmonary veins were significantly shorter in the crosstalk group compared with the control group (P < 0.05). Conclusion: The “crosstalk” phenomenon was more frequent in the left pulmonary vein. Short distance between superior and inferior pulmonary vein and PVP delay during ablation could predict the “crosstalk” phenomenon.

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Background: Permanent His bundle pacing (HBP) is a promising therapy in cardiac pacing field with high challenge of the heart structure. Cardiac mapping system provides us a comprehensive model of heart structure. The study aimed to investigate the feasibility and efficacy of HBP guided by three-dimensional (3D) mapping system. Subjects and Methods: Thirty patients undergoing permanent HBP through 3D mapping system were enrolled in this observational study between January 2016 and May 2018. The study was approved by the Ethics Review Committee of Fuwai Central China Cardiovascular Hospital. The average age of the study population was 59.2 years old, with 17 male patients. Factors including the whole operation time, the X-ray exposure time, the lead parameters, and QRS duration before and after the surgery were analyzed. Results: The study population was divided into two groups: 20 patients in selective HBP group (only capture His bundle) and 10 patients in nonselective HBP group (capture both His bundle and Para-Hisian ventricular tissue). The average whole operation time of HBP guided by 3D mapping system was 113 minutes, and there is no significant difference in the X-ray exposure time between selective HBP and nonselective HBP (P > 0.05). Four patients received HBP with zero fluoroscopy. The intraprocedural lead parameters threshold was significantly increased (1.80 ± 0.50 V vs. 1.21 ± 0.41 V) while sensing was significantly decreased (3.30 ± 0.63 mV vs. 7.40 ± 0.99 mV) in the selective HBP group compared with in the nonselective HBP group (P < 0.05 and P < 0.01). Conclusion: The permanent HBP guided by 3D mapping system was feasible clinically in decreasing X-ray exposure time and achieving perfect lead parameters.

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Background: The role of implantable loop recorders (ILRs) in the evaluation strategy for recurrent syncope in China is limited. This study aimed to clarify the clinical usefulness of ILRs in the diagnosis and management of patients with unexplained syncope. Subjects and Methods: This was an observational cohort study in unexplained syncope patients. This retrospective study enrolled 37 patients (24 men and 13 women; mean age: 59.5 ± 19.1 years) who were implanted with ILRs and diagnosed with unexplained syncope in the First Affiliated Hospital of Dalian Medical University between January 2013 and October 2018. All patients were followed up every 3–6 months after implantation to record the patients' conditions, electrocardiogram (ECG) data, and presence of syncope. Any patients with a history of postimplantation syncope were recommended for prompt medical attention. The study was approved by the Institutional Review Board of the First Affiliated Hospital of Dalian Medical University (approval No. 2017-046) on March 22, 2017. Results: In the 37 patients, 22 (59.46%) experienced syncope within 187.73 ± 177.12 days after loop recorder implantation, including 9 cases of sinus bradycardia or sinus arrest, 6 of third-degree (advanced) atrioventricular block, 1 of ventricular tachycardia, 2 of supraventricular tachycardia, and 4 of atrial fibrillation accompanied by long RR intervals (>5 seconds). In addition, there was one syncope-free atrial fibrillation case with long RR intervals. Among all the patients, 16 were implanted with permanent pacemakers, 1 received an implantable cardioverter-defibrillator, and 2 received catheter ablation. Based on the analysis of sex, age, underlying comorbid conditions, preimplantation syncope episodes, and ECG data, syncope could be predicted from the occurrence of long RR intervals (≥2 seconds) on Holter. Conclusions: The ILR was an effective tool to establish the cause of unexplained syncope in 59.46% of the study patients and to assist these patients in medical treatment. The occurrence of long RR intervals (≥2 seconds) on Holter was an important predictor for arrhythmic syncope.

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At present, remote monitoring (RM) is available for almost all cardiac implantable electronic devices. RM systems allow for enhanced surveillance and earlier detection of clinically significant events. In recent guidelines, RM is a Class I indication for device follow-up, and the Expert Consensus Statement endorses the use of RM to improve patient compliance. Many clinical studies including randomized clinical trials showed favorable outcomes with RM. This technology reduces costs, allows for early detection of arrhythmias, as well as lead to malfunctions. RM also lowers hospitalization rates, decreases inappropriate implantable cardioverter defibrillator shocks, and detects asymptomatic atrial fibrillation earlier than routine office visits. However, whether RM reduces mortality remains unclear. Prevention of heart failure exacerbation with early detection of surrogate markers of heart failure with RM has not been demonstrated using a single measure such as intrathoracic impedance. However, the use of multiple parameters has encouraging early results, showing improved detection of impending heart failure exacerbation.

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Trigger and reentry are the main mechanisms of atrial fibrillation (AF), but underlying diseases and causes may provide necessary conditions for trigger and reentry, which suggests the importance of primary prevention. For the treatment of AF itself, we should pay more attention to the methods of ablation to improve the long-term success rate. In addition, we should pay close attention to the stroke prevention by anticoagulation and left atrial appendage occlusion, to reduce the incidence of embolism events. This article reviews basic and clinical studies of AF over the past century.

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