Diverse QRS morphology reflecting variations in lead placement for left bundle branch area pacing.

AIMS: Left bundle branch area pacing (LBBAP) is a potential alternative to His bundle pacing. This study aimed to investigate the impact of different septal locations of pacing leads on the diversity of QRS morphology during non-selective LBBAP. METHODS AND RESULTS: Non-selective LBBAP and left ventricular septal pacing (LVSP) were achieved in 50 and 21 patients with atrioventricular block, respectively. The electrophysiological properties of LBBAP and their relationship with the lead location were investigated. QRS morphology and axis showed broad variations during LBBAP. Echocardiography demonstrated a widespread distribution of LBBAP leads in the septum. During non-selective LBBAP, the qR-wave in lead V1 indicated that the primary location for pacing lead was the inferior septum (93%). The non-selective LBBAP lead was deployed deeper than the LVSP lead in the inferior septum. The Qr-wave in lead V1 with the inferior axis in aVF suggested pacing lead placement in the anterior septum. The penetration depth of the non-selective LBBAP lead in the anterior septum was significantly shallower than that in the inferior septum (72 ± 11 and 87 ± 8%, respectively). In lead V6, the deep S-wave indicated the time lag between the R-wave peak and the latest ventricular activation in the coronary sinus trunk, with pacemaker leads deployed closer to the left ventricular apex. CONCLUSION: Different QRS morphologies and axes were linked to the location of the non-selective LBBAP lead in the septum. Various lead deployments are feasible for LBBAP, allowing diversity in the conduction system capture in patients with atrioventricular block.

Effect of Catheter Ablation for Atrial Fibrillation in Heart Failure With Mid-Range or Preserved Ejection Fraction　- Pooled Analysis of the AF Frontier Ablation Registry and Hokuriku-Plus AF Registry.

BACKGROUND: A recent randomized trial demonstrated that catheter ablation for atrial fibrillation (AF) in patients with heart failure with reduced ejection fraction (EF) is associated with a reduction in death or heart failure. However, the effect of catheter ablation for AF in patients with heart failure with mid-range or preserved EF is unclear.Methods and Results: We screened 899 AF patients (72.4% male, mean age 68.4 years) with heart failure and left ventricular EF ≥40% from 2 Japanese multicenter AF registries: the Atrial Fibrillation registry to Follow the long-teRm Outcomes and use of aNTIcoagulants aftER Ablation (AF Frontier Ablation Registry) as the ablation group (525 patients who underwent ablation) and the Hokuriku-Plus AF Registry as the medical therapy group (374 patients who did not undergo ablation). Propensity score matching was performed in these 2 registries to yield 106 matched patient pairs. The primary endpoint was a composite of cardiovascular death and hospitalization for heart failure. At 24.6 months, the ablation group had a significantly lower incidence of the primary endpoint (hazard ratio 0.32; 95% confidence interval 0.13-0.70; P=0.004) than the medical therapy group. CONCLUSIONS: Compared with medical therapy, catheter ablation for AF in patients with heart failure and mid-range or preserved EF was associated with a significantly lower incidence of cardiovascular death or hospitalization for heart failure.

Temporal and spatial pacemap parameters for identification of cardiac surfaces with critical sites for ventricular tachycardia.

INTRODUCTION: Multisurface pacemapping may help identify the surface of interest in scar-related ventricular tachycardia (VT). This study aimed to investigate the performance of pacemap parameters for detecting critical sites through multisurface mapping. METHODS AND RESULTS: In 26 patients who underwent scar-related VT ablation, pacemap parameters including a matching score, the difference between the longest and shortest stimulus-QRS intervals (Δs-QRS), and the distance between the good pacemap sites were measured. The parameters were compared between surfaces with and without critical sites and ablation outcomes. A total of 941 pacemap at 56 surfaces targeting 35 VTs were analyzed. A greater Δs-QRS (40 vs. 8 ms, p < .001) and longer distance between two good pacemap sites (24 vs. 13 mm, p < .001) were observed on the surfaces with critical sites. A similar trend was seen in multisurface pacemapping for the same VTs (52 vs. 18 ms in Δs-QRS, p = .021; 37 vs. 12 mm in distance, p = .019), although the best pacemap scores were comparable (94 vs. 87, p = .295). The Δs-QRS > 20 ms and the distance >19 mm showed high positive likelihood ratios (19.8 and 6.1, respectively) for discriminating the surface harboring the critical site. Ablation of VTs fulfilling these parameters was successful on the surfaces, but without the required multisurface ablation. CONCLUSION: Temporal (Δs-QRS) and spatial (distance) parameters for good pacemap match sites were excellent markers for detecting the surface harboring critical sites in scar-related VT. A multisurface pacemapping can successfully identify the surface of interest.

Fluoroscopic predictors of acceptable capture threshold during the implantation of the micra transcatheter pacing system.

INTRODUCTION: Few predictors of low capture threshold before the deployment of the Micra transcatheter pacing system (Micra TPS) have been determined. We aimed to identify fluoroscopic predictors of an acceptable capture threshold before Micra TPS deployment. METHODS: Sixty patients were successfully implanted with Micra TPS. Before deployment, gooseneck appearance of the catheter shaft was quantified using the angle between the tangent line of the shaft and the cup during diastole in the right anterior oblique (RAO) view. The direction of the device cup toward the ventricular septum was evaluated using the angle between the cup and the horizontal plane in the left anterior oblique (LAO) view. RESULTS: Of the 95 deployments we evaluated, 56 achieved an acceptable capture threshold of ≤2.0 V at 0.24 ms. In this acceptable threshold group, the deflection angle of the gooseneck shaft was significantly larger and the device cup was placed more horizontally with a lower elevation angle compared with those in the high threshold group. A deflection angle of ≥6° and an elevation angle of ≤30° were identified as the predictors of an acceptable capture threshold after deployment. An acceptable capture threshold was achieved in 24/31 (77.4%) patients in whom either angle criterion was satisfied at the first deployment. CONCLUSIONS: Diastolic gooseneck appearance of the delivery catheter in the RAO view or near-horizontal direction in the LAO view predicts an acceptable capture threshold after deployment. The shape of the delivery catheter before deployment should be evaluated using multiple fluoroscopic views to ensure successful implantation of Micra TPS.

Different Determinants of the Recurrence of Atrial Fibrillation and Adverse Clinical Events in the Mid-Term Period After Atrial Fibrillation Ablation.

BACKGROUND: It is unclear whether there are differences in the clinical factors between atrial fibrillation (AF) recurrence and adverse clinical events (AEs), including stroke/transient ischemic attack (TIA), major bleeding, and death, after AF ablation.Methods and Results:We examined the data from a retrospective multicenter Japanese registry conducted at 24 cardiovascular centers between 2011 and 2017. Of the 3,451 patients (74.1% men; 63.3±10.3 years) who underwent AF ablation, 1,046 (30.3%) had AF recurrence and 224 (6.5%) suffered AEs (51 strokes/TIAs, 71 major bleeding events, and 36 deaths) over a median follow-up of 20.7 months. After multivariate adjustment, female sex, persistent and long-lasting persistent AF (vs. paroxysmal AF), and stepwise increased left atrial diameter (LAd) quartiles were significantly associated with post-ablation recurrences. A multivariate analysis revealed that an age ≥75 years (vs. <65 years), body weight <50 kg, diabetes, vascular disease, left ventricular (LV) ejection fraction <40% (vs. ≥50%), Lad ≥44 mm (vs. <36 mm), and creatinine clearance <50 mL/min were independently associated with AE incidences, but not with recurrences. CONCLUSIONS: This study disclosed different determinants of post-ablation recurrence and AEs. Female sex, persistent AF, and enlarged LAd were determinants of post-ablation recurrence, whereas an old age, comorbidities, and LV and renal dysfunction rather than post-ablation recurrence were AEs determinants. These findings will help determine ablation indications and post-ablation management.

Impact of sinus rhythm maintenance on major adverse cardiac and cerebrovascular events after catheter ablation of atrial fibrillation: insights from AF frontier ablation registry.

The impact of catheter ablation for atrial fibrillation (AF) on cardiovascular events and mortality is controversial. We investigated the impact of sinus rhythm maintenance on major adverse cardiac and cerebrovascular events after AF ablation from a Japanese multicenter cohort of AF ablation. We investigated 3326 consecutive patients (25.8% female, mean age 63.3 ± 10.3 years) who underwent catheter ablation for AF from the atrial fibrillation registry to follow the long-term outcomes and use of anti coagulants after ablation (AF frontier ablation registry). The primary endpoint was a composite of stroke, transient ischemic attack, cardiovascular events, and all-cause death. During a mean follow-up of 24.0 months, 2339 (70.3%) patients were free from AF after catheter ablation, and the primary composite endpoint occurred in 144 (4.3%) patients. The AF nonrecurrence group had a significantly lower incidence of the primary endpoint (1.8 per 100 person-years) compared with the AF recurrence group (3.0 per 100 person-years, p = 0.003). The multivariate analysis revealed that freedom from AF (hazard ratio 0.61, 95% confidence interval 0.44-0.86, p = 0.005) was independently associated with the incidence of the composite event. In the multicenter cohort of AF ablation, sinus rhythm maintenance after catheter ablation was independently associated with lower rates of major adverse cardiac and cerebrovascular events.

Clinical outcomes of ablation versus non-ablation therapy for atrial fibrillation in Japan: analysis of pooled data from the AF Frontier Ablation Registry and SAKURA AF Registry.

Whether ablation for atrial fibrillation (AF) is, in terms of clinical outcomes, beneficial for Japanese patients has not been clarified. Drawing data from 2 Japanese AF registries (AF Frontier Ablation Registry and SAKURA AF Registry), we compared the incidence of clinically relevant events (CREs), including stroke/transient ischemic attack (TIA), major bleeding, cardiovascular events, and death, between patients who underwent ablation (n = 3451) and those who did not (n = 2930). We also compared propensity-score matched patients (n = 1414 in each group). In propensity-scored patients who underwent ablation and those who did not, mean follow-up times were 27.2 and 35.8 months, respectively. Annualized rates for stroke/TIA (1.04 vs. 1.06%), major bleeding (1.44 vs. 1.20%), cardiovascular events (2.15 vs. 2.49%) were similar (P = 0.96, 0.39, and 0.35, respectively), but annualized death rates were lower in the ablation group than in the non-ablation group (0.75 vs.1.28%, P = 0.028). After multivariate adjustment, the risk of CREs was statistically equivalent between the ablation and non-ablation groups (hazard ratio [HR] 0.89, 95% confidence interval [CI] 0.71-1.11), but it was significantly low among patients who underwent ablation for paroxysmal AF (HR 0.68 [vs. persistent AF], 95% CI 0.49-0.94) and had a CHA2DS2-VASc score < 3 (HR 0.66 [vs. CHA2DS2-VASc score ≥ 3], 95% CI 0.43-0.98]). The 2-year risk reduction achieved by ablation may be small among Japanese patients, but AF ablation may benefit those with paroxysmal AF and a CHA2DS2-VASc score < 3.

Left Atrial Reverse Remodeling Following the Modified Box Isolation with Centerline in Patients with Persistent Atrial Fibrillation.

Esophageal injury is a rare but serious complication of atrial fibrillation (AF) ablation. To minimize esophageal injury, our persistent AF (PerAF) protocol involves complete left atrial posterior wall (LAPW) and pulmonary vein (PV) isolation (box isolation), with a centerline away from the esophagus. However, there has been a concern that extensive LA isolation might deteriorate LA function. There has been a paucity of data on LA remodeling after box isolation. Therefore, we compared LA size pre- and post-box isolation with an LAPW centerline in patients with PerAF.Patients who underwent catheter ablation (CA) for PerAF between November 2016 and December 2018 were retrospectively evaluated.The LAPW, including all PVs, was completely isolated in 105 consecutive patients (75 men; mean age: 68 ± 10 years) with PerAF, including 58 patients with long-standing PerAF. During a follow-up of 660 ± 332 days, 76 patients (72%) were arrhythmia-free. The LA dimension (38 ± 6 mm versus 42 ± 7 mm; P < 0.0001) and volume index (38 ± 13 mL/m2 versus 47 ± 14 mL/m2; P < 0.0001) at 6 months post-ablation were significantly decreased in patients who maintained sinus rhythm compared to pre-ablation. In patients with recurrent AF/atrial tachycardia (AT), these parameters were also significantly decreased (P < 0.001, respectively).Box isolation with a posterior centerline has no esophageal complications and a high clinical success rate in patients with PerAF. Reverse remodeling could be achieved even when using extensive isolation of the PV and LAPW in patients with PerAF.

Clinical Outcomes of Off-Label Underdosing of Direct Oral Anticoagulants After Ablation for Atrial Fibrillation.

Direct oral anticoagulants (DOACs) are sometimes prescribed at off-label under-doses for patients who have undergone ablation for atrial fibrillation (AF). This practice may be an attempt to balance the risk of bleeding against that of stroke or AF recurrence.We examined outcomes of 1163 patients who continued use of a DOAC after ablation. The patients were enrolled in a large (3530 patients) multicenter registry in Japan. The study patients were classified as 749 (64.4%) appropriate standard-dose DOAC users, 216 (18.6%) off-label under-dose DOAC users, and 198 (17.0%) appropriate low-dose DOAC users.Age and CHA2DS2-VASc scores differed significantly between DOAC dosing regimens, with patients given an appropriate standard-dose being significantly younger (63.3 ± 9.4 versus 64.8 ± 9.5 versus 73.2 ± 6.8 years, P < 0.0001) and lower (2.1 ± 1.5 versus 2.4 ± 1.6 versus 3.4 ± 1.4, P < 0.0001) than those given an off-label under-dose or an appropriate low-dose. During the median 19.0-month follow-up period, the AF recurrence rate was similar between the appropriate standard-dose and off-label under-dose groups but relatively low in the appropriate low-dose group (42.5% versus 41.2% versus 35.4%, P = 0.08). Annualized rates of thromboembolic events, major bleeding, and death from any cause were 0.47%, 0.70%, and 0.23% in the off-label under-dose group, while those rates were 0.74%, 0.73%, and 0.65% in the appropriate standard-dose, and 1.58%, 2.12%, and 1.57% in the appropriate low-dose groups.In conclusion, the clinical adverse event rates for patients on an off-label under-dose DOAC regimen after ablation, predicated on careful patient evaluations, was not high as seen with that of patients on a standard DOAC dosing regimen.

Current Status and Clinical Outcomes of Oral Anticoagulant Discontinuation After Ablation for Atrial Fibrillation in Japan　- Findings From the AF Frontier Ablation Registry.

BACKGROUND: The safety of discontinuing oral anticoagulant (OAC) after ablation for atrial fibrillation (AF) in Japanese patients has not been clarified.Methods and Results:A study based on the Atrial Fibrillation registry to Follow the long-teRm Outcomes and use of aNTIcoagulants aftER Ablation (AF Frontier Ablation Registry) was conducted. Data were collected from 3,451 consecutive patients (74.1% men; age, 63.3±10.3 years) who had undergone AF ablation at any of 24 cardiovascular centers in Japan between August 2011 and July 2017. During a 20.7-month follow-up period, OAC therapy was discontinued in 1,836 (53.2%) patients; 51 patients (1.5%) suffered a stroke/transient ischemic attack (TIA), 71 (2.1%) suffered major bleeding, and 36 (1.0%) died. Patients in whom OAC therapy was discontinued were significantly younger than those in whom OACs were continued, and their CHA2DS2-VASc scores were significantly lower. The incidences of stroke/TIA, major bleeding, and death were significantly lower among these patients. Upon multivariate adjustment, stroke events were independently associated with relatively high baseline CHA2DS2-VASc scores but not with OAC status. CONCLUSIONS: Although the incidences of stroke/TIA, major bleeding, and death were relatively low among patients for whom OAC therapy was discontinued, stroke/TIA occurrence was strongly associated with a high baseline stroke risk rather than with OAC status. Thus, discontinuation of OAC therapy requires careful consideration, especially in patients with a high baseline stroke risk.

Accuracy of wristwatch-type photoplethysmography in detecting atrial fibrillation in daily life.

Aims: Detection of asymptomatic paroxysmal atrial fibrillation is challenging. Smartphone- or smartwatch-based photoplethysmography is efficient at detecting irregular rhythms using pulse waves but is too complex for older patients. We aimed to evaluate the detection accuracy of atrial fibrillation by a wristwatch-type continuous pulse wave monitor (PWM) in daily life. Methods and results: Patients at high risk of atrial fibrillation but with no history of atrial fibrillation (n = 163; mean CHADS2 score, 1.9) and patients with known atrial fibrillation (n = 123, including 34 with persistent atrial fibrillation) underwent PWM and telemetry electrocardiogram recording for 3 days. Risk of atrial fibrillation was judged using the 'Kyorin Atrial Fibrillation Risk Score', a scoring system based on previously reported atrial fibrillation risk scoring systems. The PWM assessed the presence of atrial fibrillation at 30 min intervals, and the results were compared with the telemetry electrocardiogram findings. The PWMs accurately diagnosed two patients with paroxysmal atrial fibrillation in the high-risk group. The PWMs accurately diagnosed 48 of the 55 patients with atrial fibrillation in the known-atrial fibrillation group. The PWM accuracy in detecting patients with atrial fibrillation was as follows: sensitivity, 98.0%; specificity, 90.6%; positive predictive value, 69.4%; negative predictive value, 99.5%. The respective values for intervals with atrial fibrillation were 86.9%, 98.8%, 89.6%, and 98.5%. Conclusion: The wristwatch-type PWM has shown feasibility in detecting atrial fibrillation in daily life and showed the possibility of being used as a screening tool.

Safety of Distal His Bundle Pacing Via the Right Ventricle Backed Up by Adjacent Ventricular Capture.

OBJECTIVES: This study investigated the differences between distal His bundle pacing (HBP) via the right ventricle and proximal HBP via the right atrium with regard to pacing and sensing parameters. BACKGROUND: HBP preserves physiological ventricular activation. The capture threshold of the adjacent ventricle accompanying HBP has not been evaluated after implantation. METHODS: Fifty patients with bradycardia (58% with atrioventricular block) underwent successful HBP and were followed for 1 year. Precise locations of the lead tips were confirmed using follow-up echocardiography. RESULTS: HBP leads were fixed via the right atrium or right ventricle (25 patients each). Overall, the local ventricle and HBP thresholds were elevated during follow-up. The distal HBP thresholds did not significantly differ from the proximal HBP thresholds, although local ventricular thresholds of distal HBP were markedly lower than those of proximal HBP. At 6 months, the accepted ventricular threshold (≤2.5 V) was maintained in 39 patients (78%). An amplitude of ventricular electrogram post-fixation of ≥2.0 mV and a capture threshold of ≤1.1 V at implantation were determined to be optimal values for predicting the accepted threshold at 6 months, with areas under the curve of 0.86 and 0.84, respectively. Atrial oversensing was often detected in proximal HBP but not distal HBP. CONCLUSIONS: Distal HBP via the right ventricle captured the His bundle, similar to proximal HBP via the right atrium, with a superior local ventricular threshold during follow-up. Anatomy and electrophysiological ventricular properties at implantation may be critical for maintaining adjacent ventricle capture to prevent lead revision (Evaluation of Electrophysiological Parameters related to His Bundle Pacing in Patients With Bradyarrhythmias; UMIN000031364).

Stellate Ganglion Phototherapy Using Low-Level Laser: A Novel Rescue Therapy for Patients With Refractory Ventricular Arrhythmias.

OBJECTIVES: This study investigates the effect of stellate ganglion (SG) phototherapy in healthy participants and assesses its efficacy in suppressing electrical storm (ES) refractory to antiarrhythmic drugs and catheter ablation. BACKGROUND: Modulation of the autonomic nervous system has been shown to be an effective adjunctive therapy for ES. METHODS: Ten-minute SG phototherapy was performed twice weekly for 4 weeks in 20 healthy volunteers. To evaluate the acute and chronic effects of SG phototherapy, heart rate variability and serum concentrations of adrenaline, noradrenaline, and dopamine were obtained before phototherapy, immediately after the first phototherapy session, after 8 sessions of phototherapy, and 3 months after the first phototherapy session. In addition, the efficacy of SG phototherapy was evaluated in 11 patients with ES refractory to medication, sedation, and catheter ablation. RESULTS: In healthy participants, serum adrenaline concentration significantly decreased after phototherapy, whereas low-frequency power/high-frequency power significantly decreased during phototherapy. Moreover, the effect on heart rate variability did not last beyond 3 months. In the clinical pilot study, 7 patients had a suppression of ES after SG phototherapy; however, without maintenance therapy, 2 patients had a recurrence of ventricular arrhythmias. Furthermore, it did not control ES in 4 patients. CONCLUSIONS: SG phototherapy reduced sympathetic activity and may be a safe and effective adjunctive therapy to control ES in some patients, but its long-term efficacy remains unknown. Chronic phototherapy might help reduce ES recurrence.

Assessing the perforation site of cardiac tamponade during radiofrequency catheter ablation using gas analysis of pericardial effusion.

BACKGROUND: The incidence of pericardial effusion (PE) during radiofrequency catheter ablation (CA) for atrial fibrillation is approximately 1%. PE is a major complication during CA, but there has been limited literature about the perforation site responsible. OBJECTIVE: This study aimed to retrospectively investigate the characteristics of the procedure and the patients in whom PE developed during CA. METHODS: Of 1363 consecutive patients who underwent catheter ablation from January 2015 to June 2019 in Kyorin University Hospital, we reviewed patients who developed PE during CA. RESULTS: PE during CA occurred in 18 (1.32%) patients (median age, 71 [interquartile range (IQR) 65-77] years, 7 women). The median body mass index was 24 (IQR 20-27). Target arrhythmias for CA of patients with PE include atrial fibrillation (AF) (n = 13, 72%), premature ventricular contraction (n = 2, 11%), ventricular tachycardia (n = 1, 6%), atrial flutter (n = 1, 6%), and orthodromic reciprocating tachycardia (n = 1, 6%). Seventeen patients required pericardiocentesis, resulting in 300 (IQR 192.5-475) mL of drainage. Two patients required emergency surgical repair, and 1 died from aortic dissection. Based on the gas analysis, the drained blood was of venous origin in 47% of the total events and 54% of AF ablation. CONCLUSION: PE caused by a diagnostic catheter in the right heart is not uncommon, even in AF ablation.

Reducing radiation exposure during atrial fibrillation ablation using lectures to promote awareness.

Objective: Recently, concern has increased regarding the hazards of radiation exposure in patients and laboratory staff. Since the numbers of complex catheter ablations (CA) performed, duration of procedure times, and need for multiple sessions have increased, radiation exposure during each session needs to be minimised. Our study aimed to assess the impact of awareness on radiation exposure during CA for atrial fibrillation (AF). Methods: Mini-course lectures was delivered to the physicians and staff in the electrophysiology division. Its effect on the fluoroscopic time and radiation dose during AF ablation before (Group I, n=70), shortly after (Group II: n=70) and remotely after the mini-lecture (Group III, n=70) were evaluated. Patient demographics, preoperative testing and procedural parameters were collected. Results: The fluoroscopic time significantly reduced after the lecture (Group I and II: 25.1±10.0 and 15.1±7.3 min, respectively (p<0.0001)), and remained so in Group III (13.0±5.4 min), despite the increase in the number of persistent AFs. The radiation dose also significantly reduced (Groups I, II, III: 295.0±263.0, 109.6±103.5 and 110.1±89.6 mGy, respectively (p<0.0001)). Conclusion: Awareness on radiation exposure led to a significant reduction in fluoroscopic time and radiation dose during CA for AF, the effect of which persisted even to remote periods following the procedure.

Deep Negative Deflection in Unipolar His-Bundle Electrogram as a Predictor of Excellent His-Bundle Pacing Threshold Postimplant.

Background His-bundle pacing (HBP) is a physiological form of pacing. Although high capture thresholds are common, few predictors of low HBP threshold have been determined. We aimed to identify electrophysiological predictors. Methods Fifty-one patients (53% with atrioventricular block) underwent HBP for bradycardia with an intrinsic QRS duration of <120 ms. Attempts to anchor the HBP lead were guided by unipolar His-bundle electrograms (HB EGMs) recorded with an electrophysiology recording system. Patients were followed-up for >6 months. Results In total, 153 attempts at anchoring the HBP lead were made, of which, 45 achieved acceptable HBP thresholds (≤2.5 V at 1 ms). The amplitude of negative deflection in HB EGM and the selective HBP form at fixation were independently associated with achieving an acceptable threshold. A negative amplitude of ≥0.060 mV in HB EGM was determined as the optimal value for identifying the acceptable threshold. This deep negative HB EGM was recorded with an HBP threshold of 1.4±1.3 V (in 34 attempts), significantly lower than that of positive HB EGM without deep negative deflection (2.8±1.3 V, in 31 trials; or >5 V, in 38 trials). The permanent HBP lead remained with deep negative (≥0.060 mV) or positive HB EGMs in 28 and 14 patients, respectively, and with positive or negative HB injury current in 19 and 23 patients, respectively. During follow-up, increased HBP threshold of >1 V was significantly more prevalent in the positive HB EGM group. The HBP thresholds of deep negative HB EGM and HB injury current, but not of the selective HBP group, were significantly lower than the other subgroups during follow-up. Conclusions Deep negative HB EGM at fixation was associated with an excellent short-term HBP threshold, similar to HB injury current. Analysis of unipolar HB EGM postfixation may enable prediction of permanent HBP threshold.