Implantable cardiac monitor and leadless pacemaker in the management of syncope due to intermittent high-degree atrioventricular block: a case report.

BACKGROUND: Lead dislodgements, tricuspid valve failure, and wound infections are prominent issues addressed by leadless pacemakers (LPM). These devises have emerged as viable alternatives to conventional transvenous pacemakers. LPMs offer minimized complications and effective pacing, particularly beneficial for elderly patients with a low body mass index (BMI) who are at heightened infection of risk. The Micra AV leadless pacemaker was released in the US in 2020, featuring a VDD pacing mode akin to conventional pacemakers. It senses atrial activity to pace ventricular beats while maintaining the natural atrioventricular activation sequence. Micra AV achieves atrioventricular synchronization through mechanical sensing principles. Ongoing research aims to assess its efficacy, implantation feasibility, and clinical safety. CASE PRESENTATION: An 83-year-old man with a history of syncope was the focus of this case study. An implantable cardiac monitor (ICM) recorded occasional high-degree atrioventricular block in the patient. Subsequently, the Micra AV was implanted via the left femoral vein, and its settings were adjusted in accordance with data obtained from the ICM. No significant issues regarding pacing threshold or impedance were found during the follow-up examinations post-surgery. Importantly, the patient experienced a noticeable reduction in symptoms compared to before the implantation. DISCUSSION: This case underscores the significance of ICM monitoring in elucidating cardiac events leading to syncope and guiding appropriate treatment. It also highlights the successful outcomes and reliable implantation of the Micra AV for managing high-degree atrioventricular block. This study contributes to the growing body of evidence supporting the adoption of leadless pacemakers as a viable option for patients requiring cardiac pacing, particularly those vulnerable to complications associated with traditional pacemakers. It provides real-world evidence of Micra AV's efficacy and safety, further validating its role in clinical practice.

Clinical analysis of temporary pacemaker implantation in 6 children with fulminant myocarditis.

BACKGROUND: There is little literature on the use of temporary pacemakers in children with fulminant myocarditis. Therefore, we summarized the use of temporary cardiac pacemakers in children with fulminant myocarditis in our hospital. METHODS: The clinical data of children with fulminant myocarditis treated with temporary pacemakers in Wuhan Children's Hospital from January 2017 to May 2022 were retrospectively analyzed. RESULTS: A total of 6 children were enrolled in the study, including 4 boys and 2 girls, with a median age of 50 months and a median weight of 15 kg. The average time from admission to pacemaker placement was 2.75 ± 0.4 h. The electrocardiogram showed that all 6 children had third-degree atrioventricular block (III°AVB). The initial pacing voltage, the sensory sensitivity of the ventricle and the pacing frequency were set to 5-10 mV, 5 V and 100-120 bpm respectively. The sinus rhythm was recovered in 5 patients within 61 h (17-134) h, and the median time of using temporary pacemaker was 132 h (63-445) h. One of the children had persistent III°AVB after the temporary pacemaker. With parental consent, the child was fitted with a permanent pacemaker on the 12th day of his illness. CONCLUSIONS: When fulminant myocarditis leads to severe bradycardia or atrioventricular block in children, temporary pacemakers have the characteristics of high safety to improve the heart function.

Intrinsic Electrical Remodeling Underlies Atrioventricular Block in Athletes.

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Injectable conductive hydrogel can reduce pacing threshold and enhance efficacy of cardiac pacemaker.

Background: Pacemaker implantation is currently used in patients with symptomatic bradycardia. Since a pacemaker is a lifetime therapeutic device, its energy consumption contributes to battery exhaustion, along with its voltage stimulation resulting in local fibrosis and greater resistance, which are all detrimental to patients. The possible resolution for those clinical issues is an injection of a conductive hydrogel, poly-3-amino-4-methoxybenzoic acid-gelatin (PAMB-G), to reduce the myocardial threshold voltage for pacemaker stimulation. Methods: PAMB-G is synthesized by covalently linking PAMB to gelatin, and its conductivity is measured using two-point resistivity. Rat hearts are injected with gelatin or PAMB-G, and pacing threshold is evaluated using electrocardiogram and cardiac optical mapping. Results: PAMB-G conductivity is 13 times greater than in gelatin. The ex vivo model shows that PAMB-G significantly enhances cardiac tissue stimulation. Injection of PAMB-G into the stimulating electrode location at the myocardium has a 4 times greater reduction of pacing threshold voltage, compared with electrode-only or gelatin-injected tissues. Multi-electrode array mapping reveals that the cardiac conduction velocity of PAMB-G group is significantly faster than the non- or gelatin-injection groups. PAMB-G also reduces pacing threshold voltage in an adenosine-induced atrial-ventricular block rat model. Conclusion: PAMB-G hydrogel reduces cardiac pacing threshold voltage, which is able to enhance pacemaker efficacy.

Cardiotoxic Effects of Micrurus surinamensis (Cuvier, 1817) Snake Venom.

Micrurus surinamensis is a coral snake from the Elapidae family of wide distribution in Amazonia Forest. Its venom contains neurotoxins that induce muscular and respiratory paralysis; however, its cardiovascular action is not yet characterized. The aim of this study was to investigate the cardiotoxic effects caused by M. surinamensis poisoning in rodents. Twelve guinea pigs (Cavia porcellus) were distributed in two groups (n = 6) named as control and envenomed. The control group received 0.2 ml of PBS/BSA via intramuscular injection (IM), while envenomed animals received 0.75 µg of venom per g of body weight, also via IM. Electrocardiographic examination (ECG) and biochemical serum tests were conducted before and 2 h after inoculation. ECG of the envenomed animals revealed severe progressive arrhythmias including atrioventricular block, supraventricular, and ventricular extrasystoles. Serum biochemistry showed significant increase in CK, CK-MB, and LDH enzymes corroborating the skeletal and cardiac muscle damage. Myonecrosis and degeneration were observed in both skeletal and heart muscle; nevertheless, transmission electron microscopy revealed cardiac muscle fibers fragmentation. In conclusion, M. surinamensis venom has a potent cardiotoxic activity eliciting arrhythmogenic effects and heart damage after only 2 h of envenomation.

Atrioventricular Block after Tricuspid Valve Surgery.

Tricuspid valve (TV) surgery is associated with a high risk of postoperative pacemaker requirement. We set out to identify the incidence of atrioventricular block (AVB) after TV surgery and determine whether atrioventricular conduction recovers within time.We investigated pre/intra- and postoperative predictors of AVB in patients who underwent tricuspid valve surgery (not only isolated TV surgery) at our institution between 2004 and 2017. Patients who had pacemakers prior to surgery were excluded.One year after surgery, 5.8% of the surviving cohort had received a pacemaker due to AVB. In the complete follow-up time, 33 out of 505 patients required pacemaker implantation because of AVB. Of the 37 patients who presented to the intensive care unit postoperatively with AVB III, 14 (38%) underwent pacemaker implantation for AVB, and 20 (54%) did not require a pacemaker. AVB III at ICU admission was identified as a predictor of pacemaker implantation (OR: 9.7, CI: 3.8-24.5, P < 0.001). TV endocarditis was also identified as a predictor (OR: 12.4, CI: 3.3-46.3, P < 0.001). Eleven out of 32 patients (34%) with tricuspid endocarditis required a pacemaker for AVB. The mean ventricular pacing burden within the first 5 years after pacemaker implantation was 79%.The issue of AVB after TV surgery is significant. Both the initial rhythm after surgery and etiology of the tricuspid disease can help predict pacemaker requirement. Within the first 5 years after surgery, the ventricular pacing burden remains high without relevant rhythm recovery.

Long-term outcomes of arrhythmia and distinct electrophysiological features in congenitally corrected transposition of the great arteries in an Asian cohort.

Congenitally corrected transposition of the great arteries (ccTGA) is associated with various types of arrhythmia, including supraventricular tachycardia (SVT) and complete atrioventricular block (cAVB). Our study aims to characterize the arrhythmia burden, associated risk factors, arrhythmia mechanisms, and the long-term follow-up results in patients with ccTGA in a large Asian cohort. METHODS: We enrolled 104 patients (43 women and 61 men) diagnosed with ccTGA at our institution. The mean age at last follow-up was 20.8 years. RESULTS: For 40 patients (38%) with tachyarrhythmia, paroxysmal SVT (PSVT) and atrial arrhythmia were observed in 17 (16%) and 27 (26%) patients, respectively, with 4 patients (4%) having both types of SVT. The 20-year and 30-year SVT-free survival rates were 68% and 54%, respectively. Seven patients (7%) developed cAVB: 2 (2%) developed spontaneously, and the other 5 (5%) was surgically complicated (surgical risk of cAVB: 7%, all associated with ventricular septal defect repair surgery). PSVT was mostly associated with accessory pathways (5/9) but also related to twin atrioventricular nodal reentry tachycardia (3/9) and atrioventricular nodal reentry tachycardia (1/9). Most of the accessory pathways were located at tricuspid valve (9/10). Catheter ablation successfully eliminated all PSVT substrates (10/10) and most of the atrial arrhythmia substrates (3/5), with low recurrence rate. CONCLUSIONS: The arrhythmia burden in patients with ccTGA is high and increases over time. However, cAVB incidence was relatively low and kept stationary in this Asian cohort. The mechanisms of SVT are complicated and can be controlled through catheter ablation.

An Experimental Study on Rapid Localization of the Atrioventricular Node During Open-Heart Surgery.

BACKGROUND: To verify the validity and feasibility of using a mechanical compression method to locate the atrioventricular node in open-heart surgery. METHODS: Ten healthy miniature pigs were used to establish an animal model of the beating heart under cardiopulmonary bypass. During the operation, the atrioventricular node and its surrounding areas were stimulated by mechanical compression (mechanical compression method), and the occurrence of complete atrioventricular block was judged by real-time electrocardiograph monitoring and direct observation of the heart rhythm to identify the position of the atrioventricular node. The final localization of the atrioventricular node was determined using the iodine staining method, and the results were used as the "gold standard" to test the effectiveness and feasibility of the mechanical compression method for locating the atrioventricular node. RESULTS: With the beating heart model, complete atrioventricular block occurred after mechanical compression of the "atrioventricular node" area in 10 pigs. Nine pigs regained normal conduction immediately after the compression was released, and one pig failed to recover. No atrioventricular block or other arrhythmias occurred after mechanical compression of the "non-atrioventricular node" area. The sensitivity of the method was 86.6%, specificity was 100.0%, misdiagnosis rate was 0.0%, missed diagnosis rate was 13.4%, positive predictive value was 100.0%, negative predictive value was 97.9%, positive likelihood ratios were +∞, negative likelihood ratios were 13.4%, accuracy was 98.1%, and diagnostic odds ratio was +∞. CONCLUSION: This study innovatively proposes the application of the mechanical compression method to locate the atrioventricular node during operation and preliminarily proves that this method is effective and feasible through animal experiments.

Implantation of leadless pacing systems in patients early after tricuspid valve surgery: A feasible option.

BACKGROUND: After tricuspid valve (TV) surgery due to tricuspid regurgitation (TR), patients needing a permanent pacemaker often receive an epicardial lead implantation. This may result in delayed recovery from open-chest surgery and increased postoperative risk. Leadless pacemaker (LPM) implantation may represent a valuable option. METHODS AND RESULTS: A total of 14 consecutive patients underwent LPM implantation (Micra Transcatheter Pacing System, Medtronic, Minneapolis, MN) early after TV surgery. The pacing indication in those patients was atrial fibrillation with a slow atrio-ventricular (AV) conduction or atrial fibrillation and a concomitant AV block III. Three patients already had a pacemaker prior to surgery, which was explanted during TV repair. Three patients received a valve replacement with a bioprosthesis, while the remaining eight patients received a TV repair. All procedural data and device measurements during and after LPM implantation were recorded. Transthoracic echocardiography was performed prior and post LPM implantation, showing no changes in TV or bioprosthesis performance. The device measurements were within an adequate range: threshold: 0.83 ± 0.34 V @ 0.24 ± 0 ms, impedance: 480 ± 58.88 ohm, and R-wave: 10.10 ± 3.60 mV. LPM implantation was successful in all patients with a mean procedural time of 32 ± 11.8 minutes, fluoroscopy time of 3.71 ± 3.15 minutes, and dose-area product of 536.67 ± 811.26 cGy/m2 . CONCLUSIONS: Implantation of an LPM early after TV surgery is a feasible option. LPM implantation does not affect TV or bioprosthesis performance in transthoracic echocardiography.

Toward detection of conduction tissue during cardiac surgery: Light at the end of the tunnel?

Postoperative conduction block requiring lifetime pacemaker placement continues to be a considerable source of morbidity for patients undergoing repair of congenital heart defects. Damage to the cardiac conduction system (CCS) during surgical procedures is thought to be a major cause of conduction block. Intraoperative identification and avoidance of the CCS is thus a key strategy to improve surgical outcomes. A number of approaches have been developed to avoid conduction tissue damage and mitigate morbidity. Here we review the historical and contemporary approaches for identification of conduction tissue during cardiac surgery. The established approach for intraoperative identification is based on anatomic landmarks established in extensive histologic studies of normal and diseased heart. We focus on landmarks to identify the sinus and atrioventricular nodes during cardiac surgery. We also review technologies explored for intraoperative tissue identification, including electrical impedance measurements and electrocardiography. We describe new optical approaches, in particular, and optical spectroscopy and fiberoptic confocal microscopy (FCM) for identification of CCS regions and working myocardium during surgery. As a template for translation of future technology developments, we describe research and regulatory pathways to translate FCM for cardiac surgery. We suggest that along with more robust approaches to surgeon training, including awareness of fundamental anatomic studies, optical approaches such as FCM show promise in aiding surgeons with repairs of heart defects. In particular, for complex defects, these approaches can complement landmark-based identification of conduction tissue and thus help to avoid injury to the CCS due to surgical procedures.

The Utility of Rapid Atrial Pacing Immediately Post-TAVR to Predict the Need for Pacemaker Implantation.

OBJECTIVES: The aim of this study was to determine the utility of rapid atrial pacing immediately after transcatheter aortic valve replacement (TAVR) to predict the need for permanent pacemaker implantation (PPI). BACKGROUND: Risk stratification for patients without high-grade atrioventricular block (AVB) after TAVR is imprecise and based on anatomic considerations, electrocardiographic characteristics, and clinical suspicion. A more reliable assessment is necessary to minimize inpatient rhythm monitoring and/or reduce unnecessary PPI. METHODS: Consecutive patients undergoing TAVR at 2 centers were included. After valve implantation in patients without pacemakers who did not have complete heart block or atrial fibrillation, the temporary pacemaker was withdrawn from the right ventricle and placed in the right atrium. Rapid atrial pacing was performed from 70 to 120 beats/min, and patients were assessed for the development of Wenckebach AVB. Patients were then followed for clinical outcomes, including PPI. RESULTS: A total of 284 patients were included. Of these, 130 (45.8%) developed Wenckebach AVB. There was a higher rate of PPI within 30 days of TAVR among the patients who developed Wenckebach AVB (13.1% vs. 1.3%; p < 0.001), with a negative predictive value for PPI in the group without Wenckebach AVB of 98.7%. A greater percentage of patients receiving self-expanding valves required PPI than those receiving a balloon-expandable valves (15.9% vs. 3.7%; p = 0.001), though these rates were still relatively low among patients who did not develop Wenckebach AVB (2.9% and 0.8%). CONCLUSIONS: Atrial pacing post-TAVR is easily performed and can help identify patients who may benefit from extended rhythm monitoring. Patients who did not develop pacing-induced Wenckebach AVB demonstrated an extremely low likelihood of PPI.

Cardiomyocyte Expression of ZO-1 Is Essential for Normal Atrioventricular Conduction but Does Not Alter Ventricular Function.

RATIONALE: ZO-1 (Zonula occludens-1), a plasma membrane-associated scaffolding protein regulates signal transduction, transcription, and cellular communication. Global deletion of ZO-1 in the mouse is lethal by embryonic day 11.5. The function of ZO-1 in cardiac myocytes (CM) is largely unknown. OBJECTIVE: To determine the function of CM ZO-1 in the intact heart, given its binding to other CM proteins that have been shown instrumental in normal cardiac conduction and function. METHODS AND RESULTS: We generated ZO-1 CM-specific knockout (KO) mice using α-Myosin Heavy Chain-nuclear Cre (ZO-1cKO) and investigated physiological and electrophysiological function by echocardiography, surface ECG and conscious telemetry, intracardiac electrograms and pacing, and optical mapping studies. ZO-1cKO mice were viable, had normal Mendelian ratios, and had a normal lifespan. Ventricular morphometry and function were not significantly different between the ZO-1cKO versus control (CTL) mice, basally in young or aged mice, or even when hearts were subjected to hemodynamic loading. Atrial mass was increased in ZO-1cKO. Electrophysiological and optical mapping studies indicated high-grade atrioventricular (A-V) block in ZO-1cKO comparing to CTL hearts. While ZO-1-associated proteins such as vinculin, connexin 43, N-cadherin, and α-catenin showed no significant change with the loss of ZO-1, Connexin-45 and Coxsackie-adenovirus (CAR) proteins were reduced in atria of ZO-1cKO. Further, with loss of ZO-1, ZO-2 protein was increased significantly in ventricular CM in a presumed compensatory manner but was still not detected in the AV nodal myocytes. Importantly, the expression of the sodium channel protein NaV1.5 was altered in AV nodal cells of the ZO-1cKO versus CTL. CONCLUSIONS: ZO-1 protein has a unique physiological role in cardiac nodal tissue. This is in alignment with its known interaction with CAR and Cx45, and a new function in regulating the expression of NaV1.5 in AV node. Uniquely, ZO-1 is dispensable for function of the working myocardium.

Treatment of atypical pacemaker-mediated tachycardia with ablation of the retrograde atrioventricular nodal pathway.

A 25-year-old runner received a single-lead, VDD pacemaker after ablation of AV nodal reentrant tachycardia complicated by intermittent AV block. The rate-adaptive AV delay algorithm (RAAV), which shortens the sensed AV interval (SAV) at faster atrial rates, was programmed to provide a physiologic SAV with exercise. She developed repetitive, atypical, long-RP pacemaker-mediated tachycardia (PMT) because the RAAV shortened the antegrade SAV and retrograde conduction occurred over the slow AV nodal pathway. PMT was refractory to usual programming solutions. Using high-density electroanatomic mapping, we were able to ablate the retrograde limb of PMT without further damaging AV conduction.

Immediate and long-term need for permanent cardiac pacing following aortic valve replacement.

Introduction: Atrioventricular (AV) node conduction disturbances are common following surgical aortic valve replacement (SAVR), and in some cases the patient needs a permanent pacemaker (PPM) implantation before discharge from hospital. Little is known about the long-term need for PPM and the PPM dependency of these individuals. We determined the incidence of PPM implantation before and after discharge in SAVR patients. Methods: We studied 557 consecutive patients who underwent SAVR for aortic stenosis in Iceland between 2002 and 2016. Timing and indication for PPM were registered, with a new concept, ventricular pacing proportion (VPP), defined as ventricular pacing ≥90% of the time, being used to approximate pacemaker dependency. The median follow-up time was 73 months. We plotted the cumulative incidence of pacemaker implantation, treating death as a competing risk. Results: Of the 557 patients, 22 (3.9%) received PPM in the first 30 days after surgery, most commonly for complete AV block (n = 14) or symptomatic bradycardia (n = 8); Thirty-eight other patients (6.8%) had a PPM implanted >30 days postoperatively, at a median of 43 months after surgery (range 0‒181), most often for AV block (n = 13) or sick-sinus syndrome (n = 10). The cumulative incidence of PPM implantation at 1, 5, and 10 years postoperatively was 5.0%, 9.2%, and 12.3%, respectively. During follow-up, 45.0% of the 60 patients had VPP ≥90%. Conclusion: The cumulative incidence of permanent pacemaker implantation following SAVR was about 12% at 10 years, with every other patient having VPP ≥90% during follow-up. This suggests that AV node conduction disturbances extend significantly beyond the perioperative period.

Energy Sources for the Surgical Treatment of Atrial Fibrillation.

The surgical treatment of atrial fibrillation has evolved over the past 2 decades due to the advent of ablation technology, and the introduction of less invasive surgical approaches. Current devices produce ablation lines that aim to replace the incisions of traditional surgical ablation strategies, such as the Cox-Maze procedure. This has helped to simplify and shorten surgical ablation procedures and has allowed for the development of minimally invasive surgical techniques. This review discusses surgical ablation energy sources and devices, providing background on device characteristics, mechanism of tissue injury, and success in creating transmural lesions.

Aetiologies and temporal trends of atrioventricular block in young patients: a 20-year nationwide study.

AIMS: To describe aetiologies and temporal trends in young patients with atrioventricular block (AVB). METHODS AND RESULTS: We identified all patients in Denmark, receiving their first pacemaker because of AVB before the age of 50 years between 1996 and 2015. Medical records were reviewed and clinical information and diagnostic work-up results were obtained to evaluate the aetiology. We used Poisson regression testing for temporal trends. One thousand and twenty-seven patients were identified, median age at time of implantation was 38 (interquartile range 25-45) years, 584 (56.9%) were male. The aetiologies were complications to cardiac surgery [n = 157 (15.3%)], congenital AVB [n = 93 (9.0%)], cardioinhibitory reflex [n = 52 (5.0%)], congenital heart disease [n = 43 (4.2%)], complication to radiofrequency ablation [n = 35 (3.4%)], cardiomyopathy [n = 31 (3.0%)], endocarditis [n = 18 (1.7%)], muscular dystrophy [n = 14 (1.4%)], ischaemic heart disease [n = 14 (1.4%)], sarcoidosis [n = 11 (1.1%)], borreliosis [n = 9 (0.9%)], hereditary [n = 6 (0.6%)], side-effect to antiarrhythmics [n = 6 (0.6%)], planned His-ablation [n = 5 (0.5%)], complication to alcohol septal ablation [n = 5 (0.5%)], and other known aetiologies [n = 11 (1.1%)]. The aetiology remained unknown in 517 (50.3%) cases. While the number of patients with unknown aetiology increased during the study period (P < 0.001), we observed no significant change in the number of patients with identified aetiology (P = 0.35). CONCLUSION: In a nationwide cohort, the aetiology of AVB was identified in only half the patients younger than 50 years referred for first-time pacemaker implantation. The number of patients with unknown aetiology increased during the study period. These findings indicate need for better insight into aetiologies of AVB and improved diagnostic work-up guidelines.

A rat model of complete atrioventricular block recapitulates clinical indices of bradycardia and provides a platform to test disease-modifying therapies.

Complete atrioventricular block (CAVB) is a life-threatening arrhythmia. A small animal model of chronic CAVB that properly reflects clinical indices of bradycardia would accelerate the understanding of disease progression and pathophysiology, and the development of therapeutic strategies. We sought to develop a surgical model of CAVB in adult rats, which could recapitulate structural remodeling and arrhythmogenicity expected in chronic CAVB. Upon right thoracotomy, we delivered electrosurgical energy subepicardially via a thin needle into the atrioventricular node (AVN) region of adult rats to create complete AV block. The chronic CAVB animals developed dilated and hypertrophied ventricles with preserved systolic functions due to compensatory hemodynamic remodeling. Ventricular tachyarrhythmias, which are difficult to induce in the healthy rodent heart, could be induced upon programmed electrical stimulation in chronic CAVB rats and worsened when combined with ß-adrenergic stimulation. Focal somatic gene transfer of TBX18 to the left ventricular apex in the CAVB rats resulted in ectopic ventricular beats within days, achieving a de novo ventricular rate faster than the slow atrioventricular (AV) junctional escape rhythm observed in control CAVB animals. The model offers new opportunities to test therapeutic approaches to treat chronic and severe CAVB which have previously only been testable in large animal models.

Permanent left bundle branch area pacing for atrioventricular block: Feasibility, safety, and acute effect.

BACKGROUND: Left bundle branch area pacing (LBBAP), a new pacing approach, lacks adequate evaluation. OBJECTIVE: To assess the feasibility, safety, and acute effect of permanent LBBAP in patients with atrioventricular block (AVB). METHODS: A total of 33 AVB patients with indications for ventricular pacing were recruited. Electrocardiograms, pacing parameters, echocardiographic measurements, and complications associated with LBBAP were evaluated perioperatively and at 3-month follow-up. Successful LBBAP was defined as a paced QRS morphology of right bundle branch block pattern in lead V1 and QRS duration (QRSd) less than 130 ms. RESULTS: LBBAP was successfully performed in 90.9% (30/33) of patients (mean age: 55.1 ± 18.5 years; 66.7% male). The mean capture threshold was similar during the procedure (0.76 ± 0.26 V at 0.4 ms) and at the 3-month follow-up (0.64 ± 0.20 V at 0.4 ms). The paced QRSd was 112.8 ± 10.9 ms during the procedure and 116.8 ± 10.4 ms at the 3-month follow-up. Baseline left or right bundle branch block was corrected (intrinsic QRSd 153.3 ± 27.8 ms vs paced QRSd 122.2 ± 9.9 ms) with a success rate of 68.7% (11/16). One ventricular septal lead perforation occurred soon after the procedure with characteristics of pacing failure, and lead revision was successful. Cardiac function and left ventricular synchronization by 2-dimensional echocardiographic strain imaging at the 3-month follow-up slightly improved compared with that at baseline. CONCLUSIONS: Permanent LBBAP yielded a stable threshold, a narrow QRSd, and preserved left ventricular synchrony with few complications. Our preliminary results indicate that LBBAP holds promise as an attractive physiological pacing strategy for AVB.

Late complete heart block post-tetralogy of Fallot repair: a possible new predicting, precipitating factor and review of related cases.

Tetralogy of Fallot (TOF) is the most common form of cyanotic congenital heart disease beyond the age of 3 months. Complete heart block (CHB) is rare but a serious sequalae post-repair of TOF. We present a case of an 18-month-old child who developed late CHB after around 1 year of the corrective surgery of the congenital anomaly. On the regular follow-up visit, the patient assessment was unremarkable. However, there was bradycardia, 55 beats/min. The ECG showed complete atrioventricular dissociation. Echocardiogram was done and demonstrated severe tricuspid regurgitation (TR). The patient required a permanent pacemaker and he is currently well. We are presenting this case as a late unexpected CHB, with a possibility of progressive right-side dilatation as a contributing factor to CHB due to severe TR.