Atrioventricular Conduction Block Research Articles

Strategy and technique for surgical treatment of Ebstein's anomaly.

Ebstein's anomaly (EA) is a rare and complex congenital heart anomaly, and the effect of surgical treatment is not ideal. This study aims to introduce our experience in management strategies, surgical techniques, and operative indications for patients with Ebstein's anomaly. A retrospective study of 258 operations was performed in 253 patients by the same cardiac surgeon in The First Hospital of Tsinghua University between March 2004 and January 2020. 32 patients had previously received cardiac surgery in other hospitals. The clinical data including diagnosis, operative indications, techniques, pathological changes, and survival rates were collected and analyzed. Anatomical correction was performed in 203 (78.7%) operations, 1½ ventricle repair in 38 (14.7%) operations, tricuspid valve repair only in four operations (1.6%), tricuspid valve replacement in ten (3.9%), total cavopulmonary connection (TCPC) in two (0.8%), and Glenn operation in one operation (0.4%). Reoperation was performed in five patients (2.0%) during hospitalization. Among them, tricuspid valve replacement was performed in one patient, 1½ ventricle repair in two patients, and tricuspid valve annulus reinforcement in two patients. Five patients died with an early mortality rate of 2.0%. Complete atrioventricular conduction block was complicated in one patient (0.4%). A total of 244 patients was followed up (four in the 253 patients lost) with a duration of 3.0-168.0 (87.6 ± 38.4) months. Cardiac function of 244 patients improved significantly with mean New York Heart Association (NYHA) functional class recovery from 3.5 to 1.1. The mean grade of tricuspid valve regurgitation improved from 3.6 to 1.5. Three late deaths (1.2%) occurred. The survival rates at five and ten years after surgery were 98.6% and 98.2%, respectively. Reoperation was performed in five patients (2.0%) during the follow-up period. Based on our management strategies and operative principles and techniques, anatomical correction of EA is capable of achieving excellent long-term results, and low rates of TCPC, 1½ ventricle repair and valvular replacement.

A novel method for septal reduction therapy by three-dimensional guided transvenous intraseptal pulsed-field ablation

BackgroundPulsed-field ablation (PFA) is a nonthermal method for achieving selective cell death with little inflammation response. However, there are no reports of PFA for septal reduction therapy (SRT). ObjectiveThe purpose of this study was to investigate the effectiveness and safety of PFA for SRT. MethodsA novel transvenous intraseptal PFA method with 3-dimensional (3D) guidance was introduced in Yorkshire pigs. Electrocardiographic parameters, transthoracic echocardiography, and histopathology were used to evaluated. ResultsThe maximum injury diameter of intramyocardial PFA increased with electric field intensity. After PFA, bipolar electrogram amplitude and pacing threshold measured by the PFA electrodes significantly decreased (F = 6.945, P = .007) or increased (F = 5.842, P = .024), respectively. In the ablated septal region, motion amplitude and systolic wall thickening rate significantly decreased and remained at low levels (motion amplitude: F = 20.793, P = .000; systolic wall thickening rate: F = 14.343, P = .000); however, septal thickness did not significantly change after PFA (F = 1.503, P = .248). Histologic examination showed specific cardiomyocyte death with gradually increased hyperchromatic cytoplasm and nuclear pyknosis, without obvious inflammatory cell infiltration in acute phase. TUNEL stain for fragmented DNA showed extensively positive in the ablation region 24 hours after PFA. During PFA, no sustained ventricular arrhythmia or atrioventricular conduction block occurred. ConclusionA novel intraseptal PFA method with 3D guidance was described. Intraseptal PFA resulted in effective myocardial injury and local hypokinesis without significant acute edema. Histologic examination showed widely programmed cardiomyocyte death with little inflammatory cell infiltration.

Abstract 17229: Atrioventricular Conduction System Changes During Transcatheter Aortic Valve Replacement (TAVR)

Introduction: Transcatheter aortic valve replacement (TAVR) is complicated by atrioventricular (AV) conduction disturbance in 8-15% of cases. Prior studies have not utilized complete electrophysiology studies (EPS) with continuous recording during TAVR. We sought to better understand the potential utility of intraprocedural electrophysiologic study to identify patients at risk for developing high-grade AV conduction disturbances after TAVR. Hypothesis: Intraprocedural EPS has the potential to identify patients at risk of developing AV conduction block after TAVR. Methods: We conducted a prospective study of TAVR patients at BIDMC between 5/2021-3/2023, excluding those with pre-existing pacemakers/defibrillators. We performed EPS in the cath lab prior to and after valve replacement: atrial pacing to AV block, recording His bundle electrogram (HBE) and RV pacing to assess VA conduction. When possible we recorded the HBE continuously during valve implant. Results: We studied 400 consecutive patients. Forty-three patients (10.8%) received permanent pacemakers (PPMs). Patients receiving PPM had significantly longer post-HV intervals, greater change in HV interval as well as longer AV Wenckebach cycle length after valve replacement. There were no differences in pre-TAVR AV Wenckebach cycle length or VA conduction. Twenty patients (46.5% of all PPMs) were implanted for AV block post discharge, and after adjustment for age, gender, and baseline HV interval, the only predictor of need for post-discharge PPM was peri-TAVR change in HV interval with an adjusted OR of 1.19 per each 10 ms increase. Conclusions: In contrast to prior studies, we have found that EPS at the time of TAVR may have utility in predicting AV conduction disturbances. Larger increases in HV interval and AV block CL were associated with need for PPM. Measuring the peri-TAVR change in HV interval may be useful in predicting late AV block.

Adaptive versus conventional cardiac resynchronisation therapy in patients with heart failure (AdaptResponse): a global, prospective, randomised controlled trial

Continuous automatic optimisation of cardiac resynchronisation therapy (CRT), stimulating only the left ventricle to fuse with intrinsic right bundle conduction (synchronised left ventricular stimulation), might offer better outcomes than conventional CRT in patients with heart failure, left bundle branch block, and normal atrioventricular conduction. This study aimed to compare clinical outcomes of adaptive CRT versus conventional CRT in patients with heart failure with intact atrioventricular conduction and left bundle branch block. This global, prospective, randomised controlled trial was done in 227 hospitals in 27 countries across Asia, Australia, Europe, and North America. Eligible patients were aged 18 years or older with class 2-4 heart failure, an ejection fraction of 35% or less, left bundle branch block with QRS duration of 140 ms or more (male patients) or 130 ms or more (female patients), and a baseline PR interval 200 ms or less. Patients were randomly assigned (1:1) via block permutation to adaptive CRT (an algorithm providing synchronised left ventricular stimulation) or conventional biventricular CRT using a device programmer. All patients received device programming but were masked until procedures were completed. Site staff were not masked to group assignment. The primary outcome was a composite of all-cause death or intervention for heart failure decompensation and was assessed in the intention-to-treat population. Safety events were collected and reported in the intention-to-treat population. This study is registered with ClinicalTrials.gov, NCT02205359, and is closed to accrual. Between Aug 5, 2014, and Jan 31, 2019, of 3797 patients enrolled, 3617 (95·3%) were randomly assigned (1810 to adaptive CRT and 1807 to conventional CRT). The futility boundary was crossed at the third interim analysis on June 23, 2022, when the decision was made to stop the trial early. 1568 (43·4%) of 3617 patients were female and 2049 (56·6%) were male. Median follow-up was 59·0 months (IQR 45-72). A primary outcome event occurred in 430 of 1810 patients (Kaplan-Meier occurrence rate 23·5% [95% CI 21·3-25·5] at 60 months) in the adaptive CRT group and in 470 of 1807 patients (25·7% [23·5-27·8] at 60 months) in the conventional CRT group (hazard ratio 0·89, 95% CI 0·78-1·01; p=0·077). System-related adverse events were reported in 452 (25·0%) of 1810 patients in the adaptive CRT group and 440 (24·3%) of 1807 patients in the conventional CRT group. Compared with conventional CRT, adaptive CRT did not significantly reduce the incidence of all-cause death or intervention for heart failure decompensation in the included population of patients with heart failure, left bundle branch block, and intact AV conduction. Death and heart failure decompensation rates were low with both CRT therapies, suggesting a greater response to CRT occurred in this population than in patients in previous trials. Medtronic.

Novel pathogenic variant in LMNA gene identified in a six-generation family causing atrial cardiomyopathy and associated right atrial conduction arrhythmias.

To characterize the cardiac phenotype associated with the novel pathogenic variant (c.1526del) of LMNA gene, which we identified in a large, six-generation family. A family tree was constructed. The clinical data of living and deceased family members were collected. DNA samples from 7 family members were analyzed for LMNA mutations using whole-exome high-throughput sequencing technology. The clinical presentation of pathogenic variant carriers was evaluated. In this six-generation family (n = 67), one member experienced sudden death at the age of 40-years-old. Three pathogenic variant carriers were identified to possess a novel heterozygous deletion mutation in LMNA gene (HGVS: NM_170707.4, c.1526del) located at exon 9 of LMNA chr1:156137145, which creates a premature translational stop signal (p.Pro509Leufs*39) in the LMNA gene and results in an mutant lamin A protein product. The main symptoms of the pathogenic variant carriers were palpitation, fatigue, and syncope, which typically occurred around 20-years-old. AV-conduction block and non-sustained ventricular tachycardia were the first signs of disease and would rapidly progress to atrial standstill around 30-years-old. Significant right atrial enlargement and bicuspid aortic valve malformation was also commonly seen in patients who carried this pathogenic variant. The pathogenic variant of c.1526del p.P509Lfs*39 was a frameshift deletion located at exon 9 of LMNA chr1:156137145 and causes severe right atrial enlargement, sick sinus syndrome, atrial standstill, ventricular tachycardia, and bicuspid aortic valve malformation. Our findings expand the phenotypic spectrum of novel LMNA gene mutations.

Efficient generation of TBX3+ atrioventricular conduction-like cardiomyocytes from human pluripotent stem cells

Atrioventricular conduction cardiomyocytes (AVCCs) regulate the rate and rhythm of heart contractions. Dysfunction due to aging or disease can cause atrioventricular (AV) block, interrupting electrical impulses from the atria to the ventricles. Generation of functional atrioventricular conduction like cardiomyocytes (AVCLCs) from human pluripotent stem cells (hPSCs) provides a promising approach to repair damaged atrioventricular conduction tissue by cell transplantation. In this study, we put forward the generation of AVCLCs from hPSCs by stage-specific manipulation of the retinoic acid (RA), WNT, and bone morphogenetic protein (BMP) signaling pathways. These cells express AVCC-specific markers, including the transcription factors TBX3, MSX2 and NKX2.5, display functional electrophysiological characteristics and present low conduction velocity (0.07 ± 0.02 m/s). Our findings provide new insights into the understanding of the development of the atrioventricular conduction system and propose a strategy for the treatment of severe atrioventricular conduction block by cell transplantation in future.

Prospective observational study on the accuracy of predictors of high-grade atrioventricular conduction block after transcatheter aortic valve implantation (CONDUCT-TAVI): study protocol, background and significance

IntroductionAortic stenosis is the most common cardiac valve pathology worldwide and has a mortality rate of over 50% at 5 years if left untreated. Transcatheter aortic valve implantation (TAVI) is...

Bradyarrhythmia in acute massive pulmonary embolism

Pulmonary embolism (PE) can present with a variety of electrocardiographic findings. Bradycardia is a rare finding in acute PE, which typically manifests with sinus tachycardia. Bradycardia in acute PE might arise from the physiologic Bezold–Jarisch reflex, which describes the constellation of bradycardia, peripheral vasodilation, and hypotension. We report the case of a woman in her 60s who was admitted initially for submassive PE and found to have sinus bradycardia. She had progressed to massive PE with acute worsening of atrioventricular conduction block in the setting of atrial flutter. Her bradyarrhythmia resolved and hemodynamics improved after catheter directed thrombolysis. This case revisits the pathophysiology of Bezold–Jarisch reflex, and the importance of recognizing that it signifies an underlying pathologic insult, especially a life-threatening one like PE.

Arrhythmia in a COVID-19 patient: A case report

In this study, we considered an 83-year-old male patient admitted to the Al-Zahra hospital emergency department in Isfahan. He complained of fatigue, weakness, headache, and cough. In addition, he had hallucinations and delusions for two days; but he had no fever and chill. His physical examination showed a blood pressure of 170/100 mm Hg, heart rate of 142 beats per minute (bpm), respiratory rate of 23 pbm, oxygen saturation (in room air) of 83%, and oxygen bag reserve mask of 93%. We realized cardiac involvement during hospitalization, including sinus bradycardia, first-degree atrioventricular (AV) block, recurrent premature ventricular from tricuspid ring, atrial tachycardia (AT) rhythm with variable AV conduction block, increased heart rate with functional bundle branch block, and negative troponin. The patient was treated with medicines to control heart rate and admitted to the cardiac care unit (CCU). Next, the patient was intubated due to a worsening lung condition. Afterward, he was admitted to the intensive care unit (ICU) and died the next day. According to the literature, compromised cardiac vascular is the most common complications in hospitalized patients due to COVID-19 infection and has a higher mortality risk. Cardiac arrhythmias are additionally common clinical manifestations. These arrhythmias seem to be caused by inflammatory responses in the myocardium, electrolyte disorders, and hypoxia. Our patient showed that the COVID-19 virus might induce different types of arrhythmias.

Percutaneous Transcatheter Closure of Congenital Ventricular Septal Defects.

Ventricular septal defects (VSDs) are the most common kind of congenital heart disease and, if indicated, surgical closure has been accepted as a gold-standard treatment. However, as less-invasive methods are preferred, percutaneous device closure has been developed. After the first VSD closure was performed percutaneously by Lock in 1988, both techniques and devices have developed consistently. A perventricular approach for closure of muscular VSD in small patients and the closure of perimembranous VSD using off-label devices are key remarkable developments. Even though the Amplatzer membranous VSD occluder (Abbott) could not be approved for use due to the high complete atrioventricular conduction block rate, other new devices have shown good results for closure of perimembranous VSDs. However, the transcatheter technique is slightly complicated to perform, and concerns about conduction problems after VSD closure with devices remain. There have been a few reports demonstrating successful closure of subarterial-type VSDs with Amplatzer devices, but long-term issues involving aortic valve damage have not been explored yet. In conclusion, transcatheter VSD closure should be accepted as being as effective and safe as surgery but should only be performed by experienced persons and in specialized institutes because the procedure is complex and requires different techniques. To avoid serious complications, identifying appropriate patient candidates for device closure before the procedure is very important.

533 MOBITZ TYPE I AND HIGH-DEGREE ATRIO-VENTRICULAR BLOCK AS LATE SEQUELAE OF ASYMPTOMATIC COVID-19 INFECTION: A CASE REPORT

Abstract Background It is now well-acknowledged that patients with overt COVID-19 are at increased risk of a broad range of acute cardiovascular disorders including myocardial infarction, myocarditis, pericarditis, pulmonary embolism, vasculitis and thromboembolic disease. However, long-term cardiac sequelae of COVID-19 are still poorly understood, especially in young asymptomatic patients. Case summary A 40 years-old man, with a history of COVID-19 infection 8 weeks earlier, was admitted to the Emergency Department for detection of type 2 atrio-ventricular block (AVB) Mobitz I at 12-lead ECG during regular medical checkup. The patient was asymptomatic and hemodynamically stable (resting blood pressure 125/75 mmHg). An ECG performed 10 weeks earlier showed no conduction abnormalities. At echocardiographic examination, a preserved left ventricular ejection fraction, no abnormal regional wall motion and no valvular abnormalities were found. Routine laboratory tests showed normal values of blood count, electrolytes, thyroid hormones, C-reactive protein and no elevation in high-sensitivity troponin-I levels. Renal function was preserved. A maximal ECG treadmill test was performed using the Bruce protocol that showed no ectopy during exercise, no ST segment changes during exercise or recovery. During the exercise, the patient remained asymptomatic and the AVB disappeared at stage IV and came back at the end of the test. During in-hospital stay, a paroxysmal high-grade AVB was also detected at ECG telemetry monitoring. The electrophysiological study revealed normal HV conduction and intranodal Wenckebach AVB. A cardiac magnetic resonance (CMR) was performed which revealed myocardial edema and septal fibrosis. At the end, the patient underwent a loop recorder implantation and was prescribed 600 mg of ibuprofen twice a day and dexamethasone 1 mg with progressively decreasing doses for a total of 4 weeks. At 3-month follow-up the patient remained asymptomatic and a persistence of type 2 AVB Mobitz I yet no events of high-grade AVB, were recorded at loop recorder monitoring. In addition, the 3-month follow-up CMR showed no signs of edema or fibrosis. Discussion Myocardial injury and conduction disorders have been well-described to complicate the acute COVID-19 infection. However, this is the first report of an atrioventricular conduction block as isolated long-term consequence of COVID-19 in asymptomatic patient. The persistence of AVB during follow-up could be probably explained by microscopic affection of conduction system non detectable at CMR imaging. To date, there is no long-term data to suggest whether such isolated conduction abnormalities are temporary or permanent. The decision of implanting a definitive pacemaker should be based on accurate analysis aimed at evaluating the reversible nature of arrhythmia, especially in young patients. In our case, at 3-month follow-up, CMR showed no macroscopic edema/fibrosis of the myocardium and the high grade AVB disappeared. Serious conduction disorders following asymptomatic or mild COVID-19 may occur and a tailored management is advisable.

Hybrid Approach Using the Cusp-Overlap Technique for Transcatheter Aortic Valve Replacement With a Balloon-Expandable Valve

BackgroundThe cusp-overlap (CO) technique has recently been advocated and is being increasingly adopted for self-expandable transcatheter heart valve (THV) implantation. ObjectivesThe aim of this study was to evaluate the feasibility, implantation depth, and outcomes of the CO technique for the balloon-expandable SAPIEN 3 THV. MethodsThe CO technique was used in consecutive patients undergoing balloon-expandable THV implantation at one center between April 2021 and March 2022. Optimal fluoroscopic angles were determined from preprocedural computed tomography and confirmed on predeployment angiography. The THV radiolucent line was positioned 2 to 4 mm below the noncoronary cusp in the CO view, and positioning was confirmed in the 3-cusp view. Postdeployment THV implantation depth was assessed in both views. One-month outcomes were assessed using Valve Academic Research Consortium 3 criteria. ResultsAmong 137 patients eligible for the CO technique, the CO view was not used because of unfavorable ergonomics in 27 patients (26.5%) and hemodynamic instability in 8 patients (7.8%). Among 102 patients, the mean age was 81.1 ± 6.6 years, the mean Society of Thoracic Surgeons score was 3.3% ± 2.2%, and 64.7% were men. The mean measured THV implantation depth was 3.0 ± 1.4 mm in the CO view and 2.5 ± 1.4 mm in the 3-cusp view. At 1-month follow-up, 1 patient (1.0%) had died, 1 (1.0%) had had a stroke, and 7 (6.8%) had undergone permanent pacemaker implantation. ConclusionsThe CO technique is feasible and safe and may facilitate more accurate balloon-expandable THV positioning, especially when deep implantation needs to be avoided. Further studies are required to explore potential reduction in atrioventricular conduction block, pacemakers, or paravalvular regurgitation.

Prospective Observational Study on the Accuracy of Predictors of High-Grade Atrioventricular CONDUCTion Block After TAVI (CONDUCT-TAVI): Background, Trial Protocol and Significance

High-grade atrioventricular block (HGAVB) is a common complication of transcatheter aortic valve implantation (TAVI), occurring in 7–19% of cases. Patients are typically monitored for 48 hours post-TAVI; however, 40% of HGAVB occurs after discharge. Delayed HGAVB can cause syncope or death, and no accurate methods currently exist to identify patients at risk.

Abstract 12297: Myocardial Bridging Increases the Risk of Preoperative Atrial Fibrillation in Adult Patients with Obstructive Hypertrophic Cardiomyopathy

Background: Myocardial bridging (MB) was associated with various arrhythmia forms like supraventricular tachycardia, ventricular tachycardia, atrioventricular conduction block, and sudden cardiac death. However, the relationship between MB and preoperative atrial fibrillation (AF) remains unknown. Hypothesis: The presence of MB increases the risk of preoperation AF in adult patients with obstructive hypertrophic cardiomyopathy (OHCM). Method: We recruited 968 consecutive patients with OHCM who underwent surgical myectomy at Fuwai Hospital in Beijing, China, from January 2015 to December 2019. Patients were divided into two groups based on invasive coronary angiography: patients with MB group (N=144) and patients without MB group (N=824). Result: Patients with MB were much younger (43.6 vs. 48.8 years, p < 0.001), more likely to have palpitation (37.4% vs. 25.5%, p = 0.003), had a lower body mass index (24.8 vs. 25.7 kg/m2, p = 0.009), a lower incidence of hypertension (14.6% vs. 27.9% p = 0.001), a higher prevalence of AF (26.4% vs. 11.5%, p <0.001). After adjusting for age, sex, left atrial diameter, and LVOT gradient, multivariate logistic regression analysis revealed that the presence of MB was independently associated with AF (Odds ratio [OR] 3.73; 95% Confidential interval [CI] 2.32-5.98, p < 0.001). Furthermore, we conducted a LASSO logistic regression to select variables associated with AF from patients with MB subgroup, and five non-zero variables were included in the multivariate logistic regression model. The results indicated that compared to patients with MB on the middle left anterior descending coronary (LAD), those with MB on the proximal LAD had a higher likelihood to develop AF (OR 4.22; 95% CI 1.40-12.68, p = 0.01). Moreover, MB compression (OR 1.04; 95% CI 1.04-1.08, p = 0.013) and MB length (OR 1.06; 95% CI 1.004-1.11, p = 0.034) were independently associated with a higher prevalence of AF after adjusting for age and left atrial diameter. Conclusion: The presence of MB and its location, length, and compression degree were independently associated with an increased risk of preoperative AF in adult HOCM patients, which suggested that whether MB needed surgical treatment during septal myectomy should be considered.

Left bundle branch pacing in patients with right bundle branch block.

Abstract Background The paced morphology of right bundle branch block (RBBB) pattern is one of the parameters which can be used to confirm the left bundle branch capture during left bundle branch pacing (LBBP) implantation. However, changes of paced morphology after LBBP performed in patients with RBBB have not been well discussed. Objective To compare the paced morphology in patients with RBBB before and after LBBP and to discuss the possible mechanisms behind such changes. Methods Patients with RBBB who underwent LBBP implantation were selected. The QRS duration was measured before and after the implantation of LBBP for each patient and compared Student t test. Results We included 34 consecutive patients (median age 72.76 years, 73.53% male), of whom 3 had sick sinus syndrome (SSS) and 31 had high-grade atrioventricular conduction block (AVB). The average QRS duration was 144.87±5.22ms before LBBP implantation and 116.18±6.15ms after LBBP implantation, with a mean decrease in QRS duration of 28.70±3.30ms (95% CI: 27.55-29.85 ms, P < 0.01). Conclusion In patients with RBBB, the QRS duration after LBBP is narrower than that before LBBP. The specific mechanism is still unclear.

Comparing predictors of permanent pacemaker insertion after TAVR in new-generation versus early generation heart valves

Abstract Introduction Transcatheter Aortic Valve Replacement (TAVR) has emerged as the standard of care for patient with severe aortic stenosis. Conduction abnormalities leading to permanent pacemaker (PPM) implantation is one of the most common complication after TAVR. Newer generation valves (NGV) such as Sapien S3, XT and Evolut are widely being used in real time practice. The aim of this analysis is to compare the predictors associated with increased risk of PPM implantation after TAVR in newer generation valves (NGV) as compared to older generation valves (OGV). Methods A comprehensive literature search was performed in PubMed, Embase, and Cochrane to identify relevant trials. Summary effects were calculated using a DerSimonian and Laird random-effects model as odds ratio with 95% confidence intervals for all the clinical endpoints. Results 18 observational studies with 16,004 patients were identified. The incidence of PPM implantation after TAVR in our analysis was 8.9%. For the NGV, right bundle branch block (RBBB) and atrioventricular (AV) block were independent predictors of PPM insertion after TAVR. Baseline heart rate, presence of atrial fibrillation, and baseline intraventricular conduction delay were not significant predictors. However, for the OGV, risk of PPM implantation after TAVR was higher in presence of RBBB, depth of implant, valve size/annulus size, presence of atrial fibrillation and post-procedure AV block. Conclusions Our analysis identified 2 factors that were significantly associated with increased risk of PPM insertion after TAVR in NGV compared to 6 factors with OGV. With the increasing physician expertise with TAVI and use of NGV, the incidence of post TAVR PPM insertion has reduced but baseline RBBB and AV conduction block still continue to be significant predictors of increased PPM insertion after TAVR. Funding Acknowledgement Type of funding sources: None.

Atrioventricular-block necessitating ventricular pacing after tricuspid valve surgery in patients with a systemic right ventricle: long term follow-up

Abstract Background Patients with transposition of the great arteries (TGA) after atrial switch or congenitally corrected TGA (ccTGA) are prone to systemic right ventricular (sRV) failure. Atrioventricular (AV)-conduction disturbances and tricuspid regurgitation aggravate the course of sRV dysfunction. Timely tricuspid valve (TV) surgery stabilizes sRV function. However, TV surgery is an independent risk for AV-block and ventricular pacing in non-congenital cardiothoracic surgery patients. Chronic subpulmonary ventricular pacing-induced dyssynchrony further contributes to sRV failure, potentially reducing the beneficial effects of the tricuspid valve surgery. Purpose The aim of this study is to explore the incidence, timing and functional consequences of AV-conduction block requiring ventricular pacing after TV surgery in sRV patients. Methods Consecutive adolescent and adult patients with a sRV who underwent TV surgery in the period 1989–2020 and follow-up at our tertiary care center were included in this observational cohort study. Patients who were &amp;lt;10 years of age at the time of operation and/or died in perioperative, in-hospital, setting were excluded from analysis (n=5). Demographic and clinical data was collected from the patient records. Results Data of 28 patients (54% female, 57% ccTGA) was analysed (Figure). The mean age at surgery was 38±13 years, 5 patients (18%) received chronic ventricular pacing preoperatively. Mean follow-up was 9.7±6.8 years, during which 7 patients (25%) died and 3 (11%) underwent ventricular assist device implantation (VAD). Two patients died awaiting VAD/HTx, one patient died awaiting CRT upgrade. Seven (25%) patients underwent a re-operation, of which 3 (11%) TV replacement, 3 (11%) VAD and 1 (4%) pulmonary valve replacement. Of the 23 patients at risk of developing AV-block, 11 (48%) developed an indication for chronic ventricular pacing, of which 6 within 24 months postoperatively (4 before hospital discharge). Of the 21 patients with a device, 7 (25%) had successful resynchronization therapy (2 before TV surgery). Patients with chronic ventricular pacing had a wider QRS-duration (mean 121 ms vs 194 ms in those without pacing, p&amp;lt;0.001) and 43% had a severely reduced sRV function (vs 36% in those without pacing) at latest follow-up. Conclusions Patients with a failing sRV who undergo TV surgery are prone to AV-conduction abnormalities with 48% of this group developing an indication for chronic ventricular pacing during follow-up. Pacing-induced dyssynchrony can further contribute to sRV dysfunction. Implantation of an epicardial sRV lead at the time of TV surgery for future CRT may be considered to attenuate the detrimental effects of subpulmonary ventricular pacing in this heart failure prone patient group with complex anatomy, limiting transvenous possibilities. Funding Acknowledgement Type of funding sources: None.

Cardiac Scintigraphy and Screening for Transthyretin Cardiac Amyloidosis: Caveat Emptor.

Cardiac Scintigraphy and Screening for Transthyretin Cardiac Amyloidosis: Caveat Emptor.

The SUMO-specific protease SENP2 plays an essential role in the regulation of Kv7.2 and Kv7.3 potassium channels

Sentrin/small ubiquitin-like modifier (SUMO)-specific protease 2 (SENP2)-deficient mice develop spontaneous seizures in early life because of a marked reduction in M currents, which regulate neuronal membrane excitability. We have previously shown that hyper-SUMOylation of the Kv7.2 and Kv7.3 channels is critically involved in the regulation of the M currents conducted by these potassium voltage-gated channels. Here, we show that hyper-SUMOylation of the Kv7.2 and Kv7.3 proteins reduced binding to the lipid secondary messenger PIP2. CaM1 has been shown to be tethered to the Kv7 subunits via hydrophobic motifs in its C termini and implicated in the channel assembly. Mutation of the SUMOylation sites on Kv7.2 and Kv7.3 specifically resulted in decreased binding to CaM1 and enhanced CaM1-mediated assembly of Kv7.2 and Kv7.3, whereas hyper-SUMOylation of Kv7.2 and Kv7.3 inhibited channel assembly. SENP2-deficient mice exhibited increased acetylcholine levels in the brain and the heart tissue because of increases in the vagal tone induced by recurrent seizures. The SENP2-deficient mice develop seizures followed by a period of sinus pauses or atrioventricular conduction blocks. Chronic administration of the parasympathetic blocker atropine or unilateral vagotomy significantly prolonged the life of the SENP2-deficient mice. Furthermore, we showed that retigabine, an M-current opener, reduced the transcription of SUMO-activating enzyme SAE1 and inhibited SUMOylation of the Kv7.2 and Kv7.3 channels, and also prolonged the life of SENP2-deficient mice. Taken together, the previously demonstrated roles of PIP2, CaM1, and retigabine on the regulation of Kv7.2 and Kv7.3 channel function can be explained by their roles in regulating SUMOylation of this critical potassium channel.

B-PO05-159 CLINICAL PROFILE OF YOUNG PATIENTS WITH ATRIOVENTRICULAR CONDUCTION BLOCKS REQUIRING PERMANENT PACING

Atrioventricular (AV) conduction blocks are uncommon at a young age, most common causes being congenital or genetic. Other causes include inflammatory cardiomyopathies (IC) which can infiltrate the His-Purkinje system leading to AV blocks. The clinical profile of this group of patients has not been described previously. To describe the clinical and imaging profile of young patients with AV blocks and IC. We included young (<60 years) patients presenting with AV blocks (requiring permanent pacing) between August 2019 and December 2020. All patients underwent clinical evaluation, transthoracic echocardiography, and positron emission tomography computed tomography (PET-CT) of the chest to look for associated IC. Patients with mediastinal lymphadenopathy underwent transbronchial lymph node biopsy for histopathological confirmation of IC. Patients were categorized into clinical cardiac sarcoidosis (CS), isolated CS, or nonspecific IC based on the 2016 Japanese Circulation Society guidelines (JCS). A total of 21 patients were included in the study with a mean age of 40.4±12.4 years with a male predominance (M:F=2:1). Complete AV block was the commonest type of AV block (85.7%), with a mean ventricular escape rate of 39.7±11 bpm and a wide QRS morphology in 66% of the patients. Five of the patients (23.8%) had left ventricular systolic dysfunction. The mean left ventricular ejection fraction was 53.1±10.9%. Ten (47.6%) patients showed a combination of metabolic and perfusion defect on PET CT whereas seven (33.3%) patients had mediastinal lymphadenopathy. Four patients (19.1%) underwent transbronchial lymph node biopsy, of which only one (4.8%) had granulomatous lymphadenitis. After complete evaluation, the most common classification was nonspecific inflammatory cardiomyopathy in 13 (61.9%) patients, followed by isolated cardiac sarcoidosis in seven (33.3%) patients, and one patient (4.8%) had clinical cardiac sarcoidosis. Patients presenting with AV blocks at a young age (<60 years) should be evaluated for inflammatory cardiomyopathy, even with normal LVEF. They can be considered for appropriate anti-inflammatory medications for the underlying cardiomyopathy.