AV Conduction Research Articles

PO-688-02 BOTH ATRIOVENTRICULAR AND VENTRICULAR DYSSYNCHRONY DETERMINE OUTCOME TO CARDIAC RESYNCHRONIZATION THERAPY IN PROLONGED PR INTERVAL

Previous studies suggested that patients with prolonged PR interval receiving cardiac resynchronization therapy (CRT) have a worse outcome. The PR interval is determined by P-wave duration and PR segment. To obtain better insight in the relation of the components of PR interval and CRT response, as well as the interaction of PR interval and ventricular dyssynchrony (quantified as QRS area) with CRT response. In a retrospective multicenter study data from 631 CRT patients were analyzed. PR interval, P-wave duration and PR segment were determined from baseline ECG. Three-dimensional vectorcardiograms were synthesized from the ECG to calculate QRS area. Cut-off for QRS area was 109 μVs based on previous studies. Parameters were evaluated for their association with occurrence of the combined primary endpoint of all-cause mortality, left ventricular assist device implantation (LVAD) and heart transplantation (HTX). Secondary endpoint was echocardiographic reduction in left ventricular end-systolic volume. During a mean follow-up period of 4.2±2.3 years, 28% of patients reached the primary endpoint. Multivariate analysis showed that prolonged PR interval (≥190ms) and PR segment (≥66 ms) above optimal cut-off are independent predictors of primary endpoint occurrence (figure 1) and reduced echocardiographic response, but not for P-wave duration. Occurrence of the primary endpoint depended on PR interval in both small and large QRS area subgroups (<109 μVs versus ≥109 μVs) (figure 2). The risk of reaching the primary endpoint was significantly less in patients with PR prolongation and large QRS area compared to those with the same PR interval and small QRS area. Prolonged PR segment rather than P-wave duration relates to poor CRT outcome, suggesting that slower AV conduction is a marker of advanced cardiac disease. Second, prolonged PR interval is an independent predictor of worse clinical and echocardiographic response to CRT, but CRT is useful in patients with PR prolongation and significant ventricular dyssynchrony.View Large Image Figure ViewerDownload Hi-res image Download (PPT)

PO-656-01 PSEUDOINFARCT PATTERN IN CARDIAC SARCOIDOSIS: CORRELATION OF Q WAVES ON 12-LEAD ELECTROCARDIOGRAM WITH LATE GADOLINIUM ENHANCEMENT ON CARDIAC MRI AND PREDICTION OF VENTRICULAR TACHYARRHYTHMIAS

Screening for cardiac sarcoidosis (CS) with a 12-lead ECG is recommended in all patients with extra-cardiac sarcoidosis. Previous studies have characterized the poor sensitivity of AV conduction disease in screening for CS, but few have evaluated the presence of a pseudoinfarct pattern as a screening tool and a possible predictor of ventricular arrhythmias (VA).

Feasibility of electrocardiogram screening in the USA prior to high school sport participation

BackgroundSudden cardiac death in young athletes is a catastrophic event with an incidence of 1:40,000–1:80,000. Pre-participation sport screening utilizes a 14-point targeted evaluation. Recently, some states have added an ECG to the traditional history and physical. ObjectivesThe study describes a large-scale ECG screening program for middle and high school students. The aim is to depict important components, partners, and plans that can be adopted by other municipalities to help prevent sudden cardiac arrest in this population. MethodsIn 2019, Brevard County School Board in Florida mandated ECGs before participation in middle and high school sports. They partnered with a non-profit group that provides ECGs for a $20.00 fee. Volunteer pediatric cardiologists interpreted the ECGs. Results were emailed to participants, and abnormal results received a phone call to ensure appropriate follow-up care. ResultsThere were 5877 ECG screenings between 4/1/19–12/31/19 with 3% (199/5877) abnormal: 30% (60/199) ventricular conduction, 26% (51/199) arrhythmias, 13% (25/199) ventricular hypertrophy/chamber enlargement, 11% (21/199) ST-T abnormalities, 8% (16/199) prolonged QTc, 6% (12/199) WPW syndrome, and 4% (7/199) AV conduction and axis deviation. The incidence of critical heart disease with a risk of sudden cardiac arrest was 0.1% (8/5877) in those with a confirmed final diagnosis: 6 who underwent an ablation procedure for WPW syndrome, 1 with gene-positive long QTc, and 1 with left ventricular hypertrophy who is undergoing genetic evaluation for hypertrophic cardiomyopathy. ConclusionsTo our knowledge, this is the first large school district in Florida to mandate this level of cardiovascular screening. This pilot project demonstrates that large volume ECG screening prior to school sport participation is feasible at a low cost when utilizing appropriate manpower and providing access to follow up-care.

Ivabradine Use in a Pediatric Heart Transplant Recipient with Refractory Atrial Tachycardia

<h3>Introduction</h3> Ivabradine, an oral I_f channel antagonist, has been used in pediatric and adult heart failure patients for heart rate control, and in adult heart transplant (HT) recipients with sinus tachycardia secondary to cardiac graft denervation. There are little data describing the use of ivabradine in pediatric HT patients. We describe the use of ivabradine in a pediatric HT recipient with refractory ectopic atrial tachycardia (EAT) causing hemodynamic instability. <h3>Case Report</h3> A 3 year old male underwent HT for restrictive cardiomyopathy. Post-transplant course was complicated by pulmonary hypertensive crisis and cardiac arrest, followed by the development of EAT at a rate of >200 bpm and periods of atrial flutter 2 weeks post-transplant. Steroids were started for suspected clinical rejection, but endomyocardial biopsy was reassuring (ACR grade 1R/1A, pAMR0). Hypotension was noted when EAT rate was >170 bpm. Patient was refractory to esmolol, sotalol, and amiodarone. He underwent EP study with ablation of a posterolateral atrial focus, with recurrence of EAT several hours later. Given ongoing hemodynamic instability with EAT, repeat ablation was performed 1 week later with termination of EAT. However, periodic EAT recurred 3 weeks later and he was again symptomatic with recurrent emesis with rates >170 bpm. Ivabradine 0.05 mg/kg twice daily was initiated. After a single dose, the duration and frequency of EAT periods decreased. Rhythm was mostly sinus (SR) with a rate of 90-100 bpm with premature atrial contractions (PACs), few atrial couplets and blocked PACs. No hypotension, bradycardia, or hemodynamic instability was noted. He was discharged home and dose was up-titrated as an outpatient to 0.2 mg/kg twice daily. Six weeks later, a 72 hour Holter monitor showed predominately SR with short bursts of EAT with variable AV conduction, atrial ectopy overall making up <10% of beats, and rare premature ventricular contractions (PVCs). All subsequent clinic ECGs with follow up to 3 months demonstrated SR. Repeat Holter 3 months after initiation of ivabradine showed SR with rare, isolated PACs and PVCs with no EAT. <h3>Summary</h3> Ivabradine can be considered for EAT treatment in pediatric patients post-HT, with no identified side effects.

Sarcoidosis: Hiding in Plain Sight

<h3>Introduction</h3> Sarcoidosis is a systemic disease that can masquerade as many conditions. Due to its often patchy distribution, myocardial biopsy is only ∼30% sensitive. Herein we present a case of sarcoidosis diagnosed from an extra-cardiac biopsy years after the onset of cardiomyopathy. <h3>Case Report</h3> A 54 year old man initially presented with dyspnea and fatigue due to new onset HFrEF of 20%. He had a significant family history of SCD. His workup revealed non-obstructive CAD, a myxomatous mitral valve with bileaflet prolapse and moderate regurgitation, and a cystic structure attached to the tricuspid valve. Given his frequent ventricular ectopy, he was discharged on guideline therapy for HFrEF and a wearable cardioverter defibrillator. Genetic testing for dilated cardiomyopathies revealed EYA4 and TTN variants of unknown significance. A cardiac MRI a few months later demonstrated no abnormal late gadolinium enhancement and persistent systolic dysfunction, so he underwent AICD implant. His course was further complicated by recurrent admissions for supraventricular and ventricular tachyarrhythmias. A cardiopulmonary exercise stress test demonstrated low-risk results. Further evaluation noted prolonged AV conduction. A RHC revealed mild post-capillary pulmonary hypertension and a mildly decreased cardiac index at 2.01 L/min/m². Months later, he underwent CRT-D upgrade. He started improving functionally until he developed left eyelid swelling, initially thought to be lymphoma. An orbital biopsy revealed non-caseating granulomas. A PET/CT demonstrated FDG uptake within subcarinal lymph nodes but no cardiac uptake. Initially he declined immunomodulatory therapy, but as his symptoms worsened, he started corticosteroids and transitioned to mycophenolate mofetil due to intolerance of methotrexate. Due to disease progression on repeat FDG-PET, he was switched to infliximab. <h3>Summary</h3> The diagnosis of sarcoidosis can be difficult due to its variable presentation, including heart block, heart failure, ventricular arrhythmias and sudden cardiac death. Cardiac involvement occurs in 25% of cases. Our case was complicated by a cMRI that was negative for cardiac involvement, which emphasizes the importance of complimentary inflammatory imaging with FDG-PET. A multidisciplinary approach is needed that engages sarcoid specialists for earlier diagnosis to ensure rapid initiation of therapy to reduce end-organ dysfunction.

Pacing for complete heart block in pregnancy

Whereas sinus tachycardia and paroxysmal supraventricular tachycardia are common during pregnancy, bradyarrhythmias are infrequent. Moreover, bradyarrhythmias are generally well tolerated during pregnancy. Nevertheless, a 12-lead ECG is indicated for pregnant women who present with bradycardia, to rule out sinoatrial (SA) node dysfunction or AV conduction abnormalities. Third-degree AV block (complete heart block, CHB) requires multidisciplinary care during pregnancy, with combined input from Cardiologists and Obstetricians. As CHB is associated with increased mortality and morbidity if left untreated, permanent pacing is usually indicated during pregnancy, even if the patient remains asymptomatic. However, not all pregnant patients with CHB require urgent pacing. In a pregnant patient who has CHB with an escape rhythm with narrow QRS complexes and rate of &gt;50bpm, permanent pacemaker implantation can be delayed until after delivery, as described in this case report.

629 CPVT and complete atrio-ventricular block: two faces of the same coin?

Abstract Aims Catecholaminergic polymorphic ventricular tachycardia (CPVT) is an electrical genetic disease characterized by induction of malignant ventricular arrhythmias during adrenergic stress in structurally normal hearts. CPVT is correlated to syncope or sudden cardiac death (SCD). Usually, it is caused by an autosomal dominant mutation in the cardiac ryanodine receptor (RyR2), an essential gene for Ca2+ homeostasis. Methods and results Our case series refers to: a man (59 years) who came to our attention for a clinical check-up 4 years after implanting bicameral pacemaker at the age of 55 years for complete AV block; and his three sons (E. female 27 years; D. male 25 years; and B. female 17 years) who had evidence of polymorphic non-sustained ventricular tachycardia (NSVT) with increasing effort during stress test. The three sons performed cardiac MRI and underwent genetic test. All three were found to be carriers of the same microdeletion of the RYR 2 gene (1q43- extended for about 49 kb) at the genetic test. They also have non-compacted myocardium at cardiac MRI. The father was also found to be a carrier of the same genetic microdeletion, while the mother was negative to the genetic test. The man was diagnosed to be a carrier of the mutation 4 years after pacemaker implantation. Conclusions Mutation of the RyR2 may have different phenotypic expressions and can be correlated to various clinical manifestations. CPVT is the most common one, and its prompt identification is crucial to prevent subjects from sport-related risks and to plan an efficient therapy. Our case series provides evidence for a careful consideration of such a genetic disorder even in presence of a major AV conduction disease in a relatively young subject. In the present case series, no major adverse events occurred. However, we can, in the aftermath, speculate that if a genetic disorder had been suspected when AV block occurred, a timely diagnosis could have been made earlier also for the sons.

C8. An Extremely Rare Case: Cardiac Contusion Presenting with an Atrioventricular Block, An Unfortunate Fall

Abstract Background Blunt cardiac injury (BCI), also referred to cardiac contusion, is a known cause of myocardial injury. It is often challenging to diagnose in the absence of clear diagnostic criteria. The clinical manifestation ranges from none to fatal arrhythmias to cardiac wall rupture seen on post-mortem examination. Cardiac biomarkers and electrocardiograms are usually helpful in identifying cardiac trauma but are not necessarily abnormal in all cases. Case Illustration A 55-year-old male with no history of cardiac disease was brought to the emergency department after a motor vehicle collision resulted in chest wall injury. The patient was found to have left clavicle fracture, left costae II-VII fractures, and hematothorax followed by chest tube insertion. The patient had multiple episodes of complete heart block with junctional escape rhythm alternate with high degree 2:1 AV conduction, and sometimes became a normal sinus rhythm. A temporary pacemaker was inserted. After the patient underwent the ORIF procedure, cardiac rhythm revealed normal sinus rhythm and temporary pacemaker is removed. Discussion High-degree AV block has been reported in human studies following BCI, secondary to necrosis, inflammation, or fibrotic changes in the subendocardial tissue. 50% of patients reviewed in the literature had a recurrence or permanent complete heart block requiring pacemaker implantation and complete heart block secondary to BCI which was associated with a 20% mortality in the post-traumatic period. Our patient developed a fatal heart block in the early period which could have easily been missed.

C8. An Extremely Rare Case: Cardiac Contusion Presenting with an Atrioventricular Block, An Unfortunate Fall

Abstract Background Blunt cardiac injury (BCI), also referred to cardiac contusion, is a known cause of myocardial injury. It is often challenging to diagnose in the absence of clear diagnostic criteria. The clinical manifestation ranges from none to fatal arrhythmias to cardiac wall rupture seen on post-mortem examination. Cardiac biomarkers and electrocardiograms are usually helpful in identifying cardiac trauma but are not necessarily abnormal in all cases. Case Illustration A 55-year-old male with no history of cardiac disease was brought to the emergency department after a motor vehicle collision resulted in chest wall injury. The patient was found to have left clavicle fracture, left costae II-VII fractures, and hematothorax followed by chest tube insertion. The patient had multiple episodes of complete heart block with junctional escape rhythm alternate with high degree 2:1 AV conduction, and sometimes became a normal sinus rhythm. A temporary pacemaker was inserted. After the patient underwent the ORIF procedure, cardiac rhythm revealed normal sinus rhythm and temporary pacemaker is removed. Discussion High-degree AV block has been reported in human studies following BCI, secondary to necrosis, inflammation, or fibrotic changes in the subendocardial tissue. 50% of patients reviewed in the literature had a recurrence or permanent complete heart block requiring pacemaker implantation and complete heart block secondary to BCI which was associated with a 20% mortality in the post-traumatic period. Our patient developed a fatal heart block in the early period which could have easily been missed.

Abstract 9355: Home Monitoring to Detect Emergent Anti-Ro/SSA Antibody Mediated Fetal Av Block: Preliminary Results of the STOP BLOQ Study

Introduction: Fetal complete AV block (CAVB), complicates 2% of anti-Ro antibody positive pregnancies and carries substantial perinatal morbidity and mortality. Anti-inflammatory treatment of 1° and 2° (emergent) AVB may prevent progression to CAVB, yet the optimal surveillance strategy to detect emergent CAVB is unknown. Methods: We examined participants in a multicenter, open label clinical trial of pregnancies risk stratified by anti-Ro antibodies into high (≥1000 IU) or low (&lt;1000 IU) titers. Low titer mothers were followed by echocardiograms or routine OB care; high titer mothers underwent 3x/day fetal heart rate monitoring (FHRM) and weekly or biweekly fetal echocardiograms from 17-26 weeks. If mothers suspected abnormal FHRM, they texted fetal heart sounds to cardiologist, who assessed FHRM and reassured or referred for emergency fetal echocardiogram (performed in &lt; 6 hours). Postnatal electrocardiograms (ECG) were evaluated. Results: Sixty-five subjects from 7 centers were recruited and 60 (92%) enrolled at 14 (5-19) weeks. There were 24 (40%) low titer and 36 (60%) high titer mothers. High titer mothers underwent FHRM; 92% completed FHRM and 100% completed surveillance echocardiograms. Of 3,360 FHRM recordings, mothers texted 39 (1%) recordings of concern; cardiologist deemed 2/39 (5%) as abnormal and emergency echocardiograms revealed atrial ectopy. No fetus developed emergent or CAVB. Postnatal ECGs demonstrated normal AV conduction in all neonates: 2 miscarried at &lt;12 weeks and 48 are in utero. Conclusion: These data support FHRM in the surveillance of anti-Ro antibody positive pregnancies because of high enrollment, feasibility, and accuracy in arrhythmia detection.

Abstract 13795: Deep Learning of Electrocardiogram Waveforms for Diagnosis of Heart Failure With Reduced Left Ventricular Ejection Fraction

Introduction: A deep learning-aided electrocardiogram (Deep-ECG) was trained to identify left ventricular systolic dysfunction (LVSD) of ejection fraction (EF) less than 40%. We evaluated the performance of Deep-ECG among patients with symptomatic heart failure (HF) in Korean acute HF registry. Hypothesis: Deep-ECG may be useful for identifying EF in HF with reduced EF (HFrEF). Methods: We included 1,292 symptomatic HF patients from 2011 to 2014 who underwent echocardiography and ECG within 30 days. The performance of Deep-ECG for LVSD was determined using receiver-operator characteristic curve (AUC) values. Results: Mean age was 67.8±14.4 years and 56% of patients were men. HFrEF, HF with mid-range EF and HF with preserved EF(HFpEF) was present in 42.3%, 17.9% and 39.8%, respectively. Using the optimal cut-off by Youden’s index, AUC value was 0.844 for identifying HFrEF among HF patients. AUC values were significantly higher for patients with normal AV conduction (0.872 vs. 0.759, p =0.002) and normal interventricular conduction (0.848 vs. 0.812, p=0.037) when compared to each conduction delay. Interestingly, corrective (true-positive) results in Deep-ECG for LVSD were acquired in patients bigger LV end systolic dimension (LVESD) than in false negative group (54.4±10.1mm vs. 49.7±8.7mm, p&lt;0.001). Conclusions: The Deep-ECG algorithm had very good discrimination for HFrEF in real world HF cohort. This algorithm may be useful for identification of LVSD in resource-limited settings. Figure 1. Scatterplot demonstrating LVESD and the performance of Deep-ECG for identifying LVSD (LVEF &lt; 40%)

Efficacy of left bundle branch area pacing in patients with indication for cardiac resynchronization therapy

Abstract Background Cardiac resynchronization therapy (CRT) with biventricular pacing has demonstrated clinical benefits in heart failure patients with left bundle branch block (LBBB) and ventricular dysfunction. Left bundle branch area pacing (LBBAP) results in a relatively short QRS duration (QRSd) with fast left ventricular activation and could be considered as an alternative to conventional CRT. Purpose The aim of the present study was to evaluate the feasibility and outcomes of LBBAP in patients with indications for CRT. Methods Consecutive patients with indications for CRT were included. LBBAP was performed via transventricular septal approach (1–3). We aimed to achieve a paced QRS with right bundle branch conduction delay morphology, a stimulus to peak left ventricular activation time (S-LVAT) &amp;lt;100ms and/or a QRSd ≤130ms. AV delay programming was individualized in patients in sinus rhythm, taking consideration of the AV conduction, programming the one that generated the shortest QRSd at rest. Rate adaptive AV was also activated in these patients. Pacing electrical and echocardiographic parameters were recorded at baseline and during follow-up. Results LBBAP was achieved in 19 of 21 (90.5%) patients with indication for CRT. Indications were heart failure with LBBB and left ventricular ejection fraction (LVEF) ≤35% in 8 (42%), AV node ablation or AV block with LVEF &amp;lt;50% and high expected RV pacing burden in 9 (47%), 1 pacing-induced cardiomyopathy and 1 patient with biventricular pacemaker malfunction (high LV capture threshold). The mean follow-up was 4.6±1.7 months and the percentage of ventricular pacing was 93.4±13.9%. There were no device-related complications during this period. LBBA capture threshold was 0.6±0.3V at 0.4ms at the implantation, and remained stable (0.7±0.1 V, p=0.17). The lead impedance and R-wave amplitude at implantation were 636±106 ohms and 13.4±6.8 mV, and 541±88 ohms and 13.0±5.1 mV during the follow-up (p&amp;lt;0.001 and p=0.27, respectively). Mean S-LVAT was 85.5±13.9 ms, and mean QRSd was 122±9 ms, that remained stable during follow-up (122 vs 124 ms, p=0.21). In patients with LBBB, a significant narrowing of paced QRSd was achieved (160.9±16.7 vs. 123.9±9.7 ms, p&amp;lt;0.001). Mean LVEF increased by 15.9%, from 35.4±8.9% at baseline to 51.3±9.8% at follow-up (p&amp;lt;0.001) in the overall population, and 14.5% (from 32.7±4.8% to 47.2±10.7%, p=0.001) in patients with LBBB. After one month, estimated time for elective replacement was 11.9±0.4 years. Conclusions LBBPA was successfully achieved in 90.5% of the patients with indication for CRT, with good and stable pacing electrical parameters, long estimated battery longevity and relatively narrow QRS, and was associated with improvement in cardiac function. LBBAP may be considered as a first-line option for patients with indications for CRT. Funding Acknowledgement Type of funding sources: None.

Prospective evaluation of the learning curve and electrical characteristics of left bundle branch area pacing

Abstract Background Left bundle branch area pacing (LBBAP) has recently been introduced as a physiological pacing technique with a synchronous ventricular activation. Objective To prospectively evaluate the feasibility and learning curve, as well as the electrical characteristics of LBBAP. Methods In 80 consecutive LBBAP pacemaker patients, ECG characteristics during intrinsic rhythm, RV septum pacing (RVSP) and LBBAP were evaluated. From the ECG's QRS duration and LVAT (stimulus to V6 R-wave peak time, RWPT) were measured. Also, the left bundle branch potential (LBBpot) to V6 RWPT interval was measured and compared to the LVAT. After conversion of the ECG into VCG (Kors conversion matrix), QRS area, as measurement for electrical dyssynchrony, was calculated. Results Permanent lead implantation was successful in 77/80 patients (96%) undergoing an attempt at LBBAP. LBBAP lead implantation time as well as fluoroscopy time were significantly shorter during last 25% of implantation compared to first 25% of implantations (17±5 min vs. 33±16 min and 12±7 min vs. 21±13 min, respectively, panel A and B). LBB capture was obtained in 54/80 patients (68%). In 36/45 patients (80%) with intact AV conduction and narrow QRS an LBBpot was present. The mean interval between the LBBpot and the onset of QRS was 22±6 ms. In the patients with narrow QRS (n=45), QRS duration increased significantly during both RVSP (139±24 ms) and LBBAP (123±21 ms), compared to intrinsic rhythm (95±13 ms). QRS area on the other hand, increased during both RVSP (73±20 μVs) but decreased during LBBAP (41±15 μVs), to values close to intrinsic rhythm (32±16 μVs, panel C). For all patients, QRS area was significantly lower in patients with LBB capture compared to patients without capture (43±18 μVs vs 54±21 μVs, respectively). In patients with LBB capture (n=54), LVAT was significantly shorter compared to patients without LBB capture (75±14 vs. 88±9 ms, respectively). In the patients with LBB capture, there was a significant correlation between the LBBpot – V6 RWPT and S – V6 RWPT intervals (Pearson correlation 0.739, P&amp;lt;0.001). Conclusion LBBAP is a safe and feasible technique, with a clear learning curve that seems obtained after ± 40–60 implantations. LBB capture is obtained in two-thirds of patients. Although QRS duration remains prolonged, LBBAP largely restores ventricular electrical synchrony to values close to intrinsic (narrow QRS) rhythm. Funding Acknowledgement Type of funding sources: None.

Emery-Dreifuss muscular dystrophy presenting as a heart rhythm disorders in children

Abstract Introduction Emery-Dreifuss muscular dystrophy (EDMD) is an inherited muscle dystrophy often accompanied by cardiac abnormalities in the form of supraventricular arrhythmias, conduction defects, sinus node dysfunction. Cardiac phenotype typically arises years after skeletal muscle presentations, though, can be severe and life-threatening. The disease usually manifests during the third decade of life with elbow joint contractions and progressive muscle weakness and atrophy. Objective To present our clinical experience of diagnosis and treatment of arrhythmias in children with Emery-Dreifuss muscular dystrophy Materials and methods We enrolled 5 patients with different forms of EDMD (X-linked and autosomal dominant) linked to the mutations in EMD and LMNA genes, presented with early onset of cardiac abnormalities and no leading skeletal muscle phenotype. The predominant forms of cardiac pathology were atrial flutter, atrial fibrillation and conduction disturbances that progress over time. Clinical examination included physical examination, 12-lead electrocardiography, Holter ECG monitoring (HM), transthoracic echocardiography, neurological examination and biochemical and hormone tests. Also we performed CMR, electrophysiological study (EPS), treadmill test of some patients. One patient underwent an endomyocardial biopsy to exclude inflammatory heart disease. Target sequencing was performed using a panel of 108 or 172 genes Results We observed five patients with EDMD and cardiac debut during first-second decades of life: 3 with 1st subtype (variants in EMD gene) and 2 with 2nd subtype (variants in LMNA gene). All patients were males. The mean age of cardiac manifestation was 13,2±3,11 (from 9 to 16 y.o.). The mean follow-up period was 7,4±2,6 years. All patients presented with sinus node dysfunction and four out of five with AV conduction abnormalities. The leading arrhythmic phenotypes included various types of supraventricular arrhythmias: multifocal atrial tachycardia (AT) (n=4), premature atrial captures (PACs) (n=4), atrial flutter, (AF) (n=3), atrial fibrillation (AFib) (n=3) and AV nodal recurrent tachycardia (AVRNT). Heart rhythm disorders were the first manifestation in all three patients with 1st EDMD subtype. Radiofrequency ablation was performed in 2 patients, one of them received permanent pacemaker implantation. Conclusions In conclusion, while being the rare cases, heart rhythm disorders can represent the first and for a long time, the only clinical symptom of EDMD even in the pediatric group of patients. Therefore, thorough laboratory and neurological screening along with genetic studies, are of importance in each pediatric patient presenting with complex heart rhythm disorders of primary supraventricular origin to exclude EDMD or other neuromuscular disorders. Funding Acknowledgement Type of funding sources: None.

Long-term outcome of patients with cardiolaminopathy undergoing defibrillator implantation: single-center experience

Abstract Background Mutations in the LMNA gene are associated with a high arrhythmic risk. The history of the disease in patients undergoing ICD implantation is poorly characterized. Purpose To evaluate the phenotype of patients with cardiolaminopathy at the time of first ICD implantation, the incidence, characteristics and timing of ventricular arrhythmias (VAs) during follow up and the predictive value of the European score (that assigns a point each to non-sustained VT (NSVT), left ventricular ejection fraction (LVEF)&amp;lt;45% at first contact, male sex and non-missense mutations) and of the Wahbi score (that also includes conduction disturbances) for both VAs and heart failure (HF) related outcomes. Methods Patients were identified retrospectively. Clinical and device data were collected at baseline and during follow-up. Results We identified 26 patients (54% male, 42±8 years, 31% with familial history of sudden cardiac death, 31% with non-missense mutation) undergoing ICD implantation, 96% in primary prevention, 47% with single chamber ICD, 38% with dual chamber ICD. At the time of implantation, 30% had skeletal muscle involvement, 15% history of syncope, 4% of cardiac arrest, 62% previous NSVT. Also, 38% had a history of supraventricular arrhythmias and 61% had AV conduction disturbances. LVEF was 41±11%, 35% were in NYHA class ≥2, the mean European and Wahbi scores were 2.1±0.8 and 18.2±8.9, respectively. During 8.3±5 years, 15% were transplanted, 8% died due to HF, 4% underwent LVAD implantation, despite 31% having received an upgrade to CRT-D. Appropriate device interventions occurred in 46% of patients with a median time to first event of 29 months (IQR 13–93), for a total of 137 ATP, 51% of which effective (median 3ATP/patient, IQR 1–8) and of 26 shocks, 96% of which effective (median 2 shocks/patient, IQR 1–3); 12% had an arrhythmic storm. The first treated arrhythmia was a polymorphic VT/VF in 17%, a monomorphic VT in the others (medium cycle length 293±37 msec). Survival free from appropriate ICD interventions at 1 and at 5 years was 75% and 19% respectively in case of a European score ≥3 vs 94% and 82% in case of a score &amp;lt;3 (Logrank test p&amp;lt;0.01), 72% and 46% in case of Wahbi score ≥30 vs 100% and 86% with score &amp;lt;30 (p&amp;lt;0.01), with no differences in terms of death/transplant (figure). At last follow-up, 92% of patients a were taking beta-blocker, 42% amiodarone, 8% sotalol, 4% flecainide, 8% mexiletine. Also, 4% had undergone invasive VT ablation, 8% bilateral cardiac sympathetic denervation. Conclusions Patients with cardiolaminopathy are at a high risk of both arrhythmic and heart failure progression over the first decade after implantation of the first ICD. A European score ≥3 identifies patients with 5-year shock/ATP free survival of less than 20% but does not predict death/transplantation. The first arrhythmic event in these patients is more frequently a rapid monomorphic VT with modest ATP efficacy. Funding Acknowledgement Type of funding sources: None.

Cryofreezing for slow-pathway modification in patients with slow-fast AVNRT: Efficacy, safety, and electroanatomical relation between sites of transient AV block and sites of successful cryoablation.

Cryoablation has emerged as an alternative to radiofrequency ablation for treating atrioventricular nodal reentrant tachycardia (AVNRT). The aim of this prospective study was to evaluate the efficacy and safety of cryoapplication at sites within the mid/high septal region of Koch's triangle and the relation between sites of transient AV block (AVB) and sites of successful cryoablation. Included were 45 consecutive patients undergoing slow-fast AVNRT cryoablation. Initial delivery of cryoenergy was to the mid-septal to high septal region of Koch's triangle. Transient AVB occurred during cryoenergy delivery in 62% (28/45) of patients. Median distance between sites at which cryofreezing successfully eliminated slow pathway conduction and sites of AVB was 4.0 (3.25-5.0) mm. Sites of successful cryoablation tended to be to the left and inferior to the AVB sites. The atrial/ventricular electrogram ratio was significantly lower at sites of successful cryoablation than at AVB sites (0.25 [0.17-0.56] vs. 0.80 [0.36-1.25], p < .001). Delayed discrete or fractionated atrial electrograms were recorded more frequently at sites of successful cryoablation than at AVB sites (78% vs. 20%, p < .001). No persistent AV conduction disturbance occurred, and 96% (43/45) of patients showed absence of recurrence at a median follow-up time of 25.0 months. Cryoablation of slow-fast AVNRT and targeting the mid/high septal region of Koch's triangle was highly successful. AVB frequently emerged near the site at which the slow pathway was eliminated but always resolved by regulating the energy delivery under careful monitoring, and it may be distinguishable by its local electrogram features.

LONG TERM OUTCOMES IN TREATED LYME CARDITIS: A CASE SERIES

<h3>BACKGROUND</h3> Lyme disease (LD) is a tick-born bacterial infection caused by Borrelia burgdorferi. Lyme carditis (LC) is an early-disseminated manifestation of LD, commonly manifesting as high-degree atrioventricular block (AVB) that fluctuates rapidly over minutes to days. Most conduction abnormalities caused by LC resolves with appropriate antibiotic therapy. However, the long-term outcomes of treated LC are not known. In this case series, we describe and characterize the long-term outcomes of patients treated with LC. <h3>METHODS AND RESULTS</h3> Prospective study of patients with serologically-confirmed LC. All were treated with the standard protocol designed at our center including 10 days of intravenous ceftriaxone followed by oral antibiotics for a total course of 3 weeks. All patients performed a stress test at discharge with 1:1 AV conduction above 120 bpm. Seven patients (mean age 31.3 years, 86% male) with LC presented with second-degree type I/II or third-degree AVB to our center. Presenting symptoms included malaise (71%), presyncope (43%), syncope (29%), palpitations (57%), and dyspnea (43%). 2 patients required temporary pacing for symptomatic bradycardia. Mean follow-up was 20.8 months, at which time all patients were asymptomatic and resumed usual physical activities. All were in sinus rhythm without any repolarization abnormalities. None required permanent pacing. A summary of short- and long-term outcomes is shown in Table 1. The progression of atrioventricular block at admission, discharge, and long-term follow-up is shown in Figure 1. <h3>CONCLUSION</h3> To our knowledge, this is the first prospective study characterizing long-term LC follow-up. All patients in this study were asymptomatic, in sinus rhythm, and had no conduction abnormalities in long-term follow-up. Given the lack of literature on long-term outcomes of LC, further prospective studies are necessary to develop evidence-based guidelines.

Bradyarrhythmic Cardiac Arrest—A Rare Manifestation of Fexofenadine Cardiotoxicity

A 66-year-old diabetic, hypertensive, and hypothyroid female presented in the emergency department with cardiac arrest, for which cardiopulmonary resuscitation was immediately initiated. She had been on oral fexofenadine for 36 h prior to the event. Post successful resuscitation, her cardiac rhythm showed high-grade atrioventricular block. Patient was treated with mechanical ventilatory support and temporary transvenous pacing. No treatable cause could be identified, and she recovered completely following fexofenadine discontinuation, without need for a permanent pacemaker. She has remained asymptomatic during 1 year of follow-up with no documented arrhythmias. An electrophysiological study at 6 months revealed prolonged HV interval (70 ms) with 1:1 AV conduction and no inducible arrhythmias. This is probably the first reported case of fexofenadine-induced cardiac arrest in a patient without previous history of heart disease.

Interest of ivabradine in pediatric arrhythmia. About a case and review of the literature

By inhibiting the pacemaker current if of the sinoatrial node (SN), ivabradine was first use as an alternative to betablockers in the treatment of heart failure [1] . For a few years, it has been proposed as an adjuvant therapy for postoperative [2] or congenital junctional ectopic tachycardia [3] . But ivabradine can also be effective on atrial and ventricular abnormal automaticity [4] . We report the case of a 9 years old girl who was diagnosed of polymorphic atrial tachycardia at birth. The child was first treated by amiodarone. When amiodarone had to be withdraw because of thyroid dysfunction, multiple antiarrhythmic drugs were tested alone or in association: betablockers, flecainide, digoxine. Despite medication, the child experimented multiple high rate non-sustained tachycardia per day. After an antiarrhythmic washout, ivabradine was started. Fig. 1 is the patient Holter without any treatment showing a very anarchic rhythm, mostly rapid arrhythmia. Fig. 2 is the patient Holter after only 2 takes of ivabradine that shows a marked efficacy of the drug. Ivabradine inhibits selectively the If current that is responsible of the pacemaker activity of the SN and the AV node. If current can also be responsible of abnormal automaticity of the atrial and ventricular myocardium. In such case, ivabradine is highly effective to control the arrhythmia. Still, ivabradine efficacy is difficult to predict, but regarding its overall safety, it can be tested. In a randomized, double-blind trial of pediatric patient with dilated cardiomyopathy, Bonnet et al. did not report more adverse event with ivabradine than with placebo [5] . The outcome of atrial ectopic arrhythmia in the pediatric population is good: 78% will resolve spontaneously when diagnosed under 3 years old [6] . Ivabradine could be an alternative to catheter ablation in the very young or in pediatric patient with multifocal arrhythmia or organized arrhythmia close to the AV conduction system.

The Tale-Tell Heart: Evolutionary tetrapod shift from aquatic to terrestrial life-style reflected in heart changes in axolotl (Ambystoma mexicanum).

During amphibian metamorphosis, the crucial moment lies in the rearrangement of the heart, reflecting the changes in circulatory demands. However, little is known about the exact shifts linked with this rearrangement. Here, we demonstrate such myocardial changes in axolotl (Ambystoma mexicanum) from the morphological and physiological point of view. Micro-CT and histological analysis showed changes in ventricular trabeculae organization, completion of the atrial septum and its connection to the atrioventricular valve. Based on Myosin Heavy Chain and Smooth Muscle Actin expression we distinguished metamorphosis-induced changes in myocardial differentiation at the ventricular trabeculae and atrioventricular canal. Using optical mapping, faster speed of conduction through the atrioventricular canal was demonstrated in metamorphic animals. No differences between the groups were observed in the heart rates, ventricular activation times, and activation patterns. Transition from aquatic to terrestrial life-style is reflected in the heart morphology and function. Rebuilding of the axolotl heart during metamorphosis was connected with reorganization of ventricular trabeculae, completion of the atrial septum and its connection to the atrioventricular valve, and acceleration of AV conduction.