Atrioventricular Conduction Research Articles

PO-03-073 CARDIONEUROABLATION FOR THE MANAGEMENT OF PATIENTS WITH RECURRENT VASOVAGAL SYNCOPE AND SYMPTOMATIC BRADYARRHYTHMIAS: THE CNA-FWRD CROSS-OVER TRIAL AND PROSPECTIVE REGISTRY

Cardioneuroablation (CNA) has been introduced as a potential alternative treatment strategy in appropriately selected patients for prevention of recurrent cardioinhibitory vasovagal syncope (VVS) and functional atrioventricular block (AVB). The Cardioneuroablation for the Management of Patients with Recurrent Vasovagal Syncope and Symptomatic Bradyarrhythmias (CNA-FWRD) Registry is a multicenter prospective registry and Cross-Over Trial with the objective of examining acute and long-term outcomes of CNA in appropriately selected patients with recurrent VVS and AVB. The main study will be a prospective cross-over design with patients randomized to two groups receiving 6-month treatment interventions in alternate order: Medical therapy followed by CNA (Group 1) or CNA followed by Medical therapy (group 2). Patients declining the cross-over study will be eligible for inclusion in a parallel prospective registry. Details of inclusion and exclusion criteria are provided in Table 1. Functional AVB is defined as sudden change from physiologic atrioventricular conduction to transient second- or third-degree AVB resulting in symptomatic pauses longer than 2 seconds. All fragmented EGMs that demonstrated 3 or more deflectionsin the regions that are known to be consistent with probable localization of ganlionated plexus (GP) will be identified and tagged (Figure 1). In each VVS patient, the GPs will be targeted in the following order: the superior left atrial GP, the Marshall tract GP (MTGP), the inferior left atrial GP, the superior right atrial GP (RSGP), and finally the inferior right atrial GP. Additional right atrial ablation on the superior aspect on the interatrial septum will be performed for RSGP. In patients with AVB, the posteromedial left atrial GP, MTGP and RSGP will be ablated, respectively. The primary outcome is 12-month syncope recurrence post catheter ablation. Secondary outcomes include procedure-related complications, freedom from syncope at 12 months, freedom from AVB at 12 months, need for repeat GP ablation, quality of life at 12 months. Study enrollment began for (8) sites on June 20, 2022. So far, 59 patients have been enrolled into the registry. There remains lack of procedural standardization CNA as a treatment strategy and limited long-term data for key outcomes including recurrence of syncope, durable impact of disruption of the autonomic nervous system and long-term complications. CNA-FWRD has the potential to help fill this information gap.Tabled 1Inclusion and Exclusion Criteria for Study Cohort (PO-03-073)DiagnosisInclusion criteriaExclusion criteriaVVSAt least 3 vasovagal syncope episodes in the preceding 12 monthsPresence of arrhythmic conditions that can cause syncopeAge < 60 yearsPresence of evidence related to structural heart disease> 3s asystole on head-up tilt testingPrevious history of catheter ablation> 3s asystole on ambulatory ECG monitoringPresence of inheritable arrhythmic conditionsPositive response to atropine testOrthostatic hypotension on Head-up tilt table testUnresponsiveness to conventional treatment modalitiesPseudo-syncopePresence of proven indication for Pacemaker implantationAbnormal thyroid function levelsUsage of negative chronotropic drugsChronotropic incompetence at exercise stress testAVBAll AVB casesHistorySymptomatic bradycardiaUse of negative chronotropic or dromotropic drugsLaboratoryassessmentNormal thyroid function testsThyroid function abnormalitySuspicionof obstructive sleep apneaNegative polysomnogramPositive polysomnogramBaselineECGLeft bundle brunch blockExerciseStress TestChronotropic incompetenceOccurrence or worsening of AVB with exerciseEPSSupra-Hisian AVBIntra/infra-Hisian AVBParoxysmal AVBBaselineECGNormal PR interval or first degree AVBSecond or third degree AVBHolter RecordingPR prolongation before second or third degree AVB episodeConstant PR before second or third degree AVB episodeDecrease in sinus rate during or just prior to second or third degree AVB episodeIncrease in sinus rate during second or third degree AVB episodeResolution of AVB with an increase in sinus rateResolution of AVB with a constant sinus rateEPSBaseline H-V interval <55msecBaseline H-V interval ≥55 msecIntra/infra-Hisian AVB by atrial pacing at rates of 150 bpm or lessPersistent AVBBaselineECGSecond or third degree AVBAtropine responseComplete resolution of atrioventricular conduction or conversion to first degree AVB with atropine infusionAVB unresponsive to atropine testExercise stress testComplete resolution of AVB or conversion to first degree AVB with exercise testAVB unresponsive to exercise stress testEPSBaseline H-V interval <55msecBaseline H-V interval ≥55 msecIntra/infra-Hisian AVB by atrial pacing at rates of 150 bpm or less Open table in a new tab

PO-04-109 OUTCOMES OF RADIOFREQUENCY CATHETER ABLATION OF DISTINCT ANTERO-SEPTAL ACCESSORY PATHWAYS BY CONVENTIONAL ELECTROPHYSIOLOGICAL MAPPING

Ablation of para-hisian accessory pathways (APs) is challenging because of their proximity to the conduction system. A high incidence of atrio-ventricular (AV) conduction injury (up to 50%) was observed for the ablation of true para-hisian APs. In this retrospective study, we report the outcomes of a large series of patients with antero-septal APs (including true para-hisian APs) who underwent radiofrequency catheter ablation (RFCA). Among 1676 consecutive patients undergoing RFCA of APs between January 2016 and September 2022 in our center, 276 patients with an isolated antero-septal AP were enrolled. Conventional intracardiac mapping and fluoroscopy were used in all procedures. All procedures were performed by an experienced operator with a standard 3.5 mm irrigated tip catheter. A para-hisian AP was confirmed when an His potential was recorded by the distal ablation catheter at the site of earliest atrial activation during orthodromic AVRT or after ablation of the manifest AP. APs were categorized as true para-hisian if a sharp high-amplitude His potential was recorded. Among the 276 patients (mean age 27±10 years; 150 males) with an antero-septal AP: 55 patients (20%) had a true para-hisian AP (Group 1); 89 patients (32%) had a not-sharp low-amplitude His potential (Group 2); 132 patients (48%) had no His potential recorded (Group 3). The three Groups showed no significant difference in clinical (age, sex, history of AF and AVRT, structural heart disease) and EPS variables (conduction properties of APs and inducibility of AVRT and AF). Inferior vena cava (n=260) and aortic retrograde (n=16, targeting the left basal septum) approaches were used. Procedural acute success (no evidence of residual preexcitation or abnormal retrograde conduction) was obtained in all patients. No patient experienced acute severe complications. RF ablation time was longer in Group 1 (135±41 sec vs 115±27 sec [Group 2] vs 92 sec ±18 sec [Group 3], p=0.03). Accelerated junctional rhythm during RFCA was more frequent in Group 1 (25% vs 14% [Group 2] vs 3% [Group 3], p=0.02). After a median follow-up of 40 (2-78) months no high-grade AV block was reported. 1 patient of Group 1 had a recurrent para-hisian AP and underwent a second successful RFCA. In this large series of antero-septal APs (including a high number of true para-hisian APs), electrophysiologically-guided RFCA was safe and highly effective.

CE-452779-1 IVABRADINE FOR CONTROLLING HEART RATE IN PERMANENT ATRIAL FIBRILLATION: RESULTS OF THE TRANSLATIONAL CLINICAL TRIAL BRAKE-AF

Ivabradine has been postulated to reduce the ventricular rate in atrial fibrillation. However, the mechanisms responsible for that reduction and its performance as rate-control drug are not known To evaluate the mechanism of inhibition of atrioventricular conduction produced by ivabradine and to determine its efficacy and safety compared with digoxin in permanent atrial fibrillation The effects of ivabradine in atrioventricular nodal and ventricular cells were studied by in-vitro whole-cell patch-clamp experiments . Changes in If, INa, ICaL, ICaT, IKs, IKr, and IK1 conductances were integrated in mathematical simulations of nodal and ventricular action potentials. In parallel, a multicenter, randomized, open-label, phase III clinical trial compared ivabradine (5mg BID increased to 7.5mg BID after one month) versus digoxin (0.10-0.25mg QD adjusted by serum levels) for uncontrolled permanent atrial fibrillation despite beta-blockers or calcium channel blockers. Primary efficacy and safety endpoints were the reduction of the mean daytime heart rate at 3 months and a combination of syncope, clinically significant bradycardia or serious drug-related adverse events, respectively. The primary efficacy endpoint was evaluated by intention to treat using the O'Brien–Fleming method. Safety endpoints were evaluated with χ2 or Fisher’s exact tests Ivabradine 1 μM inhibited If and IKr by 28.9% and 22.8% (P<0.05) respectively. INa and ICaL were also reduced but only at 10 μM. Ivabradine slowed the firing frequency of a modelled human AV nodal action potential by 10.6% and induced a minimal prolongation of the ventricular action potential. The clinical trial randomized 35 patients to ivabradine and 33 to digoxin. Mean daytime heart rate decreased by 11.6 bpm (-11.5%) in the ivabradine arm (p=0.02) Vs 19.6 (-20.6%) in the digoxin arm (p<0.001) however, the non-inferiority margin of efficacy was not met (Z:-1.95; p=0.97). Primary safety endpoint occurred in 3 (8.6%) patients on ivabradine and in 8 (24.2%) on digoxin (p=0.10). Therapeutic adherence was lower in the digoxin arm (78.8% vs. 97.1%; p=0.02) Ivabradine produced a discrete heart rate reduction in patients with permanent atrial fibrillation. Compared with digoxin, ivabradine was less effective, better tolerated and had a similar rate of serious adverse events.The inhibition of If in the AV node seems the main mechanism responsible for the ivabradine-induced heart rate reduction in atrial fibrillation.

Clinical, electrocardiographic, and echocardiographic parameters associated with the development of pacing and implantable cardioverter-defibrillator indication in patients with transthyretin amyloid cardiomyopathy.

This study aimed to identify factors for attention leading to future pacing device implantation (PDI) and reveal the necessity of prophylactic PDI or implantable cardioverter-defibrillator (ICD) implantation in transthyretin amyloid cardiomyopathy (ATTR-CM) patients. This retrospective single-center observational study included consecutive 114 wild-type ATTR-CM (ATTRwt-CM) and 50 hereditary ATTR-CM (ATTRv-CM) patients, neither implanted with a pacing device nor fulfilling indications for PDI at diagnosis. As a study outcome, patient backgrounds were compared with and without future PDI, and the incidence of PDI in each conduction disturbance was examined. Furthermore, appropriate ICD therapies were investigated in all 19 patients with ICD implantation. PR-interval ≥220 msec, interventricular septum (IVS) thickness ≥16.9 mm, and bifascicular block were significantly associated with future PDI in ATTRwt-CM patients, and brain natriuretic peptide ≥35.7 pg/mL, IVS thickness ≥11.3 mm, and bifascicular block in ATTRv-CM patients. The incidence of subsequent PDI in patients with bifascicular block at diagnosis was significantly higher than that of normal atrioventricular (AV) conduction in both ATTRwt-CM [hazard ratio (HR): 13.70, P = 0.019] and ATTRv-CM (HR: 12.94, P = 0.002), whereas that of patients with first-degree AV block was neither (ATTRwt-CM: HR: 2.14, P = 0.511, ATTRv-CM: HR: 1.57, P = 0.701). Regarding ICD, only 2 of 16 ATTRwt-CM and 1 of 3 ATTRv-CM patients received appropriate anti-tachycardia pacing or shock therapy, under the number of intervals to detect for ventricular tachycardia of 16-32. According to our retrospective single-center observational study, prophylactic PDI did not require first-degree AV block in both ATTRwt-CM and ATTRv-CM patients, and prophylactic ICD implantation was also controversial in both ATTR-CM. Larger prospective, multi-center studies are necessary to confirm these results.

Dual-chamber leadless pacing: Atrioventricular synchrony in preclinical models of normal or blocked atrioventricular conduction

Dual-chamber leadless pacemakers (LPs) require robust communication between distinct right atrial (RA) and right ventricular (RV) LPs to achieve atrioventricular (AV) synchrony. The purpose of this preclinical study was to evaluate a novel, continuous implant-to-implant (i2i™) communication methodology for maintaining AV-synchronous, dual-chamber DDD(R) pacing by the 2 LPs. RA and RV LPs were implanted and paired in 7 ovine subjects (4 with induced complete heart block). AV synchrony (% AV intervals <300 ms) and i2i communication success (% successful i2i transmissions between LPs) were evaluated acutely and chronically. During acute testing, 12-lead electrocardiographic and LP diagnostic data were collected from 5-minute recordings, in 4 postures and 2 rhythms (AP-VP and AS-VP, or AP-VS and AS-VS) per subject. Chronic i2i performance was evaluated through 23 weeks postimplant (final i2i evaluation period: week 16-23). Acute AV synchrony and i2i communication success across multiple postures and rhythms were median [interquartile range] 100.0% [100.0%-100.0%] and 99.9% [99.9%-99.9%], respectively. AV synchrony and i2i success rates did not differ across postures (P = .59, P = .11) or rhythms (P = 1, P = .82). During the final i2i evaluation period, the overall i2i success was 98.9% [98.1%-99.0%]. Successful AV-synchronous, dual-chamber DDD(R) leadless pacing using a novel, continuous, wireless communication modality was demonstrated across variations in posture and rhythm in a preclinical model.

Pacing or ablation for vasovagal syncope: one size does not fit all.

Practical decision pathway for the management of vasovagal syncope. Please see text for details. White circles demonstrate sites of grouping of autonomic ganglia defined as ganglionated plexi (GP). The superior right atrial GP (RSGP) located on the posterosuperior surface of the right atrium adjacent to the junction of the superior vena cava and the right atrium; the superior left atrial GP (LSGP) is on the posterosuperior surface of the left atrium between the pulmonary veins; the inferior (posterior) right atrial GP (RIGP) located adjacent to the interatrial groove; the inferior left atrial GP (LIGP) is identified on the posterolateral surface of the left atrium; and the Marshall tract GP (MTGP) located adjacent the vein of Marshall. *Response to atropine which accelerates sinus node automaticity and increases the speed of atrioventricular conduction should be evaluated in all cases prior recommending CNA to confirm adequate procedural response. A sinus rate increase of ≥25% or a sinus rate ≥90 bpm in the first 15 min after infusion should be considered as a positive response.7,13 CLS, closed loop stimulation; CNA, cardioneuroablation; HUT, head-up tilt table test; and ILR, implantable loop recorder.

The impact of chronotropic incompetence on atrioventricular conduction times in heart failure patients.

Intrinsic atrioventricular (AV) conduction is used to optimize AV intervals with cardiac resynchronization therapy (CRT) in most device algorithms. Atrial pacing and heart rate affect conduction times, but little is known regarding differeces among chronotropic incompetent(CI) and competent(CC) patients to guide programming. RAVE was a multicenter prospective trial of CRT patients. Heart rate was increased with incremental atrial pacing and with submaximal exercise. According to the maximal heart rate achieved during exercise, patients were classified as either CI or CC. For CI patients, an additional symptom-limited exercise with rate-adaptive pacing activated was performed. Intracardiac intervals were measured from the implantable lead electrograms in multiple postures. There were 12 subjects with CI and 24 with CC. With atrial pacing, AV interval immediately increased and gradually increased with incremental atrial pacing in all patients. However, the changes in the atrial to right ventricular (ARV) and atrial to left ventricular (ALV) intervals with increasing atrial pacing rates were about threefold greater in CI patients compared to CC patients (24.3 ± 28.9 vs. 7.2 ± 5.5ms/10bpm for ARV and 22.7 ± 25.6 vs. 7.1 ± 5.7ms/10bpm for ALV in the standing position, p < 0.05). In CI pacing with rate-adaptive pacing during exercise, AV interval changes with paced heart rate were variable. The AV response to overdrive atrial pacing at rest may provide a simple means of identifying chronotropic competence in CRT patients. For patients with CI, who often require rate-adaptive atrial pacing, rate-adaptive AV algorithms should be adjusted individually.

Effectiveness of the repurposed drug isotretinoin in an experimental murine model of Chagas disease

Benznidazole and nifurtimox are the drugs currently used for the treatment of Chagas disease, however its side effects may affect patient adherence. In the search for new alternative therapies, we previously identified isotretinoin (ISO), an FDA-approved drug widely used for the treatment of severe acne through a drug repurposing strategy. ISO shows a strong activity against Trypanosoma cruzi parasites in the nanomolar range, and its mechanism of action is through the inhibition of T. cruzi polyamine and amino acid transporters from the Amino Acid/Auxin Permeases (AAAP) family. In this work, a murine model of chronic Chagas disease (C57BL/6 J mice), intraperitoneally infected with T. cruzi Nicaragua isolate (DTU TcI), were treated with different oral administrations of ISO: daily doses of 5 mg/kg/day for 30 days and weekly doses of 10 mg/kg during 13 weeks. The efficacy of the treatments was evaluated by monitoring blood parasitemia by qPCR, anti-T. cruzi antibodies by ELISA, and cardiac abnormalities by electrocardiography. No parasites were detected in blood after any of the ISO treatments. The electrocardiographic study of the untreated chronic mice showed a significant decrease in heart rate, while in the treated mice this negative chronotropic effect was not observed. Atrioventricular nodal conduction time in untreated mice was significantly longer than in treated animals. Mice treated even with ISO 10 mg/kg dose every 7 days, showed a significant reduction in anti-T. cruzi IgG levels. In conclusion, the intermittent administration of ISO 10 mg/kg would improve myocardial compromise during the chronic stage.

Lack of evidence for longitudinal dissociation of the atrioventricular conduction axis.

Longitudinal dissociation of the aggregated specialized cardiomyocytes within the non-branching portion of atrioventricular conduction axis has proved a controversial topic for both morphologists and electrophysiologists. We have now used morphological methods, including three-dimensional assessment, to revisit, in human, canine, and bovine hearts, the presence or absence of interconnections between the aggregated cardiomyocytes making up the non-branching bundle. We analyzed three datasets from human and canine hearts, and two from bovine hearts, using longitudinal and orthogonal serial histological sections. In addition, we assessed three hearts using translucent India ink injected specimens, permitting assessment of the three-dimensional arrangement of the cardiomyocytes. Using the longitudinal sections, we found numerous oblique interconnections between the groups of specialized cardiomyocytes. When assessing orthogonal sections, we noted marked variation in the grouping of the cardiomyocytes. We interpreted this finding as evidence of bifurcation and convergence of the groups seen in the longitudinal sections. The three-dimensional assessment of the bovine material confirmed the presence of the numerous interconnections. The presence of multiple connections between the cardiomyocytes in the non-branching bundle rules out the potential for longitudinal dissociation. This article is protected by copyright. All rights reserved.

Evidence for concealed fasciculo-ventricular connections as revealed by His bundle pacing.

It is almost 100 years ago since Mahaim described the so-called paraspecific connections between the ventricular conduction axis and the crest of the muscular ventricular septum, believing such pathways to be ubiquitous. These pathways, however, have yet to be considered as potential pathways for septal activation during His bundle pacing. So as to explore the hypothesis that specialised septal pathways might provide the substrate for septal activation during His bundle pacing, we compared the findings from 22 serially sectioned histological datasets and 34 different individuals undergoing His bundle pacing. We found histologically specialised pathways connecting the branching component of the atrioventricular conduction axis with the crest of the muscular ventricular septum in almost four-fifths of the histological datasets. In 32 of 34 patients undergoing His bundle pacing, the QRS complex closely resembled published images of known conduction through fasciculo-ventricular pathways. In only two patients was a delta wave not seen at any pacing voltages. Capture of these connections varied according to pacing voltage, a finding which correlated with the distance of the pathways from the site of penetration of the ventricular conduction axis. Ventricular activation times remained normal in the presence of the delta wave at higher pacing voltage but were prolonged at lower voltages. Our histologic findings confirm fasciculo-ventricular connections, initially described by Mahaim as being paraspecific, are likely ubiquitous. Analysis of 12-lead electrocardiograms leads us to conclude that fasciculo-ventricular pathways, concealed during sinus rhythm, become manifest with His bundle pacing.

Validation of a Fully Automated Hybrid Deep Learning Cardiac Substructure Segmentation Tool for Contouring and Dose Evaluation in Lung Cancer Radiotherapy

Background and purposeAccurate and consistent delineation of cardiac substructures is challenging. The aim of this work was to validate a novel segmentation tool for automatic delineation of cardiac structures and subsequent dose evaluation, with potential application in clinical settings and large-scale radiation-related cardiotoxicity studies. Materials and methodsA recently developed hybrid method for automatic segmentation of 18 cardiac structures, combining deep learning, multi-atlas mapping and geometric segmentation of small challenging substructures, was independently validated on 30 lung cancer cases. These included anatomical and imaging variations, such as tumour abutting heart, lung collapse and metal artefacts. Automatic segmentations were compared with manual contours of the 18 structures using quantitative metrics, including Dice similarity coefficient (DSC), mean distance to agreement (MDA) and dose comparisons. ResultsA comparison of manual and automatic contours across all cases showed a median DSC of 0.75–0.93 and a median MDA of 2.09–3.34 mm for whole heart and chambers. The median MDA for great vessels, coronary arteries, cardiac valves, sinoatrial and atrioventricular conduction nodes was 3.01–8.54 mm. For the 27 cases treated with curative intent (planned target volume dose ≥50 Gy), the median dose difference was –1.12 to 0.57 Gy (absolute difference of 1.13–3.25%) for the mean dose to heart and chambers; and –2.25 to 4.45 Gy (absolute difference of 0.94–6.79%) for the mean dose to substructures. ConclusionThe novel hybrid automatic segmentation tool reported high accuracy and consistency over a validation set with challenging anatomical and imaging variations. This has promising applications in substructure dose calculations of large-scale datasets and for future studies on long-term cardiac toxicity.

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...

Narrow QRS Complex Tachycardia With Variable R-R Intervals and Discrete P Waves

Irregular narrow QRS complex tachycardia is associated with a wide range of differential diagnoses, including atrial fibrillation and atrial tachyarrhythmia with altered atrioventricular conduction. Here, we present a case of narrow QRS complex tachycardia with variable R-R intervals and discrete P waves. (Level of Difficulty: Intermediate.)

Differences in Electrical Delay Between the Mid-septum and Apex with the Right Ventricular Lead: Novel Implications for Pacemaker Sensing.

Ventricular sensing relies on the analysis of a local intracardiac electrogram in reference to the QRS on the surface electrocardiogram. If both signals do not coincide in time, there is a delay in sensing intrinsic ventricular activity. We evaluated possible differences in the electrical delay between the mid-septum and apex as determined by the right ventricular (RV) lead position using a pacing system analyzer (PSA) during conventional pacemaker implantation. Patients without significant heart disease and intrinsic atrioventricular conduction underwent their first Medtronic (Minneapolis, MN, USA) or Abbott (Chicago, IL, USA) dual-chamber pacemaker implantation with the RV lead first positioned at the apex and then subsequently at the mid-septum. Real-time ventricular sensing data were obtained through PSA to determine the electrical delay Q-VS value as the time difference between the QRS and the released RV-sensed event marker "VS." Among 212 patients, 139 had narrow QRS and 73 had complete right bundle branch block (RBBB). Overall, both narrow QRS and RBBB patients exhibited shorter Q-VS lengths at the mid-septum compared to the apex (50.4 ± 24.2 ms and 66.7 ± 32.3 ms vs. 63.9 ± 27.6 ms and 71.7 ± 32.2 ms; P < .0001 and P < .001, respectively). The Q-VS in patients with Abbott devices was significantly shorter compared to that in patients with Medtronic devices at both the mid-septum and the apex in both patient groups (P < .0001). In conclusion, RV lead positioning at the mid-septum is associated with a shorter electrical delay compared to positioning at the apex in both narrow QRS and RBBB patients.

The Pacemaker and Implantable Cardioverter-Defibrillator Registry of the Italian Association of Arrhythmology and Cardiac Pacing - Report 2021

The Pacemaker (PM) and Implantable Cardioverter-Defibrillator (ICD) Registry of the Italian Association of Arrhythmology and Cardiac Pacing (AIAC) collects information about demographics, clinical characteristics, main indications for PM/ICD therapy and device types from the voluntary Italian collaborating centers. For the year 2021 main data about national PM and ICD implantation activity were obtained on the basis of European Cards and subsequently analyzed to create a standard report. PM Registry: data about 18 631 PM implantations were collected (15879 first implants and 2752 replacements). The number of collaborating centers was 121. Median age of treated patients was 82 years (76 quartile I; 87 quartile III). Main ECG indications included atrioventricular conduction disorders in 26.8% of first PM implants, sick sinus syndrome in 12.2%, atrial fibrillation plus bradycardia in 9.6%, other unspecified ECG and electrophysiological abnormalities in 43.0%. For first PM implants, pacing in DDDR mode was reported in 46.5%, followed by DDD mode (20.6%), VVIR mode (15.0%), VVI mode (9.0%) and finally VDD-VDDR (5.8%). Median value of longevity of explanted PMs was 8.9 years. ICD Registry: data about 6878 ICD implantations were obtained (4708 first implants and 2170 replacements). The number of collaborating centers was 345. Median age of treated patients was 72 years (70 quartile I; 75 quartile III). Primary prevention indication was reported in 86.3% of first implants, secondary prevention in 13.7% (cardiac arrest in 4.4% of records). A single-chamber ICD was used in 32.1% of first implants, dual-chamber ICD in 30.3% and biventricular ICD in 37.6%. Median value of longevity of explanted ICDs was 6.9 years. In the calendar year 2021, the Italian PM Registry showed stable electrocardiographic and symptom indications, with an important prevalence of dual-chamber pacing. The ICD Registry documented a large use of prophylactic and biventricular ICDs, reflecting a favorable adherence in the clinical practice to trials and guidelines. The ICD longevity and the number of recalls demonstrated a favorable trend. In order to increase and optimize the cooperation of Italian PM and ICD implanting centers, the online data entry (https://www.aiac.it/riprid) should be adopted at large scale.

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.

Right Ventricular Electromechanical Dyssynchrony and Its Relation to Right Ventricular Remodeling, Dysfunction, and Exercise Capacity in Ebstein Anomaly

Abnormal atrioventricular and intraventricular electrical conduction and dysfunction of the functional right ventricle (fRV) are common in Ebstein anomaly (EA). However, fRV mechanical dyssynchrony and its relation to fRV function are poorly characterized. We evaluated fRV mechanical dyssynchrony in EA patients in relation to fRV remodeling, dysfunction, and exercise intolerance. We retrospectively analyzed data from nonoperated EA patients and age-matched controls who underwent echocardiography, cardiovascular magnetic resonance imaging, and cardiopulmonary exercise testing to quantify right ventricular (RV) remodeling, dysfunction, and exercise capacity. The relation of these to fRV dyssynchrony was retrospectively investigated. Right ventricular mechanical dyssynchrony was defined by early fRV septal activation (right-sided septal flash), RV lateral wall prestretch/late contraction, postsystolic shortening, and intra-RV delay using two-dimensional strain echocardiography. The SD of time to peak shortening among the fRV segments was calculated as a parameter of mechanical dispersion. Thirty-five EA patients (10 of whom were <18years of age) and 35 age-matched controls were studied. Ebstein anomaly patients had worse RV function and increased intra-RV dyssynchrony versus controls. Nineteen of 35 (54%) EA patients had early septal activation with simultaneous stretch and consequent late activation and postsystolic shortening of RV lateral segments. Intra-fRV mechanical delay correlated with fRV end-diastolic volume index (r=0.43, P<.05) and fRV end-systolic volume index (r=0.63, P<.001). The fRV ejection fraction was lower in EA with versus without right-sided septal flash (44.9±11.0 vs 54.2±8.2, P=.012). The fRV mechanical dispersion correlated with the percentage of predicted peak VO2 (r=-0.35, P<.05). In EA, fRV mechanical dyssynchrony is associated with fRV remodeling, dysfunction, and impaired exercise capacity. Mechanical dyssynchrony as a therapeutic target in selected EA patients warrants further study.

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.

Dependence of the Atrioventricular Conduction Time on the Conduction through the Atrioventricular Node and His-Purkinje System.

The electrical depolarization of the heart passes through various structures of the cardiac conduction system, which modify its conduction to different extents. In this study, we investigated the relationship between the atrioventricular conduction time (AV interval) and its contributors, the atrioventricular node (AVN) and the His-Purkinje system (HPS), as represented by the AH and HV intervals, respectively. We also compared sex differences in these intervals and their relations. Resting intracardiac tracings lasting 5 min were obtained from 64 patients (33 women) during an invasive electrophysiological study. The aforementioned intervals were measured for all consecutive beats. The mean AH interval was 85.9 ms, HV 43.7 ms, and AV 129.6 ms. Men had longer AH (80.0 vs. 65.9 ms), HV (38.4 vs. 35.3 ms), and AV intervals (124.7 vs. 108.5 ms) than women. The AV intervals were linearly correlated with AH intervals in all patients (r2 = 0.65). No significant correlation was found between AV and HV intervals in all patients (r2 = 0.05). There were no sex differences in these associations. Our results suggest that the atrioventricular conduction time depends mainly on the conduction through the AVN and less on the HPS. These relations are similar in both sexes, although men had longer conduction times through the AVN, HPS, and total atrioventricular conduction time.

Update in LV Only Fusion CRT Pacing: Annals and Future Perspectives.

Triple-chamber cardiac devices are utilized for cardiac resynchronization therapy (CRT) and is the standard-of-care therapy for heart failure (HF) patients in the current guidelines. In the setting of biventricular (BIV) pacing it involves a mandatory implantation of right ventricular (RV) lead that allows simultaneous BIV pacing with 0 ms VV (ventricular to ventricular) interval. Nevertheless, it seems that response to CRT is not related to RV lead position. RV pacing is known for deleterious effects on RV/Left Ventricle (LV) function and should not be used in persons with normal atrioventricular conduction (AV) and sinus rhythm. As it compensates for the additional asynchrony induced by unnecessary stimulation of RV pacing, only pacing the left ventricle (LV) may result in improved cardiac resynchronization therapy (CRT) outcomes and a decrease in the number of individuals who do not respond to the procedure. Furthermore, leadless LV fusion CRT pacing without RV lead could be a potential CRT therapy alternative to BIV pacing in nonischemic heart failure patients with preserved AV conduction. The aim of our study is to made an update in cardiac resynchronization therapy with LV only fusion pacing.