Atrioventricular Node Research Articles

Diagnosis of Narrow QRS Tachycardia

Narrow QRS tachycardia is a common clinical condition characterized by a heart rate exceeding 100 beats per minute and a QRS complex duration of less than 120 ms. This article provides an overview of the diagnostic approach to narrow QRS tachycardia, focusing on the differentiation between various supraventricular tachycardias, such as atrioventricular nodal reentrant tachycardia (AVNRT), atrioventricular reentrant tachycardia (AVRT), atrial tachycardia (AT), and sinus tachycardia. The discussion includes an analysis of the presenting symptoms, electrocardiographic (ECG) findings, and the use of vagal maneuvers and pharmacological agents in diagnosis.

Conflicting responses with simultaneous atrioventricular pacing. What is the mechanism?

A 60-year-old woman presented with recurrent episodes of palpitations, documented short RP, narrow QRS tachycardia and absence of preexcitation in the electrocardiogram during sinus rhythm. During an electrophysiology study, programmed stimulation induced a narrow QRS tachycardia with cycle length of 380 ms, VA interval of 164 ms and earliest atrial activation in the His region. Ventricular overdrive pacing failed to entrain the atrium even with isoprenaline infusion and atrial burst pacing repeatedly terminated the tachycardia. Difference in AH interval with pacing and SVT was 27 msec. Simultaneous atrial and ventricular pacing was done with atrial pacing from the high right atrium and showed a His signal as the first return electrogram suggestive of atrioventricular nodal reentrant tachycardia (AVNRT). The manoeuvre was repeated with atrial pacing from the proximal coronary sinus and showed an atrial signal as the first return electrogram suggestive of atrial tachycardia (AT). What is the explanation for the conflicting results of the two pacing maneuvers?

Registro español de ablación con catéter. XXIII informe oficial de la Asociación del Ritmo Cardiaco de la Sociedad Española de Cardiología (2023)

Introduction and objectivesWe report the results of the 2023 Spanish catheter ablation registry. MethodsProcedural data were collected and incorporated into the REDCap platform by all participating centers through a specific form. ResultsThere were 104 participating centers in 2023 compared with 103 in 2022. In 2023, the total number of ablation procedures was 26 207, indicating a stabilization of the increase observed in 2022 following the pandemic. The increase was mainly due to procedures for atrial fibrillation (AF), with a total of 9942 ablations, representing 38% of all substrates. Notably, pulse-field ablation represented 10.3% of all AF ablation procedures, leading single-shot ablation strategies to outnumber point-by-point AF ablation for the first time in the history of the registry. Cavotricuspid isthmus ablation remained the second most targeted substrate (19% of all substrates, n=5067). The overall acute success rate remained high (97%), with a downward trend in the complication rate (1.6% vs 1.8% in 2022) and mortality rate (0.03%; n=7). Compared with 2022, there was a significant increase in procedures performed using electro-anatomical mapping and zero-fluoroscopy techniques for cavotricuspid isthmus ablation (52% vs 26%), AV node re-entrant tachycardia (48% vs 34%), and accessory pathways (62% vs 22%). We registered 466 ablations in pediatric patients. ConclusionsThe data indicate a stabilization in the post-pandemic increase in ablation procedures, with an absolute and relative increase in AF as the predominant substrate. Success rates remained stable with a modest reduction in complication and mortality rates.

A stroke patient with an unusual electrocardiogram

We present a case of a 70 year old man with a history of paroxysmal atrial flutter who was admitted to the hospital with symptoms and imaging consistent with an acute stroke. Physical exam was notable for a pulse rate of 50 beats per minute and right sided facial droop with mild dysarthria. Admission ECG shows a junctional bradycardia with evidence of dual AV node physiology, rarely manifested in a retrograde fashion on a standard ECG. The patient likely experienced parasympathetic sinus node slowing in the setting of acute stroke. During post-stroke monitoring, the patient demonstrated return of sinus rhythm with chronotropic competence and he had no additional arrhythmia during admission.

Electrophysiological differences of randomized deep sedation with dexmedetomidine versus propofol

BackgroundDexmedetomidine and propofol are common sedatives in intensive care units and for interventional procedures. Both may compromise sinus node function and atrioventricular conduction.The objective of this prospective, randomized study is to compare the effect of dexmedetomidine with propofol on sinus node function and atrioventricular conduction.MethodsIn a tertiary care center in Switzerland we included from September 2019 to October 2020 160 patients (65 ± 11 years old; 32% female) undergoing first ablation for atrial fibrillation by cryoballoon ablation or by radiofrequency ablation.Patients were randomly assigned to deep sedation with dexmedetomidine (DEX group) versus propofol (PRO group). A standard electrophysiological study was performed after pulmonary vein isolation with the patients still deeply sedated and hemodynamically stable.ResultsEighty patients each were randomized to the DEX and PRO group. DEX group patients had higher baseline sinus cycle length (1022 vs. 1138 ms; p = 0.003) and longer sinus node recovery time (SNRT400; 1597 vs. 1412 ms; p = 0.042). However, both corrected SNRT and normalized SNRT did not differ. DEX group patients had longer PR interval (207 vs. 186 ms; p = 0.002) and AH interval (111 vs. 95 ms, p = 0.008), longer Wenckebach cycle length of the atrioventricular node (512 vs. 456 ms; p = 0.005), and longer atrioventricular node effective refractory period (390 vs. 344 ms; p = 0.009). QRS width and HV interval were not different. An arrhythmia, mainly atrial fibrillation, was induced in 33 patients during the electrophysiological study, without differences among groups (20% vs. 15%, p = 0.533).ConclusionsDexmedetomidine has a more pronounced slowing effect on sinus rate and suprahissian AV conduction than propofol, but not on infrahissian AV conduction and ventricular repolarization. These differences need to be taken into account when using these sedatives.Trial registrationClinicalTrials.gov number NCT03844841, 19/02/2019

Sudden Death in Pediatric Patient With Dilated Cardiomyopathy Due to Founder Variant in NKX2-5: Case Report.

Background: The NKX2-5 gene encodes a transcription factor that plays a role in atrioventricular nodal and myocardial development. Pathogenic variants of NKX2-5 are associated with congenital heart disease and sudden cardiac death. The missense variant in this case is one of the more common ones in Northern Europe and has high penetrance in familial cases. To our knowledge, this is the youngest person who died due to this variant. Case summary: This was a healthy, asymptomatic 14-year-old male with well-managed mild congenital dilated cardiomyopathy who died unexpectedly in his home. Postmortem examination revealed the NKX2-5 pathogenic missense variant, p.Phe145Leu, as the only explicable cause of death. Discussion: We propose that immediate family members of those who die suddenly due to NKX2-5 disease undergo genetic counseling and longitudinal screening to include this gene, as pathogenic variants in the NKX2-5 gene may manifest in a time-dependent manner.

Caseous Calcification of the Mitral Annulus: Calcified Toothpaste of the Heart.

Caseous calcification of the mitral annulus (CCMA) is a rare variant of mitral annular calcification (MAC) usually described as an antemortem finding. We report a case of sudden cardiac arrest in a 39-year-old male with end-stage renal disease undergoing hemodialysis with a history of Fabry disease by kidney biopsy. Autopsy revealed significant circumferential annular calcification in both mitral and aortic valves with a caseous gross appearance. Histologically, these areas consisted of amorphous basophilic material accompanied by a surrounding granulomatous-appearing infiltrate. Von Kossa staining on non-decalcified tissue revealed strong positive staining, confirming CCMA diagnosis. While identifiable, the atrioventricular node was displaced and distorted by caseous deposits. Toluidine blue staining of myocardium showed osmophilic accumulations, and electron microscopy (EM) showed myeloid/zebra bodies, consistent with Fabry disease. We posit that Fabry disease leads to end-stage kidney disease, altering calcium phosphate metabolism, a proposed mechanism for CCMA. This case highlights the multifactorial nature of sudden cardiac death in decedents with various structural cardiac changes and potential renal-disease-induced electrolyte imbalances. We aim to bring awareness to this rare entity, its potential role in a sudden cardiac death, and to highlight the need to use non-decalcified tissue when staining for calcium to establish the diagnosis.

Novel insight into atrioventricular node conduction.

Novel insight into atrioventricular node conduction.

RF catheter ablation of AVNRT in a patient with interrupted inferior vena cava anomaly with hemiazygos continuity with persistent left superior vena cava

Intrahepatic interruption of the inferior vena cava (IVC) with continued hemizygous is a very rare abnormality and sometimes it may be accompanied by other cardiovascular abnormalities. Continuation of the hemizygous vein draining into the right atrium through the left superior vena cava (LSVC) is much rarer. In this paper, we have presented a patient who had simultaneous IVC interrupted with persistent LSVC and suffered from Atrioventricular nodal reentrant tachycardia (AVNRT). Finally, radiofrequencies (RF) catheter ablation for AVNRT was successfully performed through a left subclavian vein access.

SVT quest: The adventure diagnosing narrow QRS tachycardia.

In the field of cardiac electrophysiology, there is a universal desire: the discovery of a flawless diagnostic maneuver for supraventricular tachycardias (SVTs). This is not merely a wish but a shared odyssey. To improve diagnostic accuracy and achieve sufficient sensitivity and specificity, numerous diagnostic maneuvers have been proposed. However, each has its limitations and prompts a search for new diagnostic techniques. This continuous cycle of discovery and refinement, which we titled "SVT Quest" is reviewed in chronological sequence. This adventure in diagnosing narrow QRS tachycardia unfolds in 3 steps: Step 1 involves differentiating atrial tachycardia from other SVTs based on the observations such as V-A-V or V-A-A-V response, ΔAA interval, VA linking, the last entrainment sequence, and response to the atrial extrastimulus. Step 2 focuses on differentiating orthodromic reciprocating tachycardia from atrioventricular nodal reentrant tachycardia based on the observations such as tachycardia reset upon the premature ventricular contraction during His refractoriness, uncorrected/corrected postpacing interval, differential ventricular entrainment, orthodromic His capture, transition zone analysis, and total pacing prematurity. Step 3 characterizes the concealed nodoventricular/nodofascicular pathway and His-ventricular pathway-related tachycardia based on observations such as V-V-A response, ΔatrioHis interval, and paradoxical reset phenomenon. There is no single diagnostic maneuver that fits all scenarios. Therefore, the ability to apply multiple maneuvers in a case allows the operator to accumulate evidence to make a likely diagnosis. Let's embark on this adventure!

High-density visualization of antegrade fast pathway activation during atypical fast/slow atrioventricular nodal reentrant tachycardia in two cases.

High-density visualization of antegrade fast pathway activation during atypical fast/slow atrioventricular nodal reentrant tachycardia in two cases.

Biallelic variants in POPDC2 cause a novel autosomal recessive syndrome presenting with cardiac conduction defects and variable hypertrophic cardiomyopathy.

ABSTRACTPOPDC2encodes for the Popeye domain-containing protein 2 which has an important role in cardiac pacemaking and conduction, due in part to its cAMP-dependent binding and regulation of TREK-1 potassium channels. Loss ofPopdc2in mice results in sinus pauses and bradycardia and morpholino knockdown ofpopdc2 inzebrafish results in atrioventricular (AV) block. We identified bi-allelic variants inPOPDC2in 4 families that presented with a phenotypic spectrum consisting of sinus node dysfunction, AV conduction defects and hypertrophic cardiomyopathy. Using homology modelling we show that the identifiedPOPDC2variants are predicted to diminish the ability of POPDC2 to bind cAMP. Inin vitroelectrophysiological studies we demonstrated that, while co-expression of wild-type POPDC2 with TREK-1 increased TREK-1 current density, POPDC2 variants found in the patients failed to increase TREK-1 current density. While patient muscle biopsy did not show clear myopathic disease, it showed significant reduction of the expression of both POPDC1 and POPDC2, suggesting that stability and/or membrane trafficking of the POPDC1–POPDC2 complex is impaired by pathogenic variants in any of the two proteins. Single-cell RNA sequencing from human hearts demonstrated that co-expression of POPDC1 and 2 was most prevalent in AV node, AV node pacemaker and AV bundle cells. Sinoatrial node cells expressed POPDC2 abundantly, but expression of POPDC1 was sparse. Together, these results concur with predisposition to AV node disease in humans with loss-of-function variants inPOPDC1and POPDC2 and presence of sinus node disease inPOPDC2,but not inPOPDC1related disease in human. Using population-level genetic data of more than 1 million individuals we showed that none of the familial variants were associated with clinical outcomes in heterozygous state, suggesting that heterozygous family members are unlikely to develop clinical manifestations and therefore might not necessitate clinical follow-up. Our findings provide evidence forPOPDC2as the cause of a novel Mendelian autosomal recessive cardiac syndrome, consistent with previous work showing that mice and zebrafish deficient in functionalPOPDC2display sinus and AV node dysfunction.GRAPHICAL ABSTRACT

Low-Power Long-Duration Versus High-Power Short-Duration Radiofrequency Ablation of the Atrioventricular Node.

Atrioventricular node (AVN) radiofrequency (RF) ablation is a highly effective treatment of atrial tachyarrhythmias that are resistant to other management modalities. To date, there is limited research that compares the properties of different RF ablation catheters. The current study aims to compare the effectiveness of several types of RF catheters in AVN ablation. 66 patients, with a mean age of 73.27 years, underwent AVN RF ablation. The catheters used were categorized as: un-irrigated (UI), externally-irrigated (EI), and contact force-sensing with 10-20 grams of force. EI catheters were divided into two different settings: low-power long-duration (LPLD) (30W, 45°C, and 60 sec) and high-power short-duration (HPSD) (50W, 43°C, and 12 sec). We compared the success rate of the different RF catheters using logistic regression and lesion times using linear regression. The distribution of the types of catheters used is: UI in 48%, LPLD in 16%, and HPSD in 36% of patients. All ablation procedures were successful, with no immediate post-procedure complications. HPSD had a significantly shorter lesion time than UI catheters by 403.42 sec [-631.67, -175.17]. UI catheters, LPLD, and HPSD were equally safe and effective in ablation procedures. The HPSD catheter had a significantly shorter lesion time and, thus, overall decreased procedure time.

Outcomes of combined left bundle branch area pacing with atrioventricular nodal ablation in patients with atrial fibrillation and pulmonary disease.

Concomitant left bundle branch area pacing (LBBAP) with atrioventricular (AV) nodal ablation is emerging as a viable management option in atrial fibrillation refractory to medical management. Its viability in patients with pulmonary disease and atrial fibrillation is unknown. This is a retrospective, observational cohort study in consecutive patients who underwent concomitant LBBAP with AV nodal ablation with advanced pulmonary disease at the Cleveland Clinic Fairview Hospital between January 2019 and January 2023. Patient characteristics, comorbidities, and medication use were extracted via chart review. Rates of hospitalizations, medication use, and structural disease seen on echocardiography were compared before and after the procedure. There were 27 patients with group 3 pulmonary hypertension who underwent the procedure. In the 24 months preprocedure, there were 114 admissions for heart failure or atrial fibrillation compared to 9 admissions postprocedure (p<.001). Mean follow up was 17.3±12.1 months. There were no significant complications or lead dislodgements. Echocardiographic characteristics were similar prior to and after pacemaker implantation. Use of medications for rate and rhythm control was common preprocedure, and was reduced dramatically postprocedure. This small, retrospective cohort study suggests concomitant LBBAP with AV nodal ablation may be safe and efficacious for management of atrial fibrillation in patients with advanced pulmonary disease.

Pulmonary Vein Isolation or Pace and Ablate in Elderly Patients With Persistent Atrial Fibrillation (ABLATE Versus PACE)—Rationale, Methods, and Design

Age is a major risk-factor for atrial fibrillation (AF) and associated hospitalisations. With increasing emphasis on rhythm control, pulmonary vein isolation (PVI) is often suggested, even to elderly patients (≥ 75 years of age). Efficacy of PVI aiming at rhythm control is limited in persistent AF. Pacemaker implantation with atrioventricular node (AVN) ablation may represent a reasonable alternative, with the aim of controlling symptoms and improving quality of life in elderly patients. In this investigator-initiated, randomised, multicentre trial, we test the hypothesis that pacemaker implantation and AVN ablation provides superior symptom control over PVI in elderly patients with symptomatic persistent AF, without any increase in adverse event profile. In the ABLATE Versus PACE (NCT 04906668) prospective open-label superiority trial, 196 elderly patients with normal ejection fraction and symptomatic persistent AF despite guideline-indicated medical therapy will be randomised to either cryoballoon PVI (ABLATE) or dual-chamber pacemaker implantation with subsequent AVN ablation (PACE), and followed for a minimum of 12 months. The primary efficacy outcome is a composite end point of rehospitalisation for atrial arrhythmia or cardiac decompensation/heart failure, (outpatient) electrical cardioversion, or upgrade to cardiac resynchronisation therapy owing to worsening of left ventricular ejection fraction to ≤ 35%. Secondary end points include death from any cause, stroke, quality of life, and procedure-related complications. Sample size is designed to achieve 80% power for the primary end point (2-tailed alpha of 5%). ABLATE Versus PACE will determine whether pacemaker implantation and AVN ablation can improve symptom-control in elderly patients with persistent AF over PVI without increasing safety end points.

An Unusual ECG Finding during Adenosine Stress Myocardial Perfusion Imaging

Adenosine is extensively utilized in myocardial stress perfusion imaging for the detection and risk stratification of coronary artery disease. It has a well-established safety profile. The majority of the undesirable effects experienced during adenosine infusion are transient (owing to its brief half-life of ~10 s) and arise from the stimulation of receptors in the atrio-ventricular (AV) node (AV block) and bronchial smooth muscles (bronchospasm). We hereby report an unusual electrocardiographic finding during adenosine stress perfusion imaging, in a patient who had previously undergone single chamber pacemaker insertion and was referred for the assessment of atypical chest pain.

Analysis of ST segment depression in supraventricular tachycardia and its relationship with underlying mechanism

BackgroundElectrocardiographic diagnosis of causes of supraventricular tachycardia (SVT) is sometimes difficult and application of routine algorithms can lead to misdiagnosis in as many as 37 % of patients. ST segment depression may be useful in diagnosing the nature of SVT. MethodsWe reviewed surface electrocardiogram (ECG) characteristics of 300 patients having SVT with 1:1 AV relationship and correlated findings with electrophysiology study (EPS) findings. Final diagnosis of AVNRT (Atrioventricular nodal reentrant tachycardia), Orthodromic AVRT (atrioventricular reentrant tachycardia) and atrial tachycardia (AT) was correlated with ECG parameters like heart rate, ST segment depressions and QRS morphology. ResultsOut of 300 patients, majority patients included in study, were having AVNRT or AVRT. ST depression predicted AVRT if the ST depression was ≥ 2 mm (overall sensitivity of 38.3 % and specificity of 93.8 % to predict AVRT) and was downsloping in morphology (sensitivity of 36.9 % and specificity of 94.7 % to predict AVRT). At heart rates ≥214 beats per minute (bpm) as measured by 7 small squares of ECG at 25 mm/s, downsloping ST depression ≥2 mm had a sensitivity 37.9 % of and specificity of 89.2 % to predict AVRT. At heart rate <214 bpm, downsloping ST depression ≥2 mm had sensitivity of 37.2 % and specificity of 96.5 % to predict AVRT. Downsloping ST depression of ≥2 mm helps to differentiate AVNRT from AVRT. ConclusionA downsloping ST segment depression ≥2 mm predicted SVT being an AVRT and can be used as a useful criteria in diagnosing the tachycardia.

Valsalva Aneurysm of Right Sinus: A Case Report and Review of Literature

In this case report, we describe the diagnostic modality of sinus of Valsalva aneurysm (SOVA) in combination with congenital cardiac defect, aortic valve involvement, and conduction abnormality in a 19-year-old patient. Aim of article was to understand the importance of clinicians being cautious about SOVA presenting in young patients, despite cases being rare, and that SOVA requires a thorough SOVA diagnostic approach. We further provide a review of literature highlighting and comparing the treatment options for both unruptured and ruptured SOVAs. The patient presented for examination due to tachycardia and palpitations. A murmur was heard, and the patient was found to have an atrioventricular nodal reentry tachycardia. Echocardiographic evaluation, magnetic resonance imaging, and computed tomography angiography confirmed an aneurysmally dilated aortic root, aortic regurgitation, and ventricular septal defect. Surgical intervention was indicated; however, the patient refused to undergo surgery.

Predictive factors of atrioventricular conduction disorders

Atrioventricular conduction disorders represent an alteration in the normal function of the heart’s electrical conduction system, a system that connects the atria and ventricles through the atrio-ventricular node and the His-Purkinje system. Consequently, bradycardia can develop and lead to the occurrence of symptoms (dizziness, loss of consciousness, tachyarrhythmias, heart failure phenomena). Identifying patients at risk of developing atrioventricular conduction disorders will allow early interventions on risk factors and improvements in prognosis. This narrative review explores the risk factors that determine the development and progression of atrioventricular conduction disorders. We will discuss traditional risk factors (age, sex, arterial hypertension, ischemic cardiac disease, diabetes, chronic kidney disease), but also risk factors that are currently being researched (genetic predisposition and inflammatory markers). Finally, we will discuss the limitations and challenges of predicting risk factors for atrioventricular conduction disorders.

Evaluation of pediatric patients with palpitations via cardiac event recorder, Holter monitoring and transesophageal electrophysiologic study in detecting arrhythmia

Objective: Palpitations are a common reason for referral to pediatric cardiologists, the diagnostic workup involves ambulatory, non-invasive recording devices and invasive procedures. We aimed to evaluate arrhythmic symptoms of pediatric patients with a cardiac event recorder, Holter monitoring and transesophageal electrophysiologic study (TEEPS) results. Materials and Methods: Retrospective evaluation of pediatric patients who fitted an event recorder at tertiary University Hospital between January 2002 and August 2012. The data obtained from the same patients’ as cardiac event recorder, Holter monitoring and TEEPS results were studied for comparison. Results: During the study period, 40 patients who had all data of cardiac event recorder, Holter monitoring and TEEPS were included. The median age of the patients included in the study was 12 [interquartile range, 7-15] years. Using the Holter monitoring, supraventricular extrasystoles (SVEs) were detected in six (15%) patients and ventricular extrasystoles (VESs) in three (7.5%). According to the event recorder data of the 40 patients, there was sinus tachycardia in 20 (50%), supraventricular tachycardia (SVT) in three (7.5%), and SVEs in two (5%) patients. The event recorder data of the remaining 15 patients were assessed as normal. The analysis of the TEEPS results revealed atrioventricular nodal reentrant tachycardia in four (10%), atrioventricular reentry tachycardia in three (7.5%), and normal results in the remaining 33 (82.5%) patients. Conclusions: This study demonstrated that a cardiac event recorder may also be considered as an important diagnostic tool in the diagnosis and ruling out of SVT in pediatric patients for whom the cause of arrhythmia cannot be identified with the Holter monitor, in patients who do not accept the use of TEEPS method following the use of Holter monitor, and in patients in whom SVT cannot be stimulated by TEEPS yet complaints persist.