Rare Variant in MRC2 Associated With Familial Supraventricular Tachycardia and Wolff-Parkinson-White Syndrome.

BACKGROUND: Accessory pathways are a common cause of supraventricular tachycardia (SVT) and can lead to sudden cardiac death in otherwise healthy children and adults when associated with Wolff-Parkinson-White syndrome. The goal of this study was to identify genetic variants within a large family with structurally normal hearts affected by SVT and Wolff-Parkinson-White syndrome and determine causality of the gene deficit in a corresponding mouse model. METHODS: Whole exome sequencing performed on 2 distant members of a 3-generation family in which multiple members were affected by SVT or Wolff-Parkinson-White pattern (preexcitation) on ECG identified MRC2 as a candidate gene. Serial electrocardiograms, intracardiac electrophysiology studies, echocardiography, optical mapping studies, and histology were performed on both Mrc2 mutant and WT (wild-type) mice. RESULTS: A rare HET (heterozygous) missense variant c.2969A>G;p.Glu990Gly (E990G) in MRC2 was identified as the leading candidate gene variant segregating with the cardiac phenotype following an autosomal-dominant Mendelian trait segregation pattern with variable expressivity. In vivo electrophysiology studies revealed reentrant SVT in E990G mice. Optical mapping studies in E990G mice demonstrated abnormal retrograde conduction, suggesting the presence of an accessory pathway. Histological analysis of E990G mouse hearts showed a disordered ECM (extracellular matrix) in the annulus fibrosus. Finally, Mrc2 knockdown in human cardiac fibroblasts enhanced accelerated cell migration. CONCLUSIONS: This study identified a rare nonsynonymous variant in the MRC2 gene in individuals with familial reentrant SVT, Wolff-Parkinson-White ECG pattern, and structurally normal hearts. Furthermore, Mrc2 knock-in mice revealed an increased incidence of reentrant SVT and bypass tract formation in the setting of preserved cardiac structure and function.

Meta-Analysis of Genome-Wide Association Studies Reveals Genetic Mechanisms of Supraventricular Arrhythmias.

BACKGROUND: Substantial data support a heritable basis for supraventricular tachycardias, but the genetic determinants and molecular mechanisms of these arrhythmias are poorly understood. We sought to identify genetic loci associated with atrioventricular nodal reentrant tachycardia (AVNRT) and atrioventricular accessory pathways or atrioventricular reciprocating tachycardia (AVAPs/AVRT). METHODS: We performed multiancestry meta-analyses of genome-wide association studies to identify genetic loci for AVNRT (4 studies) and AVAP/AVRT (7 studies). We assessed evidence supporting the potential causal effects of candidate genes by analyzing relations between associated variants and cardiac gene expression, performing transcriptome-wide analyses, and examining prior genome-wide association studies. RESULTS: Analyses comprised 2384 AVNRT cases and 106 489 referents, and 2811 AVAP/AVRT cases and 1,483 093 referents. We identified 2 significant loci for AVNRT, which implicate NKX2-5 and TTN as disease susceptibility genes. A transcriptome-wide association analysis supported an association between reduced predicted cardiac expression of NKX2-5 and AVNRT. We identified 3 significant loci for AVAP/AVRT, which implicate SCN5A, SCN10A, and TTN/CCDC141. Variant associations at several loci have been previously reported for cardiac phenotypes, including atrial fibrillation, stroke, Brugada syndrome, and electrocardiographic intervals. CONCLUSIONS: Our findings highlight gene regions associated with ion channel function (AVAP/AVRT), as well as cardiac development and the sarcomere (AVAP/AVRT and AVNRT) as important potential effectors of supraventricular tachycardia susceptibility.

Torsades de pointes and myocardial infarction following reversal of supraventricular tachycardia with adenosine: a case report

ABSTRACT Adenosine is an antiarrhythmic drug that slows conduction through the atrioventricular node and acts as a coronary blood vessel dilator. This case report highlights two unusual life-threatening events following the use of adenosine to revert supraventricular tachycardia in a structurally normal heart: non-sustained polymorphic ventricular tachycardia and myocardial infarction. A 46-year-old woman presented to the emergency department with a two-hour history of palpitations and was diagnosed with supraventricular tachycardia. Vagal maneuvers were ineffective, and after intravenous adenosine administration, the patient presented with chest pain and hypotension. The rhythm degenerated into non-sustained polymorphic ventricular tachycardia and spontaneously reverted to sinus rhythm with ST elevation in lead aVR and ST depression in the inferior and anterolateral leads. The patient spontaneously recovered within a few minutes. Despite successful arrhythmia reversal, the patient was admitted to the intensive care unit because of an infarction without obstructive atherosclerosis. This report aims to alert emergency physicians about the potential complications associated with supraventricular tachycardia and its reversal with adenosine.

Palpitations in athletes: diagnosis, workup and treatment.

Palpitations are a common reason for athletes to seek medical care. Although often benign, palpitations may serve as a harbinger for underling cardiac pathology. Given the unique challenges in this population, this review will serve to discuss the basic underlying pathophysiology, which may predispose athletes to palpitations. In addition, we will review the aetiologies, diagnostic evaluation, management and counselling strategies for some of the most common diagnoses seen in athletes.

Rate control in atrial fibrillation, calcium channel blockers versus beta-blockers.

OBJECTIVE: To investigate heart rate differences between non-dihydropyridine calcium channel blockers and beta-blockers in patients with non-permanent atrial fibrillation (AF). METHODS: Using data from 'A Comparison of Rate Control and Rhythm Control in Patients with Atrial Fibrillation' (AFFIRM), where patients were randomised 1:1 rate or rhythm control, we compared the effect of rate control drugs on heart rate during AF as well as during sinus rhythm. Multivariable logistic regression was used to adjust for baseline characteristics. RESULTS: A total of 4060 patients were enrolled in the AFFIRM trial, mean age was 70±9 years, 39% were women. Out of the total, 1112 patients were in sinus rhythm at baseline and used either non-dihydropyridine channel blockers or beta-blockers. Of them, 474 had AF during follow-up while remaining on the same rate control drugs, 218 (46%) on calcium channel blockers and 256 (54%) on beta-blockers. Mean age of calcium channel blocker patients was 70±8 years and 68±8 for beta-blocker patients (p=0.003), 42% were women. A resting heart rate <110 beats per min during AF was achieved in 92% of patients using calcium channel blockers and 92% of patients using beta-blockers (p=1.00). Bradycardia during sinus rhythm occurred in 17% of patients using calcium channel blockers vs 32% using beta-blockers (p<0.001). After adjusting for patient characteristics, calcium channel blockers were associated with a reduction in bradycardia during sinus rhythm (OR 0.41, 95% CI 0.19 to 0.90). CONCLUSION: In patients with non-permanent AF, calcium channel blockers instituted for rate control were associated with less bradycardia during sinus rhythm compared with beta-blockers.

Brady- and tachyarrhythmias detected by continuous rhythm monitoring in paroxysmal atrial fibrillation.

OBJECTIVE: Atrial fibrillation (AF) is associated with adverse events including conduction disturbances, ventricular arrhythmias and sudden death. The aim of this study was to examine brady- and tachyarrhythmias using continuous rhythm monitoring in patients with paroxysmal self-terminating AF (PAF). METHODS: In this multicentre observational substudy to the Reappraisal of Atrial Fibrillation: interaction between hyperCoagulability, Electrical remodelling and Vascular destabilisation in the progression of AF (RACE V), we included 392 patients with PAF and at least 2 years of continuous rhythm monitoring. All patients received an implantable loop recorder, and all detected episodes of tachycardia ≥182 beats per minute (BPM), bradycardia ≤30 BPM or pauses ≥5 s were adjudicated by three physicians. RESULTS: Over 1272 patient-years of continuous rhythm monitoring, we adjudicated 1940 episodes in 175 patients (45%): 106 (27%) patients experienced rapid AF or atrial flutter (AFL), pauses ≥5 s or bradycardias ≤30 BPM occurred in 47 (12%) patients and in 22 (6%) patients, we observed both episode types. No sustained ventricular tachycardias occurred. In the multivariable analysis, age >70 years (HR 2.3, 95% CI 1.4 to 3.9), longer PR interval (HR 1.9, 1.1-3.1), CHA2DS2-VASc score ≥2 (HR 2.2, 1.1-4.5) and treatment with verapamil or diltiazem (HR 0.4, 0.2-1.0) were significantly associated with bradyarrhythmia episodes. Age >70 years was associated with lower rates of tachyarrhythmias. CONCLUSIONS: In a cohort exclusive to patients with PAF, almost half experienced severe bradyarrhythmias or AF/AFL with rapid ventricular rates. Our data highlight a higher than anticipated bradyarrhythmia risk in PAF. TRIAL REGISTRATION NUMBER: NCT02726698.

Prevalence and clinical significance of arrhythmias during labour in women with structurally normal hearts.

OBJECTIVES: Examine the association between arrhythmias and adverse maternal outcomes in women with structurally normal hearts. METHODS: This was a case-control study of women admitted in labour to one of eight hospitals of Northwell Health from January 2015 to June 2021. After excluding women with structurally abnormal hearts, we identified women with an arrhythmic event and randomly subsampled the rest of the cohort to create a control group of 1025 patients. Multivariate analysis was performed to examine the association between arrhythmias and the incidence of caesarean section (CS), preterm labour (PTL), admission to the neonatal intensive care unit and longer length of stay (LOS). RESULTS: Of 1 41 769 women admitted in labour with a structurally normal heart, 137 had at least one arrhythmic event (0.097%). Supraventricular tachycardia (SVT), atrial fibrillation/flutter (AF) and frequent premature ventricular complexes or non-sustained ventricular tachycardia (VA) were present in 65 (0.046%), 22 (0.016%) and 46 (0.032%) women, respectively. Arrhythmia was previously diagnosed in 58.0% SVT cases but only in 9.7% AF and 8.1% VA cases. After adjusting for age, parity and comorbidities, the presence of any arrhythmia was an independent predictor of CS (OR 1.7 95% CI 1.2 to 2.5), PTL (OR 1.8, CI 1.1 to 3.0) and LOS (mean ratio 1.6, CI 1.4 to 1.8). This association was driven by presence of SVT and AF, whereas VAs were not associated with adverse outcomes. CONCLUSIONS: Arrhythmias, specifically SVT and AF, during labour in women with structurally normal heart are independently associated with adverse obstetrical outcomes.

Importance of the Activation Sequence of the His or Right Bundle for Diagnosis of Complex Tachycardia Circuits.

In this review, we emphasize the unique value of recording the activation sequence of the His bundle or right bundle branch (RB) for diagnoses of various supraventricular and fascicular tachycardias. A close analysis of the His to RB (H-RB) activation sequence can help differentiate various forms of supraventricular tachycardias, namely atrioventricular nodal reentry tachycardia from concealed nodofascicular tachycardia, a common clinical dilemma. Furthermore, bundle branch reentry tachycardia and fascicular tachycardias often are included in the differential diagnosis of supraventricular tachycardia with aberrancy, and the use of this technique can help the operator make the distinction between supraventricular tachycardias and these other forms of ventricular tachycardias using the His-Purkinje system. We show that this technique is enhanced by the use of multipolar catheters placed to span the proximal His to RB position to record the activation sequence between proximal His potential to the distal RB potential. This allows the operator to fully analyze the activation sequence in sinus rhythm as compared to that during tachycardia and may help target ablation of these arrhythmias. We argue that 3 patterns of H-RB activation are commonly identified-the anterograde H-RB pattern, the retrograde H-RB (right bundle to His bundle) pattern, and the chevron H-RB pattern (simultaneous proximal His and proximal RB activation)-and specific arrhythmias tend to be associated with specific H-RB activation sequences. We show that being able to record and categorize this H-RB relationship can be instrumental to the operator, along with standard pacing maneuvers, to make an arrhythmia diagnosis in complex tachycardia circuits. We highlight the importance of H-RB activation patterns in these complex tachycardias by means of case illustrations from our groups as well as from prior reports.

Validação de um Algoritmo Simples para Detecção de Taquicardia Ventricular no Eletrocardiograma / Validation of a Simple Electrocardiographic Algorithm for Detection of Ventricular Tachycardia

Resumo Fundamento O diagnóstico diferencial de taquicardia de QRS largo, entre taquicardia ventricular (TV) ou taquicardia supraventricular com condução aberrante (TSV-A) é algumas vezes difícil de ser feito na sala de emergência. Objetivo Avaliar a acurácia de um algoritmo novo e simples para a detecção de TV no eletrocardiograma (ECG) em pacientes com taquicardia de QRS largo. Métodos ECGs de 12 derivações para detecção de taquicardia de QRS largo foram obtidos prospectivamente de 120 pacientes durante estudo eletrofisiológico. Seis médicos com diferentes experiências analisaram os ECGs, e fizeram o diagnóstico com base no algoritmo D12V16, que envolve a análise da polaridade predominante do complexo QRS nas derivações I, II, V1 e V6. O diagnóstico foi comparado com os obtidos pelo algoritmo tradicional de Brugada e pelo estudo eletrofisiológico, o qual é considerado padrão ouro. Adotou-se um nível de significância de 5% (p<0,05) nas análises estatísticas. Resultados De acordo com o estudo eletrofisiológico, 82 ECGs eram de TV e 38 de TSV-A. Doenças cardíacas estruturais estavam presentes em 71 (86,6%) dos pacientes com TV e em oito (21,1%) com TSV-A. O algoritmo de Brugada teve uma maior sensibilidade global (87,2%), enquanto o algoritmo D12V16 apresentou maior especificidade global (85,1%) para TV. Tanto o algoritmo D12V16 como o de Brugada apresentou um alto valor preditivo positivo (90,9% vs. 85,8%, respectivamente) e acurácia similar (73,8% vs. 81,4%, respectivamente) para o diagnóstico de TV. Nos avaliadores experientes, a acurácia foi maior utilizando o algoritmo de Brugada que o algoritmo D12V16, mas a acurácia dos dois algoritmos foi similar segundo os avaliadores menos experientes. Conclusão O algoritmo simplificado pode ser um método útil para reconhecer TV no ECG, principalmente para médicos menos experientes. (Arq Bras Cardiol. 2021; [online].ahead print, PP.0-0)

Abstract Background The differential diagnosis of wide QRS complex tachycardia (WCT) between ventricular tachycardia (VT) or supraventricular tachycardia with aberrant conduction (SVT-A) is sometimes difficult in the emergency room. Objective The aim of this study was to evaluate the accuracy of a new simple electrocardiographic algorithm to recognize VT in patients with wide complex tachycardia. Methods The 12-lead electrocardiograms (ECG) for WCT were prospectively obtained from 120 patients during electrophysiological study. Six physicians with different expertise analyzed the electrocardiographic recordings, and made the diagnosis based on the D12V16 algorithm, that involves the analysis of the predominant polarity of QRS in leads I, II, V1 and V6. The diagnosis was compared with that made using the traditional Brugada algorithm and the "gold-standard" electrophysiological study. Statistical analyses were performed with a significance level of 5% (p<0.05). Results According to the EPS study, 82 ECG recordings were VT and 38 SVT-A. Structural heart diseases were present in 71 (86.6%) patients with VT and in 8 (21.1%) with SVT-A. The Brugada algorithm had higher global sensitivity (87.2%), and the D12V16 algorithm had higher global specificity (85.1%) for VT. Both D12V16 and Brugada's algorithms presented a high positive predictive value (90.9% vs 85.8%, respectively) and similar accuracy (73.8% vs 81.4%, respectively) for the diagnosis of VT. Experienced evaluators were more accurate using Brugada algorithm than the D12V16 algorithm, but the accuracy of both algorithms was similar according to less experienced examiners. Conclusion The simplified algorithm may be a useful method to recognize VT in the ECG, especially for less experienced doctors. (Arq Bras Cardiol. 2021; [online].ahead print, PP.0-0)

[Radiofrequency catheter ablation in pediatric population: clinical, electrophysiological and therapeutic characteristics in a Peruvian pediatric hospital]. / Ablación por radiofrecuencia en pediatría: características clínicas, electrofisiológicas y terapéuticas en un hospital pediátrico peruano.

Objective: This study aims to describe the clinical, electrophysiological and therapeutic characteristics of pediatric patients with supraventricular tachycardia undergoing radiofrequency ablation. Materials and methods: Observational, descriptive, retrospective study of children admitted for supraventricular tachycardia treatment at the Instituto Nacional de Salud del Niño during 2018 to 2021. Results: Data from 62 procedures were collected, corresponding to 59 patients (mean age: 9.91 years, 61% male), 23% of procedures were performed in patients under 15kg, and two were in patients under 5kg. 63% of patients had a structurally normal heart, while 37% had some type of congenital heart disease, the most common being Ebstein's anomaly. The most widely used group of drugs were beta-blockers, mainly propranolol. Among the arrhythmias treated, 21.7% had preexcitation Syndrome, 33.3% had at least one hidden accessory pathway, 5% corresponded to permanent reciprocating junctional tachycardia, 5% intranodal tachycardia, 11.7% atrial tachycardia, 10 % atrial flutter, 5% had other types of tachycardia and in 5 cases no tachycardia was induced. Of the total procedures, 76% corresponded to electrophysiological study and ablation, four patients recurred. Conclusions: The most common supraventricular tachycardia substrate in children was the presence of some accessory pathway. Radiofrequency catheter ablation could be applied in children with a high success rate and a low complication rate.

[Incessant focal atrial tachycardia as a cause of cardiomyopathy. About a case]. / Taquicardia atrial focal incesante como causa de cardiomiopatía. A propósito de un caso.

Focal atrial tachycardia is a rare type of supraventricular tachyarrhythmia, generally present in young people, and is a rare cause of tachycardiomyopathy (10%). We present a clinical case of tachycardiomyopathy in a 30-year-old man, without comorbidities, who was diagnosed with incessant focal atrial tachycardia, refractory to medical therapy, and electrical cardioversion. Successful endocardial ablation was performed, and in outpatient follow-up at 6 months, he showed a recovery of the left ventricular ejection fraction and reduction of the left chambers to normal ranges, with progressive decrease of dyspnea.

[Pregnancy with pre-excitation syndrome influence on pregnancy outcomes].

Objective: To investigate the characteristics of pregnancy with pre-excitation syndrome and its influence on pregnancy outcomes. Methods: A retrospective analysis was made on the clinical data of 62 cases of pregnancy complicated with pre-excitation syndrome in Beijing Anzhen Hospital from Jan. 2008 to Dec. 2008. According to whether there was a supraventricular tachycardia (SVT) in pregnancy, they were divided into two groups. There were 16 pregnant women in the SVT seizure group during pregnancy, and 46 pregnant women in no SVT seizure group, with a multi-disciplinary comprehensive diagnosis and treatment model. SPSS software was used to analyze the data and compare the gestational age, age and weight of the newborn, and then compare the pregnancy outcomes. Results: (1) The total number of deliveries in Beijing Anzhen Hospital during the study period was 21 786, and the patients with pregnancy combined with pre-excitation syndrome account for 0.28% (62/21 786). (2) Totally 44 patients (71%, 44/62) were diagnosed with pre-excitation syndrome before pregnancy, and 18 patients (29%, 18/62) were diagnosed for the first-time during pregnancy. Among patients diagnosed with pre-excitation syndrome before pregnancy, 16 patients (36%, 16/44) had seizures before pregnancy, 28 patients (64%, 28/44) had asymptomatic before pregnancy, and 4 of asymptomatic patients had SVT during pregnancy. (3) Of the 16 pregnant women in the SVT seizure group during pregnancy, 2 patients (2/16) had SVT episodes in the first trimester, 5 patients (5/16) had SVT episodes in the second trimester, 9 patients (9/16) had SVT episodes in the third trimester. In the SVT seizure group, 8 patients (8/16) had SVT episodes before pregnancy, and 8 patients (8/16) had no SVT episodes before pregnancy. There were 46 patients in the SVT seizure-free group during pregnancy, including 9 patients with SVT attacks before pregnancy and 37 patients without SVT before pregnancy. (4) Compared with the pregnant women in the SVT seizure group, the age, weight gained during pregnancy, delivery gestation week, newborn weight, and the time of the first and second labors were not statistically different between the two groups of pregnant women (all P>0.05). However, the total duration of labor in the SVT seizure group during pregnancy was shorter and pre-pregnancy weight was lower (all P<0.05). The rate of cesarean section in pregnant women with SVT attack was 12/16, and the rate of cesarean section in pregnant women without SVT was 50% (23/46; P=0.051). No pregnant woman had an arrhythmia during delivery. Conclusions: SVT episode in patients during pregnancy most occurs in the third trimester. Patients who are asymptomatic before pregnancy may also have SVT during pregnancy. Pre-excitation syndrome patients with SVT attacks during pregnancy increase adverse pregnancy outcomes. Multidisciplinary comprehensive management could effectively control pregnant women with pre-excitation syndrome, effectively reduce the occurrence of serious arrhythmia risk events during pregnancy, so that most patients could get good pregnancy outcomes.

Assessment of the hemogram parameters in patients with paroxysmal supraventricular tachycardia: a retrospective study

SUMMARY OBJECTIVE: Inflammation has been suggested as a potential mechanism in the pathogenesis of arrhythmia. Hemogram parameters such as monocyte count to high-density lipoprotein cholesterol ratio (MHR), neutrophil/lymphocyte ratio (NLR), and monocyte/lymphocyte ratio (MLR) have been considered to be markers of inflammation and new cardiovascular risk predictors. This retrospective study aimed to investigate the relationship between MHR, NLR, and MLR in patients with paroxysmal supraventricular tachycardia (PSVT). METHODS: A retrospective study conducted at a university hospital in Bolu, Turkey, between 2017 and 2019. Our study included 196 patients who underwent electrophysiological study (EPS) due to palpitation or documented PSVT on electrocardiography (ECG). Patients having documented atrioventricular nodal re-entrant tachycardia (AVNRT) on ECG or inducible AVNRT on EPS were included in the PSVT group (n=130), and patients with palpitation but without inducible arrhythmia on EPS (n=66) were included in the control group. Routine biochemical and hemogram tests were performed before the EPS procedure. RESULTS: When hemogram parameters were compared, there was no statistically significant difference in MHR values [0.010 (0.001-0.030) vs 0.010 (0.001-0.020) p =0.67]. Additionally, both NLR [2.21(0.74-11.36) vs 1.98(0.72-24.87) p=0.13] and MLR [0.25 (0.03-1.05) vs 0.24(0.07-1.39) p=0.41] were not statistically significant between the two groups. CONCLUSION: There is no significant difference in PSVT patients regarding hemogram parameters including white blood cell subtypes, MLR, NLR, and MHR. Therefore the evaluation of hemogram parameters may not be clinically relevant for PSVT patients.

RESUMO OBJETIVO: A inflamação tem sido sugerida como um mecanismo potencial na patogênese da arritmia. Parâmetros do hemograma, como contagem de monócitos e razão de colesterol lipoproteína de alta densidade (MHP), proporção de neutrófilos / linfócitos (NLP) e proporção de monócitos / linfócitos (MLR), foram considerados marcadores de inflamação e novos preditores de risco cardiovascular. Este estudo retrospectivo teve como objetivo investigar a relação entre MHP, NLP e MLP em pacientes com taquicardia paroxística supraventricular (PSVT). MÉTODOS: Estudo retrospectivo realizado em um hospital universitário em Bolu, Turquia, entre 2017 e 2019. Nosso estudo incluiu 196 pacientes submetidos a estudo eletrofisiológico (EPS) devido a palpitações ou PSVT documentada na eletrocardiografia (ECG). Os pacientes com taquicardia nodal atrioventricular reentrante (AVNRT) no ECG ou AVNRT indutível no EPS foram incluídos no grupo PSVT (n = 130) e os pacientes com palpitações sem arritmia induzível no EPS (n = 66) foram incluídos no grupo controle. Testes bioquímicos e de hemograma de rotina foram realizados antes do procedimento de EPS. RESULTADOS: Quando os parâmetros do hemograma foram comparados, não houve diferença estatisticamente significante nos valores de MHP (0,010 (0,001-0,030) vs 0,010 (0,001-0,020) p = 0,67). Além disso, tanto o NLP (2,21 (0,74-11,36) vs 1,98 (0,72-24,87) p = 0,13) quanto o MLP (0,25 (0,03-1,05) vs 0,24 (0,07-1,39) p = 0,41) não foram estatisticamente significantes entre os dois grupos. CONCLUSÃO: Não há diferença significativa nos pacientes com PSVT em relação aos parâmetros do hemograma, incluindo os subtipos de glóbulos brancos, MHP, NLP e MHP. Portanto, a avaliação dos parâmetros do hemograma pode não ser clinicamente relevante para pacientes com PSVT.

Differentiating Atrioventricular Reentry Tachycardia and Atrioventricular Node Reentry Tachycardia Using Premature His Bundle Complexes.

BACKGROUND: Current maneuvers for differentiation of atrioventricular node reentry tachycardia (AVNRT) and atrioventricular reentry tachycardia (AVRT) lack sensitivity and specificity for AVRT circuits located away from the site of pacing. We hypothesized that a premature His complex (PHC) will always perturb AVRT because the His bundle is obligatory to the circuit. Further, AVNRT could not be perturbed by a late PHC (≤20 ms ahead of the His) due to the retrograde His conduction time. Earlier PHCs can advance the AVNRT circuit but only by a quantity less than the prematurity of the PHC. METHODS: High-output pacing at the distal His location delivered PHCs. AVRT was predicted when late PHCs perturbed tachycardia or when earlier PHCs led to atrial advancement by an amount equal or greater than the degree of PHC prematurity. RESULTS: Among the 73 supraventricular tachycardias, the test accurately predicted AVRT (n=29) and AVNRT (n=44) in all cases. Late PHC advanced the circuit in all 29 AVRTs and none of the AVNRTs (sensitivity and specificity, 100%). With earlier PHCs, the degree of atrial advancement was equal or greater than the PHC prematurity in 26/29 AVRTs and none of the AVNRTs (90% sensitivity and 100% specificity). The mean prematurity of the PHC required to perturb AVNRT was 48 ms (range, 28-70 ms) and the advancement less than the prematurity of the PHC (mean, 32 ms; range, 18-54 ms). CONCLUSIONS: The responses to PHCs distinguished AVRT and AVNRT with 100% specificity and sensitivity.

Variable Presentations and Ablation Sites for Manifest Nodoventricular/Nodofascicular Fibers.

BACKGROUND: Nodofascicular and nodoventricular (NFV) accessory pathways connect the atrioventricular node and the Purkinje system or ventricular myocardium, respectively. Concealed NFV pathways participate as the retrograde limb of supraventricular tachycardia (SVT). Manifest NFV pathways can comprise the anterograde limb of wide-complex SVT but are quite rare. The purpose of this report is to highlight the electrophysiological properties and sites of ablation for manifest NFV pathways. METHODS: Eight patients underwent electrophysiology studies for wide-complex tachycardia (3), for narrow-complex tachycardia (1), and preexcitation (4). RESULTS: NFV was an integral part of the SVT circuit in 3 patients. Cases 1 to 2 were wide-complex tachycardia because of manifest NFV SVT. Case 3 was a bidirectional NFV that conducted retrograde during concealed NFV SVT and anterograde causing preexcitation during atrial pacing. NFV was a bystander during atrioventricular node re-entrant tachycardia, atrial fibrillation, atrial flutter, and orthodromic atrioventricular re-entrant tachycardia in 4 cases and caused only preexcitation in 1. Successful NFV ablation was achieved empirically in the slow pathway region in 1 case. In 5 cases, the ventricular insertion was mapped to the slow pathway region (2 cases) or septal right ventricle (3 cases). The NFV was not mapped in cases 5 and 7 because of its bystander role. QRS morphology of preexcitation predicted the right ventricle insertion sites in 4 of the 5 cases in which it was mapped. During follow-up, 1 patient noted recurrent palpitations but no documented SVT. CONCLUSIONS: Manifest NFV may be critical for wide-complex tachycardia/manifest NFV SVT, act as the retrograde limb for narrow-complex tachycardia/concealed NFV SVT, or cause bystander preexcitation. Ablation should initially target the slow pathway region, with mapping of the right ventricle insertion site if slow pathway ablation is not successful. The QRS morphology of maximal preexcitation may be helpful in predicting successful right ventricle ablation site.