Crazy accessory pathway- going round the bend!

A 15-year-old boy with manifest preexcitation and recurrent palpitations had undergone an unsuccessful ablation procedure elsewhere and was subsequently referred to us. The ECG suggested a left free wall pathway but there was a pattern break in lead V2. This helped localise the accessory pathway to the summit region and achieve success.

Clinical profile and electrophysiological characteristics of atypical atrioventricular nodal reentrant tachycardia: A decade's experience.

OBJECTIVE: To assess the clinical features and inducibility characteristics of atypical atrioventricular nodal reentrant tachycardia (AVNRT) and compare it with typical AVNRT. BACKGROUND: AVNRT is the commonest form of paroxysmal supraventricular tachycardia. The mechanism of AVNRT is very varied. Several classification systems evolved with better understanding but a simplified approach of classification into typical and atypical AVNRT is justifiable and clinically more relevant. In our study, we have assessed the epidemiological profile of atypical AVNRT in a single institute over 10 years and analysed pertinent electrophysiological characteristics. METHOD: In this retrospective observational single center study we analysed data of all AVNRT cases from January 2011 to June 2021. In our study we classified atypical AVNRT and typical AVNRT based on the HA interval; HA≤70 ms in the His bundle region during tachycardia was considered as typical AVNRT. Other parameters were also analysed during tachycardia, such as: induction by atrial or ventricular pacing, AH/HA ratio, tachycardia cycle length and site of the earliest atrial activation. The demographic profile of the patients were also compared between 2 groups. RESULTS: Atypical AVNRT was found in 75/1431 patients (5.2%) of all cases of AVNRT. The age of patients with atypical AVNRT was 52.4 ± 15.2 years (range 9-82 years) while that for typical AVNRT it was 48.2 ± 15.7 years (2-89 years), p = 0.023. There was no gender difference. Atypical AVNRT was induced by only ventricular extrastimuli (VES) in 17/75 (22.6%) while in typical AVNRT this was seen in only 12/1356 patients (0.9%, p < 0.001). Induction of atypical AVNRT was seen by both atrial extrastimuli (AES) and VES in 17/75 patients (22.6%) while in typical AVNRT this was seen in 64/1356 patients (4.8%, p < 0.001). Atypical AVNRT was induced by only AES in 40/75 patients (53.3%) while in typical AVNRT this was seen in 1280/1356 patients (94.3%, p < 0.001). An AH >200 ms during tachycardia was seen in all patients with typical AVNRT and in only 31/75 patients (41.3%) of atypical AVNRT (p < 0.00001). An interesting finding in atypical AVNRT was the earliest atrial activation at the His bundle region in 10/75 (13.3%) patients. CONCLUSION: Atypical AVNRT prevalence depends on the way it is classified; this was 5.2% of all AVNRT cases in our study. Typical AVNRT was seen more frequently in comparatively younger age group and was more often induced by AES. Atypical AVNRT was much more commonly induced by only VES compared to typical AVNRT. It was not so unusual in atypical AVNRT to find the earliest atrial activation in the His bundle region.

Adenosine-sensitive perinodal atrial tachycardia. What is the mechanism?

Termination of focal atrial tachycardia with adenosine is considered a defining feature for triggered activity. Recent evidence, however, suggests that the perinodal adenosine-sensitive AT has reentry as the mechanism of tachycardia. In this report, we were able to confirm the mechanism of AT as reentry by observing the response to programmed electrical stimulation and demonstrating the fallacy of traditional teaching that the adenosine responsiveness of AT is a criterion for labeling the mechanism as triggered activity.

Diagnostic and therapeutic application of thoracic epidural in a child with intractable cardiac arrhythmias: A case report.

A 3-year-old boy presented with episodes of uneasiness and transient loss of consciousness. Atrial tachyarrhythmias with rapid ventricular rate was diagnosed and initially unsuccessfully treated with oral antiarrhythmic drugs. Subsequent Holter monitoring revealed ventricular arrhythmias. Despite pharmacologic treatment, he needed numerous cardioversions. Surgical sympathectomy was planned. Initially, sympathectomy was achieved using a continuous high thoracic epidural block and was performed to ascertain the efficacy of the thoracic sympathectomy. This successfully reduced the ventricular arrhythmias and the need for antiarrhythmic agents. The epidural infusion was also used for pain relief following the subsequent surgical sympathectomy.

Long-term, real world experience of ventricular tachycardia and granulomatous cardiomyopathy.

BACKGROUND: Granulomatous cardiomyopathy (GCM) is relatively uncommon in patients presenting with ventricular tachycardia (VT). Sarcoidosis and tuberculosis are the most common causes of GCM with VT. The aim of study was to evaluate their clinical characteristics and the long-term outcomes. METHODS: We retrospectively analyzed patients from March 2004 to January 2020, presenting with VT and subsequently diagnosed to have GCM. Patients were divided into three groups (sarcoid, tuberculosis and indeterminate) based on serologic tests, imaging and histopathology. The response to anti-arrhythmic and disease specific therapy on long-term follow-up were analyzed. RESULTS: There were 52 patients, comprising 27 males and 25 females, age 40 ± 10 years. The follow-up period was 5.9 ± 3.9 years. Sarcoidosis was diagnosed in 20 (38%); tuberculosis (TB) in 15(29%) and 17(33%) patients were indeterminate. Left ventricular ejection fraction (LVEF) of the entire cohort was 0.45 ± 0.14. Erythrocyte Sedimentation Rate(ESR) was found to be significantly higher in TB(43.6 ± 18.4) patients vs sarcoid(18.9 ± 6.7)p < 0.0001, but not the indeterminate group (36.2 ± 21.1), p = 0.3. Implantable Cardioverter Defibrillator (ICD) implantation was performed in 12/20(60%) patients in the sarcoid group, in 4/15(27%) patients in the TB group and in 10/17(59%) patients in the indeterminate group. At a mean follow-up of six years, VT recurrences were noted in 6, 2, and 7 patients in the sarcoid, TB and indeterminate groups respectively. CONCLUSION: Despite the advances in diagnostic modalities for tuberculosis and sarcoidosis, in real-world practice, almost one-third of the patients with VT and GCM have uncertain etiology. Long term outcomes of patients presenting with GCM and VT with mild left ventricle dysfunction treated appropriately seems favorable.

Miniseries 2-Septal and paraseptal accessory pathways-Part IV: Inferior paraseptal accessory pathways-lessons from surgical and catheter ablation.

Surgeons and electrophysiologists performing accessory pathway ablation procedures have used the term 'posteroseptal' region. This area, however, is neither septal nor posterior, but paraseptal and inferior; paraseptal because it includes the fibro-adipose tissues filling the pyramidal space and not the muscular septum itself and inferior because it is part of the heart adjacent to the diaphragm. It should properly be described, therefore, as being inferior and paraseptal. Pathways in this region can be ablated at three areas, which we term right inferior, mid-inferior, and left inferior paraseptal. The right- and left inferior paraseptal pathways connect the right and left atrial vestibules with the right and left paraseptal segments of the parietal ventricular walls. The mid-inferior paraseptal pathways take a subepicardial course from the myocardial sleeves surrounding the coronary sinus and its tributaries. Our review addresses the evolution of the anatomical concept of the inferior paraseptal region derived from surgical and catheter ablation procedures. We also highlight the limitations of the 12-lead electrocardiogram in identifying, without catheter electrode mapping, which are the pathways that can be ablated without a coronary sinus, or left heart approach.

Miniseries 2-Septal and paraseptal accessory pathways-Part III: Mid-paraseptal accessory pathways-revisiting bypass tracts crossing the pyramidal space.

The mid-paraseptal region corresponds to the portion of the pyramidal space whose right atrial aspect is known as the triangle of Koch. The superior area of this mid-paraseptal region is also para-Hisian, and is close to the compact atrioventricular node and the His bundle. The inferior sector of the mid-paraseptal area is unrelated to the normal atrioventricular conduction pathways. It is, therefore, a safe zone in which, if necessary, to perform catheter ablation. The middle part of the mid-paraseptal zone may, however, in some patients, house components of the compact atrioventricular node. This suggests the need for adopting a prudent attitude when considering catheter ablation in this area. The inferior extensions of the atrioventricular node, which may represent the substrate for the slow atrioventricular nodal pathway, take their course through the middle, and even the inferior, sectors of the mid-paraseptal region. In this review, we contend that the middle and inferior areas of the mid-paraseptal region correspond to what, in the past, was labelled by most groups as the 'midseptal' zone. We describe the electrocardiographic patterns observed during pre-excitation and orthodromic reciprocating tachycardia in patients with pathways ablated in the middle or inferior sectors of the region. We discuss the modification of the ventriculo-atrial conduction times during tachycardia after the development of bundle branch block aberrancy. We conclude that the so-called 'intermediate septal' pathways, as described in the era of surgical ablation, were insufficiently characterized. They should not be considered the surrogate of the 'midseptal' pathways defined using endocardial catheter electrode mapping.

Miniseries 2-Septal and paraseptal accessory pathways-Part II: Para-Hisian accessory pathways-so-called anteroseptal pathways revisited.

Surgeons, when dividing bypass tracts adjacent to the His bundle, considered them to be 'anteroseptal'. The area was subsequently recognized to be superior and paraseptal, although this description is not entirely accurate anatomically, and conveys little about the potential risk during catheter interventions. We now describe the area as being para-Hisian, and it harbours two types of accessory pathways. The first variant crosses the membranous septum to insert into the muscular ventricular septum without exiting the heart, and hence being truly septal. The second variant inserts distally in the paraseptal components of the supraventricular crest, and consequently is crestal. The site of ventricular insertion determines the electrocardiographic expression of pre-excitation during sinus rhythm, with the two types producing distinct patterns. In both instances, the QRS and the delta wave are positive in leads I, II, and aVF. In crestal pathways, however, the QRS is ≥ 140 ms, and exhibits an rS configuration in V1-2. The delta wave in V1-2 precedes by 20-50 ms the apparent onset of the QRS in I, II, III, and aVF. In the true septal pathways, the QRS complex occupies ∼120 ms, presenting a QS, W-shaped, morphology in V1-2. The delta wave has a simultaneous onset in all leads. Our proposed terminology facilitates the understanding of the electrocardiographic manifestations of both types of para-Hisian pathways during pre-excitation and orthodromic tachycardia, and informs on the level of risk during catheter ablation.

Arrhythmia spectrum and outcome in children with myocarditis.

INTRODUCTION: Myocarditis remains an under-diagnosed entity among children. We evaluated the spectrum of electrocardiogram (ECG) changes and arrhythmias in children with myocarditis. METHODS: A single-center prospective observational study was conducted over a period of 18 months at a public university hospital, which included all cases with myocarditis from the ages of 1 month to 12 years. Myocarditis was diagnosed according to standard criteria. Arrhythmias were detected by 12-lead ECG or by multiparameter monitors. RESULTS: There were 63 children with myocarditis. Sinus tachycardia remained the most important ECG finding (61, 96.8%) followed by ST-T changes (30, 47.6%), low voltage QRS complexes (23, 36.5%), and premature complexes (11, 17.4%). Sustained arrhythmias were seen in 14/63 (22.2%) of the children (Group A), while the remaining 49 patients were designated as Group B. There were 11 (17.5%) cases with sustained tachyarrhythmias, comprising 5 with supraventricular tachycardia, 4 with ventricular tachycardia, and 2 with atrial flutter/fibrillation. Bradyarrhythmias were seen in 3 patients, including 2 children with atrioventricular block and 1 with severe sinus bradycardia. A longer hospital stay of 18.5 (4.75) days vs. 13 (4) days, P = 0.001), and more ST-T changes [12 (85.7%) vs. 18 (36.73%), P = 0.003] were seen in Group A. Multivariate regression analysis found only the presence of ST-T changes as predictors for arrhythmia. CONCLUSIONS: A variety of arrhythmias and other ECG changes were commonly seen in children with myocarditis. Sustained arrhythmias were seen in one-fifth of the patients, being associated with ST-T changes and a longer hospital stay.

QRS alternans during right ventricular pacing while ablating a concealed left sided accessory pathway.

A 16-year-old boy was referred for an electrophysiological study for documented regular narrow complex tachycardia. A diagnosis of a concealed left lateral accessory pathway was made with an eccentric atrial activation sequence both during tachycardia and right ventricular (RV) pacing. The pathway was mapped at the left posterior mitral vestibule during RV pacing, performed through the distal tip of the His bundle catheter pushed into right ventricular outflow tract. An unusual response to ventricular stimulation with alternation of QRS complex width and morphology was noted. The possible mechanisms are hereby discussed.