Right Meets Left: A Common Mechanism Underlying Right and Left Ventricular Outflow Tract Tachycardias

Anatomical approach to suppression of para-Hisian ventricular arrhythmias with changes in QRS morphology after ablation at the earliest activation site

BACKGROUND

The anatomical approach for the management of para-Hisian ventricular arrhythmias (VAs) with QRS morphological changes after catheter ablation (CA) has not been well investigated.

OBJECTIVE

We aimed to evaluate the electrocardiographic and electrophysiological findings and ablation outcomes of para-Hisian VAs with QRS morphological changes after CA.

METHODS

Of the 30 patients who underwent CA for para-Hisian VAs at 4 institutions, 10 (33%) had QRS morphological changes after ablation. All 10 patients underwent an anatomical approach, targeting the site anatomically opposite to the site where the QRS morphology had been changed by ablation. We investigated the safety and efficacy of the anatomical approach.

RESULTS

Of the 10 patients evaluated, the approach was switched from the right ventricular septum to the left ventricular septum/aortic root in 7 (70%) (RL group) whereas 3 (30%) underwent left-to-right switches (LR group). After CA, the precordial transition zone tended to be earlier in the RL group and later in the LR group. In the RL group, successful VA suppression was achieved, despite suboptimal pace map concordance from the left side or a relatively delayed earliest activation time. Of the 10 patients who underwent an anatomical approach, 8 (80%) had procedural success, and ablation was discontinued in 1 (10%) because of the risk of atrioventricular block.

CONCLUSION

The anatomical approach showed promising results regarding safety and efficacy. Therefore, it should be considered when QRS morphological changes are observed during or after CA of para-Hisian VAs.

A High-Precision Machine Learning Algorithm to Classify Left and Right Outflow Tract Ventricular Tachycardia

Introduction

Multiple algorithms based on 12-lead ECG measurements have been proposed to identify the right ventricular outflow tract (RVOT) and left ventricular outflow tract (LVOT) locations from which ventricular tachycardia (VT) and frequent premature ventricular complex (PVC) originate. However, a clinical-grade machine learning algorithm that automatically analyzes characteristics of 12-lead ECGs and predicts RVOT or LVOT origins of VT and PVC is not currently available. The effective ablation sites of RVOT and LVOT, confirmed by a successful ablation procedure, provide evidence to create RVOT and LVOT labels for the machine learning model.

Methods

We randomly sampled training, validation, and testing data sets from 420 patients who underwent successful catheter ablation (CA) to treat VT or PVC, containing 340 (81%), 38 (9%), and 42 (10%) patients, respectively. We iteratively trained a machine learning algorithm supplied with 1,600,800 features extracted via our proprietary algorithm from 12-lead ECGs of the patients in the training cohort. The area under the curve (AUC) of the receiver operating characteristic curve was calculated from the internal validation data set to choose an optimal discretization cutoff threshold.

Results

The proposed approach attained the following performance: accuracy (ACC) of 97.62 (87.44–99.99), weighted F1-score of 98.46 (90–100), AUC of 98.99 (96.89–100), sensitivity (SE) of 96.97 (82.54–99.89), and specificity (SP) of 100 (62.97–100).

Conclusions

The proposed multistage diagnostic scheme attained clinical-grade precision of prediction for LVOT and RVOT locations of VT origin with fewer applicability restrictions than prior studies.

A High-Precision Machine Learning Algorithm to Classify Left and Right Outflow Tract Ventricular Tachycardia

Introduction

Multiple algorithms based on 12-lead ECG measurements have been proposed to identify the right ventricular outflow tract (RVOT) and left ventricular outflow tract (LVOT) locations from which ventricular tachycardia (VT) and frequent premature ventricular complex (PVC) originate. However, a clinical-grade machine learning algorithm that automatically analyzes characteristics of 12-lead ECGs and predicts RVOT or LVOT origins of VT and PVC is not currently available. The effective ablation sites of RVOT and LVOT, confirmed by a successful ablation procedure, provide evidence to create RVOT and LVOT labels for the machine learning model.

Methods

We randomly sampled training, validation, and testing data sets from 420 patients who underwent successful catheter ablation (CA) to treat VT or PVC, containing 340 (81%), 38 (9%), and 42 (10%) patients, respectively. We iteratively trained a machine learning algorithm supplied with 1,600,800 features extracted via our proprietary algorithm from 12-lead ECGs of the patients in the training cohort. The area under the curve (AUC) of the receiver operating characteristic curve was calculated from the internal validation data set to choose an optimal discretization cutoff threshold.

Results

The proposed approach attained the following performance: accuracy (ACC) of 97.62 (87.44-99.99), weighted F1-score of 98.46 (90-100), AUC of 98.99 (96.89-100), sensitivity (SE) of 96.97 (82.54-99.89), and specificity (SP) of 100 (62.97-100).

Conclusions

The proposed multistage diagnostic scheme attained clinical-grade precision of prediction for LVOT and RVOT locations of VT origin with fewer applicability restrictions than prior studies.

Park Algorithm as Predictor of Premature Ventricular Contraction Origin in Three-Dimensional Mapping Electrophysiological Studies

PURPOSE

In the past few years, premature ventricular contraction (PVC) has attracted immense attention, both in patients with or without structural heart disease. Despite the technological advancement, no guiding tools are currently available to assist in the prediction of origin of PVC using a 12-lead electrocardiogram (ECG) before electrophysiology and ablation procedures. Park and co-workers compiled the existing algorithms for the morphology of ECG from the literature and generated a single algorithm based on specific features of ECG for the prediction of PVC origin. The Park algorithm is limited to idiopathic PVC and has not been evaluated clinically. In the present study, the Park algorithm was used to predict PVC origin in patients with or without structural heart disease and compared with the gold standard examination based on three-dimensional electrophysiological mapping studies.

PATIENTS AND METHODS

A cross-sectional study employing ECG data and electrophysiology study (EPS) reports from patients' medical records at Integrated Heart Center Wahidin Sudirohusodo Hospital, Makassar, Indonesia was conducted. The study was performed from April 2018 to June 2019 with a total of 31 samples; however, four samples were excluded during the EPS.

RESULTS

In the present study, the incidence of structural heart disease was 45.2%. The suitability of the Park algorithm for electrophysiological evaluation was 85.2%, both in the case of PVC with and/or without structural heart disease. The prediction of the origin of PVC in the right or left heart using the Park algorithm showed a sensitivity of 95%, specificity of 100%, positive predictive value of 100%, negative predictive value of 87.5%, and accuracy of 96%.

CONCLUSION

The findings of the study suggest significant accuracy of the Park algorithm in the prediction of location of origin of PVC. High sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of the Park algorithm highlight its suitability to be used for determining the location of PVC origin in the right or left heart.

A Simplified Two-Stepwise Electrocardiographic Algorithm to Distinguish Left from Right Ventricular Outflow Tract Tachycardia Origin

BACKGROUND

There are several electrocardiographic algorithms to predict the origin of idiopathic outflow tract ventricular arrhythmias (OT-VAs). This study aimed to develop a more accurate and efficient stepwise electrocardiographic algorithm to discriminate left ventricular outflow tract (LVOT) from right ventricular outflow tract (RVOT) origin.

METHODS AND RESULTS

We analyzed 12-lead electrocardiographic characteristics of 173 consecutive OT-VAs patients who underwent successful radiofrequency catheter ablation in the RVOT (n = 124) or LVOT (n = 49). Based on the areas under the receiver operating characteristic curves, the combination of transitional zone (TZ) index <0 and V2S/V3R index ≤1.5 exhibited 93.5% sensitivity, 85.9% specificity, and 87.3% accuracy. A further analysis was performed in the 71 OT-VAs with a V3-lead precordial transition. The sensitivity, specificity, and accuracy of the integration of V2S/V3R index ≤1.5 and R-wave deflection interval in lead V3 >80 ms were 91.7, 83.1, and 85.9%, respectively. In the prospective evaluation, the combination of TZ index and V2S/V3R index could identify the correct origin sites with 91.2% accuracy in the overall analysis, and the integration of V2S/V3R index ≤1.5 and R-wave deflection interval in lead V3 >80 ms exhibited 94% accuracy in V3-lead precordial transition.

CONCLUSIONS

The combination of TZ index <0 and V2S/V3R index ≤1.5 is a simple and efficient stepwise electrocardiographic algorithm for predicting LVOT origin. For the OT-VAs with a V3-lead precordial transition, the integration of V2S/V3R index ≤1.5 and R-wave deflection interval in lead V3 >80 ms would be a better choice.

Clinical and electrophysiological characteristics of ventricular arrhythmias arising from pulmonary cusps

Introduction

Ventricular arrhythmias (VAs) have been successfully ablated from the pulmonary sinus cusps establishing pulmonary artery (PA) as a distinct site of arrhythmic foci. The aim of the present study was to determine the clinical presentation, electrocardiographic, and ablation characteristics of PA‐VAs.

Methods

Thirty consecutive patients with right ventricular outflow tract (RVOT)‐type VAs were included in this retrospective study. Three‐dimensional electroanatomic mapping was performed in all patients. Mapping was performed initially in RVOT, and later within the PA. Mapping was performed in the PA if there was no early activation, unsatisfactory pace‐map, or ablation in RVOT were unsuccessful. All PA‐VAs were mapped and ablated by looping the catheter in a reverse U fashion.

Results

Among 30 patients, 8 (26.6%) patients VAs were successfully ablated within PA. Electrocardiography (ECG) revealed that the QRS duration was significantly wider in the PA‐VAs group compared to the RVOT‐VAs group (155 ± 14.14 vs 142.40 ± 8.12 ms, P < .01). Mapping by reversed U method of PA‐VAs revealed earlier activation (55 ± 9.66 vs 12.00 ± 8.61 ms, P < .01) in PA compared to RVOT. An isolated discrete prepotential was present at the successful site in 50% (n = 4).

Conclusion

Pulmonary artery‐VAs are an important subset of VA originating from the outflow tract. They have a wider baseline QRS duration compared to RVOT‐VAs. Presence of a prepotential aids in the identification of a successful ablation site. Mapping utilizing the reversed U method can help in localization and successful ablation of PA‐VAs.

Ventricular arrhythmias originating from the cardiac crux and the basal inferior segment of the interventricular septum in the patients with structural heart diseases: characteristics, mapping, and electrophysiological properties

PURPOSE

There are few reports describing ventricular arrhythmias (VAs) from the crux and the corresponding endocardial site, i.e., the basal inferior segment of the interventricular septum (IVS). We aimed to investigate a distinct clinical group of VAs arising from the endocardium at this area in patients with structural heart diseases (SHD).

METHODS

We included 17 patients with SHD and clinically documented VAs. Thirteen patients underwent endocardial mapping only. Three patients underwent both epicardial and endocardial approaches and one had only epicardial mapping. Eighteen VAs were identified, 14 focal and 4 reentrant VAs, confirmed by entrainment.

RESULTS

There were 2 VAs from the crux, 5 VAs from the corresponding endocardial site in the right ventricle (RV), and 11 from the site in the left ventricle (LV). Compared with the VAs from RV endocardium, VAs from LV endocardium had a higher R wave in V3 than V2 (V2R/V3R ratio, 1.83 ± 0.84 vs. 0.86 ± 0.38, P = 0.008) and a higher V3 transition ratio percentage (2.16 ± 2.07 vs. 0.58 ± 0.62, P = 0.008). Combining all 16 patients with endocardial mapping, there were also lower bipolar voltages (1.21 ± 1.05 vs. 3.10 ± 2.65 mv, P < 0.0001), lower unipolar voltages (4.05 ± 1.92 vs. 5.75 ± 2.90 mv, P < 0.0001), and longer local electrocardiogram (EGM) lateness (157.6 ± 47.9 vs.140.3 ± 52.5 ms, P = 0.0001) in the dominant chambers.

CONCLUSIONS

In VAs from the crux and the corresponding endocardial site, the complete ECG V2R/V3R ratio and V3 transition ratio percentage could differentiate the VAs from the RV or LV endocardium. The lower unipolar, bipolar voltage mapping, and longer EGM lateness are helpful to identify the abnormal substrate in the endocardium in these patients.

Kill two birds with one stone: curing accessory pathways and premature ventricular contractions with one ablation

Radiofrequency catheter ablation has been used for treating cardiac arrhythmias, such as premature ventricular contractions and accessory pathway. We report two cases with successful ablation of left‐sided accessory pathways and premature ventricular contractions from mitral annulus with one ablation. To our knowledge, no similar reports have been found so far.

Which Is The Appropriate Arrhythmia Burden To Offer RF Ablation For RVOT Tachycardias?

Premature ventricular complexes (PVCs) and ventricular tachycardia (VT) in patients with structurally normal hearts originate from the right ventricular outflow tract (RVOT) in the majority of cases. In the last few decades catheter ablation of these arrhythmias has been proven to be effective. RVOT VT/PVCs may cause disabling symptoms or arrhythmia induced cardiomyopathy. However, the PVC burden at which catheter ablation should be recommended is still controversial. What adds to the controversy is why some patients with only a low number of PVCs can be highly symptomatic and may even develop arrhythmia induced cardiomyopathy, whilst others may have a higher PVC/VT burden and remain asymptomatic and do not develop cardiomyopathy for a long period of time. Therefore, although catheter ablation of RVOT PVCs has high success and low complication rates, the time point of when ablation should be recommended is currently still under debate. This review discusses the treatment strategies and prognosis for RVOT tachycardias and focuses on the question of which arrhythmia burden is appropriate to offer RF ablation.

Idiopathic Ventricular Arrhythmia Originating From the Cardiac Crux or Inferior Septum

Background—

Idiopathic ventricular arrhythmia (VA) can arise from the epicardium near the posteroseptal region (cardiac crux). There are only 2 prior reports describing idiopathic VA from the cardiac crux. The purpose of this study was to characterize the clinical and the electrocardiographic features of idiopathic crux VA.

Methods and Results—

Crux VA was identified in 18 patients undergoing catheter ablation. We divided patients into 2 groups, those with VA originating from the apical crux (n=9) and the basal crux (n=9). We described the clinical and electrocardiographic characteristics of crux VA as well as the ablation results. Furthermore, we compared clinical features of crux VA with other sites of idiopathic VA. Fifteen crux VA patients (83%) had sustained ventricular tachycardia and 3 patients required implantable cardioverter defibrillator implantation because of syncope. All patients had a left superior axis and 16 patients had R>S wave in V2. In apical crux VA, all patients had a deep S wave in V6 and 8 patients (89%) had R>S wave in aVR. All apical crux patients underwent attempted ablation in the middle cardiac vein without success. In 4 of these patients, epicardial ablation with subxiphoid approach was performed successfully. All basal crux VA patients had either negative or isoelectric pattern in V1 and had R>S in V6. Patients had successful ablation within the middle cardiac vein.

Conclusions—

Apical versus basal crux VA is identified as a new category of idiopathic VA with distinctive electrocardiographic characteristics; ablation via the middle cardiac vein is effective for eliminating basal crux VA, whereas apical crux VA often requires a subxiphoid epicardial approach.

Structure, function and clinical relevance of the cardiac conduction system, including the atrioventricular ring and outflow tract tissues

It is now over 100years since the discovery of the cardiac conduction system, consisting of three main parts, the sinus node, the atrioventricular node and the His-Purkinje system. The system is vital for the initiation and coordination of the heartbeat. Over the last decade, immense strides have been made in our understanding of the cardiac conduction system and these recent developments are reviewed here. It has been shown that the system has a unique embryological origin, distinct from that of the working myocardium, and is more extensive than originally thought with additional structures: atrioventricular rings, a third node (so called retroaortic node) and pulmonary and aortic sleeves. It has been shown that the expression of ion channels, intracellular Ca(2+)-handling proteins and gap junction channels in the system is specialised (different from that in the ordinary working myocardium), but appropriate to explain the functioning of the system, although there is continued debate concerning the ionic basis of pacemaking. We are beginning to understand the mechanisms (fibrosis and remodelling of ion channels and related proteins) responsible for dysfunction of the system (bradycardia, heart block and bundle branch block) associated with atrial fibrillation and heart failure and even athletic training. Equally, we are beginning to appreciate how naturally occurring mutations in ion channels cause congenital cardiac conduction system dysfunction. Finally, current therapies, the status of a new therapeutic strategy (use of a specific heart rate lowering drug) and a potential new therapeutic strategy (biopacemaking) are reviewed.

Preferential Conduction Across the Ventricular Outflow Septum in Ventricular Arrhythmias Originating From the Aortic Sinus Cusp

OBJECTIVES

The purpose of this study was to examine the relationship between the origin and breakout site of idiopathic ventricular tachycardia (VT) or premature ventricular contractions (PVCs) originating from the myocardium around the ventricular outflow tract.

BACKGROUND

The myocardial network around the ventricular outflow tract is not well known.

METHODS

We studied 70 patients with idiopathic VT (n = 23) or PVCs (n = 47) with a left bundle branch block and inferior QRS axis morphology. Electroanatomical mapping was performed in both the right ventricular outflow tract (RVOT) and aortic sinus cusp (ASC) during VT or PVCs.

RESULTS

The earliest ventricular activation (EVA) was recorded in the RVOT in 55 patients (group R) and in the ASC in 15 (group A). In all group R patients, the closest pace map and successful ablation were achieved at the EVA site. Although a successful ablation was achieved at the EVA site in all group A patients, the closest pace map was obtained at the EVA site in 8 and RVOT in 7 (with an excellent pace map in 4). The stimulus to QRS interval was 0 ms during pacing from the RVOT and 36 +/- 8 ms from the ASC. The distance between the EVA and perfect pace map sites in those 4 patients was 11.9 +/- 3.0 mm.

CONCLUSIONS

Ventricular arrhythmias originating from the ASC often show preferential conduction to the RVOT, which may render pace mapping or some algorithms using the electrocardiographic characteristics less reliable. In some of those cases, an insulated myocardial fiber across the ventricular outflow septum may exist.

Demonstration of Ventricular Myocardial Extensions into the Pulmonary Artery and Aorta Beyond the Ventriculo-Arterial Junction

BACKGROUND

A subgroup of outflow tract (OT) ventricular tachycardias (VT) originate from the aortic sinuses or the main stem of the pulmonary artery. The anatomic substrate for these tachycardias is unknown. The aim of this study was to investigate the presence of ventricular myocardial extensions (VME) into the pulmonary artery (PA) and aorta (Ao) beyond the ventriculo-arterial junction (VAJ) and determine the anatomical and histological characteristics of these muscle extensions.

METHODS

Ninety-five consecutive human hearts obtained at autopsy were studied. Longitudinal strips of tissue containing each cusp, aortic, and pulmonary artery walls and left and right ventricular outflow tracts were excised and histologically analyzed. Anatomical measurements, including length and thickness of VMEs, obtained at autopsy, were made.

RESULTS

VMEs beyond the VAJ were found in 21 of 95 (22%) patients studied. VMEs were found in 16 of 95 PAs (17%) and 7 of 95 Aos (7%) were examined. VMEs were located within the adventitia in 23 (88%) and on the epicardial surface in three (12%). The majority of VMEs were in continuity with the underlying ventricular OT muscle tissue. Myocellular hypertrophy and fibrosis were present in 19 (73%) and fatty tissue between the layers of VME in 18 (69%). Clinical data were available in 14 of 21 patients with positive VME. None of the patients (clinical data available group) had history of cardiac disease or signs or symptoms (palpitations or syncope) of cardiac disease.

CONCLUSIONS

VMEs into the PA and Ao beyond the VAJ are relatively common. It seems that their mere presence does not predispose to OT VTs. There are probably intrinsic arrhythmogenic properties in tissues specific to these regions in those patients who develop OT VTs.