Search

The specialized cardiomyocytes that constitute the conduction system in the human heart, initiate the electric impulse and result in rhythmic and synchronized contraction of the atria and ventricles. Although the atrioventricular (AV) conduction axis was described more than a century ago by Sunao Tawara, the anatomic pathway for propagation of impulse from atria to the ventricles has been a topic of debate for years. Over the past 2 decades, there has been a resurgence of conduction system pacing (CSP) by implanting pacing leads in the His bundle region in lieu of chronic right ventricular pacing that is associated with worse clinical outcomes. The inherent limitations of implanting the leads in the His bundle region has led to the emergence of left bundle branch area pacing in the past 3 years as an alternative strategy for CSP. The clinical experience from performing CSP has helped electrophysiologists gain deeper insight into the anatomy and physiology of cardiac conduction system. This review details the anatomy of the cardiac conduction system, and highlights some of the recently published articles that aid in better understanding of the AV conduction axis and its variations, the knowledge of which is critical for CSP. The remarkable evolution in technology has led to visualization of the cardiac conduction system using noninvasive, nondestructive high‐resolution contrast‐enhanced micro‐computed tomography imaging that may aid in future CSP. We also discuss from anatomical perspective, the differences seen clinically with His bundle pacing and left bundle branch area pacing. [ABSTRACT FROM AUTHOR]

Aims: Outcome data on ventricular tachycardia (VT) ablation has been limited to few experienced centres. We sought to identify complication rates, predictors, and create a risk score model for predicting complications in patients from real-world data.Methods and Results: A total of 25 451 patients undergoing VT ablation from year 2006 to 2013 were identified from the National Inpatient Sample (NIS) database. The whole cohort was randomly divided into derivation cohort to derive the model and validation cohort to validate the model. Multivariate predictors of any complication were identified using regression model. Each predictor was assigned a risk score and each patient was assigned to one of the four groups (risk score in parenthesis) based on total combined risk score: Group 0 (0), Group 1 (1-5), Group 2 (6-10), and Group 3 (>11). The rate of 'any complication' and 'in-hospital mortality' in whole cohort was 14.7% and 2.8%, respectively. The predictors of any complication include chronic kidney disease, coagulopathy, chronic liver disease, stroke (cerebrovascular accident), emergency procedure, age ≥ 65 years, coronary artery disease, peripheral vascular disease, and female gender. There was a significant increase in complication rate in a linear fashion as the risk score increased. The incidence of any complications increased from 2.7% in Group 0 to 31% in Group 3. The risk score model performed well in predicting complications associated with VT ablation.Conclusion: Patients with higher risk scores have significant increase in any complication and in-hospital mortality from VT ablation. The simple risk score model can help to risk stratify patients prior to VT ablation. [ABSTRACT FROM AUTHOR]

Aims: The electrocardiographic (ECG) signs used to differentiate ventricular tachycardia (VT) from supraventricular tachycardia (SVT) with aberrancy are specific but not highly sensitive. The purpose of this study was to define the utility of an underappreciated form of atrioventricular (AV) dissociation at the onset of tachycardia, a single dissociated P wave, in the differentiation of non-sustained monomorphic wide complex tachycardia (WCT) in hospitalized patients.Methods and Results: We prospectively analysed tracings from 102 consecutive hospitalized patients who had an episode of non-sustained (≥5 beats, <30 s), monomorphic, WCT (≥100 b.p.m.) on telemetry. WCT was classified as VT, SVT with aberrancy, or undifferentiated WCT based on predefined criteria. Of 102 patients with WCT, 3 (3%) had SVT with aberrancy, 43 (42%) had an undifferentiated WCT, and 56 (55%) had VT. ECG evidence of a single dissociated P wave at the onset of tachycardia (i.e. AV dissociation at the onset) was identified in 29 patients (28%) compared with less frequent traditional signs of VT including second-degree ventriculoatrial (VA) block in 18 patients (18%), AV dissociation during tachycardia in 17 patients (17%), fusion beats in 10 patients (10%), and capture beats in 3 patients (3%). On multivariate analysis, only the prematurity index predicted the occurrence of AV dissociation at the onset of the tachycardia (odds ratio 1.239, 95% confidence interval 1.033-1.486, P = 0.021).Conclusion: When evaluating WCT in hospitalized patients, a single dissociated P wave at the onset of tachycardia is an easily recognizable diagnostic sign of VT, and is observed more frequently than the other accepted criteria for VT. [ABSTRACT FROM AUTHOR]

Lyme borreliosis is a multisystem infectious disease with well-known cardiac involvement, including potential carditis as well as conduction abnormalities.1 We report a case of Lyme disease in a previously healthy 24-year-old male presenting with alternating right- and left-bundle branch block, indicating infra-Hisian atrioventricular (infra-His) block with an accelerated fascicular escape rhythm. In less than 12 hours, the conduction abnormalities progressed to asystole requiring the urgent placement of a temporary transvenous pacemaker. Subsequently, with appropriate antibiotic treatment, the patient's conduction abnormalities resolved in a week without the need for a permanent pacemaker. [ABSTRACT FROM AUTHOR]

A 56-year-old male with a history of orthotopic cardiac transplantation secondary to cardiac sarcoidosis presented with recurrent episodes of syncope preceded by dizziness. While on telemetry, he had transient episodes of high-grade atrioventricular (AV) block that reproduced his prodrome. After excluding allograft rejection, ischemia, recurrent cardiac sarcoidosis, and vagally mediated block as a cause of high-grade AV block, adenosine testing was done which reproduced the spontaneous high-grade AV block. We concluded that hypersensitivity to endogenously released adenosine was the likely mechanism of AV block in our patient. This is the first reported case of adenosine testing in a cardiac transplant patient for diagnosing episodic high-degree AV block of unclear etiology. [ABSTRACT FROM AUTHOR]

Aims: Ventricular arrhythmias (VAs) from the basal inferoseptal (BIS) area are rare and can pose unique challenges during catheter ablation (CA) due to the anatomic complexity. The study sought to describe the electrocardiographic and clinical characteristics of VAs originating from the BIS area., Methods and Results: Patients with VAs and successful ablation at the BIS area from 2016 to 2020 were included. The 12-lead electrocardiogram (ECG), intracardiac findings, and outcomes were analysed. Of 482 patients with VAs referred for CA, 17 (3.5%) had successful ablation at BIS area. There were 12 males, mean age was 66.7 ± 9 years, 82% had ejection fraction <50%. Mean baseline premature ventricular complex burden was 28.6 ± 9%. All patients had a leftward superior axis. Left bundle branch block (LBBB) with early transition in V2 was noted in eight patients and right bundle branch block (RBBB) in nine patients. Detailed mapping of the right ventricle (RV) was performed in 15 patients (88%), coronary sinus (CS)/middle cardiac vein (MCV) in 13 (76%), right atrium (RA) adjacent to the inferoseptal process (ISP) of left ventricle (LV) in 5 (29%), ISP-LV in 13 (76%), and epicardium in 2 (12%). Successful ablation site was in LV in 10 (59%), RV in 2 (12%), CS/MCV in 1 (6%), RA in 1 (6%), and epicardium in 2 (12%). Fifteen patients (88%) required mapping in at least two chambers (range 2-5) and seven patients (41%) required ablation in at least two chambers (range 2-3)., Conclusions: Ventricular arrhythmias originating in the BIS are uncommon. The most common ECG patterns were leftward superior axis, LBBB with transition in V2 or RBBB. The VA foci can be endocardial or epicardial and meticulous mapping/ablation from multiple chambers is often required to eliminate these foci successfully., (Published on behalf of the European Society of Cardiology. All rights reserved. © The Author(s) 2021. For permissions, please email: journals.permissions@oup.com.)

Aims: Outcome data on ventricular tachycardia (VT) ablation has been limited to few experienced centres. We sought to identify complication rates, predictors, and create a risk score model for predicting complications in patients from real-world data., Methods and Results: A total of 25 451 patients undergoing VT ablation from year 2006 to 2013 were identified from the National Inpatient Sample (NIS) database. The whole cohort was randomly divided into derivation cohort to derive the model and validation cohort to validate the model. Multivariate predictors of any complication were identified using regression model. Each predictor was assigned a risk score and each patient was assigned to one of the four groups (risk score in parenthesis) based on total combined risk score: Group 0 (0), Group 1 (1-5), Group 2 (6-10), and Group 3 (>11). The rate of 'any complication' and 'in-hospital mortality' in whole cohort was 14.7% and 2.8%, respectively. The predictors of any complication include chronic kidney disease, coagulopathy, chronic liver disease, stroke (cerebrovascular accident), emergency procedure, age ≥ 65 years, coronary artery disease, peripheral vascular disease, and female gender. There was a significant increase in complication rate in a linear fashion as the risk score increased. The incidence of any complications increased from 2.7% in Group 0 to 31% in Group 3. The risk score model performed well in predicting complications associated with VT ablation., Conclusion: Patients with higher risk scores have significant increase in any complication and in-hospital mortality from VT ablation. The simple risk score model can help to risk stratify patients prior to VT ablation., (Published on behalf of the European Society of Cardiology. All rights reserved. © The Author(s) 2018. For permissions please email: journals.permissions@oup.com.)

Aims: The electrocardiographic (ECG) signs used to differentiate ventricular tachycardia (VT) from supraventricular tachycardia (SVT) with aberrancy are specific but not highly sensitive. The purpose of this study was to define the utility of an underappreciated form of atrioventricular (AV) dissociation at the onset of tachycardia, a single dissociated P wave, in the differentiation of non-sustained monomorphic wide complex tachycardia (WCT) in hospitalized patients., Methods and Results: We prospectively analysed tracings from 102 consecutive hospitalized patients who had an episode of non-sustained (≥5 beats, <30 s), monomorphic, WCT (≥100 b.p.m.) on telemetry. WCT was classified as VT, SVT with aberrancy, or undifferentiated WCT based on predefined criteria. Of 102 patients with WCT, 3 (3%) had SVT with aberrancy, 43 (42%) had an undifferentiated WCT, and 56 (55%) had VT. ECG evidence of a single dissociated P wave at the onset of tachycardia (i.e. AV dissociation at the onset) was identified in 29 patients (28%) compared with less frequent traditional signs of VT including second-degree ventriculoatrial (VA) block in 18 patients (18%), AV dissociation during tachycardia in 17 patients (17%), fusion beats in 10 patients (10%), and capture beats in 3 patients (3%). On multivariate analysis, only the prematurity index predicted the occurrence of AV dissociation at the onset of the tachycardia (odds ratio 1.239, 95% confidence interval 1.033-1.486, P = 0.021)., Conclusion: When evaluating WCT in hospitalized patients, a single dissociated P wave at the onset of tachycardia is an easily recognizable diagnostic sign of VT, and is observed more frequently than the other accepted criteria for VT., (Published on behalf of the European Society of Cardiology. All rights reserved. © The Author 2015. For permissions please email: journals.permissions@oup.com.)