Abstract
Background
We describe a successful ablation of ventricular arrhythmia (VA) originating from the epicardial anterior interventricular groove.
Case Summary
A 16-year-old boy with high-burden VA was referred to an electrophysiology laboratory. Endocardial pace mapping pointed to near right ventricular apex with 92% surface QRS correlation, but ablation resulted in right bundle branch block and maintenance of VA. Epicardial mapping revealed VA origin in the midsection of the anterior interventricular groove. Successful radiofrequency ablation was achieved while a guidewire was maintained inside the left anterior descending artery as a precautionary measure. The patient remained arrhythmia-free and without left anterior descending artery injury after the procedure.
Discussion
Epicardial idiopathic VAs usually arise from the crux of the heart or left ventricle summit; thus, an interventricular groove origin is unusual. Epicardial fat in the region may play a role in arrhythmogenesis.
Take-Home Message
VA with a QS pattern in leads I and V1 to V6 may prompt epicardial mapping, particularly when insufficient pace mapping or the absence of an earliest local signal is found during endocardial mapping.
Key Words: ablation, electroanatomical mapping, electrophysiology, ventricular tachycardia
Visual Summary
Visual Summary.
Epicardial Septal Ablation Near the Left Anterior Descending Coronary Artery
History of Presentation
A 14-year-old boy presented to our emergency department with recent onset of palpitations and exertional dyspnea. There was no history of syncope or chest pain. His physical examination identified an irregular rhythm and the absence of congestive findings. The initial electrocardiogram is shown in Figure 1.
Take-Home Messages
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Surface QRS correlation with an inferior axis and a QS pattern in leads I and V1 to V6 may pinpoint ventricular arrhythmia origin to the epicardial interventricular septum.
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Radiofrequency ablation can be successfully performed with appropriate care to avoid potential thermal left anterior descending artery injury.
Figure 1.
Initial Electrocardiogram Showed Sinus Rhythm With Right-Axis Deviation and Ventricular Bigeminy With an Left Bundle Branch Block Morphology
The presence of a QS pattern in lead I can be noted.
Past Medical History
His past medical history included primary membranoproliferative glomerulonephritis, under remission with prednisone 1 mg/kg and azathioprine, and secondary hypertension, treated with ramipril and amlodipine. There was also no familial history of sudden death or heart failure.
Differential Diagnosis
The patient underwent 24-hour electrocardiogram monitoring, which revealed 16% density of ventricular arrhythmia (VA) without ventricular tachycardia episodes. Differential diagnosis included dyssynchronous heart failure due to high-burden VA or subjacent primary cardiomyopathy, especially arrhythmogenic cardiomyopathy.
Investigations
Cardiac magnetic resonance showed severe biventricular heart failure (left ventricular ejection fraction = 31%) without late gadolinium enhancement, fibrofatty tissue substitution, or right ventricle wall motion abnormalities compatible with arrhythmogenic cardiomyopathy, therefore not fulfilling current Padua criteria for definitive diagnosis. Initially, interpretation of idiopathic VA causing secondary ventricular dysfunction was made.
Management
Based on symptomatic dyssynchronous heart failure due to high-burden VA, the patient was referred to an electrophysiological study. A decapolar deflectable catheter (Webster CS 2-5-2 mm; Biosense Webster) and a high-density mapping catheter (Pentaray; Biosense Webster) were positioned in the coronary sinus and right ventricle, respectively, through femoral venipuncture. Endocardial electroanatomic mapping with the CARTO 3 v8 system (Biosense Webster) located the earliest local signal of VA on the anterior right ventricle free wall, which, combined with surface QRS characteristics, indicated a possible origin in the moderator band at first (Figure 2). Pace mapping showed only 92% of correlation, but due to the lack of a more suitable site, a radiofrequency (RF) session was indicated. Ablation resulted in RBBB and the absence of VA suppression, which prompted for reevaluation (Figure 3).
Figure 2.
Endocardial Mapping With CARTO 3 Showed the Most Acceptable Site on the Right Ventricle Free Wall With 10-ms Earliness to Surface QRS Correlation
Ablation did not result in success.
Figure 3.
Surface ECG After Initial Endocardial Ablation Displayed Induction of RBBB and Maintenance of VA
ECG = electrocardiogram; VA = ventricular arrhythmia.
Endocardial left ventricular mapping did not add information. Epicardial subxiphoid access was then granted with a 17G Tuohy epidural needle (B. Braun Medical Inc) after general anesthesia, as primarily described by Sosa et al.1 Electrophysiological mapping did not find any low voltage or late potential areas. Activation mapping pinned down VA origin in the midsection of the anterior interventricular groove, near the left anterior descending artery (LAD) (Figure 4). A local ventricular signal was 52 milliseconds earlier than surface QRS correlation, and 98% correlation was obtained with pace mapping at the site (Figure 5).
Figure 4.
Coronary Angiography During Epicardial Ablation
Coronary angiography in the left anterior oblique (A) and right anterior oblique (B) projections made during RF ablation demonstrated close proximity to the LAD. LAD = left anterior descending artery; RF = radiofrequency.
Figure 5.
Epicardial Mapping of the Interventricular Groove
Left: Fluoroscopy LAO projection with a high-density multipolar catheter sitting over the target site, inside the pericardial space, with concurrent 3D epicardial activation mapping (CARTO). Right: Prepotential and earliest ventricular local signal annotated with 15-16 pole of the Pentaray catheter during epicardial mapping. 3D = three-dimensional; LAO = left anterior oblique.
Successful RF ablation was achieved at the site while an extra-support guidewire was maintained inside the LAD in case of need for coronary intervention (Video 1). Repeated angiographies were performed during RF ablation to search for vascular injury. The patient remained arrhythmia-free and without LAD damage after the procedure (Figure 6, Video 2).
Figure 6.
Successful RF Ablation on the Epicardial Surface of the Interventricular Septum
Endocardial right ventricle and left ventricle chambers can be seen on transparency, delineating the exact path of the anterior interventricular groove. RF = radiofrequency.
Outcome and Follow-Up
Clinical assessment of the patient at 6 months demonstrated suppression of VAs and exertional symptoms. His transthoracic echocardiogram confirmed improvement of left ventricular ejection fraction, compatible with heart failure secondary to desynchrony. Ambulatory coronary computed tomography (CT) discarded late-onset coronary stenosis.
Discussion
Idiopathic VAs may rarely originate from the epicardial surface, with the crux of the heart and left ventricle summit being the most common sites.2 Therefore, VAs arising from the anterior interventricular groove are unusual. In a report by Ju et al,3 anterior wall origin comprised only 11% of a distinct sample of patients with idiopathic epicardial VA ablation, whose foci were remote from the crux or left ventricle summit. The presence of a QS pattern in lead I and precordial leads helped differentiate from endocardial sites, as opposed to QRS width, pseudo-delta waves, or maximum deflection index.3
Epicardial fat in the region may play a role in arrhythmogenesis, as a positive relationship between epicardial fat volume measured by CT and burden of VA was found in patients enrolled for ablation.4
Almost the entire surface of the ventricles is covered by fat, most abundant over coronary vessels, such as in the anterior interventricular groove, where lies the LAD.5 Potential mechanisms in arrhythmia development are increased afterdepolarizations due to secretion of proinflammatory cytokines, formation of reentry substrates secondary to anisotropic conduction, or fibrosis and imbalance of the cardiac autonomic system.5
RF ablation can be successfully performed in the region through standard epicardial subxiphoid access, with appropriate care to avoid potential thermal LAD injury. Prior animal studies showed variable degrees of vascular damage when RF is applied adjacent to the LAD, being the most extensive when delivered exactly above.6 Coronary angiography is advised during ablation to check for acute injury, with appropriate preparations set for possible ad hoc angioplasty.7 In our institution, continuous fluoroscopy and repeated coronary angiography are not performed routinely for every epicardial ablation. However, this patient was 16-year-old whose arrhythmic focus lay directly adjacent to the LAD. Because of the patient's age and the proximity of the target to a major coronary vessel, we intentionally incorporated real-time fluoroscopic guidance and serial coronary angiograms throughout RF delivery in this case to minimize the risk of vascular injury.
Also, ambulatory coronary CT may be considered after ablation to look for chronic lesions, as late-onset coronary stenosis was already reported.8 Although the patient remained asymptomatic, coronary CT was performed postprocedure to exclude delayed vascular injury. In cases where ablation is performed near major coronary arteries, we consider routine follow-up imaging—such as coronary CT or functional testing—a reasonable strategy, particularly in younger patients or when symptoms arise. This case underscores the importance of procedural planning, coronary monitoring, and risk mitigation strategies when ablating in close proximity to epicardial coronary arteries. Given the anatomical complexity and potential complications, similar cases may help inform the development of procedural checklists and future consensus guidelines for epicardial ablation near critical vascular structures.
Conclusions
Ablation of VAs with a QS pattern in leads I and V1 to V6 may prompt early epicardial mapping, particularly when insufficient pace mapping or the absence of an earliest local signal is found during endocardial mapping. Although the crux of the heart and left ventricle summit are the commonest sites of epicardial idiopathic VA, unusual foci as the anterior interventricular groove can also be found. Particular attention may be required when ablating in the region due to the risk of LAD damage or occlusion.
Equipment List.
Ventricular Arrhythmia Epicardial Ablation
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Funding Support and Author Disclosures
The authors have reported that they have no relationships relevant to the contents of this paper to disclose.
Footnotes
The authors attest they are in compliance with human studies committees and animal welfare regulations of the authors’ institutions and Food and Drug Administration guidelines, including patient consent where appropriate. For more information, visit the Author Center.
Appendix
For supplemental videos, please see the online version of this paper.
Appendix
Epicardial Mapping of the Interventricular Groove
Successful Ablation Near the Left Anterior Descending Coronary Artery Without Vascular Injury
References
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Associated Data
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Supplementary Materials
Epicardial Mapping of the Interventricular Groove
Successful Ablation Near the Left Anterior Descending Coronary Artery Without Vascular Injury