Idiopathic left posterior fascicular ventricular tachycardia in a military tactical athlete

Key Teaching Points.

• ▪Idiopathic left posterior fascicular ventricular tachycardia (LPF-VT) is a rare ventricular arrhythmia typically occurring in structurally normal hearts and is highly amenable to catheter ablation.
• ▪When LPF-VT is noninducible during electrophysiology study, empirical ablation targeting fragmented antegrade Purkinje potentials may be curative.
• ▪In tactical athletes, ventricular arrhythmias carry unique operational risks in high exertion activities, austere environments, and high-risk missions requiring high interteam reliability, posing unique management considerations in this population.
• ▪Successful ablation can enable safe and unrestricted return to military duty and other tactical occupations without implantable cardioverter-defibrillator implantation.

Introduction

Idiopathic fascicular ventricular tachycardia (VT), first described by Zipes et al¹ and Cohen et al² in the 1970s, is a calcium channel blocker–sensitive reentrant tachycardia most commonly originating from the left posterior fascicle.1, 2, 3, 4 It typically presents in young, otherwise healthy individuals with structurally normal hearts, most commonly presenting in the third to fifth decade of life with recurrent palpitations and presyncopal symptoms.^5,6 Although overall prognosis is generally good and comparable with that of other types of idiopathic VT, the condition can still occasionally lead to malignant syncope and degenerate to ventricular fibrillation in a minority of cases.^5,7 Catheter ablation is highly effective and may obviate the need for chronic medical therapy or implantable cardioverter-defibrillator (ICD) placement.

Although management of idiopathic VT in the civilian population often focuses on symptom control and return to routine activity, the clinical and occupational implications differ substantially for tactical athletes. Ventricular arrhythmia in this population may not only jeopardize personal safety but also team readiness, ability to perform in austere environments, and mission successes. These occupational considerations often demand definitive therapy, more rigorous postprocedural monitoring, and more stringent return to play/duty determinations than in nontactical populations.

We present a case of left posterior fascicular VT (LPF-VT) in a young, active-duty military combat medic successfully managed with catheter ablation. This case not only highlights the clinical aspects of diagnosis and management of LPF-VT but also the unique considerations, decision-making pathways, and return-to-duty implications relevant to tactical athlete populations.

Case report

A 29-year-old active-duty combat medic with no significant medical history presented with recurrent, sustained palpitations and presyncopal symptoms. Owing to these symptoms, the patient presented to the emergency room. On arrival, she was noted to be tachycardic with otherwise normal vital signs. Electrocardiogram (ECG) demonstrated a regular, wide complex tachycardia refractory to intravenous adenosine and emergency room staff then decided to proceed with direct current cardioversion to restore normal sinus rhythm. ECG was notable for a wide complex tachycardia with right bundle branch morphology with a superior leftward mean frontal plane axis consistent with LPF-VT (Figure 1). The postconversion ECG was significant for normal sinus rhythm without evidence of pre-excitation or repolarization abnormalities (Figure 1).

Figure 1.

ECG showing a wide complex tachycardia with QRS duration of 148 ms, right bundle branch morphology, V3 precordial transition, precordial RS duration between 60 and 80 ms, and superior leftward axis consistent with LPF-VT. Differences in 12-lead ECG morphology can predict the exit site origin of LPF-VT, which may originate from the proximal, middle, and distal Purkinje fibers. ECG = electrocardiogram; LPF-VT = left posterior fascicular ventricular tachycardia.

In discussion with the patient, she denied any family history of sudden cardiac death or inherited arrhythmias. Laboratory evaluation including electrolyte, thyroid levels, and urine drug screen was unremarkable. The patient was then initiated on verapamil therapy and admitted for further workup. Inpatient transthoracic echocardiography and cardiac magnetic resonance imaging demonstrated a structurally normal heart with normal biventricular function and no evidence of fibrosis or late gadolinium enhancement. Given benign laboratory findings, a structurally normal heart on cardiac imaging, and an ECG with evidence of LPF-VT, shared decision making with the patient was pursued and ultimately elected to proceed with catheter ablation.

A comprehensive electrophysiology study was performed using a fluoroless approach. Via a retrograde transaortic approach, a multipolar mapping catheter was used to obtain a three-dimensional electroanatomic map demonstrating normal bipolar voltage throughout the left ventricle and to identify the fascicular conduction system (Figure 2). The proximal conduction system including the His, left anterior and posterior fascicles were mapped and anterograde fragmented Purkinje potentials were identified in the region of the midposterior fascicle. The midposterior fascicle demonstrated fractionated signals, whereas the remaining areas demonstrated normal signals and voltage (Figure 3). Despite programmed electrical stimulation at multiple sites and isoproterenol infusion, no VT was inducible for activation or entrainment mapping. Substrate modification targeting the fragmented Purkinje potentials was performed with radiofrequency ablation delivered intended to transect the left posterior fascicle (Figure 4). Verapamil was subsequently discontinued post procedure, and a loop recorder was implanted for arrhythmia surveillance monitoring.

Figure 2.

Bipolar 3-dimensional electroanatomic bipolar voltage map of the left ventricle showing grossly normal voltage throughout the left ventricle.

Figure 3.

Bipolar recording signals showing fragmented antegrade Purkinje potentials (purple) at the location of the left posterior fascicle compared with normal left anterior fascicle Purkinje potentials (green).

Figure 4.

Mapping demonstrating the final ablation lesion set transecting the left posterior fascicle.

At 6 months, remote monitoring and serial recorder interrogations revealed no recurrence of any ventricular arrhythmias and clinical resolve of symptoms. The patient was able to return to full active duty without occupational restrictions, including high-intensity physical and occupational demands.

Discussion

Idiopathic LPF-VT is the most common of all fascicular VTs accounting for up to 70%–80% of all fascicular VT cases.⁸ The most common reentrant anatomy for this circuit involves a slow conduction pathway with proximal-to-distal activation represented by pre-Purkinje potentials and a rapid distal-to-proximal activation limb arising from the left posterior fascicle.^6,9, 10, 11 Recognition of surface ECG features is salient to accurate diagnosis and aides in predicting the site of VT origin, often relying on QRS duration and R/S ratio to delineate proximal, middle, and distal fascicular locations. Principally, the narrower the QRS duration, the more proximal the origin and the more the R/S ratio is greater, the more proximal the LPF-VT, owing to more septal and basal origin.

Catheter ablation of the VT circuit is the preferred treatment as it is often curative. Activation mapping or entrainment mapping of VT is an optimal and highly efficacious therapy as it allows for more precise VT ablation. However, in up to 40% of cases, VT is not inducible at the time of VT ablations.¹² When the VT is unable to be induced, judicious use of isoproterenol has been shown to increase the induction of sustained fascicular VT in up to 60%–70% of those with initially noninducible VT, although even this is ineffective at times.⁸ Fragmented antegrade Purkinje potentials (FAPs) identified during sinus rhythm are strongly predictive of critical sites for reentry and a suitable target for substrate modification in the absence of inducible VA. FAPs have been reported and identified at the middle segment of the posterior septal left ventricle in most patients with LPF-VT.¹² In a study by Wei et al,¹² targeted FAP ablation with a follow-up period of 61 ± 16.8 months showed a 94% success rate as defined by the absence of symptoms without documented recurrence of VT. In a subset of patients, repeat ablation showed success with elimination of FAP in the remaining patients.

Idiopathic fascicular VTs are generally regarded as highly treatable and nonmalignant in young patients with structurally normal hearts. In civilian populations, treatment generally consists of catheter ablation or pharmacotherapy with return to normal activity upon complete resolution of symptoms. However, ventricular arrhythmias in military tactical athletes carry unique considerations not encountered in competitive athletes or the general public, requiring a more stringent approach to treatment, monitoring of recurrence, and return-to-duty decision making. This patient’s military status and symptomatic ventricular arrhythmia specifically drove the unique clinical decision to deliver radiofrequency ablation to the left posterior fascicle despite being the VT being noninducible during the electrophysiology study. This compares with many civilian cases of fascicular VT where observation without catheter ablation could be safely offered without significant impacts on a broader community or occupational impact.

Tactical athletes, including service members, aviators, firefighters, and law enforcement, operate in unpredictable, high-risk environments where complications of loss of consciousness, hemodynamic compromise, or recurrent arrhythmia may endanger not only the individual but the broader team and mission. Their duties often involve exposure to heavy load carriage, high-intensity exertion, extremes of heat/cold, sleep deprivation, and deployment to remote and austere environments with limited medical support.¹³ These occupational, mission, and team considerations place these individuals in a distinct clinical population that should not be managed identically to competitive athletes.

Within the US military, symptomatic ventricular arrhythmias are generally disqualifying for full duty, aviation status, and deployment. Historically, medical retention standards in aviation, military service, or special forces have also disqualified individuals with current use of antiarrhythmic or rate control therapy for ventricular arrhythmias. For this reason, definitive therapy options such as ablation are strongly preferred over pharmacotherapy. Although the individual in this case was initially managed with verapamil, this was incompatible with their ability to return to unrestricted duty. This consideration contributed to the shared decision-making process and their ultimate desire to pursue catheter ablation in an effort to preserve their military occupation.

After initial treatment and management, military return-to-duty determinations involve formal pathways, consideration of occupational restrictions, and weighing these determinants against published medical retention standards. Retention standard documents across the various service branches generally emphasize a high degree of confidence that treatment is successful before returning a service member to a fully operational status. Documentation of cure from arrhythmia is vital to prove the efficacy of treatment. The use of an implantable loop recorder in this case allowed for extended postablation monitoring and was critical to confirm the absence of further arrhythmia episodes and the efficacy of this patient’s ablation.

Our case highlights the importance of considering high-risk occupational implications when managing ventricular arrhythmia in tactical athletes. Successful catheter ablation provided a definitive therapy that avoided long-term duty restrictions, deployment restrictions, ICD implantation, or the need for chronic pharmacotherapy. For tactical athletes, this outcome preserves not only personal functional capacity but also mission readiness and unit safety.

Conclusion

Empirical catheter ablation targeting FAPs offers a curative strategy for idiopathic LPF-VT in cases where the arrhythmia is noninducible despite a high-quality electrophysiology study. In military and athletic populations, successful ablation can facilitate safe return to unrestricted physical activity and duty without the need for other restrictions or ICD implantation.

Declaration of Generative AI and AI-Assisted Technologies in the Writing Process

ChatGPT-5 (OpenAI, San Francisco, CA) was used to assist with grammatical editing and formatting of the manuscript. Microsoft Copilot (Microsoft Corporation, Redmond, WA) was used to aid in the design and layout of figures. No generative AI tools were used to generate original content or draw scientific conclusions. The authors have carefully reviewed the edits provided by generative AI tools and take full responsibility for the integrity and accuracy of the content presented.

Disclosures

The authors have no conflicts of interest to disclose. The views expressed herein are those of the authors and do not reflect the official policy or position of Brooke Army Medical Center, the US Army Medical Department, the US Army Office of the Surgeon General, the Department of the Air Force, the Department of the Army, the Department of Defense, or the US government.