European Journal of Cardiovascular Medicine

Ventricular tachycardia (VT) during pregnancy is a rare but potentially serious cardiac arrhythmia, requiring timely diagnosis and careful therapeutic consideration to ensure maternal and fetal safety. Among the spectrum of ventricular arrhythmias, Idiopathic Left Fascicular Ventricular Tachycardia (ILFVT) is an uncommon, structurally benign form that predominantly affects young adults and is characterized by a right bundle branch block (RBBB) morphology with a Right-axis deviation on electrocardiogram (ECG) [1]. First described by Zipes et al., ILFVT is thought to originate from the left posterior fascicle and is typically sensitive to calcium channel blockers, particularly verapamil, which remains the treatment of choice [2].

Pregnancy presents a unique cardiovascular environment marked by increased plasma volume, cardiac output, and hormonal changes, which can exacerbate underlying arrhythmias or unveil previously silent conduction disorders [3,4]. The occurrence of ILFVT in pregnancy is rare but poses a clinical dilemma, especially when accompanied by structural heart abnormalities. Bicuspid aortic valve (BAV), a congenital defect affecting 1–2% of the population, is often associated with progressive aortic regurgitation and a risk of endocarditis or aortic dissection [5]. The coexistence of mitral valve prolapse (MVP) further complicates the hemodynamic landscape and may contribute to arrhythmogenic potential due to myocardial stretch and fibrosis [6].

Despite being classified as idiopathic, ILFVT in such structurally altered cardiac conditions challenges the traditional view and emphasizes the need for multimodal evaluation including echocardiography, Holter monitoring, and cardiac MRI, when feasible [7]. Management is further complicated in pregnancy due to concerns over teratogenicity, fetal exposure, and the limited use of electrophysiological studies or catheter ablation during gestation. In such cases, verapamil is considered safe and effective for acute and chronic control, and definitive radiofrequency ablation is typically deferred until the postpartum period [8].

Several case series and reviews have advocated for a conservative approach during pregnancy, emphasizing maternal-fetal monitoring and drug safety while maintaining rhythm control [9]. However, coexistent valvular anomalies, as seen in this patient, can influence the arrhythmia threshold and alter therapeutic response, making individualization of treatment crucial. The recognition and management of such complex interplay during pregnancy are sparse in literature and underscore the need to document rare but instructive clinical experiences [10].

This case highlights a rare clinical scenario of ILFVT during pregnancy, coinciding with a newly diagnosed bicuspid aortic valve, moderate aortic regurgitation, and mitral valve prolapse, successfully managed with verapamil during pregnancy and radiofrequency ablation in the postpartum period.

CASE REPORT

This case report presents the clinical findings, diagnostic evaluation, and management of a single patient diagnosed with idiopathic left fascicular ventricular tachycardia (ILFVT) during pregnancy, in conjunction with newly identified bicuspid aortic valve, moderate aortic regurgitation, and mitral valve prolapse. The patient was evaluated and managed at a tertiary care teaching hospital. All clinical, electrocardiographic, and echocardiographic data were retrieved from hospital records with informed consent obtained from the patient for publication. A comprehensive review of the patient's antenatal history, cardiac symptoms, and arrhythmic episodes was conducted. Investigations included 12-lead electrocardiography (ECG), 2D transthoracic echocardiography, and routine blood work. Management decisions, including the administration of verapamil and postpartum electrophysiological evaluation followed by radiofrequency ablation, were based on a multidisciplinary approach involving obstetrics, cardiology, and electrophysiology teams. Ethical approval for reporting the case was obtained in accordance with institutional guidelines, and patient confidentiality was maintained throughout.

Patient Information

A 26-year-old primigravida at 32 weeks of gestation presented with sudden-onset palpitations, dizziness, and mild chest discomfort of approximately two hours’ duration. She had no previous history of cardiovascular disease, syncope, or arrhythmias. At presentation, she remained conscious, oriented, and hemodynamically stable without chest pain or signs of heart failure.

Clinical Findings

Vital signs revealed a heart rate of 205 bpm, blood pressure of 140/80 mmHg, and oxygen saturation of 98% on room air. Cardiovascular examination uncovered a newly appreciated diastolic murmur at the left sternal border, suggestive of aortic regurgitation (AR), and a mid-systolic click consistent with mitral valve prolapse (MVP). There were no signs of volume overload or pulmonary congestion.

Electrocardiographic and Laboratory Evaluation

ECG showed a regular, monomorphic ventricular tachycardia with a right bundle branch block (RBBB) morphology, right axis deviation, QRS duration of 110 ms, and a corrected QT interval (QTc) of 512 ms. The electrocardiographic features were consistent with idiopathic left fascicular ventricular tachycardia (ILFVT). Laboratory investigations, including electrolytes, thyroid function, and cardiac enzymes, were within normal ranges. (Figure 1 to 3)

Figure 1: ECG on admission

Figure 2: ECG after 1^st dose of verapamil

Figure 3: ECG after transcutaneous pacing

Figure 4: Post Ablation ECG

Imaging Studies

Transthoracic echocardiography identified a previously undiagnosed bicuspid aortic valve with moderate aortic regurgitation, along with mitral valve prolapse without significant regurgitation. Left ventricular size and function were normal. Fetal ultrasonography demonstrated appropriate fetal growth and heart rate with no signs of intrauterine distress.

 Figure 4: EP study and RF ABLATION

Figure 5: Pre And Post Ablation EP findings

Diagnosis

The final diagnosis was idiopathic left fascicular ventricular tachycardia (ILFVT) in pregnancy, in association with newly diagnosed bicuspid aortic valve, moderate aortic regurgitation, and mitral valve prolapse.

MANAGEMENT

Acute Management

The patient was initially managed as hemodynamically stable VT. She received two doses of intravenous verapamil followed by amiodarone, without conversion to sinus rhythm. Beta-blockers (metoprolol) were subsequently introduced but failed to suppress the arrhythmia. Ultimately, transcutaneous pacing was employed, which successfully terminated the tachycardia. Notably, after pacing, the patient demonstrated a favorable pharmacological response to verapamil, indicating a transiently altered arrhythmogenic substrate that became more responsive post-interruption.

No hemodynamic instability was observed during any point, and continuous fetal monitoring revealed normal fetal heart rate and activity throughout.

Note: Although synchronized cardioversion (100 J biphasic) is the recommended treatment for unstable VT in pregnancy, it was not required in this case.

Long-Term Management During Pregnancy

Following rhythm stabilization, the patient was started on oral verapamil 120 mg TID for prophylaxis, with metoprolol 50 mg BID added to reduce sympathetic activity. Serial echocardiography was performed to monitor aortic valve function and assess regurgitation progression. Electrophysiological study (EPS) and definitive catheter ablation were deferred until after delivery, in accordance with safety protocols for pregnant patients.

Delivery and Postpartum Course

An elective lower segment cesarean section (LSCS) was performed at 38 weeks due to the patient's arrhythmic history and underlying moderate aortic regurgitation. The delivery was uneventful, and both mother and baby remained stable.

In the postpartum period, the patient underwent electrophysiological mapping, which confirmed reentrant ILFVT localized to the left posterior fascicle. A radiofrequency ablation (RFA) procedure was carried out using CARTO 3D electroanatomic mapping. The ablation employed irrigated-tip catheter technology to precisely and safely target the arrhythmogenic tissue. The arrhythmia was successfully eliminated without procedural complications.

Follow-Up and Outcome

At six months post-ablation, the patient remained in sinus rhythm and was weaned off all antiarrhythmic medications. During her second pregnancy, two years later, she reported no recurrence of arrhythmia. She had remained off verapamil for one year prior to conception. Another elective LSCS at 38 weeks was conducted without complications.

At three-year follow-up, the patient continued to remain arrhythmia-free. Her aortic regurgitation remained stable, and there was no progression of mitral valve prolapse. Her quality of life and exercise tolerance were reported as excellent, and the child from the first pregnancy remained healthy and developmentally normal.

Idiopathic left fascicular ventricular tachycardia (ILFVT) is a rare, verapamil-sensitive form of ventricular tachycardia, most commonly affecting young individuals with structurally normal hearts. However, its occurrence during pregnancy — particularly in combination with congenital valvular anomalies such as bicuspid aortic valve (BAV), moderate aortic regurgitation (AR), and mitral valve prolapse (MVP) — is extremely uncommon and presents a significant diagnostic and therapeutic challenge [11].

The physiological changes of pregnancy, including increased blood volume, cardiac output, and elevated levels of estrogen and progesterone, create a hyperdynamic cardiovascular environment that can predispose to new-onset arrhythmias or exacerbate latent ones [12]. In this case, the ILFVT may have been unmasked or triggered by pregnancy-induced hemodynamic alterations combined with mechanical stress from underlying valvular abnormalities. The presence of MVP and BAV, although not traditionally linked with ILFVT, may act synergistically in increasing myocardial irritability and arrhythmogenic potential, especially with the added preload and afterload changes of late pregnancy [13].

The initial ECG features were typical of ILFVT — a regular monomorphic VT with right bundle branch block morphology, right axis deviation, and relatively narrow QRS complexes. These characteristics, along with the patient's preserved left ventricular function and absence of ischemic or metabolic abnormalities, supported the diagnosis [14]. The partial resistance to intravenous verapamil and amiodarone initially seen in this patient is rare but has been described in the literature. Such resistance may be due to transient autonomic shifts, altered drug pharmacokinetics in pregnancy, or subtle, reversible fascicular conduction changes [15].

Transcutaneous pacing, which successfully terminated the arrhythmia, highlights the importance of non-pharmacologic modalities in refractory cases. It likely interrupted a reentrant circuit that had become transiently insensitive to calcium channel blockade, restoring responsiveness to verapamil thereafter. Similar findings have been reported in refractory ILFVT cases where mechanical interruption via pacing or overdrive techniques led to pharmacological responsiveness [16].

Long-term management during pregnancy must balance arrhythmia control and fetal safety. Verapamil, a non-dihydropyridine calcium channel blocker, is generally considered safe during pregnancy and was effective in preventing recurrence in this case. The addition of beta-blockers, specifically metoprolol, likely helped suppress adrenergical mediated triggers. Serial echocardiographic surveillance ensured that the AR and MVP did not progress or contribute to further arrhythmic risk [17].

Definitive therapy in this case was appropriately deferred to the postpartum period. Radiofrequency ablation (RFA), performed with advanced CARTO 3D mapping technology, allowed precise localization of the arrhythmogenic substrate — the left posterior fascicle. The use of irrigated catheter tips ensures deeper lesion formation with reduced risk of complications, especially in previously unablated fascicular regions [18]. The complete resolution of symptoms and the absence of recurrence even during a subsequent pregnancy strongly support the curative nature of ablation therapy in ILFVT when properly timed and executed.

This case reinforces the importance of a multidisciplinary approach in managing complex arrhythmias in pregnancy and highlights the evolving role of non-invasive and catheter-based technologies in achieving successful outcomes without compromising maternal or fetal safety.

Idiopathic left fascicular ventricular tachycardia during pregnancy is a rare and potentially misdiagnosed entity, particularly when accompanied by underlying structural valve anomalies. The present case illustrates the complexity of diagnosing and managing ILFVT in the third trimester and demonstrates that a structured, multidisciplinary approach can yield excellent maternal and fetal outcomes. The initial resistance to conventional antiarrhythmics, followed by successful termination with transcutaneous pacing and eventual stabilization with verapamil, reflects the dynamic nature of arrhythmias in pregnancy. Postpartum electrophysiological mapping and successful ablation using CARTO 3D technology provided a curative solution. The patient's sustained symptom-free status during a subsequent pregnancy underscores the long-term efficacy of this management strategy. This case emphasizes that ILFVT, even when complicated by valvular anomalies, can be managed safely and effectively with a tailored therapeutic plan.

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