Stereotactic Radioablation as First-Line Therapy for Scar-Related Ventricular Tachycardia

Condition(s) studied

Investigational drug(s) / intervention(s)

Stereotactic Arrhythmia Radioablation: Single fraction of 25 Gy stereotactic body radiotherapy (SBRT) delivered using a volumetric modulated arc therapy (VMAT) technique with 6 MV FFF photons on an Elekta Agility linear accelerator. The clinical target volume (arrhythmogenic scar) is delineated by the radiation oncologist and electrophysiologist using cardiac CT, 12-lead ECGs of the clinical arrhythmia, and (where available) non-invasive electrocardiographic mapping (252-electrode CardioInsight vest) and/or 3-D electroanatomical mapping. A 4D-CT simulation accounts for cardiac and respiratory motion. In selected cases with a large planning target volume or proximity to critical organs at risk (stomach, esophagus, spinal cord), the dose may be delivered in 2 fractions 24-48 hours apart. Treatment is delivered with image guidance (cone-beam CT) on the day of treatment. Total dose: 25 Gy in 1 or 2 fractions.

Study summary

Ventricular tachycardia (VT) is a dangerous fast heart rhythm originating from scarred areas of the heart muscle, often after a heart attack or in patients with cardiomyopathy. Patients with VT and structural heart disease typically receive an implantable cardioverter-defibrillator (ICD) to prevent sudden death. Despite the ICD, recurrent VT and ICD shocks remain common and are associated with poor quality of life. Current preventive therapies - antiarrhythmic medications and catheter radiofrequency ablation - have important limitations including side effects, incomplete effectiveness, and procedural risk.

Stereotactic Arrhythmia Radioablation (STAR) is a non-invasive treatment in which a single, precisely targeted dose of radiation is delivered to the scar tissue that gives rise to the abnormal heart rhythm. STAR has previously been studied in patients who have failed catheter ablation or are too high risk for that procedure, with promising results. However, STAR has not been formally evaluated as a first-line treatment.

This single-arm prospective feasibility study will enroll 20 adults with structural heart disease and sustained monomorphic VT. Each participant will receive a single 25 Gy fraction of stereotactic body radiotherapy (VMAT technique) targeted at the arrhythmogenic substrate identified by cardiac imaging, 12-lead ECG, and (where available) non-invasive electrocardiographic mapping or electroanatomical mapping. Participants will be followed at 6 weeks, 3, 6, 9, and 12 months to assess the primary efficacy outcomes (death, appropriate ICD shock, VT storm, and sustained VT below ICD detection rate after a 6-week blanking period) and safety outcomes (acute heart failure decompensation, drop in left ventricular ejection fraction, and STAR-specific toxicities such as pneumonitis, esophagitis, and pericarditis). The hypothesis is that STAR delivered as first-line therapy is safe and effective, with a comparable toxicity and efficacy profile to catheter radiofrequency ablation.

Eligibility

Primary outcome measure(s)

• Composite of death, appropriate ICD shock, VT storm, or sustained VT below ICD detection (after 6-week blanking period) — From 6 weeks post-treatment through 12 months follow-up
  Proportion of participants experiencing at least one of the following events after the 6-week post-treatment blanking period: (1) death from any cause; (2) appropriate ICD shock; (3) VT storm, defined as \>3 episodes of VT within 24 hours; or (4) sustained VT below the ICD detection rate requiring external cardioversion, pharmacologic conversion, or manual ICD cardioversion (shock or ATP). ICDs will be interrogated at every device-clinic visit.
• Safety: Composite of serious adverse events related to STAR — Acute (<6 weeks post-treatment) and late (up to 6 months post-treatment)
  Proportion of participants experiencing any of the following: (1) acute worsening of heart failure requiring initiation of new IV vasoactive medications (inotropes or vasopressors) within the first 6 weeks; (2) acute reduction in left ventricular ejection fraction greater than 10 percentage points within the first 6 weeks; (3) any STAR-specific symptom including esophagitis, pneumonitis, or pericarditis assessed by CTCAE v5. The pre-specified safety threshold is a serious adverse event rate of \<=20%.

Trial sites (1)

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