Miszczyk et. al study examines the efficacy of stereotactic arrhythmia radioablation (STAR) on patients with ventricular tachycardia (VT)
Whilst the IORBC has recently focused more heavily on the use of radiotherapy treatment (RT) for Musculoskeletal conditions, in this post, we examine a recent study by Marcin Miszczyk et al. which considers the “focal” aspect of RT for treating Ventricular Tachycardia (VT).
VT is a critical heart condition which presents through rapid, abnormal rhythms in the heart’s lower chambers. It is a leading cause of sudden cardiac death and is often challenging to treat effectively with conventional methods such as antiarrhythmic drugs, implantable cardiac defibrillators, or catheter ablations. Especially problematic are cases where the arrhythmogenic substrate is deeply seated or near vital structures, which can lead to a high recurrence rate of 20-50%.
To address this gap, the recent prospective safety trial study by Miszczyk et al. used STereotactic Arrhythmia Radioablation (STAR), or cardiac stereotactic body radiotherapy. This relatively new approach uses high-precision radiotherapy in a concentrated dose directly to the arrhythmic area.
The study targeted adults with VT recurrence despite previous treatments or those ineligible for catheter ablation. The new study followed previous studies and trials including Cuculich et al. and Robinson et al. which first created interest in this field – although the authors state that clinical data remains sparse.
Eleven patients with a median age of 67 (range 45-72) were enrolled. All had structural heart disease – mostly with ischemic cardiomyopathy – and a clinically significant recurrence of VT despite adequate pharmacotherapy.
Whilst one patient developed a significant adverse event (heart failure exacerbation), generally, there was an 84.3% reduction in VT episodes. The study report states that VT recurrences were observed in most patients, some requiring additional treatments. Three deaths occurred, but none were treatment-related.
Patients received a 25 Gy radiation dose to the arrhythmogenic area, identified via electro-anatomic mapping and cardiac-gated CT. The dose was delivered to the PTV using volumetric modulated arc therapy (VMAT), typically consisting of 3–4 arcs, delivered on a Varian
EDGE™ linear accelerator – see above image.
Adherence to organs at risk (OAR) dose constraints had priority over PTV coverage, including coronary artery sparing. The respiratory movement was managed using deep inspiration breath hold (preferred) or free-breathing respiratory gating. Image-guided RT included 2D kV-kV imaging, respiratory-gated cone beam CT, and continuous surface-guided RT.
ICDs were checked both before and after STAR using dedicated programmers. During RT, the arrhythmia detection was turned off. Safety, measured by the occurrence of severe adverse events, was the primary focus, with additional endpoints of efficacy, cardiac injury markers, and quality of life.
The authors concluded that STAR demonstrates safety and effectiveness, significantly reducing VT burden. The study also reported that VT recurrences are common and long-term outcomes are yet to be evaluated. The study underscores the need for further controlled trials comparing STAR with standard care to address limitations such as its single-arm design.
IORBC welcomes the report and shares the findings to highlight the need for further research to refine this treatment modality and understand its long-term effects.
Read the full article here:
Marcin Miszczyk et al. Stereotactic management of arrhythmia – radiosurgery in treatment of ventricular tachycardia (SMART-VT). Results of a prospective safety trial. Published August 17, 2023.