Increase in ventricular tachycardia burden during the blanking period after stereotactic arrhythmia radioablation - preliminary results from the CREVET study

Stereotactic arrhythmia radioablation (STAR) has emerged as a novel treatment option for patients with ventricular tachycardia (VT) who are either refractory to or have contraindications for standard therapies.

To evaluate the efficacy of STAR in patients with refractory VT.

The CREVET study is a single-centre, prospective study investigating the safety and efficacy of STAR for treating VT. Eligible participants are patients aged ≥18 years with structural heart disease who have experienced ICD therapy for monomorphic VT and are refractory to or have contraindications for adding or escalating anti-arrhythmic drugs or for catheter ablation. The CREVET protocol implements a multidisciplinary approach, involving radiation oncologists, medical physicists, radiologists, and electrophysiologists. STAR is delivered in a single fraction of 25 Gray using an image-guided linear accelerator (TrueBeam, Varian Medical Systems) precisely targeting the planning target volume, incorporating an internal target volume for respiratory motion of the heart plus 5 mm safety margin, while minimizing exposure to surrounding organs at risk. Efficacy was assessed by comparing the number of VT episodes and ICD shocks during the 6 months prior to STAR with these observed during the 6-week blanking period and the follow-up period.

Four patients with ischemic cardiomyopathy (75% men; age 75.0±5.9 years; left ventricular ejection fraction 36.3±10.3%) underwent STAR with a mean follow-up after the blanking period of 5.8±3.2 months.

In the 6 months before STAR, patients experienced a combined total of 66 VT episodes treated with 118 appropriate ICD interventions. During the blanking period, 2 patients had no new VT episodes while 2 experienced a marked increase in VT episodes with 69 VT episodes requiring 75 ICD interventions combined.

During follow-up, 3 out of 4 patients experienced VT. In 2 patients this was limited to a single VT episode, while 1 patient experienced a VT storm during hospital admission for septic shock which resolved after restarting his beta-blocker therapy. This latter patient died of non-cardiac cause 9.3 months after STAR. A total of 37 VT episodes with 48 ICD therapies were observed during the follow-up period.

Summarized data are presented in Figure 1 and 2. The number of VT episodes/month decreased with 71.9% from 2.75±2.39 before STAR to 1.15±1.55 VT episodes/month after the blanking period. The number of ICD therapies/month reduced with 78.5% from 4.92±2.80 to 1.58±1.89, respectively.

Preliminary data from the ongoing CREVET trial suggest a favorable impact of STAR on VT management. Attention is warranted as in 2 patients an increase in VT burden was observed during the blanking period, which may be related to pronounced electrical reprogramming effects. Future investigations should explore the underlying mechanisms of STAR to optimize treatment strategies.Figure 1  Figure 2