Dosimetric feasibility of stereotactic arrhythmia radioablation for ventricular tachycardia in patients with a subcutaneous implantable cardioverter defibrillator.

BACKGROUND AND PURPOSE: Subcutaneous implantable cardioverter defibrillators (S-ICDs) are increasingly used to prevent sudden cardiac death. Due to their placement near the left lateral and apical myocardium, S-ICDs can present technical challenges for stereotactic arrhythmia radioablation (STAR) of ventricular tachycardia. This study aimed to evaluate the feasibility of STAR in patients with S-ICDs.

MATERIALS AND

METHODS

Previously acquired cardiac computed tomography data from ten S-ICD patients were retrospectively analyzed. Organs at risk, S-ICD components, and hypothetical planning target volumes (PTV) for segments 8 (septal), 11 (lateral), and 17 (apical) were contoured. For each patient and segment, two treatment plans were calculated with a prescribed PTV dose of 25 Gy: one plan sparing the S-ICD from the primary radiotherapy beam ('spared') and one without this constraint ('non-spared').

RESULTS

The S-ICD was successfully spared from the primary beam in 27 out of 30 plans, with D 0.035cm 3 < 1 Gy. In three spared plans (PTV segment 11) with a distance between PTV and S-ICD <4 cm, D 0.035cm 3 exceeded 1 Gy. Spared plans for PTV segment 11 showed significant higher dose/volume metrics and reduced plan quality compared to non-spared plans (p < 0.05), although 9/10 plans remained clinically acceptable. For PTV segment 8 and segment 17, no clinical or statistical differences were observed.

CONCLUSIONS

The presence of an S-ICD is not a contraindication for STAR, although plan quality may decrease with PTVs in lateral segments. Rare cases with a distance between PTV and S-ICD <4 cm may complicate radiation treatment planning.