Magnetic guided stereotactic radioablation for mid-wall ventricular tachycardia: how to overcome limits of catheter ablation

Abstract

Figures

Workflow for magnetic resonance guided sterotactic arrhythmia radioablation (MRgSTAR). Radiotherapy target was achieved by combining electrophysiological [ECG (Panel A), electroanatomic maps (Panel C—Blue dots represent the ablation lesions)] and anatomical/functional [cardiac MRI—blue arrow showed a basal antero-septal mid-myocardial scar (Panel B)] data. A multi-disciplinary team (radiation oncologist, electrophysiologist, and cardiac radiologist) delineated the CTV and planned target volume was obtained, adding a 2–3 mm margin to the target area (Panel D). CTV, clinical target volume; MRI, magnetic resonance imaging.

Full text

Case description

A 64-year-old female was admitted to our intensive care unit for incessant ventricular tachycardia (VT) unresponsive to antiarrhythmic medication (beta-blocker plus amiodarone) (Figure 1A). Cardiac magnetic resonance imaging (MRI) revealed a preserved left ventricular function with an ejection fraction of 60% and a basal antero-septal mid-myocardial late gadolinium enhancement (Figure 1B). Ultra-high-density left ventricular endo-epicardial maps with the HD grid catheter (Abbott, Minneapolis, USA) performed in sinus rhythm did not show low voltage areas and fragmented/prolonged electrograms; VT activation map identified only the exit site of the tachycardia, and it remained inducible despite multiple radiofrequency applications performed at 50 W using the Tactiflex catheter (Figure 1C).

Workflow for magnetic resonance guided sterotactic arrhythmia radioablation (MRgSTAR). Radiotherapy target was achieved by combining electrophysiological [ECG (Panel A), electroanatomic maps (Panel C—Blue dots represent the ablation lesions)] and anatomical/functional [cardiac MRI—blue arrow showed a basal antero-septal mid-myocardial scar (Panel B)] data. A multi-disciplinary team (radiation oncologist, electrophysiologist, and cardiac radiologist) delineated the CTV and planned target volume was obtained, adding a 2–3 mm margin to the target area (Panel D). CTV, clinical target volume; MRI, magnetic resonance imaging.

Considering the acute VT recurrence after catheter ablation, the clinical implication of a partial diastolic pathway mapping^1^ and the lack of a well-established strategy for the treatment of arrhythmias originating from mid-wall substrate, we planned a magnetic resonance guided sterotactic arrhythmia radioablation (MRgSTAR). We delineated the clinical target volume (CTV)—antero-septal scar—and the planning target volume was obtained by adding a 2–3 mm margin to the CTV (Figure 1D). Radiotherapy energy (25 Gy) was delivered on the CTV, and a sagittal cine MRI was performed during the whole delivery time (see Supplementary material online, Video S1). ICD implantation was performed after MRgSTAR and the patient was discharged 2 days later. Genetic test revealed a LMNA gene mutation [c.185G > T;p.(Arg62Leu)] and ICD interrogation at 12-months after MRgSTAR did not show VT recurrence.

STAR was introduced for the treatment of VT refractory to catheter ablation and demonstrated a strong reduction in the arrhythmia burden.^2^ However, no data are available for patients with mid-myocardial scar. In this scenario, radiotherapy energy seems to provide changes in conduction tissue properties and myolisis acutely and after months myocardial fibrosis.^3^ For these reasons, MRgSTAR may represent a safe and effective strategy for the treating of these patients.

Supplementary Material

ytaf158_Supplementary_Data