CARA-VT: a Dosimetric in Silico Study

Ventricular tachycardia (VT) is a potentially deadly condition, common in patients with structural heart disease or dilated cardiomyopathy. VTpatients are currently treated with anti-arrhythmic drugs, implanted cardioverter defibrillators or invasive catheter ablation (CA) but the overall success rate of this techniqueis still suboptimal. One of the main reasons is an anatomically inaccessible location of VT's origin (within the mid-wall of the myocardium, on the epicardial site or adjacent to critical structures). Moreover, repeated invasive ablation, technical difficulties or patient comorbidities can lead to non-eligibility for CA. Accordingly, a rationale exists to adopt more effective and less invasive therapies. A promising novel non-invasive treatment option for refractory VT is stereotactic arrhythmia radio-ablation (STAR), originally born for cancer treatment, which consists in the application of high-energy photons in a single 25 Gy dose to limited areas of the ventricles, also to those inaccessible for CA, recognized through non-invasive surface ECG-mapping as the origin of VT. Preliminary small case series described good tolerance and improved VT burden during follow-up. Due to the encouraging physical and biological characteristics of protons and carbon ions, the dose to surrounding healthy tissues could potentially be better spared in comparison with photons. Especially, the cardiac healthy sub-structures might benefit from the use of particle beams instead of photons. On the other hand, due to range uncertainties affecting particle beams, delivering an ideal radiation treatment with heavy ions to fast-moving targets such as the heart, is more complex. So far, the feasibility and the safety of cardiac radiotherapy with protons and heavy ions have only been evaluated in animal models and recently in the first in man case managed by the collaboration between CNAO and San Matteo Cardiology Department in a patient treated with compassionate aim. To dat