Invasive catheter ablation is now an established modality of treatment for a wide variety of cardiac arrhythmias ranging from paroxysmal supraventricular tachycardias to life-threatening ventricular tachycardias. Now a new modality of stereotactic arrhythmia radioablation – a non invasive ablation using stereotactic body radiotherapy is being evaluated for drug refractory ventricular tachycardia which has failed catheter ablation .
ENCORE-VT trial (Electrophysiology-Guided Noninvasive Cardiac Radioablation for Ventricular Tachycardia) was a prospective single center study involving 19 patients. Seventeen of them had ischemic cardiomyopathy. Most of the patients had prior catheter ablations. Those who had contraindications to catheter ablation were also considered. One of them had a mechanical aortic and mitral prosthetic valve. Another had a mobile left ventricular thrombus and the last had severe left ventricular dysfunction and medical comorbidities precluding hemodynamic support. Median follow up period was 13 months. Patients had either 3 or more episodes of sustained monomorphic VT or cardiomyopathy with more than 20% VPC load. They had failed at least one anti-arrhythmic drug therapy.
Patients received a single dose of 25 Gy stereotactic radioablation to the arrhythmia target which was determined before the treatment schedule. Arrhythmia target was determined using a combination of cardiac CT, cardiac MRI, PET-CT, 12 lead ECG and ECG Imaging (ECGI) during ventricular tachycardia induced by non-invasive programmed stimulation.
The median number of VT episodes was reduced from 119 to 3. VT episodes or PVC burden was reduced in 94% of the patients, which was quite remarkable and usually not achievable by conventional catheter ablation! There was reduction in both ICD shocks and anti-tachycardia pacing requirements. There was improvement in quality of life and reduction in anti-arrhythmic medication usage. No acute side effects were noted following treatment. But delayed pericarditis/effusion was noted in 28% and pneumonitis in 11%. These responded to medical therapy.
This seems to be a promising novel mode of therapy provided, its long term efficacy and safety are established in future studies.