Noninvasive Cardiac Radiation for Ablation of Ventricular Tachycardia

From practiceupdate.com by Douglas P. Zipes, MD
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Seven months ago, I wrote an editorial in which I stated, “…In the not too distant future, I envision a totally noninvasive ablation approach. Using advanced ECG and cardiac imaging technology, it is possible to construct patient-specific models of the arrhythmic substrate to non-invasively identify ablation targets likely to eliminate the arrhythmia. Then, using a transcutaneous focused energy delivery source, such as laser, ultrasound, or stereotactic external beam radiation, the area can be ablated, rendering the patient arrhythmia-free without a surgical procedure.”1

The present authors have proven the prescience of that comment in a tour de force study that will transform clinical cardiac electrophysiology. Using anatomical imaging combined with noninvasive epicardial mapping, Cuculich et al. located ablation sites during ventricular tachycardia (VT) induced by implanted ICDs in 5 awake patients with recurrent VT. They delivered precise ablative radiation with a single fraction of 25 Gy stereotactic body radiation (SBRT) to targeted scar regions.

The results were impressive. The mean noninvasive ablation time was 14 minutes. Before treatment, patients had a combined history of 6577 episodes of VT in a 3-month period. After a 6-week blanking period (to allow post-ablation inflammation to subside), patients had 4 episodes of VT over the next 46 patient-months, for a reduction from baseline of 99.9%. One patient with a history of atrial fibrillation had a fatal stroke 3 weeks after treatment, despite a reduction of VT episodes and LVEF rising from 15% to 30%.

The authors appropriately caution that this procedure should not be considered suitable for clinical use until further research is performed, particularly on the effects of radiation on other cardiac structures such as coronary arteries, specialized conduction system, and overall cardiac function. Nevertheless, the observation will be transformative and ultimately noninvasive mapping and ablation of cardiac arrhythmias will become the norm. We are not there yet, but hopefully will be soon.