Background


Cardiac stereotactic body radiation therapy (SBRT) has emerged as a promising new noninvasive treatment option for refractory ventricular tachycardia (VT) and premature ventricular contractions (PVC). PVCs from the LV summit are particularly difficult to ablate, because of their inaccessible origin and  could be the ideal target to cardiac SBRT. The optimal radiation planning is from utmost importance for safety and efficacy and is still challenging.

Methods
 and Results

A 74-year-old male patient was referred via helicopter to our center with refractory VT triggered by PVC from the LV summit region. Recurrent endo- and epicardial ablation attempts in an electrical storm had failed and resulted in a parasternal hematoma ultimately needing surgical decompression. The antiarrhythmic drug (AAD) therapy included Amiodaron, Propranolol and continuous i.v. Ajmalin. Twelve-lead electrocardiography on admission revealed monomorphic PVCs with precordial QRS transition in the V1 derivation, an rS pattern in Lead I and inferior axis. Neither Heart Transplantation nor implantation of a left ventricular assist device (LVAD) was possible, because of patient’s age and the lack of severe heart failure.  

For the radiation planning, a CT-Scan was performed and the endo- and epicardial CARTO maps from the experienced external EP center were imported into a Microsoft HoloLens. Furthermore, a CT-Scan with Late Iodine Enhancements (LIE) sequences using inHeart segmentation was performed and 3D datasets also imported into the HoloLens. The radiation planning was conducted together with experienced electrophysiologists and radio oncologist with following  SBRT-treatment with 24 Gy PTV (80% Isodose) at the Linear Accelerator (LB4, 2FFF-VMAT, 4D-CBCT). Post treatment the ICD Readout showed regular function; no other sudden side effects could be detected. In continuous electrocardiac monitoring the PVC burden decreased. Four days after the treatment  Ajmalin therapy was  stopped. At dismission the AAD therapy was deescalated to Amiodaron, Propranolol and Prajmalin p.o. with discontinuation of Prajmalin 4 weeks after the patient had no VT or ICD shocks. The PVC Burden in the ICD readout was reduced to <1%. Furthermore, three months Follow Up showed neither VT or ICD shocks. PVC in the ICD readout was still <1%. Echocardiographic assessment showed no changes left ventricular ejection fraction and no other side-effects occurred up to five months after cardiac SBRT.

Conclusion


Cardiac SBRT is a safe and effective treatment option for inaccessible PVCs and VT from the LV summit. In the radiation planning process, the HoloLens can be of interest to facilitate the communication between electrophysiologists and radio oncologists. It also might be of interest to optimize image integration of different imaging modalities. Further studies and long-time data are needed to prove the benefit of this treatment option.