Review of Stereotactic Arrhythmia Radioablation Therapy for Cardiac Tachydysrhythmias

Abstract

Cardiac tachyarrhythmias are a major cause of morbidity and mortality. Treatments for these tachyarrhythmias include antiarrhythmic drugs, catheter ablation, surgical ablation, cardiac implantable electronic devices, and cardiac transplantation. Each of these treatment approaches is effective in some patients but there is considerable room for improvement, particularly with respect to the most common of the tachydysrhythmias, atrial fibrillation, and the most dangerous of the tachydysrhythmias, ventricular tachycardia (VT) or ventricular fibrillation. Noninvasive stereotactic ablative radiation therapy is emerging as an effective treatment for refractory tachyarrhythmias. Animal models have shown successful ablation of arrhythmogenic myocardial substrates with minimal short-term complications. Studies of stereotactic radioablation involving patients with refractory VT have shown a reduction in VT recurrence and promising early safety data. In this review, we provide the background for the application of stereotactic arrhythmia radioablation therapy along with promising results from early applications of the technology.

Figure 1

Illustration of volumetric modulated arc therapy (VMAT) delivery. The red contour on the computed tomography image represents the target volume. The colour wash represents the radiation dose delivered to the target volume. The radiation dose is delivered simultaneously by varying 3 parameters during treatment delivery: gantry rotation speed, treatment aperture shape via movement of multileaf collimator (MLC) leaves (shown in each square), and dose rate. Each square represents the specific MLC pattern to deliver a fraction of the dose at that specific gantry angle. Image courtesy of Varian Medical Systems, Inc. All rights reserved

Figure 2

Outcomes after left ventricular free wall irradiation. (A) Transverse and coronal plane of a treatment plan with 2 lateral carbon beams (40 Gy). (B) Anteroposterior view of by-product β+ activity shown as colour wash. (C) Intracardiac ultrasound image of the left ventricular free wall (F) after irradiation; hyperechoic lesion area marked by dotted lines. (D) Left anterior oblique view of an endocardial voltage map of the left ventricle (LV) 6 months after irradiation; local voltage > 1.0 mV is depicted in magenta, voltage < 0.5 mV depicted in red, and other colours mark voltages in between. White dots indicate fragmented potentials. (E) Macroscopic left ventricular epicardial lesion outcome 6 months after irradiation with the dashed line marking the contoured target zone. (F) Endocardial lesion outcome 6 months after irradiation. Ao, descending aorta; F, Freewall; IPV, inferior pulmonary vein; IVC, inferior vena cava; IVS, interventricular septum; LAA, left atrial appendage; LAD, left anterior descending coronary artery; LL, left lung; LV-A, left ventricular apex; MV, mitral valve; RL, right lung; RV, right ventricle; RVOT, right ventricular outflow tract; S, septal site. Modified from Lehmann et al. under Creative Commons Attribution Attribution 4.0 International (CC BY 4.0).

Figure 3

Stereotactic arrhythmia radioablation (STAR) treatment planning and protocol. Patients to consider for STAR followed by planning, delivery, and follow-up. CT, computed tomography; EP, electrophysiology; ICD, implantable cardioverter defibrillator; LV, left ventricle; MRI, magnetic resonance imaging; RV, right ventricle.