Cohort Study - SBRT for VT Radioablation

This will be a single centre single arm prospective cohort study. 12 patients with ventricular tachycardia will be recruited from those who have failed or were unable to tolerate conventional therapy. These patients will be recruited from the cardiology clinic where they will already be under the care of a heart rhythm/heart function specialist. Clinical imaging data, medical history and previous ablation data will be collected and use towards planning their treatment with SBRT. Patients will undergo further imaging (unless recently done clinically), including: 4D cardiac CT (cCT), cardiac MRI (cMRI) and a planning CT (pCT). MRIs will only be performed on patients with ICDs for whom it is considered safe to do so. Using the imaging and electroanatomic substrate mapping data collected from a previous ablation attempt, a volumetric modulated arc therapy (VMAT) treatment plan will be established. This treatment plan will be generated in consultation between the cardiac electrophysiologist, radiation oncologist and medical physicist; and will define the target volume (TV) of myocardial tissue to be treated.

Once a TV has been established and verified, patients will be set up on a TrueBeam 1 linear accelerator where the treatment will be administered. The actual time for treatment administration is approximately 30 minutes.

After the procedure, at 6 & 12 weeks, 7.5 months then every 6 months, a follow-up will occur as a part of standard care where outcome data regarding the chronic success of the ablation procedure will be collected and ICD interrogation will be performed. No imaging or mapping is planned at the follow-up. Patients will be followed for a minimum of 7.5 months to a maximum of 2 years depending on when they are enrolled.

Inclusion criteria

• Structural heart disease: ischemic or non-ischemic cardiomyopathy diagnosed with cardiac imaging demonstrating either segmental myocardial dysfunction, or presence of scar, AND
• One of the following monomorphic VT events despite prior attempted catheter ablation (or contraindication for ablation), AND despite treatment with a class III antiarrhythmic drug (contraindicated, ineffective or not tolerated): A: Documented sustained monomorphic VT terminated by pharmacologic means, DC cardioversion or manual ICD Therapy. B: ≥3 episodes of monomorphic VT treated with antitachycardia pacing (ATP), at least one of which was symptomatic C: ≥ 5 episodes of monomorphic VT treated with antitachycardia pacing (ATP) regardless of symptoms D: ≥1 appropriate ICD shocks, E: ≥3 monomorphic VT episodes within 24 hours ** VT events must be confirmed by ECG/monitor or ICD download.

Exclusion criteria

• Unable or unwilling to provide informed consent
• Have received prior radiotherapy to the likely treatment field
• Inotrope-dependent heart failure or an anticipated life-expectancy of < 1 year in the absence of VT
• Presenting arrhythmia: polymorphic VT or ventricular fibrillation (VF)
• Pregnancy
• Active ischemia (acute thrombus diagnosed by coronary angiography, or dynamic ST segment changes demonstrated on ECG) or another reversible cause of VT (e.g. drug-induced arrhythmia), had recent acute coronary syndrome within 30 days thought to be due to acute coronary arterial thrombosis, or have CCS functional class IV angina. Note that biomarker level elevation alone after ventricular arrhythmias does not denote acute coronary syndrome or active ischemia.