Cohort Study - SBRT for VT Radioablation
Cohort Study - SBRT for VT Radioablation
Ventricular tachycardia (VT) contributes to over 350,000 sudden deaths each year in the US.
 Malignant VTs involve an electrical "short circuit" in the heart, formed by narrow channels
 of surviving tissue inside myocardial scar. Current treatment for VT consists of either
 implantable defibrillators (ICDs), suppressive drug therapy, catheter ablation or a
 combination of all 3.

 Implantable Defibrillators (ICDs) reduce sudden death and can terminate some ventricular
 tachycardia (VT) without shocks, but they don't prevent VT. The occurrence of ≥1 ICD shock is
 associated with reductions in mental well-being and physical functioning, and increases in
 anxiety and sometimes depression. Further, ICD shocks have been consistently associated with
 adverse outcomes, including heart failure and death. Furthermore, the most important
 predictor of ICD shocks is a history of prior ICD shocks.

 Therapies to suppress VT include antiarrhythmic drug therapy and catheter ablation, neither
 however is universally effective. When VT recurs despite antiarrhythmic drug therapy and
 catheter ablation, novel yet invasive, approaches may be required. Such invasive procedures
 carry consequent risks of cardiac and extra-cardiac injury.

 Stereotactic body radiotherapy (SBRT) is a non-invasive technique that delivers high doses of
 radiation precisely to specified regions in the body, while minimizing exposure to adjacent
 tissue. This technique is currently, and commonly used in the treatment of cancer.
 Conventional application of SBRT has made use of its ability to spare non-target tissue,
 including for treatment of tumors near the heart. More recently, clinicians have changed the
 paradigm, by focusing radioablative energy on ventricular scar responsible for ventricular
 tachycardia. Pre-clinical studies have supported the concept and were followed by
 first-in-human VT therapeutic experience in 2017. Subsequent studies have had encouraging
 results for patients who failed or were unable to tolerate conventional treatment.
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.