A New Noninvasive Tool for Refractory Ventricular Tachycardia?
What’s the potential clinical role of the recently reported noninvasive EP-guided cardiac radioablation therapy for ventricular tachycardia? A Cleveland Clinic expert weighs in.
Cleveland Clinic electrophysiologists are teaming up with the health system’s radioablation team to offer patients with refractory ventricular tachycardia (VT) a possible new lease on life.
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Starting this year, the groups will collaboratively lead a study and a clinical program offering noninvasive treatment with electrophysiology-guided cardiac radioablation to Cleveland Clinic patients with VT who have exhausted all other options, including antiarrhythmic medications and traditional invasive catheter ablation procedures.
“We’re very excited about this,” says Oussama Wazni, MD, Section Head of Cardiac Electrophysiology and Pacing at Cleveland Clinic. “This is a potential treatment that may help many of our patients, but we still have a lot of work to do to confirm its utility and safety.”
The treatment first involves noninvasively mapping out the VT circuit via electrocardiographic imaging during VT induced by a patient’s implanted cardioverter-defibrillator (ICD), in combination with standard anatomical cardiac imaging.
Following that, stereotactic body radiation therapy (SBRT) is delivered to the arrthythmogenic scar region while the patient is awake. The use of SBRT, which involves minimal damage to adjacent tissue, is already common in cancer treatment.
“This treatment does not involve a new device or modality,” Dr. Wazni explains. “It’s just a new application.”
Cleveland Clinic’s research protocol is being developed in collaboration with Washington University in St. Louis, which published findings from a case series of five patients in the New England Journal of Medicine in December 2017.
The five patients (aged 60 to 83 years) had experienced between five and 4,312 episodes of VT each in the three months prior to treatment (mean, 1,315). All were taking at least two antiarrhythmic drugs. Catheter ablation had failed in three patients, while two had contraindications to invasive catheter ablation.
The five patients collectively had 6,577 VT episodes in the 15 patient-months prior to treatment. That number dropped to 680 during the six weeks immediately after (the “blanking period,” when arrhythmias may arise from postablation inflammation) and then to a total of just four episodes of VT during the subsequent 46 patient-months, representing a 99.9 percent reduction from baseline.
All patients had reductions in VT. Of the four still alive at 12 months, three were able to stop antiarrhythmic medications, although one restarted amiodarone nine months later. One patient required subsequent invasive ablation because of ongoing VT, with no further episodes.
Currently, Washington University is conducting the phase 1/2 ENCORE-VT study of 20 patients, which is expected to be completed in January 2019.
Cleveland Clinic plans to participate in a larger follow-up to ENCORE-VT that’s set to begin later this year. Patients who don’t meet the study’s inclusion criteria but who have refractory VT with no other options may be offered the treatment on a compassionate-use basis, if possible. In those cases, Cleveland Clinic’s radiation oncology team may modify the radiation dose and/or treatment duration with the aim of improving efficiency.
While the current aim is to establish the noninvasive treatment as a last resort, if it works consistently with no major adverse effects it could emerge as a potential noninvasive mainstay for a wider group of patients with VT — and, beyond that, possibly for other arrhythmias.
“If we find that this is applicable to all patients with medication-refractory VT, it will be a very big deal, because we won’t need to do anything invasive,” Dr. Wazni says. “But much more study is needed before we could start to consider revisiting the traditional way of doing VT ablation.”
He cites two major concerns in particular: (1) the potential for areas adjacent to the VT scar to receive inadvertent radiation exposure and (2) the fact that radiation complications are usually highly delayed and may be unaccounted for, given the unfavorable natural history of VT storm and heart failure. “This therapy, when added to optimal medical therapy and advanced heart failure treatments, could possibly prolong life, thereby making potential detection of untoward radiation effects more likely,” he notes.
For now, he says, cardiologists can consider referring eligible patients to Cleveland Clinic, Washington University or other centers that offer the noninvasive treatment, ideally within the context of a research study. “In the meantime, stay tuned,” he adds.