Single radiation treatment may reduce ventricular tachycardia burden
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A single noninvasive radiation therapy treatment safely reduced the burden of ventricular tachycardia, with effects persisting for 2 years in most patients, according to data from the ENCORE-VT trial presented at the virtual Heart Rhythm Society Annual Scientific Sessions.
“Right now, based on these results presented here at HRS 2020, we believe that cardiac radioablation is best suited for high-risk patients who have failed conventional ventricular tachycardia treatments,” Phillip S. Cuculich, MD, associate professor of medicine in the division of cardiology at Washington University School of Medicine in St. Louis, said during a press conference.
Patients with ventricular tachycardia
Researchers analyzed data from 19 patients (median age, 66 years; 90% men) with monomorphic ventricular tachycardia or premature ventricular contraction-induced cardiomyopathy who failed with at least one antiarrhythmic drug and at least one catheter ablation. Patients also had three or more ventricular tachycardia episodes over 6 months or at least 20% premature ventricular contraction burden.
“The 19 patients in this trial had weak hearts and advanced heart failure,” Cuculich said during the press conference. “Overall, compared to other catheter ablation trials, this was a very sick group.”
All patients underwent treatment with a single noninvasive radiation therapy.
“The heat from the tip of the catheter is limited, and often we can’t reach the deeper circuits within the heart muscle, so our procedures fail,” Cuculich said during the press conference. “To deliver a full thickness, gap-free ablation, we can look to our radiation oncology partners, the cancer doctors, who have the exact same goals when they’re treating tumors.”
Cuculich compared this treatment approach to cancer treatment. He said, “In the basement of most hospitals, you’ll find cancers being treated with stereotactic body radio therapy, called SBRT. In this concept, X-rays or photons are delivered by a robotic arm in sweeping arcs around the patient, delivering high doses of ablative energy to a tumor with minimal exposure to the surrounding tissue. In short, with cardiac radioablation, we simply treat an arrhythmia circuit like a tumor.”
The safety endpoint included serious adverse events up to 90 days. The efficacy endpoint was the reduction in ventricular tachycardia/premature ventricular contractions comparing 6 months before the treatment with 6 months after the treatment.
The median beam-on time for these patients was 15.3 minutes.
“Acutely, the treatment itself is short and it’s entirely noninvasive,” Cuculich said during the press conference. “There are no problems with the cardiac devices during or after treatment, and patients are treated as outpatients. They literally get up, walk out and go home after therapy.”
During the first 90 days after treatment, one patient (5%) developed grade 3 pericarditis, which was resolved with prednisone. Beyond 90 days, two patients developed pericardial effusion, which was treated with colchicine. In addition, one patient developed a gastropericardial fistula.
“To date, no patients have developed heart block, coronary artery injury or any perforation or injury to the heart,” Cuculich said during the press conference. “In general, this appears to be a very gentle ablation experience for patients.”
Overall survival was 89% at 6 months, 74% at 1 year and 52% at 2 years. The cause of death was most commonly attributed to HF and ventricular tachycardia recurrence, and there were three noncardiac deaths. No deaths were related to the treatment, according to the presentation.
Efficacy endpoint
Six months after the procedure, 94% of patients met the primary efficacy endpoint. There were 78% of patients who continued to meet the primary efficacy endpoint at 24 months.
“Importantly, very few patients were actually cured of their ventricular tachycardia,” Cuculich said during the press conference. “Most people still had small amounts of ventricular tachycardia, but cure was not the intent of this study, given the advanced illness in this patient group.” – by Darlene Dobkowski
Reference:
Cuculich PS, et al. LBCT02-02. Presented at: Heart Rhythm Society Annual Scientific Sessions; May 6-9, 2020 (virtual meeting).
Disclosure: Cuculich reports he consults for Medtronic and Varian Medical Systems, has intellectual property with Washington University and received research grants from Barnes-Jewish Hospital Foundation.
Perspective
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Peter Weiss, MD
This is longer-term follow-up for cardiac radioablation for ventricular tachycardia. Longer follow-up on prior work on patients with frequent ventricular tachycardia was often refractory to medical or catheter ablation.
This was a small patient group with 19 patients, but this was good follow-up of all patients. Ventricular tachycardia burden was significantly reduced out to 2 years. Toxicity was present in 16% including out to 2 years (often pericardial related). This was a very sick patient population often with limited recourse.
Limitations are that this was a small study with no comparison group. We still lack the understanding of basic physiology (ie, why was there an immediate effect when it can take weeks to months to get cell death from radiation therapy).
Nevertheless, this continues to move forward as an alternative treatment for some of the sickest, most difficult to care for patients who have little in the way of other options. We will need continued work on dosing and generalizability for more broad use. I’d also like to see this compared with sympathetic denervation in a comparison study.
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Cuculich PS, et al. LBCT02-02. Presented at: Heart Rhythm Society Annual Scientific Sessions; May 6-9, 2020 (virtual meeting).
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