Heated saline needle ablation safe, effective for refractory ventricular tachycardia
Intramural needle ablation using in-catheter, heated saline-enhanced radiofrequency was effective in reducing ventricular tachycardia burden for high-risk patients failing one to five prior ablations and drug therapy, researchers reported.
In a first-in-human study, researchers found that risk for perforation of the myocardium with the novel treatment was rare, and adverse events decreased with experience. The findings suggest heated saline ablation could become a viable option for patients with refractory ventricular tachycardia (VT) not controlled by prior antiarrhythmic drugs, implantable cardioverter defibrillator therapy and conventional catheter ablation.
“Due to the differences in the location of the VT, one frequently cannot get to it with a standard radiofrequency ablation catheter,” Douglas L. Packer, MD, a clinical cardiac electrophysiologist, professor of medicine and consultant in the division of heart rhythm services, department of cardiovascular medicine at Mayo Clinic in Rochester, Minnesota, told Healio. “The concept of a needle-based catheter is you can work from the inside; you do not have to go through the pericardial space from the outside. You identify the apparent location. You make good contact with the tip of the epicardial tissue and insert the needle some place between 4 mm and 8 mm. There are some biophysics of this that are quite different and quite striking. We injected saline through the needle that was heated, using convective heating. You can reach places that you otherwise would not.”
Recurrent, treatment-resistant VT
Packer and colleagues analyzed data from 32 adults from six centers who underwent needle electrode ablation (91% men). The mean age of participants was 66 years; mean ejection fraction was 35%; and 56% of VTs were ischemic. All participants had recurrent drug-refractory monomorphic VT after ICD implantation and underwent prior standard ablation.
During the heated saline procedure, researchers induced and mapped one or more VTs. The needle catheter was used to create intramural lesions at targeted VT sites. Researchers defined acute procedural success as noninducibility of the clinical VT after the procedure.
Participants were followed at 30 days, 3 and 6 months, with ICD interrogation at follow-up to determine VT recurrence.
The findings were published in Circulation: Arrhythmia and Electrophysiology.
In the 3 to 6 months before needle ablation, participants experienced a median of 45 device therapies (shock/antitachycardia pacing) for VT.
The study catheter was used to deliver an average of 10 lesions per case, with an average of 430 seconds of radiofrequency time, 122 minutes of catheter use time and a procedural duration of 4.3 hours.
Acute procedural success was 97% for eliminating the clinical VT. At mean follow-up of 5 months (n = 32), device therapies were reduced by 89%. There was a significant difference in antitachycardia pacings before vs. after ablation (mean, 31.5 vs. 17.1; P < .026).
“At the end of the ablation, clinical VTs were suppressed or gone, though some did return over time,” Packer said in an interview. “The efficacy findings were informative and encouraging. These are patients that had been through a variety of different traditional approaches, so when we used the needle, it was a nontraditional approach.”
‘There is a learning curve’
Complications included two periprocedural deaths — an embolic mesenteric infarct and cardiogenic shock, as well as two mild strokes and one pericardial effusion treated with pericardiocentesis.
“There were complications with the first 10 to 15 procedures, but the complication rate was substantially lower with the last 18 procedures,” Packer told Healio. “The question we had was, is this going to be acceptably safe when you are inserting something into the myocardium that could go close to the outside? There is a learning curve here, and you want to take that to heart as you are inserting the needle, so you are, first and foremost, safe.”
The researchers noted that the initial efficacy data are “beyond that anticipated from a further standard radiofrequency ablation,” adding that the novel method may obviate the need for epicardial ablation and accompanying risk.
“Intramural heated saline needle ablation showed complete, acute and satisfactory midterm control of difficult VTs,” Packer told Healio. “However, further study is warranted to define safety and longer-term efficacy. This was only 5 to 6 months of follow-up. The next step must be following these patients for 1 to 2 years. Are we going to find that efficacy prevails and is maintained over time? Perhaps more important, are there any late complications? We do not anticipate any; however, the world needs to know the good and bad of any trial.”
For more information:
Douglas L. Packer, MD, can be reached at packer@mayo.edu.
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