Catheter ablation is known to prolong survival free of further ventricular tachycardia (VT) for patients with ischemic heart disease and VT despite antiarrhythmic drug (AAD) therapy. Now there is evidence that ablation of AAD-refractory VT in such patients with defibrillators, compared to drug-therapy escalation, can cut the prevalence of further VT and the device shocks that elicit them.
The secondary results from a previously published trial strengthen support for catheter ablation in such patients with implantable cardioverter defibrillators (ICDs) and drug-refractory VT after a myocardial infarction (MI). Not only did ablation cut their risk of a first VT event, “it also reduced the amount and burden of VT and shocks,” John L. Sapp, MD, told theheart.org | Medscape Cardiology. “It worked better than pumping up their amiodarone to a higher dose.”
Sapp, of QEII Health Sciences Centre and Halifax Infirmary, Nova Scotia, Canada, is senior author on the VANISH trial secondary analysis, published March 22 in JACC: Clinical Electrophysiology.
In the trial’s primary outcome, catheter ablation emerged superior to AAD escalation for prolonging VT-free survival among post-MI patients with ICDs and VT despite antiarrhythmics. The current VANISH analysis shows that the ablation advantage also applied to the frequency of shock-treated VT events and of appropriate shocks throughout the median follow-up of about 2 years.
Not a Subtle Relationship
That further advantage could benefit patients clinically and functionally. Greater burdens of VT and device shocks tend to track with poorer outcomes, although whether as a cause or simply by association isn’t known.
“High burden of VT, VT storm, and shocks have all been associated with a higher mortality risk,” Sapp observed. “And it’s not a subtle relationship. As VT clusters and you get more than a couple shocks in a few months, the mortality risk just goes up and up.”
But it remains unclear whether that risk climbs because sicker hearts tend to develop VT that elicits shocks “or whether it’s the shocks themselves, even though they’re saving the patient’s life, that cause some further cardiac injury or side effects.”
Many in the field suspect the latter. It’s going “beyond the evidence” to say so, Sapp said, but lessening overall VT burden and ICD shock burden is “probably better for quality of life and probably better for cardiac function and for hard outcomes.”
There’s probably some degree of reduced VT burden “that actually may translate to less hospitalizations or decreasing mortality,” agreed Roderick Tung, MD, University of Arizona College of Medicine, Phoenix.
That threshold isn’t known, but VT doesn’t have to be completely suppressed “to drastically improve someone’s risk for hospitalization, death, and quality of life,” Tung, not associated with VANISH, told theheart.org | Medscape Cardiology. If a patient receives 20 shocks in the year before ablation but one the year after, “the patient knows that’s actually a success.”
In a way, “this is kind of an extended quality-of-life analysis,” Tung said of the new VANISH report, “because it’s assumed, and it’s clear from a patient perspective, that less shocks improves quality of life.”
Effect of AAD Choice
The VANISH secondary analysis also suggests that patients whose VT had been refractory to amiodarone, rather than sotalol, gained special benefit from catheter ablation compared to escalated AADs.
They showed significant declines in overall VT burden, burden of VT treated by antitachycardia pacing (ATP), and burden of appropriate ATP after catheter ablation, all compared to AAD escalation, the report states. Those whose VT had been refractory mainly to sotalol showed no such benefits from ablation.
That may mean the ablation benefits for burden of therapies from ICDs were more pronounced among patients who were likely the sickest, whose VT had been refractory to the more powerful of the two antiarrhythmics, Sapp proposed.
It makes sense that patients whose VT failed to respond to the more effective AAD were likelier to benefit from “the next phase of treatment,” Tung agreed. And failure with a drug that’s “intermediately effective,” such as sotalol, means there’s still another level of AAD therapy available “before you get to ablation.”
But VT Burden Unaffected Overall
VANISH had entered 259 mostly male post-MI patients with similarly programmed ICDs who experienced recent monomorphic VT while on class I or class III antiarrhythmics. Almost two thirds had been taking amiodarone, and about one third had been taking sotalol.
They were randomly assigned to undergo either VT catheter ablation or escalated AAD (intensified amiodarone or amiodarone plus mexiletine); the groups comprised 132 and 127 patients, respectively.
The two groups fared similarly during follow-up for the endpoint of VT burden, defined as the total number of VT events treated with at least one appropriate ICD therapy, that is, shocks or ATP.
But patients who underwent ablation, compared to the escalated-AAD group, showed significant reductions in the hazard ratio (HR) for the following:
Burden of shock-treated VT events, HR 0.60 (95% CI, 0.38 – 0.95)
Burden of appropriate shocks, HR 0.61 (95% CI, 0.37 – 0.96)
Among patients who entered the study with amiodarone-refractory VT, those assigned to catheter ablation vs escalated AAD showed significant reductions in burden of the following:
Overall VT, 0.54 (95% CI, 0.29 – 0.97)
ATP-treated VT events, 0.64 (95% CI, 0.29 – 0.99)
Burden of ATP, 0.52 (95% CI, 0.30 – 0.90)
The new VANISH findings should encourage more use of ablation over escalated AAD in such patients, Tung said. “That should have happened already, but it hasn’t.” Although the primary VANISH results from 2016 were already positive, “You still see in real-world practice that they just get more amiodarone.”
VANISH was funded by the Canadian Institutes of Health Research, St. Jude Medical, and Biosense Webster. Sapp has received research funding from Biosense Webster and Abbott and speaker fees or consulting honoraria from Medtronic, Abbott, Varian, and Biosense Webster. Disclosures for the other authors are in the original article. Tung has received speaking fees from and has served on advisory boards for Abbott, Biotronik, Boston Scientific, and Medtronic and has received research grant support from Abbott.
JACC Clin Electrophysiol. Published online March 22. Full text
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