Crossed Wires: Ischemia Testing and Monomorphic VT Storm
Patients with a severe form of ventricular arrhythmia who may be referred for catheter ablation are often first tested for coronary artery disease (CAD) or ischemia. But such testing seldom makes a difference to downstream management or outcomes, researchers conclude, based on registry data.
The findings, they say, question such routine CAD/ischemia testing in patients like those studied, who had episodes of monomorphic ventricular tachycardia (VT) storm but not an acute coronary syndrome (ACS) and ultimately went to ablation.
Of 97 such patients, about 44% underwent CAD/ischemia testing by invasive angiography, myocardial functional imaging, or both. But the tests didn’t predict important ablation outcomes, including pre- or postablation VT inducibility. Nor did they significantly affect the likelihood or outcomes of preablation revascularization or 2-year survival.
The findings “argue against performing routine evaluations to rule out coronary [disease] or myocardial ischemia as culprits in monomorphic VT storm” in patients without evidence of ACS, write Feras Alkhalaileh, MD, Heart and Vascular Institute, Cleveland Clinic, Ohio, and colleagues in their report published August 2 in JACC: Clinical Electrophysiology.
They suggest it’s “reasonable” not to perform tests for CAD or ischemia in such patients, senior author Ayman A. Hussein, MD, from the same center, told theheart.org | Medscape Cardiology. Although such tests may be considered “case by case,” performed routinely they “aren’t going to add much to patient care, and as a matter of fact, may delay proper care and expose them to risks,” Hussein said.
It’s “reasonable” to test for CAD or ischemia in patients with polymorphic VT storm, which is likely ischemia-driven, he observed. In contrast, monomorphic VT storm is likely caused by myocardial scar, which revascularization cannot treat. “Because there’s scar substrate, we find that ischemic evaluations are technically without much yield.”
These issues are “not very controversial” among cardiac electrophysiologists, Hussein said, but it remains “common practice” for other specialists to order angiography or ischemia testing for patients with monomorphic VT storm, typically in the cardiac care unit (CCU), before considering ablation.
“Sometimes, as electrophysiologists, we don’t get to see them before an ischemic evaluation has already been done,” he added.
It’s “very hard to convince interventional cardiologists, CCU intensivists, or general cardiologists” that a VT may not be caused by ischemia, said electrophysiologist Roderick Tung, MD, University of Arizona College of Medicine, Phoenix, who was not involved in the current study.
In patients with monomorphic VT storm, “By the time we’re consulted, they’ve already had a cath. And it’s probably just not necessary,” Tung said. “That’s why this is such a great paper, because it has an immediate message” for nonelectrophysiologist clinicians and “the potential to change clinical practice.”
The study included 97 patients with monomorphic VT storm from a prospective VT-ablation registry covering about 7 years at a major referral center. Their mean age was 64 years and 88% were men. Two-thirds were known to have ischemic cardiomyopathy and were in NYHA functional class II.
As reported, 10% of the cohort underwent coronary angiography after presentation with monomorphic VT storm, 26% had CT or PET myocardial functional imaging, and 9% had both tests.
Only four patients ultimately underwent coronary revascularization; no acute coronary occlusions were involved. Monomorphic VT recurred in all four cases, the report notes.
The 43 and 54 patients who did or did not get the CAD/ischemia tests, respectively, showed no significant procedural differences in extent of scar modification, prevalence of clinical or hemodynamically stable VT, or use of mechanical circulatory support; or in postablation, VT inducibility or overall mortality during follow-up averaging 24.3 months.
To address possible concerns about selection bias in the main cohort, all of whom underwent ablation, a secondary analysis was conducted with 91 patients with known asymptomatic coronary disease and monomorphic VT storm who were selected from the registry without regard to whether they underwent catheter ablation.
Of that cohort, 21 went to invasive angiography and 25 underwent stress testing; six of the latter went on to coronary angiography, the report states. Monomorphic VT later recurred in four of the five patients, who then underwent coronary revascularization.
Such patients with known coronary disease, Hussein said, are those “possibly more likely to get an ischemic evaluation.” And yet, “regardless of whether they had ablation, the yield of ischemic evaluations in these patients was low.”
By far most of the CAD/ischemia tests in the study’s primary cohort were performed using noninvasive imaging, notes an editorial accompanying the new report. “This raises the possibility of false negatives with very proximal and multivessel CAD, and with balanced ischemia,” write Saurabh Kumar, BSc (Med)/MBBS, PhD, and Ashwin Bhaskaran, MBBS, MSc, University of Sydney, New South Wales, Australia.
Ideally, the issues addressed by the study should be tested in large randomized, controlled trials, they state. “Achieving sufficient recruitment to address this clinical question may be difficult, leaving clinicians with the challenge of applying observational data to their patients.”
J Am Coll Cardiol EP. Published online August 2, 2023. Full Text, Editorial
Alkhalaileh, Hussein, and their coauthors report no relevant financial relationships. Tung has previously disclosed receiving speaking fees from and serving on advisory boards for Abbott, Biotronik, Boston Scientific, and Medtronic, and receiving research grants from Abbott. Kumar has received research grants from Abbott Medical and Biotronik; and honoraria from Biosense Webster, Abbott Medical, Biotronik, and Sanofi. Bhaskaran declared no relevant financial disclosures.
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