There is no magical amount of viable ventricular myocardium that makes percutaneous coronary intervention (PCI) an effective addition to optimal medical therapy (OMT) in stable patients with coronary disease and poor ventricular function, suggests an analysis from a major trial.
The REVIVED-BCIS2 trial recently made waves when it showed no clinical advantage from adding PCI to OMT in stable patients with severe ischemic left ventricular (LV) dysfunction. All the patients had shown viable but dysfunctional myocardium that could potentially be revascularized.
But in a secondary analysis, extent of such hibernating heart muscle was not a good predictor of clinical outcomes, which in the trial meant death from any cause or hospitalization for heart failure (HHF).
Burden of myocardial scar tissue, however, turned out to be a potent predictor of clinical risk regardless of coronary disease severity or even LV ejection fraction (LVEF).
Because myocardial viability tracks poorly with outcomes in patients like those enrolled in the trial, as the new analysis suggests, conventional viability testing isn’t an effective guide for deciding who among them should get PCI, Divaka Perera, MD, told theheart.org | Medscape Cardiology.
Perera, of King’s College London, United Kingdom, and the trial’s principal investigator, presented the REVIVED-BCIS2 secondary results March 4 at the American College of Cardiology (ACC) Scientific Session/World Congress of Cardiology (WCC) 2023, held live and virtually from New Orleans, Louisiana.
Viability testing for ischemia, he noted, is often used in practice to aid revascularization decisions. As the extent of myocardial viability can vary, it’s been asked — ever since the trial’s primary publication — whether there could be “a sweet spot or Goldilocks zone of viability that would allow prediction of which patients will do better with PCI compared to medical therapy,” Perera said. “The trial conclusively shows that is not the case.”
That the extent of hibernating myocardium, which is viable but dysfunctional, didn’t predict clinical outcomes or LV functional recovery “is disruptive of current practice and challenges a view that’s been held for decades.”
The trial’s 700 patients receiving OMT had been randomly assigned to undergo PCI or not, 347 and 353 patients, respectively. About 12% of the total were women.
About 70% of patients underwent baseline and follow-up myocardial viability testing using cardiac magnetic resonance (CMR) imaging with late gadolinium enhancement for estimation of scar burden; the remainder underwent dobutamine-stress echocardiography. All imaging assessments were conducted at independent core laboratories, Perera reported.
Extent of myocardial viability was defined 3 ways: volume of hibernating heart muscle, total volume of viable myocardium, and scar burden — all expressed as a percentage of total LV volume.
Every 10% increment in LV volume found to be hibernating related to a hazard ratio (HR) of 0.98 (95% CI, 0.93 – 1.04; P = .56) for all-cause mortality or HHF at a median of 3.3 years. The analysis was adjusted for age, sex, diabetes, previous HHF, chronic renal failure, extent of CAD, type of viability testing, and baseline LVEF.
The adjusted HR for the same percentage increment in total viable myocardium was marginally significantly reduced at 0.93 (95% CI, 0.87 – 1.00; P = .048).
The correlation with scar burden was stronger. The adjusted composite-endpoint HR per 10% increment in scar burden was significantly increased at 1.18 (95% CI, 1.04 – 1.33; P = .009).
Extent of myocardial viability by tertiles, regardless of viability definition, did not highlight any group with a reduced risk for death or HHF, or group with better LV functional recovery, from OMT plus PCI compared with OMT alone.
The findings appear to suggest that scar burden, but not extent of viability as it’s usually measured, may effectively guide PCI decisions in such patients, Perera said.
“I would say that viability testing as we understand it now, based on the paradigm of hibernating myocardium, is very useful,” he said, “but that is not the only information we can get from a viability test.”
Scar burden can also be determined from the same tests but isn’t typically looked at. “We’re actually collecting this information but not using it,” Perera said. “When we do, it is really powerfully predictive” of both clinical outcomes and LV functional recovery. “Yet scar burden is not in any of the guidelines for stratifying risk.”
REVIVED-BCIS2 was funded by the National Institute for Health and Care Research Health Technology Assessment Program. Perera had no disclosures.
American College of Cardiology 2023 Scientific Session. Featured Clinical Research I. Presented March 4, 2023.
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