Why is this study important?
- Primary results of this RCT, released last summer, showed that revascularization with PCI + OMT did not reduce rates of death or hospitalization for heart failure, or improve LV function after 6 months, compared with OMT alone among patients with CAD and LVEF ≤35%.
- This follow-up sub-study found that the extent of underlying myocardial viability didn’t matter: even those with extensive myocardial dysfunctional and viability did not have better outcomes with PCI + OMT compared with OMT alone. Extent of myocardial scar (as % of LV) correlated with reduced likelihood of ventricular recovery in both treatment groups, and improved LV recovery was linked to better outcomes.
What question was this study supposed to answer?
Other studies (notably the STICH RCT) found that revascularization with CABG + OMT reduced adverse event rates compared with OMT alone in low-LVEF patients when significant myocardial viability was present. REVIVED-BCIS2 tested whether revascularization with PCI could achieve similar benefits.
What did the study show?
700 patients with ischemic systolic dysfunction (LVEF ≤35%) were randomly assigned to PCI + OMT (n=347) or OMT alone (n=353). Primary outcome was all-cause death or hospitalization for heart failure. At a median follow-up of 41 months, no difference in the primary outcome was observed (37.2% vs 38%, HR = 0.99, p=0.96). For this sub-study, patients were stratified by the extent of myocardial viability and by extent of scar. Analyses evaluated “All Viable Myocardium” patients which included patients with normal or abnormal wall motion plus viable myocardium, and “Dysfunctional-Viable Myocardium” patients which assessed just those with abnormal resting wall motion and underlying viability by cardiac MR (about 70% patients) or dobutamine stress echo. A marginal association between extent of viability and the primary outcome was found for the “All Viable” sub-group but not for the “Dysfunctional-Viable” sub-group. Scar burden inversely correlated with the primary outcome. The primary outcome was not impacted by treatment assignment when assess by tertile of viability or scar burden. Left ventricular recovery at 6 months was significantly better for patients in the “All Viable” subgroup and significantly worse for those with large scar burden, regardless of treatment. Better LV recovery was associated with significantly lower rates of the primary outcome.
This sub-study of the REVIVED-BCIS2 RCT is the largest yet to assess the impact of revascularization using PCI among patients with severe ischemic systolic dysfunction. Unlike STICH, which found benefit with surgical revascularization when underlying myocardium was viable, results of REVIVED-BCIS2 found that revascularization using PCI did not improve outcomes in this population. The study was designed to find a 30% relative reduction in the primary outcome at p=0.05 significance and 85% power, there were no limiting recruitment issues, and blinded core labs were used for the MR and echo work, so the main study was well-designed and executed. Power estimates were not shown for this sub-study, but certainly the power of observations for any sub-group is less than for the entire study population. Unfortunately, this sub-study did not integrate ischemia data: while viability is necessary if PCI is to help, dysfunctional but viable myocardium with adequate flow is still unlikely to benefit from PCI. Other factors that may have influenced the findings include the possibility of patient selection bias (e.g., patients with more severe disease, and therefore greatest potential for benefit with revascularization, may have been directed away from the trial and toward CABG), loss of 50 patients due to unacceptable viability study quality or patient drop out with somewhat more dropping out of the PCI + OMT treatment group (7% vs 4.5%), and the relatively small study size (roughly half the number of patients as in STICH). Still, in current state, this study indicates that PCI should not be offered routinely to patients with stable ischemic cardiomyopathy with the intent to improve LV function, reduce risk of death or avoid hospitalization for heart failure.
All editors: Kirk N. Garratt, MD, MSc, MSCAI
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