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For patients with large, anterior ST-segment elevation MIs (STEMIs), successful reperfusion following primary percutaneous coronary intervention (PCI) is associated with smaller infarcts and better clinical outcomes at 30 days, researchers found.
In the INFUSE-AMI trial, the median infarct size was 16.7% of the left ventricular mass in patients with a myocardial blush grade of 2 or 3 after angioplasty and 19.5% in those with a grade of 0 or 1 (P=0.002), according to Sorin Brener, MD, of New York Methodist Hospital in Brooklyn, and colleagues.
Action Points
- Note that this secondary analysis of a randomized, controlled trial demonstrated that successful PCI, as defined by myocardial reperfusion on cardiac MRI, was a strong predictor of survival.
- Be aware that the relationship was evaluated only in patients with a left anterior descending artery infarct.
The smaller infarct size in those with successful reperfusion translated into a significantly lower mortality rate (1.7% versus 8.3%, P=0.0008), although other clinical outcomes occurred at similar rates in the two groups, the investigators reported in the July issue of JACC: Cardiovascular Interventions.
"These observations point to the critical importance of achieving effective myocardial reperfusion in STEMI," they wrote. "These data also may provide the mechanistic link between the previously reported independent association between myocardial blush grade and mortality."
"Thus," they concluded, "physicians should be adequately trained to assess myocardial blush grade and evaluate this measure at the end of PCI for prognostic purposes."
To explore the relationship between myocardial reperfusion, infarct size, and mortality, Brener and colleagues examined data from the INFUSE-AMI trial, which randomized 452 patients with large, anterior STEMIs who were undergoing primary PCI with bivalirudin (Angiomax) anticoagulation to an intracoronary bolus of abciximab (ReoPro) delivered to the infarct lesion versus no abciximab and to manual thrombus aspiration versus no aspiration.
The main results, reported last year, showed that intracoronary abciximab significantly reduced median infarct size measured by cardiac magnetic resonance at 30 days (15.1% versus 17.9%, P=0.03), although the relative reduction of 13% fell short of the 25% threshold for clinical relevance.
Following PCI, most of the patients (81.4%) had successful reperfusion, indicated by a myocardial blush grade of 2 or 3.
That rate did not differ based on the use of abciximab, and because of that "we can conclude that abciximab does not enhance myocardial perfusion per se, but rather it contributes to infarct size reduction by favorably affecting microthrombi present in the capillaries (and possibly by reducing associated inflammation)," according to the authors.
Similar to the finding of a smaller infarct size at 30 days among patients with successful reperfusion, infarct size was about 30% smaller at 5 days among patients who underwent cardiac imaging at that time point as part of a substudy and had a myocardial blush grade of 2 or 3 (P=0.002). Successful reperfusion at that point was also associated with about a 90% reduction in microvascular obstruction (P=0.003).
At 30 days, those with a myocardial blush grade of 2 or 3 also had a higher left ventricular ejection fraction (median 50.3% versus 46.9%, P=0.004).
All of those benefits added up to a lower 30-day death rate, a finding that was not affected by use or non-use of abciximab. There was also a significantly lower rate of major bleeding among those with successful reperfusion (0.8% versus 3.7%, P=0.04).
Rates of reinfarction, stent thrombosis, heart failure, and target vessel revascularization did not differ based on myocardial blush grade.
The authors acknowledged that the analysis was limited in that it was powered for infarct size and not myocardial blush grade, more than 20% of enrolled patients (including all of those who died within 30 days) did not undergo cardiac imaging, and the results apply only to patients with left anterior descending artery infarcts.
Also, there was no association between ST-segment resolution and myocardial blush grade, a finding that "requires additional exploration, as the electrocardiographic parameters have been validated in numerous datasets as powerful predictors of myocardial salvage and of clinical outcome, and our myocardial blush grade 0/1 was recorded in only a small proportion of our patients," according to Brener and colleagues.
From the American Heart Association:
Disclosures
INFUSE-AMI was sponsored and funded by Atrium Medical. Atrium supplied the local drug delivery catheter. Aspiration catheters were provided at a discount by Medtronic. Bivalirudin was provided at no charge by The Medicines Company. All other study devices and drugs were commercially purchased.
Brener reported that he had no conflicts of interest. His co-authors reported relationshiops with Boston Scientific, Cardiva, Cordis, The Medicines Company, Regado Biosciences, Bristol-Myers Squibb, sanofi- aventis, Atrium, Abbott Vascular, Medtronic, Merck, Janssen, Eli Lilly, Daiichi Sankyo, AstraZeneca, Baxter Healthcare, Bayer Corporation, Cardiovascular Medical Communications, CSL Behring, Cytori Therapeutics, Exeter Group, Genentech, GlaxoSmithKline, Johnson & Johnson Corporation, Ortho McNeil, St. Jude Medical, Ischemix, Portola Pharmaceuticals, Angel Medical Corporation, Ikaria, Lantheus Medical Imaging, Roche Diagnostics, Stealth Peptides, Volcano, and Walk Vascular.
Primary Source
JACC: Cardiovascular Interventions
Source Reference: Brener S, et al "Relationship between myocardial reperfusion, infarct size, and mortality: the INFUSE-AMI (Intracoronary Abciximab and Aspiration Thrmobectomy in Patients with Large Anterior Myocardial Infarction) trial" JACC Cardiovasc Interv 2013; 6: 718-724.