INFUSE-AMI Substudy: Blush Grade Key to Better Outcomes in STEMI Patients

Download this article's Factoid (PDF & PPT for Gold Subscribers)


Better myocardial reperfusion after primary percutaneous coronary intervention (PCI), as assessed by myocardial blush grade, is essential in reducing infarct size and 30-day mortality in patients with large anterior ST-segment elevation myocardial infarction (STEMI). A substudy of the INFUSE-AMI trial was published online July 15, 2013, ahead of print in JACC: Cardiovascular Interventions.

For the INFUSE-AMI (Intracoronary Abciximab and Aspiration Thrombectomy in Patients With Large Anterior Myocardial Infarction) trial, researchers randomized 452 STEMI patients with large, anterior infarcts to primary PCI plus bivalirudin anticoagulation with or without a bolus (0.25 mg/kg) of intracoronary abciximab. Patients were also randomized to treatment with or without manual aspiration thrombectomy. Neither abciximab nor thrombus aspiration made a difference in markers of reperfusion post PCI, such as corrected TIMI frame counts, myocardial blush grade, or ST-segment resolution at 60 minutes.

For the substudy, researchers led by Sorin J. Brener, MD, of New York Methodist Hospital (New York, NY), looked at results from INFUSE-AMI according to blush grade status as assessed by cardiac MRI.

Abciximab Plus Blush Grade 2/3 Improves Outcomes

Successful reperfusion (myocardial blush grade 2/3) was achieved in the majority (81.4%) of patients. Blush grade 2/3 was achieved at the same level whether or not abciximab was given (80.7% vs. 82.1%; P = 0.71). The same was true with or without thrombus aspiration (83.4% vs. 79.3%; P = 0.26). However, in patients who did achieve blush grade 2/3, the addition of abciximab improved infarct size (14.4% vs. 17.4%; P = 0.01), infarct mass (17.6 g vs. 22.8 g; P = 0.009), and total abnormal wall motion score (5.0 vs. 8.0; P = 0.04).

No such improvements were noted in patients with blush grade 0/1 given abciximab.

Final blush grade 2/3 translated to improved final TIMI flow grade 3 (95.1% vs. 75.0% in patients with blush grade 0/1; P < 0.0001) but not improved ST-segment resolution. On cardiac MRI at 5 days post PCI, patients with blush grade 2/3 had lower total microvascular obstruction than those with grade 0/1 (0.2 g vs. 2.6 g; P = 0.02) as well as lower total abnormal wall motion scores (8.0 vs. 10.0; P = 0.005).

At 30 days, markers of reperfusion and infarct size (the primary endpoint) as well as clinical outcomes were improved in patients who achieved blush grade 2/3 (table 1).

Table 1. Thirty-day Outcomes

 

Final Blush 2/3
(n = 367)

Final Blush 0/1
(n = 84)

P Value

Infarct Size

16.7%

19.5%

0.002

LVEF

50.3%

46.9%

0.004

Mortality

1.7%

8.3%

0.0008

Mortality or Reinfarction

2.0%

9.5%

0.0004

TIMI Major Bleeding

0.8%

3.7%

0.04

TIA

0

1.3%

0.03


Stroke, TVR, any revascularization, and definite/probable stent thrombosis rates were similar between groups.

The key aspects of the study, the authors note, were that successful myocardial reperfusion (blush grade 2/3) lowered infarct size, that angiographically successful reperfusion was associated with a 30% lower rate of microvascular obstruction, and that reduced infarct size was linked with lower 30-day mortality.

“These observations point to the critical importance of achieving effective myocardial reperfusion in STEMI,” they observe. “These data also may provide the mechanistic link between the previously reported independent association between [myocardial blush grade] and mortality.”

“We have a lot of data about the relationship between blush and outcome, but we never quite could demonstrate how is that happening?” Dr. Brener told TCTMD in a telephone interview. “What’s the link between the 2? We know poor myocardial reperfusion is associated with higher mortality, and here we have the opportunity to connect that to the blush, and to infarct size, so I think that’s the unique part.”

Abciximab Usefulness Debated

In terms of the contribution of abciximab, “we can conclude that [the GP IIb/IIIa inhibitor] 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),” Dr. Brener and colleagues note.

The current study “shows that infarct size is reduced by abciximab in patients with good blush scores,” commented Stephen G. Ellis, MD, of the Cleveland Clinic (Cleveland, OH) in an e-mail communication with TCTMD. “Mortality in patients with good blush scores was so good, however, that the researchers were unable to demonstrate a difference in clinical outcomes for patients who received abciximab. Given that the decision to use abciximab has to be made before finding final myocardial blush score, there seems to be little compelling evidence to use abciximab, particularly since it's associated with increased bleeding risk.”

Dr. Brener noted that while the success of reperfusion may be independent of abciximab, the link between reperfusion and mortality, meaning infarct size, is greatly affected by the GP IIb/IIIa inhibitor. “In patients who had good blush, abciximab substantially reduced infarct size, which means if we open the microcirculation and allow the drug to reach its target, then it actually works,” Dr. Brener said. “If you look at the entire study and the effect is minimal, you can argue that the reason for that is because 20% of the patients did not have an open microcirculation to allow the drug to work its magic so to speak.”

Blush Score Not Routinely Assessed

Dr. Ellis noted that blush score is routinely ascertained at some academic institutions, “but certainly . . . not evaluated in most labs. One problem with blush score is it is very difficult to modify even once you have decided it's not good enough.”

“You could make the case that if people paid attention and found that there wasn’t optimal blush—and let’s assume they could do something to optimize it—then potentially you could reduce infarct size,” Dr. Brener said. However, he agreed with Dr. Ellis that “most physicians don’t know what [blush score] is or how to assess it. It’s just training your eye to identify how the flow fills the myocardium at the end of the procedure. It’s not difficult, but it is not done.”

Note: Dr. Brener and several coauthors are faculty members of the Cardiovascular Research Foundation, which owns and operates TCTMD.

 


Source:
Brener SJ, Maehara A, Dizon JM, et al. Relationship between myocardial reperfusion, infarct size, and mortality. The INFUSE-AMI (Intracoronary Abciximab and Aspirations Thrombectomy in Patients with Large Anterior Myocardial Infarction) Trial. J Am Coll Cardiol Intv. 2013;Epub ahead of print.

 

Disclosures:

  • Drs. Brener and Ellis report no relevant conflicts of interest.

 

Related Stories:

Jason R. Kahn, the former News Editor of TCTMD, worked at CRF for 11 years until his death in 2014…

Read Full Bio

Comments