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In patients with ST-segment elevation myocardial infarction (STEMI), early treatment with a pharmacoinvasive strategy is more often associated with aborted infarction than is primary percutaneous coronary intervention (PCI), according to a substudy of the STREAM trial published online June 10, 2014, ahead of print in Heart.

Aborted MI, which has an identifiable clinical signature, carries a better short-term prognosis and may be a useful endpoint in STEMI studies, researchers say.

 
Predictors of Aborted MI

In a multivariable model, 3 factors were associated with the likelihood of experiencing an aborted MI:

• Lesser frequency of Q-wave at baseline in the infarct territory: OR 0.44 (95% CI 0.28-0.69)
• Less summed ST deviation at baseline, per mm: OR 0.96 (95% CI 0.94-0.98)
• Shorter time from symptom onset to first medical contact, per hour: OR 0.74 (95% CI 0.57-0.96)

Moreover, the time from symptom onset to fibrinolysis in the pharmacoinvasive group was briefer than the time from symptom onset to intervention in the primary PCI group. Notably, total ischemic time for aborted MI patients receiving a pharmacoinvasive strategy was 100 minutes shorter than that for patients undergoing primary PCI. In addition, aborted MI patients in both treatment groups more frequently had TIMI 3 flow before and after intervention; not surprisingly, they were also less likely to receive PCI (P = .060 for the pharmacoinvasive group and P  = .004 for the primary PCI group).

In the pharmacoinvasive group, the incidence of the primary composite endpoint (all-cause death, shock, CHF, or reinfarction) at 30 days was lower in patients with rather than without aborted MI, although the advantage was attenuated after adjustment. No such difference emerged in the primary PCI group. The same pattern was observed for the individual endpoints of cardiogenic shock and congestive heart failure (table 1).

Table 1. Comparison of 30-Day Outcomes by Treatment Strategy

Importantly, MI abortion occurred within 120 minutes of symptom onset in about two-thirds of those in the pharmacoinvasive arm, but only one-sixth of those in the primary PCI arm. There was no interaction between treatment group and aborted MI status for the composite endpoint (P = .292).

Within 1 year, all-cause mortality trended lower among aborted MI vs nonaborted MI patients in the pharmacoinvasive arm (3.1% vs 4.5%; log-rank P = .295) but not in the primary PCI arm (log-rank P = .818).

Overall, 30-day composite outcomes were lower for aborted MI compared with nonaborted MI patients regardless of treatment assignment (7.0% vs 12.5%; P = .042), driven by reductions in cardiogenic shock and congestive heart failure. After adjustment for baseline TIMI risk score, the relative risk among aborted MI patients was .58 (95% CI 0.32-1.06; P = .075) with no advantage in 1-year mortality. 

Taken together, the authors say, the 3 key factors identified in the multivariable analysis “provide a new coherent portrait” of patients with an aborted MI, suggesting that it may be “a useful endpoint in studies of STEMI especially after [pharmacoinvasive] reperfusion therapy.”

Timeliness Makes the Difference  

“Lytics work better when patients present early, so it makes sense that if somebody presents very early, you have a better chance to abort the MI,” Sorin J. Brener, MD, of Weill Cornell Medical College (New York, NY), told TCTMD in a telephone interview. He noted that the median time to lytic delivery in the pharmacoinvasive arm was about 90 minutes—approximately half the time to sheath insertion in the primary PCI arm. “So if it takes about 30 minutes for the lytic to work—when it does work—you have about an hour difference in reperfusion times,” he explained.

However, Dr. Brener continued, “the bottom line is there is no interaction between treatment and aborted MIs. In the adjusted analysis, patients with an aborted MI did not do significantly better than those without an aborted MI.”

In an email with TCTMD, Jeffrey W. Moses, MD, of New York-Presbyterian Hospital/Columbia University Medical Center (New York, NY), was more emphatic in denying that there is an advantage to a lytic-first approach per se. “This is ‘back to the future’ where we tried to achieve earlier TIMI 2 or 3 flow with pharmacoinvasive studies, which overall were a bust,” he said.

Moreover, comparison of the treatment strategies is not meaningful without looking at net clinical outcomes including bleeding, he continued, adding that “primary PCI seems superior when available in a timely fashion for overall clinical outcomes.”

Aborted MI Changes Reinfarction Risk, Not Treatment  

Moreover, Dr. Brener pointed out, the presence of an aborted MI does not alter treatment; most of those patients experience plaque rupture and so need maximal dual antiplatelet therapy.

Due to spontaneous or drug-induced lysis, about 1 in 6 STEMI patients has an open infarct artery by the time he or she undergoes angiography, Dr. Brener observed, and that patency signals a better prognosis. These fortunate few, instead of having an 8% risk of recurrent MI over the next year, quickly return to a baseline risk of about 2%, he noted, adding that the difference may be more meaningful from a population than an individual patient standpoint.  

Dr. Brener said he doubts aborted MI would be useful as a trial endpoint, at least as defined in the study. “These are aborted MIs only to the extent that [the investigators] used rather insensitive criteria,” he explained. “If you do MRI on these patients, they do have MIs. It’s just a matter of how much damage there is and whether it can be detected by enzyme rise. A more important endpoint would be no hyperenhancement on cardiac MR.”

Dr. Brener acknowledged that aborted MI may serve as a research concept, but in the end, he said, clinicians are dedicated to “reducing infarct size in everybody and getting it as close to zero as possible.”

Source:
Maleki ND, Van de Werf F, Goldstein P, et al. Aborted myocardial infarction in ST-elevation myocardial infarction: insights from the STrategic Reperfusion Early After Myocardial infarction trial. Heart. 2014;Epub ahead of print.

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