Heparin started in the ambulance or emergency department (ED) makes it more likely a patient with acute ST-segment elevation myocardial infarction (STEMI) will present to the cath lab without a coronary artery occlusion, suggests a large registry study.

An open infarct-related artery (IRA) at angiography on cath-lab arrival presents STEMI patients an opportunity for earlier reperfusion and a chance, in theory at least, for smaller infarcts and maybe improved clinical outcomes.

In the new analysis, which covers more than 40,000 patients with STEMI in Sweden, the 38% who received heparin before cath-lab arrival were 11% less likely to show IRA occlusion at angiography prior to direct percutaneous coronary intervention (PCI). They also showed a 13% lower 30-day mortality compared with patients who were started on heparin in the cath lab. Importantly, their risk of major bleeding in the hospital did not increase.

The “early reperfusion” associated with IRA patency at angiography “could have long-term benefit due to smaller infarct size,” potentially explaining the observed 30-day survival gain in the pretreatment group, Oskar Love Emilsson, Lund University, Lund, Sweden, told theheart.org | Medscape Cardiology.

Emilsson, a third-year medical student, reported the analysis August 29 at the European Society of Cardiology (ESC) Congress 2022, held in Barcelona, Spain, and is lead author on its same-day publication in the journal EuroIntervention.

He mentioned a few cautions in interpreting the study, which is based primarily on data from the Swedish Coronary Angiography and Angioplasty Registry (SCAAR). It included several sensitivity analyses that continued to back pretreatment heparin as a significant predictor of an unoccluded IRA but didn’t consistently support the 30-day mortality benefit seen in the primary analysis.

And, although the pretreatment group overall didn’t have more major bleeds, the risk did go up significantly for those older than 75 or who weighed less than 60 kg (132 lb) or underwent catheterization with an access route other than the radial artery. Extra caution should be exercised in such patients who receive heparin before cath-lab arrival for PCI, Emilsson observed.

“Our results suggest that heparin pretreatment might be a good option to improve patency of infarct related arteries in STEMI,” and potentially clinical outcomes, he said. “However, a definite answer would require a randomized controlled trial.”

Meanwhile, the current study may be the largest yet to look at clinical outcomes after pretreatment with unfractionated heparin before PCI for acute STEMI, the report states. There have been some observational studies, subanalyses of STEMI trials, and even a few limited randomized trials —including the HEAP trial published in 2000 — to weigh in on the subject. Some have supported the strategy, others have not.

“With rapid door-to-balloon times in STEMI, it can be challenging to show a significant difference between a prehospital heparin approach and heparin given in the lab,” observed Sunil V. Rao, MD, NYU Langone Health System, New York City, who is not connected with the current study.

Many EDs in the United States have “a STEMI protocol that calls for an IV bolus of heparin. It would be tougher in the US to give it in the ambulance but again, it’s not clear how much advantage that would really provide,” he told theheart.org | Medscape Cardiology.

Support from randomized trials would be needed before the practice could be formally recommended. “The SCAAR registries have set the standard for how registries should be conducted,” Rao said. “This is a very well-done observational study, but it is observational.”

The priority for STEMI patients, he added, “really should be to get them to the lab as fast as possible. If the ED protocol includes heparin before the cath lab, that’s great, but I don’t think we should delay getting these patients to the lab to accommodate pre-cath-lab heparin.”

The current analysis covered 41,631 patients with STEMI from 2008 through to 2016, of whom 38% were pretreated with heparin in an ambulance or the ED. The remaining 62% initiated heparin in the cath lab.

About one third of the group had an open IRA at angiography. The adjusted risk ratio (RR) for IRA occlusion at angiography for patients pretreated vs not pretreated with heparin was 0.89 (95% CI, 0.87 – 0.90).

The corresponding RR for death within 30 days was 0.87 (95% CI, 0.77 – 0.99) and for major in-hospital bleeding was 1.01 (95% CI, 0.86 – 1.18).

The analysis was adjusted for other medications received before cath-lab arrival, especially a long list of antiplatelets and non-heparin antithrombins. That strengthens the case for heparin pretreatment as an independent predictor of an open IRA at initial angiography, Emilsson said.

Comparisons of propensity-score matched subgroups of the total cohort, conducted separately for the IRA-occlusion endpoint and the endpoints of 30-day mortality and major bleeding, produced similar results.

Some observational data suggests that antiplatelet pretreatment with a P2Y₁₂ inhibitor may promote IRA patency on angiography after cath lab arrival, Rao observed. “This indicates that there probably is a role of earlier antithrombotic therapy in STEMI patients, but the randomized trials have not shown a consistent benefit,” he said, referring in particular to the ATLANTIC trial.

Emilsson disclosed no relevant financial relationships. Disclosures for the other authors can be found with the original article. Rao had no disclosures.

European Society of Cardiology Congress 2022. Optimizing PCI: imaging, pharmacology and more. Presented August 29, 2022.

EuroIntervention. Published online August 29, 2022. Full Text

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