Smarter artery scans after heart attack cut repeat events by 38%

After a major heart attack, using a computer to work out which other narrowed arteries really limit blood flow, instead of judging by eye, cut repeat heart problems by about a third. That was the main result of the AIR-STEMI trial, presented on 29 August 2026 at ESC Congress in Munich and published at the same time in the New England Journal of Medicine.

The approach also meant fewer stents, less X-ray dye and fewer complications.

The problem the trial tackled

A STEMI (ST-segment elevation myocardial infarction) is the most serious type of heart attack, where a coronary artery is fully or almost fully blocked. Doctors open the blocked artery, called the culprit, with a balloon and a stent.

The European Society of Cardiology (ESC) says almost half of STEMI patients also have narrowings in other coronary arteries. This is called multivessel disease. ESC guidelines recommend treating these non-culprit narrowings too, known as complete revascularisation.

The hard part is deciding which narrowings need a stent. Most hospitals decide from the angiogram, the X-ray video of dye flowing through the arteries. Lead investigator Associate Professor Simone Biscaglia of University Hospital of Ferrara pointed out the weakness of this: "Traditional coronary angiography provides a two-dimensional picture of narrowed vessels, which is subjective since it is interpreted by the human eye."

A narrowing that looks severe may not reduce blood flow much, and one that looks mild may matter more than it seems.

What functional coronary angiography does

Functional coronary angiography uses the angiogram images already taken during the emergency procedure. Software rebuilds the artery in three dimensions and estimates how much the narrowing restricts flow. The result is an angiography-derived fractional flow reserve, or FFR.

FFR is a ratio. A value of 1.0 means no drop in pressure across the narrowing. In AIR-STEMI:

• narrowings with an FFR of 0.80 or less were treated with a stent
• narrowings above 0.80 were left alone

The standard method of measuring FFR needs a pressure wire threaded into the artery and a drug to widen the vessels. The software method needs neither. In the trial, FFR analysis was done centrally in a core laboratory.

Who took part

AIR-STEMI was an investigator-led trial at 21 centres in Italy and Pakistan. It enrolled 1,823 people with STEMI and multivessel disease whose culprit artery had already been successfully opened. The median age was 66, and 24% were women.

Patients were randomly assigned to have their other narrowings treated based on either:

• functional coronary angiography, with stents only where FFR was 0.80 or less
• conventional angiography, with stents for any narrowing judged at least 50% by eye

The results

The main endpoint combined death from any cause, heart attack, stroke and repeat procedures to unblock an artery because of reduced blood supply. Median follow-up was 17.9 months.

The hazard ratio for the main endpoint was 0.62, a 38% lower risk. For the safety endpoint, the hazard ratio was 0.63, a 37% lower risk.

Heart attacks, both those linked to the procedure and those occurring later, and repeat procedures were all significantly reduced. The difference in deaths was not statistically significant (hazard ratio 0.77, with a confidence interval running from 0.50 to 1.20), so the trial does not show that the approach saves lives.

A simple way to read the main result: in 1,000 people treated with the conventional approach, about 137 had one of the main events over roughly a year and a half. With the functional approach, about 89 did. That is around 48 fewer events per 1,000 patients, from the trial's reported percentages.

Why fewer stents led to fewer problems

In the functional group, only about half of the other narrowed vessels got a stent, against almost all in the conventional group. According to the ESC, this meant fewer procedures, fewer treated vessels, shorter treated segments and less dye.

Less dye lowers the risk of kidney injury. Fewer and shorter stents mean less metal in the arteries, which may reduce later blockages within the stent and procedure-related heart damage. The trial was not designed to separate out which of these explains the benefit.

Biscaglia summed up the aim as "treating the lesions that matter, while avoiding unnecessary PCI in lesions that do not appear to limit blood flow."

Points to weigh

• Where it was run. All 21 centres were in Italy and Pakistan. Results may differ in health systems with different patient groups or catheter lab practice.
• The comparison. The control arm stented almost every narrowing of 50% or more. Some hospitals already use pressure wires to guide these decisions, and AIR-STEMI did not compare against that.
• Funding and links. The trial was supported by the University Hospital of Ferrara and Consorzio Futuro in Ricerca, which received unrestricted funding from Sahajanand Medical Technologies and Siemens Healthineers. Two imaging firms provided software licences. Biscaglia reported fees from several of these companies.
• Follow-up. Median follow-up of under 18 months is fairly short for heart outcomes.

What it means for patients

If you have had a STEMI and been told other arteries are narrowed, the question of which ones to stent is a real decision. AIR-STEMI suggests a software assessment of the angiogram can guide that choice and may spare some people stents they do not need. Availability of the software varies between hospitals.

This article explains research findings and is not medical advice. Ask your cardiology team about your own treatment.