Immediate, rather than delayed, angiography reduced by 62% the chance of both recurrent heart attack and death in patients with non–ST-segment myocardial infarction.

The significant advantage of early treatment was apparent at both 30 days and 1 year after myocardial infarction, Dr. Aleksandra Milosevic and colleagues wrote (JACC Cardiovasc Interv. 2016;10.1016/j.jcin.2015.11.018).

RIDDLE-NSTEMI (Randomized Study of Immediate vs. Delayed Invasive Intervention in Patients with Non–ST-Segment Elevation MI) is not the first to examine immediate vs. delayed outcomes in coronary angiography. But it is the first to look at a pure cohort of NSTEMI patients, and the first to use purely clinical, rather than biochemical, outcomes, said Dr. Milosevic of the Clinical Center of Serbia, Belgrade.

The study group comprised 323 patients with a confirmed NSTEMI MI to either immediate or delayed angiography. Those in the immediate treatment group went to catheterization as soon as possible (median, 1.4 hours); those in the delayed-treatment group underwent the procedure within 72 hours of randomization (median, 61 hours).

All patients received a loading dose of dual-antiplatelet therapy. For immediate-treatment patients, this consisted of 300 mg aspirin and 600 mg clopidogrel. Those in the delayed-treatment group received 300 mg aspirin and 300 mg clopidogrel. Everyone then received daily treatment of aspirin 100 mg and clopidogrel 75 mg.

Patients who had already been taking dual-antiplatelet therapy continued their maintenance dose. Low-molecular-weight heparin, nitrates, beta-blockers, and ACE inhibitors were given according to clinical guidelines; glycoprotein IIb/IIIa inhibitors were allowed at the treating physician’s discretion.

The time from symptom onset to randomization was 5 hours in the immediate- and 6.5 hours in the delayed-treatment groups. Manual thrombectomy was more common in the immediate-treatment group (3.9% vs. 1%), as was percutaneous coronary intervention (78% vs. 65%). Coronary artery bypass grafting was more common in the delayed-treatment group (23.8% vs. 12%).

At 30 days, the composite primary endpoint of mortality and new MI was significantly less common in the immediate-treatment group (4.3% vs. 13.0%; hazard ratio, 0.32). Mortality was the same in both groups (5 patients; 3%). The difference was driven by the significantly larger number of nonfatal MIs in the delayed-treatment group (16 vs. 2).

The advantage of early treatment held at 1 year, with significantly lower rates of death and new MI in the immediate-treatment group (16.8% vs. 18.8%). This was entirely driven by early events; there was no significant difference after the first 30 days.

A composite secondary endpoint of death, new MI or recurrent ischemia, was also significantly lower in the immediate-intervention group at 30 days (6.8% vs. 26.7%) and 1 year (15.4% vs. 33%).

A multivariate regression analysis controlled for demographics, past medical history, prior coronary procedures, and electrocardiogram changes. After considering these variables, immediate treatment was associated with a 62% reduction in the chance of a new MI within 30 days (HR, 0.42; P = .052).

There was no between-group difference in major bleeding, which was low both at 30 days and 1 year. One patient in the immediate-treatment group and two in the delayed-treatment group needed a transfusion. One intracranial bleed occurred in an immediately treated patient. Four patients in the delayed treatment group were treated for gastrointestinal bleeding.

The authors had no financial declarations.