Immediate invasive strategy for patients with non ST-segment elevation myocardial infarction (NSTEMI) was associated with lower mortality rates or recurring MI when compared with delayed invasive strategy, according to results from the RIDDLE-NSTEMI (Randomized study of Immediate versus Delayed Invasive Intervention in patients with Non ST-segment Elevation of Myocardial Infarction) trial.

RIDDLE-NSTEMI investigators compared immediate invasive angiography within 2 hours of patient admission against a delayed invasive strategy within 72 hours of admission. Researchers followed participants to calculate mortality and new MI rates in NSTEMI patients after a 30-day and 1-year follow-up.

“The main finding of our study is that in initially stabilized NSTEMI patients, immediate invasive intervention is associated with lower rates of death or myocardial infarction when compared to a delayed invasive treatment,” the authors wrote in their study, published in JACC: Cardiovascular Interventions. “This difference was mainly attributable to lower rates of new myocardial infarction in patients undergoing immediate invasive procedure, foremost during the pre-catheterization period.”

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Researchers randomly assigned 162 NSTEMI patients to the immediate-intervention group (<2 hours after randomization) and 161 NSTEMI patients to the delayed-intervention group (between 2 and 72 hours after randomization). Occurrence of death or new MI at 30-day follow-up served as the primary end point.

The median time from randomization to angiography in the immediate-intervention group was 1.4 hours, and 61 hours in the delayed-intervention group. After 30 days, the rate of mortality or new MI was 4.3% in the immediate-intervention group, compared with 13% in the delayed-intervention group (hazard ratio [HR]=0.32; confidence interval [CI] 95%, 0.13-0.74; P=.008). The rate of mortality, new MI, or recurrent ischemia was 6.8% in the immediate-intervention group and 26.7% in the delayed-intervention group.

After a 1-year follow-up, the difference between the groups continued. The immediate group had a mortality or new MI rate of 6.8%, compared with 18.8% in the delayed-intervention group (HR=0.34; CI 95%, 0.17- 0.67; P=.002). The rate of mortality, new MI, or recurrent ischemia at 1 year was 15.4% in the immediate-intervention group vs 33.1% in the delayed intervention group.

Patients in the immediate intervention group had the largest reduction of new MI rate in the pre-catheterization period when compared with the delayed-intervention group (0 deaths and 0 MIs vs 1 death and 10 MIs).

“Future studies with standardized protocols that include clinically oriented definition of periprocedural MI, larger sample size and longer-term follow-up are needed to assess the true effect of immediate intervention in NSTEMI patients,” the authors concluded.


Milosevic A, Vasiljevic-Pokrajcic Z, Milasinovic D, et al. Immediate vs delayed invasive intervention for non-ST-segment elevation myocardial infarction patients: the RIDDLE-NSTEMI study (randomized study of immediate vs delayed invasive intervention in patients with non-ST-segment elevation myocardial infarction). JACC Cardiovasc Interv. 2016. DOI: 10.1016/j.jcin.2015.11.018.