Many patients with non-ST segment elevation myocardial infarction (NSTEMI) undergo revascularisation outside the 24-hour window recommended in guidelines, but the delay but does not appear to be associated with an increased mortality risk, an Australian study shows.

The findings are derived from Victorian Cardiac Outcomes Registry data for 11,852 percutaneous coronary intervention (PCI) procedures performed for NSTEMI from 2014 to 2018.

While guidelines recommend that NSTEMI patients undergo PCI within 24 hours, after consideration for risk factors, the VCOR data showed that only 18.4% (n=2,178) had revascularisation within this time.

The highest proportion (45.8% ) had PCI at 24-72 hours after symptom onset  while 35.8% had PCI more than 72 hours after NSTEMI.

Multivariate logistic regression showed that as compared to immediate or early PCI (< 24 hours), PCI at 24-72 hours and  beyond 72 hours of symptom onset were associated with a decreased risk of 30-day mortality (Odds Ratios of  0.55 and 0.64, respectively).

Writing in the American Journal of Cardiology the study authors also noted the higher rate of mortality observed in patients undergoing early PCI was attenuated in subsequent analyses excluding patients with risk factors such as cardiogenic shock.

This suggested that cardiogenic shock and out of hospital cardiac arrest requiring intubation accounted for most of the early harm observed in the early PCI group, they said

In addition, age, diabetes mellitus and left ventricular systolic dysfunction were all found to be independent predictors of mortality and MACE following PCI for NSTEMI, irrespective of timing of PCI.

The study authors noted that in clinical practice at PCI centres in Australia, time from symptom onset to PCI often varies in patients with NSTEMI.

“Unstable patients with ongoing ischaemic symptoms are typically triaged for more urgent PCI. Nevertheless, stable patients with complicating comorbidities may wait over weekends for PCI during staffed hours, or until other comorbid conditions have settled,” they wrote.

The findings were therefore reassuring for more complex older patients, who often require medical stabilising for management of other comorbidities such as renal function prior to angiography, they said.

“The results of this study suggest that, despite a large number of patients falling outside the guideline recommended 24-hour window, delayed PCI in select, stable NSTEMI patients does not carry an increased risk of mortality and that, in a complex patient group, a considered approach to PCI timing may be reasonable,” they concluded.