Infections complicating the course of patients with STEMI are uncommon but associated with markedly worse 90-day clinical outcomes; thus, the APEX-AMI substudy authors suggested that mechanisms for early identification of these high-risk patients as well as design of strategies to reduce their risk of infection are warranted.

The findings were published in the July issue of the Journal of the American College of Cardiology: Cardiovascular Interventions.

Rates of infection complicating PCI are “very low,” wrote the researchers, and reported rates of infection in patients undergoing cardiac catheterization are less than 1 percent.

While cardiogenic shock complicating acute MI is often accompanied by a systemic inflammatory response, the extent of overlap between cardiogenic shock and other conditions leading to a systemic inflammatory state, including serious infection, during acute MI is “unclear,” according to the study authors. However, they acknowledged that it was a problem, as one study found that among patients with cardiogenic shock complicating STEMI, 21 percent died of noncardiac causes, and the cause of death was sepsis in 29 percent (Crit Care Med 2002;30:1987-1994).

To assess the risk, Adriano A.M. Truffa, MD, from Duke Clinical Research Institute in Durham, N.C., analyzed data from 5,745 STEMI patients enrolled in the APEX-AMI trial, on which detailed infection information was collected for all patients. They described characteristics of patients according to infection and details of infection.  

Overall, 138 patients developed a serious infection (2.4 percent), most of whom presented with a single-site infection, the researchers reported.

Among the other findings associated with these patients with infections:

• The median time until diagnosis of infection was three days.
• The most commonly identified organism was Staphylococcus aureus.
• The main location of infection was the bloodstream.
• These patients had more comorbidities and lower procedural success at index PCI than those without infections.
• Patients with serious infection had longer intensive care unit and hospital stays.
• Serious infection was associated with five-fold higher rates of 90-day death and death or MI.

Most patients who developed a serious infection 48 hours after hospital admission, according to the study authors, and patients who developed any infection were more likely to be readmitted with another serious infection within 90 days of hospital discharge.

Truffa et al concluded that the findings demonstrated that, in a contemporary cohort of STEMI patients who underwent primary PCI, serious infection was rare, occurred at a median of three days after presentation, and was more frequent among sicker patients with a history of inflammatory disease, chronic obstructive pulmonary disease and diabetes and among those with worse prognostic markers, such as higher creatinine level at baseline, more advanced Killip class, higher heart rate and larger infarcts. These patients also had worse angiographic results at the index PCI.

Thus, they suggested that further studies to identify these high-risk patients as well as to design strategies to reduce their risk of infection are warranted.

The APEX-AMI trial was jointly funded by Procter & Gamble Pharmaceuticals and Alexion Pharmaceuticals. This analysis was supported by the Duke Clinical Research Institute.