A prospective, observational cohort study found that a significant decrease in 180-day all-cause mortality among patients with non-ST-elevation MI (NSTEMI) was associated with increased use of an invasive coronary strategy.

Lead researcher Marlous Hall, PhD, of the University of Leeds in England, and colleagues published their results online in JAMA on Aug. 30.

The findings were also presented at the European Society of Cardiology’s Congress in Rome.

In this trial, the researchers evaluated 389,000 patients with NSTEMI who enrolled in the Myocardial Ischemia National Audit Project (MINAP), a database of patients hospitalized with acute MI in England and Wales. The patients were admitted to one of 247 hospitals between Jan. 1, 2003, and June 30, 2013.

The median age was 72.7 years old, and 63.1 percent of patients were males. The proportions of patients with intermediate to high Global Registry of Acute Coronary Events (GRACE) risk score decreased from 87.2 percent in 2003-04 to 82.0 percent from 2012-13, while the proportions with the lowest risk decreased from 4.2 percent to 7.6 percent, respectively.

Meanwhile, the proportion of patients with STEMI who had diabetes, hypertension, cerebrovascular disease, chronic obstructive pulmonary disease, chronic renal failure, previous invasive coronary strategy and current or ex-smoking status each significantly increased during the study. In addition, the proportion of patients with previous MI, angina, peripheral vascular disease and congestive heart failure decreased.

After a median follow-up period of 2.3 years, 29.2 percent of patients died. Within 180 days of hospital discharge, 9.6 percent of patients died.

The unadjusted all-cause mortality rates at 30 days following discharge decreased from 2.6 percent in 2003-04 to 2 percent in 2012-13, while the 180-day mortality rates decreased from 10.8 percent to 7.6 percent. The declines in 30- and 180-day mortality were greater for patients with NSTEMI who had an intermediate to high GRACE risk score compared with patients with low GRACE risk scores.

During the study, there was a 3.2 percent relative improvement in survival per year on average. In addition, in-hospital mortality decreased from 10.9 percent in 2003-04 to 5 percent in 2012-13.

The temporal survival improvements remained similar when adjusting for baseline GRACE risk, sex and socioeconomic status, comorbidities and pharmacological therapies prescribed at hospital discharge.

When the researchers added invasive coronary strategy, such as coronary angiography, PCI or CABG to the adjustment, the temporal improvements in survival were reversed. The researchers wrote that their findings suggested that invasive coronary strategy “significantly accounted for at least part of the reduction in NSTEMI mortality between 2003 and 2013 above that of reducing baseline risk, increasing comorbidities and use of pharmacological therapies.”

In addition, baseline survival decreased by an average of 2 percent per year after the researchers accounted for the use of an invasive coronary strategy. The researchers mentioned that an instrumental variable analysis found the use of an invasive coronary strategy was associated with a 46.1 percent relative decrease in mortality.

They also cited a few potential limitations of the study, including that they relied on accurate recording of the data and that missing data could have led to inaccurate estimates. The MINAP also did not collect all cases of NSTEMI. Meanwhile, they noted that factors such as drug adherence and primary care visits could have influenced survival. Further, the observational design of the study did not allow the researchers to determine causation.