Risk of Death Remains Low a Decade After Primary PCI for STEMI

The risk of dying over the next decade for STEMI patients who survive the first 90 days after primary PCI is just a few percentage points higher than people in the general population, an observational analysis from Western Denmark shows.

The lack of substantial excess mortality is largely due to the increased monitoring STEMI patients receive after their event as well as the Denmark’s high use of secondary prevention medications, Pernille Gro Thrane, MD (Aarhus University Hospital), and colleagues suggest.

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Speaking with TCTMD, Thrane said these 10-year findings extend an earlier report by the same research group showing that post-STEMI mortality was highest within the first 30 days then “tended to level out over time” up to 1 year.

In their new study, published online today in the Journal of the American College of Cardiology, the difference—at least in the long term—between people who had and had not experienced a STEMI turned out to be surprisingly small, she said.

“One thing to consider is that the general population is not a healthy control group, but individuals with comorbidities but no known coronary artery disease,” said Thrane explained, noting that “the reasons for the excess morality after STEMI is likely multifactorial.” The researchers caution, too, that their results probably don’t apply to the United States and other regions where fewer patients receive optimal medical therapy.

Still, the results provide “convincing” evidence that long-term mortality is “only mildly elevated” when patients are treated with primary PCI and have high adherence to medical therapy, knowledge that could be motivating to clinicians and patients alike, said Thrane. “I find these results very important for our dialogue with patients in cardiac rehabilitation regarding their long-term prognosis after STEMI.”

Excess Risk of 2% by 10 Years

Thrane et al used the Western Denmark Heart Registry to identify people who underwent primary PCI for their first STEMI (n = 18,818) between 2003 and 2018. Using data from the Danish Civil Registration System, the researchers matched each of these individuals by age and sex to five people from the general population (n = 94,090) who had no history of MI, PCI, or CABG. The day of the primary PCI procedure was considered the index date, and the median follow-up duration was 7.4 years.

Median age was 64 years, and 73.5% were men. Baseline comorbidity burden and medication use were comparable between the two groups.

Between days 0 to 30 after primary PCI, mortality was 5.9% higher for STEMI patients than for the general population (6.0% vs 0.2%; HR 36.44; 95% CI 30.86-43.04).

Looked at from the vantage point of 10 years, mortality among patients who survived the first 90 days was 2.1% higher than the rate in the general population (26.5% vs 24.5%; HR 1.04; 95% CI 1.01-1.08). Most of the late deaths occurred after 6 years.

Subgroup analyses shed some additional light. Female STEMI patients had an excess mortality of 7% over the general population by 10 years, while male patients had no significant excess. Mortality was increased by 2.3% in STEMI patients < 65 years but was not significantly different in older patients. Active smoking, diabetes, hypertension, body mass index < 27 kg/m², multivessel disease, heart failure, and Charlson comorbidity index values of 2 or higher all were associated with greater death risk for STEMI patients in comparison to the general population.

Use of secondary prevention drugs was high—within the first year after STEMI, 98% of patients filled a prescription for an antiplatelet agent, 93% for a statin, and 84% for a beta-blocker. Just 16%, 10%, and 13% of the general population took these medications in year 1. Between 9 to 10 years, 71% of surviving STEMI patients were still taking an antiplatelet, 70% were on statin therapy, and 57% on a beta-blocker.

“One of the key factors driving the low excess mortality might be a high level of risk management in patients surviving a STEMI,” the authors note, also crediting the impact of greater awareness and lower threshold for treating hypertension, diabetes, and hyperlipidemia in the wake of a cardiovascular event. “It is likely that STEMI patients benefit from an increased surveillance that is not present in the matched general population.”

As for the late deaths that do occur, the researchers speculate they may stem from decreases in the use of secondary prevention over time, development of heart failure or fatal arrhythmias, worsening of underlying atherosclerotic disease, and risk factors (eg, smoking) that tend to me more prevalent in STEMI patients versus general population.

Thrane said that there are many possible explanations for the sex disparity including an increased comorbidity burden in women presenting with STEMI compared to men, as well as the well-known phenomenon whereby female patients can experience treatment delays. To know for sure will require more study, she added. “The short answer is we have to look more into the reasons behind the excess mortality in women. . . . In my opinion, our results underscore the importance of considering life expectancy in the general population and illustrate that the impact of suffering STEMI is greater in women than men.”

We have to look more into the reasons behind the excess mortality in women. Pernille Gro Thrane

Myron L. Weisfeldt, MD, and Stephen D. Sisson, MD (both from Johns Hopkins University School of Medicine, Baltimore, MD), in an accompanying editorial, assert that the Danish findings are “an indictment of the fractured US healthcare system.”

“In Denmark, there is universal healthcare with government-maintained, nationwide health registries that provide longitudinal health data described as an epidemiologist’s dream,” they write. “The Thrane et al study demonstrates realization of that dream and provides a roadmap to improving cardiovascular mortality in Denmark (a homogenous population not representative of the diversity seen in the United States).” By contrast, the US medical-record system, the editorialists continue, is built more for billing and regulatory needs, with the end result that the United States spends more money on healthcare—with less to show for it—than other nations.

Weisfeldt and Sisson agree that beyond showing the importance of secondary prevention, the study also points to areas where primary prevention has room to grow, even in Denmark.

“Only 13.6% of patients were on a statin at the time of their STEMI, and nearly 40% of those patients were smokers,” they point out. STEMI patients, after their event, were much more likely to be on guideline-directed medical therapy than the general population, despite many individuals in the latter group still being at risk for a future event. “Although it is likely that STEMI patients found their acute coronary event a potent motivator for medical adherence, we must find better ways to get patients with high cardiovascular risk on preventive therapy,” especially individuals in the most vulnerable subgroups, they urge.

Thrane highlighted that same message: “We need to pay extra attention to patients presenting at young ages (below 65 years) and patients with high-risk factors, such as those with diabetes, active smoking, and hypertension.” Closer surveillance and better risk-factor management are warranted in these patients, both before and after STEMI, she said.