N Engl J Med 2024;391:1673-1684
Background: Non-ST elevation myocardial infarction (NSTEMI) is the most common acute coronary syndrome subtype in adults over 75 years old. However, these patients were underrepresented in landmark NSTEMI trials. Older adults with multiple comorbidities face an increased risk of mortality. While NSTEMI contributes to this risk, they also have competing risks such as advanced age, frailty, and chronic kidney disease. The presence of competing risks means that aggressively managing one condition may have a smaller impact on overall mortality compared to a younger, otherwise healthy adult with myocardial infarction, whose primary risk of death stems from the myocardial infarction itself. Additionally, comorbid conditions like advanced kidney disease and diffuse atherosclerosis can increase the risks associated with revascularization.
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A patient-level meta-analysis of smaller trials, including 1,479 patients, found that in elderly patients with NSTEMI, an invasive strategy reduced myocardial infarction and urgent revascularization but not mortality.
The Older Patients with Non–ST-Segment Elevation Myocardial Infarction Randomized Interventional Treatment (SENRIOR-RITA) trial sought to assess invasive vs conservative management of elderly patients with NSTEMI, in a more pragmatic design.
Patients: Eligible patients had to have type I NSTEMI and be 75 years or older.
Patients were excluded if they had cardiogenic shock or life expectancy less than 1 year.
Baseline characteristics: The trial randomized 1,518 patients from hospitals across England and Scotland – 753 randomized to invasive strategy and 765 to conservative strategy.
The average age of patients was 82 years and 55% were men. Approximately 65% had hypertension, 31% had diabetes, 31% had hyperlipidemia, 31% had prior myocardial infarction, 15% had prior stroke or TIA, 21% had kidney disease, 15% had chronic obstructive pulmonary disease, and 5% were current smokers.
The average Charlson comorbidity index was 5.
Procedures: Patients were randomly assigned in a 1:1 ratio to undergo invasive or conservative strategy.
In the invasive strategy, patients underwent coronary angiogram, and revascularization was performed as appropriate. In the conservative arm, patients were treated (unless contraindicated) with aspirin, a P2Y12 receptor antagonist, statin, beta-blocker and an angiotensin-converting enzyme inhibitor or angiotensin II receptor blocker. Patients in the conservative arm were allowed to have a coronary angiogram if they had worsening clinical status.
Endpoints: The primary end point was a composite of cardiovascular death or nonfatal myocardial infarction. Secondary outcomes included all-cause death, subsequent coronary revascularization, hospitalization for heart failure, stroke and bleeding.
Analysis was performed based on the intention-to-treat principle. The trial aimed to detect a hazard ratio of 0.78, assuming a 20% risk of the primary outcome in the conservative arm. A sample size of 1,668 patients with at least 688 primary outcome events would provide 90% power at 5% alpha, while 520 events would provide 80% power.
Results: Among the patient randomized to the invasive arm, 90% underwent coronary angiography and 50% underwent revascularization. The medium number of days from admission to coronary angiography was 5. Among patients randomized to the conservative arm, 5.6% underwent coronary angiography within 7 days. The median follow-up time was 4.1 years.
The primary outcome was not significantly different between both groups (25.6% with invasive vs 26.3% with conservative, HR: 0.94, 95%: 0.77 - 1.14; p= 0.53).
There was also no difference in all-cause death (36.1% vs 32.3%), cardiovascular death (15.8% vs 14.2%), stroke (4.2% vs 5.2%), hospitalization for heart failure (10.9% vs 10.7%), or major bleeding (8.2% vs 6.4%) “incidence for invasive mentioned first”. Future coronary revascularization was more frequent in the conservative arm (13.7% vs 3.9%). Non-fatal myocardial infarction was significantly lower with an invasive strategy (11.7% vs 15.0%).
Procedural related complications occurred in less than 1% of the patients.
There were no significant subgroup interactions for the primary outcome.
Conclusion: In older patients with NSTEMI, an invasive strategy compared to conservative strategy, did not reduce the primary composite endpoint of cardiovascular death or nonfatal myocardial infarction, over a median of 4.1 years.
The trial enrolled fewer patients than planned, and the lower-than-expected event rate reduced its statistical power. Additionally, the median 5-day delay before coronary angiography may have biased the results toward the conservative strategy.
Despite its limitations, this trial demonstrates that a conservative approach is a reasonable option for selected older patients with NSTEMI. It also highlights that, although enrolling older patients with comorbidities in trials is challenging, it is feasible, and greater effort is needed to include more of this population in future trials.
Finally, in this trial of patients with myocardial infarction, about one-third died over a median of 4.1 years, with less than half of these deaths attributed to cardiovascular disease. Even if an invasive strategy had reduced cardiovascular mortality, its impact on all-cause mortality would have been less significant. This concept extends beyond this trial; when interventions are applied to older patients with multiple competing risks, their overall benefit diminishes.
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