Inpatient-Onset Versus Outpatient-Onset ST-Segment-Elevation Myocardial Infarction in Patients With Percutaneous Coronary Intervention: A National Registry Study

Abstract

Background: Compared with patients who develop ST-segment-elevation myocardial infarction (STEMI) outside the hospital and present at the emergency department (outpatient-onset), patients with inpatient-onset STEMI may paradoxically experience a poorer prognosis due to underlying disease, despite the apparent immediate access to acute health care services.

Methods: Patients with first-onset STEMI who underwent percutaneous coronary intervention (PCI) in the Singapore Myocardial Infarction Registry (2007-2020) were included. For patients with inpatient-onset STEMI, the recognition-to-balloon time was measured from symptom onset to PCI. For outpatient-onset STEMI, the recognition-to-balloon time was defined as the sum of the symptom-to-door and door-to-balloon time. Logistic regression was used to identify factors associated with delayed PCI after inpatient-onset STEMI. Cox regression was used to assess 30-day, 1-year, 5-year, and 10-year all-cause and cardiovascular mortality.

Results: A total of 19 149 patients, 17 659 (92.2%) outpatient-onset and 1595 (7.8%) inpatient-onset, were included. The median follow-up duration was 6.91 years. Patients with inpatient-onset STEMI were older, more frequently women, nonsmokers, more likely to have comorbidities, less likely to present with typical STEMI symptoms, and more likely to experience delays in PCI than patients with outpatient-onset STEMI within the hospital setting. The independent predictors of delayed PCI for inpatient-onset STEMI were age ≥65 years, diabetes, breathlessness at presentation, and Killip class III. After adjustment for differences in baseline and clinical characteristics, inpatient-onset STEMI was associated with significantly greater 1-year, 5-year, and 10-year all-cause mortality (1-year hazard ratio [HR], 1.27 [95% CI, 1.13-1.43]; 5-year HR, 1.27 [95% CI, 1.13-1.43]). There was no difference in 30-day all-cause or short-/long-term cardiovascular mortality.

Conclusions: Inpatient-onset STEMI was linked to an increased long-term risk of all-cause mortality compared with outpatient-onset STEMI despite a shorter recognition-to-balloon time.

Keywords: all‐cause mortality; cardiovascular mortality; inpatient; myocardial infarction; percutaneous coronary intervention.

Figure 1. Flowchart for data inclusion.

A total of 133 868 patients were registered in the SMIR from 2008 to 2020. Only those with first‐onset STEMI who underwent PCI with valid symptom‐to‐door, door‐to‐balloon, and recognition‐to‐balloon times were included in the analysis. The patients were then divided into outpatient‐onset and inpatient‐onset STEMI. A total of 7177 patients with outpatient‐onset and 1591 with inpatient‐onset STEMI did not undergo PCI. AMI indicates acute myocardial infarction; PCI, percutaneous coronary intervention; SMIR, Singapore Myocardial Infarction Registry; and STEMI, ST‐segment–elevation myocardial infarction.

Figure 2. Kaplan‐Meier curves for all‐cause and cardiovascular mortality.

Kaplan‐Meier curves for all‐cause mortality (A) and cardiovascular mortality (B).

Figure 3. Subgroup analysis for all‐cause and cardiovascular mortality at 30 days and 5 years.

A, Subgroup analysis for 30‐day all‐cause mortality. B, Subgroup analysis for 5‐year all‐cause mortality. C, Subgroup analysis for 30‐day cardiovascular mortality. D, Subgroup analysis for 5‐year cardiovascular mortality. HR indicates hazard ratio.