Comparison of in-hospital outcomes and 30-days readmissions between type 1 and type 2 myocardial infarction patients: a study of the nationwide readmissions database

Abstract

Abstract Introduction Traditionally Type- 1 myocardial infarction (T1-MI) results from a plaque erosion, rupture, or fissure. In contrast, Type- 2 myocardial infarction (T2-MI) is a consequence of severe supply and demand mismatch. Despite the different mechanisms, both T1-MI and T2-MI can be associated with severe morbidity and mortality. Yet there is sparse data analyzing in-hospital outcomes and readmission rates comparing patients who present with T1-MI and T2-MI. Purpose We aimed to compare the outcome data of patients with T1-MI and T2-MI derived from the Nationwide Readmissions Database, a large national database of hospital readmissions. Method We utilized the 2018 Nationwide Readmissions Database to identify all index hospital admissions with a primary diagnosis of “acute MI” (AMI) using ICD-10 diagnosis codes. All AMI admissions were further categorized into ST-elevation myocardial infarction (STEMI), no-ST-elevation myocardial infarction (NSTEMI), or T2-MI. Primary outcomes analyzed included 30-days major adverse cardiovascular events (MACE) (defined as re-infarction, repeat revascularization and death within 30 days of admission), short term mortality and readmission rates. Results Among 556,816 total admissions for AMI, 28,250 (5.1%) were T2-MI. Table 1 compares baseline variables and short-term outcomes for patients with T1-MI vs T2-MI. Compared to patients with T1-MI patients with T2-MI were older, more likely to be female, and had a higher burden of comorbidities. Additionally, T2-MI patients were less likely to receive coronary revascularization during the index admission. The mean length of stay for T2-MI patients was 4.7±0.6 days, which is longer than the length of stay for STEMI patient (4.1±0.4 days) but slightly shorter than NSTEMI patient (4.9±0.4 days). T2-MI patients had a higher rate of all-cause 30-days readmissions but a lower rate of 30-days MACE. Early mortality rate (within 30 days of index admission) in T2-MI patients was comparable to NSTEMI patients but was lower than STEMI patients. Cox proportional-hazards model adjusting for age, sex, comorbidities and type of hospital setting demonstrated that T2-MI was associated with a lower 30-day MACE risk (T2-MI vs STEMI: [HR 0.33 (95% CI 0.31–0.36)]; T2-MI vs NSTEMI [HR 0.70 (95% CI 0.64–0.75)]) and a lower risk of early mortality (T2-MI vs STEMI: [HR 0.29 (95% CI 0.26–0.32)]; T2-MI vs NSTEMI [HR 0.71 (95% CI 0.65–0.79)]). The adjusted HR for 30-days all-cause readmissions was higher with T2-MI, (T2-MI vs STEMI: [HR 1.16 (95% CI 1.10–1.23)]; T2-MI vs NSTEMI: [HR 1.11 (95% CI 1.06–1.16)]). Conclusion T2-MI patients are older and have a higher burden of comorbidities. After adjusting for baseline comorbidities, all-cause readmission risk is higher in T2-MI but short-term MACE and mortality is lower with T2-MI. Funding Acknowledgement Type of funding sources: None.