Long-Term Prognosis of Unstable Angina: A Ten-Year Follow-Up Study Comparing Clinical Outcomes with Myocardial Infarction

Background and Objectives: Unstable angina has traditionally been considered the least severe acute coronary syndrome presentation, but ten-year prognostic data remain limited. We compared the clinical characteristics and ten-year prognosis of unstable angina versus non-ST-segment elevation myocardial infarction and ST-segment elevation myocardial infarction. Materials and Methods: This retrospective study included consecutive patients older than eighteen years admitted with suspected acute coronary syndrome to a Spanish tertiary hospital between January 2009 and December 2015. Ten-year survival and clinical outcomes were evaluated retrospectively through long-term tracking of electronic medical records and official regional death registries. Results: Of 3029 patients (10.6% with unstable angina, 45.0% with non-ST-segment elevation myocardial infarction, and 44.4% with ST-segment elevation myocardial infarction), those with unstable angina had a median age of 66.0 years (vs. 67.0 and 62.0 years in the other cohorts, respectively; p < 0.001) and a significantly higher prevalence of prior myocardial infarction (31.5% vs. 21.9% and 11.4%, respectively; p < 0.001). However, unstable angina presented lower-risk acute profiles (Killip class >I: 2.5% versus 17.5% and 20.7%; p < 0.001; median GRACE score: 89.9 versus 107.6 and 113.3; p < 0.001) and 0% in-hospital mortality (versus 3.3% and 5.4%; p < 0.001). At ten years, cumulative mortality reached 23.4% in unstable angina, converging with ST-segment elevation myocardial infarction (29.1%; p > 0.05) but remaining lower than non-ST-segment elevation myocardial infarction (35.3%; p < 0.05). In multivariable Cox analysis, unstable angina was not independently associated with ten-year mortality (overall p = 0.066; vs. STEMI p = 0.743; vs. NSTEMI p = 0.133). Conclusions: Despite favorable acute stabilization and the absence of in-hospital mortality, the survival advantage of unstable angina over ST-segment elevation myocardial infarction appears to attenuate over a ten-year period. This trend toward mortality convergence is likely associated with the baseline comorbidity burden, highlighting the clinical need for intensive secondary prevention.