COVID-19 with myocardial injury, defined as troponin elevation, is associated with worse outcomes. The temporal changes in outcomes during various phases of the pandemic remain unclear. We evaluated outcomes during the Omicron phase compared with previous phases of the pandemic. We analyzed patients who were COVID-19-positive with evidence of myocardial injury who presented to the MedStar Health system (11 hospitals in Washington, District of Columbia, and Maryland) during phase 1 of the pandemic (March to June 2020), phase 2 (October 2020 to January 2021), and phase 3 (Omicron; December 2021 to March 2022), comparing their characteristics and outcomes. The primary end point was in-hospital mortality. The cohort included 2,079 patients admitted who were COVID-19 positive and for whom troponin was elevated (phase 1: n = 150, phase 2: n = 854, phase 3: n = 1,075). Baseline characteristics were similar overall. Inflammatory markers were significantly elevated in phase 1 compared with phases 2 and 3. The use of remdesivir and dexamethasone was highest in phase 2. In phase 3, 52.6% of patients were fully vaccinated. In-hospital mortality, though high, was lower in phase 3 than in phases 1 and 2 (59.3% vs 28.1% vs 23.3%; p <0.001). Patients who were vaccinated showed more favorable in-hospital outcomes than did those who were unvaccinated (18.3% vs 24.2%, p = 0.042). In conclusion, patients with COVID-19 with elevated troponin during phase 3 tended to have improved outcomes when compared with patients in earlier waves of the pandemic. This improvement could be attributed to the implementation of the COVID-19 vaccines, advances in COVID-19 treatment options, provider experience, and less virulent variants.