Which diagnosis matches acute chest pain with evidence of myocardial necrosis but without acute ST-segment elevation or Q waves on ECG?

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When acute chest pain occurs with evidence of myocardial necrosis but the ECG lacks ST-segment elevation, the finding points to a non-ST-segment elevation myocardial infarction. The key clue is the positive biomarker of necrosis (such as troponin), which confirms actual myocardial injury, even though the ECG does not show the classic ST elevations. In NSTEMI, the ECG may show non–ST-segment changes like ST depression or T-wave inversion, or even be nondiagnostic, yet troponin elevation proves infarction has occurred. This distinguishes NSTEMI from unstable angina, which presents with similar symptoms but without biomarker evidence of necrosis (troponin remains normal). It also differentiates NSTEMI from STEMI, where persistent ST elevations (and often new Q waves) indicate transmural infarction requiring urgent reperfusion.