This patient presents with acute coronary syndrome (ACS) as indicated by an increase in the frequency and severity of his previously stable angina. The unchanged ECG and normal cardiac biomarkers indicate unstable angina (UA) rather than non-ST segment elevation myocardial infarction (NSTEMI). Patients with ACS should be admitted to a cardiac unit and their medical regimen intensified, in this case with the addition of antithrombotic therapy (IV unfractionated heparin or subcutaneous low-molecular-weight heparin) and additional antiplatelet therapy (such as clopidogrel). Intravenous nitrates, glycoprotein IIb/IIIa inhibitors, and early coronary angiography can be considered. There is no role for digoxin, which would increase myocardial oxygen consumption and exacerbate the situation. Thrombolytic therapy is reserved for the treatment for ST-segment elevation myocardial infarction (STEMI), where occlusive intracoronary thrombosis is demonstrated in 70% of patients. ACS is usually associated with unstable plaque and platelet activation but not major coronary thrombosis. The patient is at high risk for myocardial necrosis and should be admitted to the hospital for stabilization; simple observation and failure to intensify his treatment would be inappropriate.