The patients enrolled in the study will undergo a nitrate enhanced rest gated SPECT using a Tc-99m labeled tracer (sestamibi or tetrofosmine) followed by a second gated SPECT acquired during a low-dose dobutamine infusion (10 mcg/kg/mn). All patients will have a 6-month clinical and imaging follow-up, including physical examination and a nitrate enhanced rest gated SPECT using the same radiopharmaceutical. All treatments received during this 6-month period will be recorded, including medical therapy and coronary revascularization (angioplasty, stenting and CABG).