Patients presenting with NSTEMI who are scheduled to undergo elective cardiac catheterization and coronary angiography with primary PCI will be selected for participation in the study. The patients will undergo a clinically indicated resting non-contrast echocardiogram to assess LV function and regional wall motion. They will then undergo contrast echocardiography with bolus injection of Optison™ contrast to reassess LV ejection fraction, improve LV opacification and assess regional wall motion abnormalities. Finally, they will be given a continuous infusion of Optison™ and will have assessment of myocardial perfusion of each of the 17 myocardial segments using low mechanical index continuous imaging of the myocardium and blood pool.