<prompt> Answer this question truthfullyWhat is the purpose of using pharmacologic stress during perfusion scintigraphy in patients with chronic stable angina?  <response>: <reason> Class IIa 1. Adenosine or dipyridamole stress myocardial perfusion imaging or dobutamine echocardiography in patients with a low or high probability of CAD in the absence of electronically paced ventricular rhythm or left bundle-branch block. Level of Evidence: B 2. Adenosine or dipyridamole myocardial perfusion imaging in patients with a low or high probability of CAD and 1 of the following baseline ECG abnormalities: a. Electronically paced ventricular rhythm. Level of Evidence: C b. Left bundle-branch block. Level of Evidence: B 