Case Author(s): John R. Leahy, M.D. and Barry A. Siegel, M.D. , 6/23/99 . Rating: #D1, #Q3

Diagnosis: Positive pharmacologic stress test

Brief history:

Exertional chest pain and dyspnea


SPECT images from a rest/pharmacologic-stress myocardial perfusion imaging study

View main image(mi) in a separate image viewer

View second image(an). Magnified view of the left main coronary artery on coronaryv angiography

Full history/Diagnosis is available below

Diagnosis: Positive pharmacologic stress test

Full history:

51-year-old woman with no prior cardiac history presented with episodes of exercise-induced chest pain radiating to the right shoulder and accompanied by dyspnea. The patient's cardiac risk factors included hypertension, diabetes mellitis, hypercholesterolemia, and a family history of coronary artery disease.


2.5 mCi Tl-201 chloride i.v. (rest) and 21.3 mCi Tc-99m sestamibi i.v. (pharmacologic stress)


Paired sress and rest images are shown; in each row, the stress images obtained with Tc-99m sestamibi are on top and the rest images obtained with Tl-201 are on the bottom.

There is a medium-sized reversible perfusion defect of marked severity in the anteroseptal and apical segments of the left ventricle. In addition, a large reversible defect of mild to moderate severity is seen in the adjacent anterior, septal, and lateral walls. Gated images (not shown) demonstrated normal left wall thickening.

Magnified view from the coronary artery angiogram shows 70% stenosis of the left main coronary artery.


A significant number of of patients (30-50%) referred for myocardial perfusion imaging are unable to undergo exercise stress testing. This includes patients with physical or neurologic handicaps and those with poor exercise tolerance secondary to peripheral vascular disease or poor pulmonary function. Additionally, exercise stress testing may have reduced sensitivity in patients on beta blockers and may give false-positive results in patients with left bundle branch block. Under these circumstances, pharmacologic stress testing is a valuable alternative to exercise stress testing.

Both dypiridamole and adenosine cause coronary artery vasodilation; myocardial perfusion imaging performed after infusion of these agents thus evaluates myocardial perfusion reserve, which is reduced in a segment supplied by a stenotic coronary artery. The duration of action and side effects of adenosine are much shorter lived than those for dipyridamole. Sensitivity (87%) and specificity (89%) of pharmacolgic stress testing are similar to those for exercise stress testing.


Sandler MP. Diagnostic Nuclear Medicine, 3rd ed. Williams and Wilkins, Baltimore 1996. p 502-506.


The patient underwent coronary artery bypass grafting to the left main coronary artery and has had resolution of her symptoms.

ACR Codes and Keywords:

References and General Discussion of Myocardial Imaging (Anatomic field:Heart and Great Vessels, Category:Organ specific)

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Case number: mi017

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