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
Images:
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.
Radiopharmaceutical:
2.5 mCi Tl-201 chloride i.v. (rest) and 21.3 mCi Tc-99m sestamibi i.v. (pharmacologic stress)
Findings:
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.
Discussion:
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.
Reference:
Sandler MP. Diagnostic Nuclear Medicine, 3rd ed. Williams and Wilkins,
Baltimore 1996. p 502-506.
Followup:
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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