Exercise Body Surface Potential Mapping in Single and Multiple Coronary Artery Disease: Methods (6)

In: Coronary Artery Disease

14 Dec 2012

Exercise Body Surface Potential Mapping in Single and Multiple Coronary Artery Disease: Methods (6)Thallium Scintigraphy
In all patients, 1.5 mCi of thallium was injected intravenously at peak exercise and exercise was continued for a further 1 min. Initial thallium scanning was begun within 8 min of cessation of exercise, following removal of the BSPM leads. Images were obtained in the 45° left anterior oblique positiqn, as well as in the anterior and left lateral positions, using an Ohio Nuclear Series 420 scintillation camera and a high sensitivity, parallel hole collimator. Images were continued until 300,000 total counts were recorded in each view. Scanning was repeated in the same fashion 4 h postexercise.
Analog images were interpreted from x-ray transparent film without computer enhancement or background subtraction, independent of other clinical and study data. Exercise and 4-h redistribution scans were analyzed in pairs for the presence or absence of a thallium defect. Exercise defects were classified as fixed (unchanged at redistribution) or reversible (reduced or absent at redistribution). Reversible defects were considered positive scintigraphic evidence of exercise-induced ischemia. birth control pills
Scans were further classified in a semiquantitative manner, according to the method of Atwood et al. Defect size was graded on a scale of 1 to 5, with 10^20 percent of myocardial area scored as 1; 20^30 percent, 2; 30<40 percent, 3; 40^50 percent, 4; and, >50 percent, scored as 5. Defect intensity was graded as follows: 1 = normal uptake; 2= just less than normal; 3=just greater than background; and 4 = equivalent to background activity. Size and intensity scores from all three views were summed at both exercise and 4-h redistribution. Patients with reversible defects then had a net severity score calculated as the exercise score minus the redistribution score. This net score was utilized as a quantitative reflection of exercise-induced perfusion deficit and myocardial ischemia (Table 2).

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