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Assessment of myocardial perfusion and function using gated methoxy-isobutyl-isonitrile scintigraphy to detect
P G Avery1, N M Hudson, P J Hubner
1Regional Cardiothoracic Department, Groby Road Hospital, Leicester, UK.
Background:
Technetium-99m-methoxy-isobutyl-isonitrile (MIBI) has been shown to be a useful perfusion agent, and its improved imaging characteristics also allow evaluation of myocardial function. We evaluated the use of gated MIBI scintigraphy in patients undergoing percutaneous transluminal coronary angioplasty to show improvements in myocardial perfusion and function and to detect restenosis.
Methods:
Gated MIBI scintigraphy was performed in a preliminary study in 25 patients before angioplasty. Twenty-one patients who had undergone a successful procedure were re-examined 3 months later. Myocardial perfusion was evaluated and function measured using myocardial profiles along four axes.
Results:
Before angioplasty, 18 out of 21 patients had a reversible perfusion defect, and computer analysis of fractional shortening showed 19 out of 21 had abnormalities of left ventricular function during exercise. Only 11 out of 21 had a positive stress test. Mean global fractional shortening before angioplasty was 27.3% at rest and 26.6% during exercise (not significant). After angioplasty, left ventricular function was improved during exercise, with global fractional shortening increasing from 26.6% to 32.7% (P < 0.001). Repeat angiography was performed in 16 patients. Lesions in four patients had restenosed, in 11 they had not, and in one a different artery was occluded. Three of the four patients with restenosed lesions were identified using repeat perfusion imaging, and all four from abnormalities in left ventricular function. An abnormality in a new region was detected using both methods in the patient with the new occlusion. Normal perfusion and function were found in nine of the 11 patients without restenosed lesions. Two patients continued to have a positive stress test: one with a restenosed lesion and one with new disease.
Conclusion:
Dual assessment with gated MIBI scintigraphy provides useful data in patients undergoing angioplasty and may help in the selection of patients for repeat angiography.