EFFECTS OF ALTERED LEFT-VENTRICULAR GEOMETRY ON QUANTITATIVE TECHNETIUM 99M SESTAMIBI DEFECT SIZE IN HUMANS - PERFUSION IMAGING DURING CORONARY ANGIOPLASTY

Background. Serial myocardial perfusion imaging is used to assess exer cise-induced myocardial ischemia and myocardial risk area, salvage, an d viability in patients with myocardial infarction. In an experimental animal model it has beets shown that abnormal regional wall motion an d altered left ventricular geometry can produce apparent perfusion def ects independent of changes in blood flow. The effects of regional alt eration in ventricular geometry on perfusion images in humans are not defined. The purpose of our investigation was to evaluate quantitative ly the effect of altered left ventricular geometry on myocardial perfu sion imaging with technetium 99m sestamibi during coronary angioplasty . Methods and Results. Nine patients with normal baseline left ventric ular function referred for angioplasty of the left anterior descending coronary artery were studied. Tc-99m sestamibi was administered intra venously before angioplasty. Baseline planar electrocardiographic-gate d imaging was performed. Imaging was repeated in the catheterization l aboratory during angioplasty vessel occlusion when altered left ventri cular geometry was produced and again later after angioplasty. Summed static, end-systolic, and end-diastolic images were generated from the electrocardiographic-gated acquisitions. Circumferential count profil es of images obtained during percutaneous transluminal coronary angiop lasty (PTCA) were compared with those of a normal Tc-99m sestamibi dat abase and their own baseline images. Defect integral (the area below t he reference profile) and nadir (maximum percent decrease in activity) were derived. Compared with a normal database, new quantitative defec ts appeared on PTCA-summed images in only two patients. The defects we re small to moderate in size. However, compared with their own baselin e profile, six patients had quantitative defects during PTCA (mean def ect integral 3 +/- 2; mean defect nadir 12% +/- 7%). Defect nadir was larger on end-diastolic images compared with summed images (22% +/- 7% and 12% +/- 7%, respectively; p < 0.05). Conclusions. Altered left ve ntricular geometry may create apparent, albeit small, planar myocardia l perfusion defects in humans. Changes in defect size on serial images may be only partially caused by changes in regional wall motion or ge ometry.