Clinical significance of apical thinning after attenuation correction

Background. Apical thinning and other image changes at the apex have been described after attenuation correction of myocardial perfusion single photon emission computed tomography (SPECT) studies, but their clinical significance is unknown. Methods and Results. We studied 102 subjects from a multicenter trial of attenuation correction, 46 with angiographic coronary artery disease and 56 normal subjects. We graded the presence and magnitude (on a 4-point scale) of apical thinning (decrease in wall thickness, best assessed in the vertical long-axis view) in both noncorrected and attenuation-corrected images. In attenuation-corrected images, apical thinning of any degree was present in 78% of the abnormal patients and 63% of the normal subjects (P = not significant [NS]). However, moderate or severe apical thinning was present in 30% of the abnormal patients compared with 5% of the normal subjects (relative risk = 2.2, P < .001). In noncorrected images, apical thinning of any degree was present in 87% of the abnormal patients and 71% of the normal subjects (P = NS). However, moderate or severe apical thinning was present in 28% of the abnormal patients compared with 4% of the normal subjects (relative risk = 2.3, P < .001). Conclusion. The presence of mild apical thinning is common in both noncorrected and attenuation-corrected SPECT images and does not imply coronary artery disease. Moderate or severe apical thinning is 7 times more common in patients than in normal subjects, but it is relatively uncommon and thus is not a generally useful clinical tool.