Objective: The location of a myocardial lesion on a wall thickening polar map often does not coincide with the location of the lesion on a perfusion polar map, especially when the myocardial lesion is located at the mid cardiac region. The purpose of this study was to determine the frequency and extent of discrepancy in the location of the lesion between perfusion and wall thickening polar maps on gated single photon emission computed tomography (SPECT) using lesion axis angle (LAA).
Methods: One hundred and forty-seven consecutive patients (male : female = 80 : 67, age range: 41–96 years) who underwent myocardial gated 99mTc-tetrofosmin SPECT on the suspicion of myocardial ischemia or infarct between September 2003 and September 2008 and showed both reduced myocardial perfusion and wall thickening on gated SPECT at mid cardiac region were reviewed. LAA, which is the angle between the lesion axis on perfusion and wall thickening polar maps, was measured for the patients who showed a discrepancy in lesion axis between the two polar maps. LAA was said to have a positive value when the lesion axis of the wall thickening polar map showed a counterclockwise angular rotation as compared with that of a perfusion polar map. The patients with LAA of less than 10° were considered as having no lesion axis discrepancy between perfusion and wall thickening polar maps. LAA was correlated with left ventricular ejection fraction (LVEF) on gated SPECT using Pearson's correlation. Furthermore, two groups, one with LAA of ≥10° and the other with LAA less than 10° were correlated with dichotomous groups with ≥50% and less than 50% LVEF, using the χ2 test. Then, 35 patients with acute coronary syndrome (ACS group) were analyzed separately for correlation between LAA and LVEF.
Results: The mean ± SD of LAA was 44.31±30.77° (range: 0–145°). LAA was 0–10° in 25 patients, 11–30° in 24 patients, 31–60° in 58 patients, 61–90° in 30 patients, and >90° in 10 patients. In addition, the lesion axis of the wall thickening polar map as compared with that of the perfusion polar map was rotated in the counterclockwise direction in 122 patients and not rotated in 25 patients. LVEF on gated SPECT showed positive correlation with LAA (P = 0.000147). In addition, there was statistically significant correlation (P = 0.001) when the two groups with LAA of ≥10° and less than 10°, respectively, were correlated with the groups of ≥50% and less than 50% LVEF. For the ACS group, the mean ± SD of LAA was 45.88±30.30° (range: 0–135°) and LVEF showed positive correlation with LAA (P = 0.0001). There was no significant statistical difference concerning LAA and LVEF between ACS group and non-ACS group (P = 0.725 and P = 0.473, respectively).
Conclusion: In most of our patients with coronary artery disease, the lesion axis of reduced wall thickening was rotated in the counterclockwise direction as compared with that of reduced perfusion on SPECT polar maps, especially when the myocardial lesion was at mid cardiac region. The LAA decreased as the LVEF decreased. This might be related to spatiotemporal distortion of myocardial contraction mentioned in the helical heart concept.
aDepartment of Radiology, St. Paul's Hospital
Departments of bNuclear Medicine
dRadiology, and Seoul St. Mary's Hospital, The Catholic University of Korea, The College of Medicine, Seoul, Korea
eDepartment of Radiology, Division of Nuclear Medicine, Emory Hospital, Atlanta, USA
Correspondence to Dr Hyeon-Sook Kim, MD, Department of Radiology, St. Paul's Hospital, The Catholic University of Korea, The College of Medicine, Seoul, Korea
Tel: +82 2 958 2084; fax: +82 2 960 4568;
Received 26 May 2009 Revised 12 July 2009 Accepted 13 July 2009