Helical heart on ECG gated 99mTc-tetrofosmin SPECT: counterclockwise rotation of lesion axis on wall thickening polar map as compared with that on perfusion polar map in patients with coronary artery disease.

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 (99m)Tc-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 degrees 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 >or=10 degrees and the other with LAA less than 10 degrees were correlated with dichotomous groups with >or=50% and less than 50% LVEF, using the chi(2) 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 degrees (range: 0-145 degrees ). LAA was 0-10 degrees in 25 patients, 11-30 degrees in 24 patients, 31-60 degrees in 58 patients, 61-90 degrees in 30 patients, and >90 degrees 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 >or=10 degrees and less than 10 degrees , respectively, were correlated with the groups of >or=50% and less than 50% LVEF. For the ACS group, the mean +/- SD of LAA was 45.88+/-30.30 degrees (range: 0-135 degrees ) 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.