[Clinical investigation of inhomogeneity of washout rate in dipyridamole stress thallium scintigraphy: implication of new parameter for the indication of coronary intervention].
OBJECTIVE
The standard deviation of the washout rate in dipyridamole stress thallium-201 myocardial single photon emission computed tomography (SPECT) was correlated with the severity of coronary artery lesions and the viability of ischemic myocardium to provide a new quantitative parameter for judging indications for coronary intervention therapy.


METHODS
Dipyridamole stress thallium-201 SPECT was performed in 233 patients for differential diagnosis of angina pectoris during the 40 months beginning in October 1995, and 57 patients were investigated who underwent coronary angiography within 6 months of the SPECT. The washout rate standard deviation (WRSD) in 720 fractions in the bull's-eye view of the SPECT was determined. The conventional washout rate extent score (WRES) and washout rate severity score (WRSS) on the washout rate map were also determined. Based on the coronary angiography findings, patients were divided into 3 groups: zero-vessel group (zero-vessel disease, n = 20), one-vessel group (one-vessel disease, n = 18), and multivessel group (two- or three-vessel disease, n = 19). The patients were also divided into 2 other groups: Int group (n = 21), who underwent coronary intervention therapy, and Med group (n = 36), in whom intervention therapy was not indicated.


RESULTS
All 3 parameters, WRSD, WRES and WRSS, showed significant differences between the 3 groups, and more coronary arteries affected by coronary artery stenosis were associated with higher WRSD (zero-vessel group: 5.4 +/- 1.5, one-vessel group: 7.0 +/- 3.7, multivessel group 11.4 +/- 6.7; p < 0.001), WRES (3.3 +/- 5.0, 15.5 +/- 18.1, 23.0 +/- 25.4; p < 0.01), and WRSS (1.4 +/- 2.8, 25.4 +/- 40.2, 84.8 +/- 114.5; p < 0.01). WRSD (Med group: 5.9 +/- 2.7, Int group: 11.3 +/- 6.4; p < 0.001), WRES (7.3 +/- 12.0, 24.7 +/- 24.9; p < 0.01), and WRSS (9.9 +/- 29.3, 82.9 +/- 108.2; p < 0.01) were all significantly higher in the Int group compared with the Med group. There were significant correlations between Gensini's score and WRSD (r = 0.51, p = 0.00005), WRES (r = 0.37, p = 0.005), and WRSS (r = 0.29, p = 0.03). The cutoff values for the indications for coronary intervention therapy were established for each of the 3 parameters as the maximum value of average sensitivity and specificity as follows: WRSD > 9.0 (sensitivity 0.62, specificity 0.89, positive predictive value 0.76, negative predictive value 0.24); WRES > 10.0 (0.62, 0.69, 0.54, 0.46, respectively); WRSS > 13.0 (0.62, 0.83, 0.68, 0.32, respectively). WRSD > 9.0 had the highest specificity and positive predictive value for judging indications.


CONCLUSIONS
A new quantitative parameter, WRSD > 9.0, suggests the presence of viable and curable ischemic myocardium as an indication for coronary intervention therapy.
Arao
M
M
Department of Internal Medicine, Tokyo Metropolitan Komagome Hospital.
Setsuta
K
K
Seino
Y
Y
Takano
T
T
D000368:Aged; D000787:Angina Pectoris / Q000000981:diagnostic imaging*; D017023:Coronary Angiography; D004176:Dipyridamole; D005080:Exercise Test; D005260:Female; D006801:Humans; D008297:Male; D012680:Sensitivity and Specificity; D013794:Thallium Radioisotopes; D015899:Tomography, Emission-Computed, Single-Photon / Q000592:standards*
D013794:Thallium Radioisotopes; D004176:Dipyridamole