Diagnosis of extensive coronary artery disease: Intrinsic value of increased lung (201)T1 uptake with exercise SPECT

Exercise lung (TI)-T-201 uptake calculated with planar imaging has an impor tant diagnostic and prognostic value in patients with coronary artery disea se (CAD). However, its value with SPECT imaging raises methodological conce rns and is controversial. We studied its value for the discrimination betwe en extensive (E) and limited (L) angiographic CAD with exercise SPECT. Meth ods: Four methods of lung-to-heart ratio quantification were calculated in patients with a low likelihood (< 5%) of CAD (n = 62). Their dependent vari ables were defined, and corresponding correction equations were derived. Re ceiver operating characteristic (ROC) analysis was performed in a pilot gro up (L-CAD, n = 49; E-CAD, n = 126) to define the optimal method of calculat ion of the lung-to-heart ratio. Its best threshold providing the best sensi tivity for a specificity of 90% was defined. After correction for dependent variables, the 4 methods were also compared by ROC analysis and the optima l corrected method was compared with the optimal uncorrected method using R OC analysis and the best threshold. The consistency of these results in the validation group (L-CAD, n = 41; E-CAD, n = 122) and of the results of vis ual analysis of lung (TI)-T-201 uptake were then verified. Results: On ROC analysis in the pilot group, the optimal method of calculation of the lung- to-heart ratio was the mean activity in a region of interest drawn at the b ase of the lungs to the mean activity over the heart (L-b/H). For the best threshold, L-b/H presented a sensitivity of 34%. Corrected L-b/H still rema ined the best method of calculation on ROC analysis compared with the other corrected methods. On ROC analysis, there was no difference between correc ted and uncorrected L-b/H. For the best threshold, corrected L-b/H presente d a similar sensitivity of 37% compared with uncorrected L-b/H. When applie d to the validation group (L-CAD, n = 41; E-CAD, n = 122), the best-defined threshold in the pilot group for corrected L-b/H presented a diagnostic va lue similar to that in the pilot group (sensitivity, 41%; specificity, 90%) , but uncorrected L-b/H presented a higher sensitivity (47%; P < 0.04) and a slightly lower specificity (80%). Results of lung (TI)-T-201 uptake visua l analysis were inconsistent between pilot and validation groups (42% versu s 58% sensitivity, P = 0.012; 86% versus 66% specificity, P = 0.023), Concl usion: For evaluation of E-CAD versus L-CAD, quantification of the exercise lung-to-heart (TI)-T-201 uptake ratio with SPECT is feasible, reproducible , more discriminate than simple visual analysis, and best calculated as L-b /H. It presents an intrinsic diagnostic value even after correction for oth er clinically valuable dependent variables.