Correlation of Exercise and Rest Tc-99m MIBI Lung/heart Ratio at Different Areas of Lung with Left Ventricular Ejection Fraction in Patients with Coronary Artery Disease.

Increased lung uptake of thallium-201 (Tl) and technetium-99m-methoxyisobutyl isonitrite (Tc-MIBI) in myocardial perfusion imaging has been proved as a reliable marker of left ventricular dysfunction. The goal of this study was to evaluate the lung uptake at the various areas of both the right and left lung (ie, right lung base and both lung apices) and its correlation with the left ventricular dysfunction by calculating lung-to-heart (L/H) uptake ratio in exercise and rest Tc-sestamibi myocardial perfusion. There were a total of 63 patients (10 female, 53 male: age range from 30-75 years, mean age 45.3 years, median age 45 years) with chronic coronary artery disease undergoing two-dimensional (2D) echocardiogram to calculate left ventricular ejection fraction (LVEF). Planar images were taken before myocardial perfusion imaging to calculate the L/H at different sites of the lungs. The patients having LVEF ≤40% on 2D echo (32 patients) were included in group A, and the patients having LVEF >40% on 2D echo (31 patients) were included in group B. The L/H differs significantly during stress and rest at the selected lung areas (P < .05). The uptake ratio at the right lung base was greater than the ratio at apices. In group A, L/H was significantly higher during stress and rest as compared with group B. However, in both the groups, stress uptake counts were greater as compared with rest. A statistically significant inverse correlation was found between the L/H uptake ratio and LVEF during exercise and rest at both the lung base and apices. Useful clinical information regarding left ventricular dysfunction was proved by L/H, irrespective of the area selected at lung.