Lung-to-heart ratio on thallium-201 myocardial perfusion imaging in patients with chronic obstructive pulmonary disease

Background In thallium-201 (Tl-201) stress myocardial perfusion imaging (MPI), elevated lung-to-heart ratio (LHR) can help to predict adverse cardiac events and identify coronary artery disease. However, few studies have evaluated the LHR values on Tl-201 MPI in patients with chronic obstructive pulmonary disease (COPD). Objective To examine whether LHR in COPD may be altered, considering the combined effects of hypoxia, inflammation, and capillary loss. Methods We retrospectively evaluated patients with normal Tl-201 pharmacologic stress MPI, no adverse cardiac events in the subsequent 2 years, and pulmonary function tests, coronary angiography, and echocardiography results obtained within 6 months. Patients with COPD (study group) were matched 1:1 by sex and age to controls with normal pulmonary function (control group). Subgroups within the study group were established based on COPD severity determined by spirometry. MPI images were interpreted using a 17-segment american heart association (AHA) model and a 0–4-point scale. LHR and right ventricle/left ventricle (RV/LV) ratios were also documented. Results Patients with severe COPD exhibited lower poststress LHR values than those with mild-to-moderate COPD. Compared with the control group, the moderate COPD group displayed higher stress LHR, stress RV/LV ratio, and tricuspid regurgitation maximum pressure gradient (TRmaxPG) values. Moreover, poststress LHR showed a positive correlation with the stress RV/LV ratio and TRmaxPG value. These findings were statistically significant ( P < 0.05). Conclusion In Tl-201 pharmacologic stress MPI, our study suggests a nuanced relationship between COPD severity and LHR, emphasizing the need to reconsider normal LHR thresholds in COPD. Larger studies are warranted to validate and expand upon these findings.