Increased resting Tl-201 lung-to-heart ratio is associated with invasively determined measures of left ventricular dysfunction, extent of coronary artery disease, and resting myocardial perfusion abnormalities.

BACKGROUND

Stress lung thallium 201 uptake correlates with left ventricular (LV) dysfunction and extent of coronary artery disease (CAD). Although Tl-201 is used less commonly for stress imaging, dual-isotope stress and viability protocols continue to use Tl-201 for rest imaging. We sought to investigate the association between increased resting Tl-201 lung-to-heart ratio (LHR) and hemodynamic indices of LV dysfunction, indices of myocardial perfusion, and extent of CAD.

METHODS AND RESULTS

Over a 1-year period, we identified 192 consecutive patients who underwent dual-isotope stress perfusion imaging and cardiac catheterization within 30 days, without interim events or revascularization. Resting LHR was measured, and its association with invasively measured hemodynamic parameters, extent of CAD, and indices of myocardial perfusion at rest and stress was examined. Increased resting Tl-201 LHR was weakly but significantly associated with lower LV ejection fraction (EF) (r = 0.209, P <.05), higher pulmonary capillary wedge pressure (r = 0.25, P <.005), and LV end-diastolic pressure (r = 0.215, P <.01) but not with pulmonary artery systolic pressure. Increased LHR was also weakly associated with rest perfusion abnormalities including the sum rest score (r = 0.271, P <.001) and number of abnormally perfused segments (r = 0.25, P <.001) bud did not correlate with stress perfusion indices or ischemic burden. The 76 patients (40%) with LHR greater than 0.5 were more likely to have LVEF lower than 40% and 3-vessel/left main CAD.

CONCLUSIONS

Increased rest Tl-201 LHR is weakly associated with higher LV end-diastolic pressure and pulmonary capillary wedge pressure and lower LVEF. LHR is also associated with the extent of previously infarcted myocardium and may indicate the presence of 3-vessel/left main CAD.