Comparison of pulmonary uptake with transient cavity dilation after exercise thallium-201 perfusion imaging

OBJECTIVES The purpose of the study was to evaluate the relationship betwee n elevated lung/heart ratio (LHR) and transient ischemic dilation (TID) aft er stress thallium-201 myocardial perfusion imaging and to provide further insight into the mechanism of cavity dilation. BACKGROUND Because both LHR and TID have been identified as adjunctive mark ers of severe coronary disease they should be found in the same patients. A lthough the mechanism of LHR has been defined, that of transient dilation h as not. METHODS We identified 4,618 consecutive patients undergoing maximal exercis e perfusion imaging with thallium-201. Lung/heart ratio and a dilation inde x were derived and compared to each other and to relevant clinical paramete rs. RESULTS There was a very weak relationship between the LHR and dilation ind ex (r = 0.15, p < 0.001). Defining a dilation index greater than or equal t o 1.10 and LHR greater than or equal to 50% as abnormal revealed that 322 o f the patients (7%) had no only, 351 (7.8%) had LHR only and 40 (0.9%) had both. When compared to patients without these findings both TID and LHR had higher thallium stress defect and redistribution scores. When comparing su bjects who had elevated LHR uptake to those who had TID, it was found that those with LHR were more likely to have had prior myocardial infarction (MI ) (29% vs. 9%), coronary artery bypass grafting (22% vs. 8%), lower ejectio n fraction (33 +/- 17% vs. 55 +/- 11%) and had more evidence of ischemia ba sed on thallium stress defect and redistribution scores. However, patients with cavity dilation had a higher frequency of positive electrocardiographi c response (31% vs. 19%) despite lower scintigraphic markers. CONCLUSIONS Although pulmonary uptake and transient cavity dilation have bo th been associated with severe coronary disease, they have a very weak corr elation, which, in combination with the different clinical parameters assoc iated with each, suggests that they represent different pathophysiologic re sponses to exercise-induced ischemia. Our data support the hypothesis that TID represents transient subendocardial ischemia rather than physical dilat ion from increased end-diastolic pressure. (C) 1999 by the American College of Cardiology.