Early post-stress pulmonary uptake of 99mTc tetrofosmin during exercise (SPECT) myocardial perfusion imaging: correlation with haemodynamic, perfusion and function parameters

OBJECTIVE: To test the association of early post-stress lung/heart ratio (LHR) of 99mTc tetrofosmin radioactivity with gated-SPECT findings and angiographic results. METHODS: We studied 158 consecutive patients, with stress/rest 99mTc tetrofosmin myocardial SPECT and coronary angiography. Rest scans were obtained as gated SPECT and the left ventricular ejection fraction and end diastolic volume were calculated. To evaluate myocardial ischaemia, we calculated the summed stress score, summed rest score and summed difference score indices. For the LHR calculation, we acquired an anterior image, 4-6 min after radiotracer injection at stress; LHR was defined as mean counts/pixel in the lung region of interest divided by the mean counts/pixel in the myocardial region of interest. RESULTS: An early post-stress LHR value of 0.500 was defined as the upper normal limit. The most significant correlation (P<0.001) was observed among early post-stress LHR, summed stress score and the number of stenosed vessels. The incidence of multi-vessel coronary artery disease in the subgroup of patients with increased values of early post-stress LHR, was significantly higher than in the normal group (81% vs. 42%, P<0.001). There was a significant difference (P<0.001) of the early post-stress LHR value between patients with normal coronary arteries or one-vessel disease and patients with multi-vessel disease. Early post-stress LHR was an independent predictor of multi-vessel coronary artery disease (coefficient 1.85, SD 0.16, P<0.001), with an incremental value for its identification. CONCLUSIONS: Our results suggest that early post-stress 99mTc tetrofosmin LHR appears to be a useful index of extensive myocardial ischaemia dysfunction and multi-vessel coronary artery disease.