Long-term prognostic value of early poststress 99mTc-tetrofosmin lung uptake during exercise (SPECT) myocardial perfusion imaging

Purpose The aim of this study was to determine the long-term prognostic value of early poststress lung/heart ratio (LHR) of 99m Tc-tetrofosmin radioactivity. Methods We studied 276 patients (aged 62.2±8.9 years, 168 men) with stress/rest 99m Tc-tetrofosmin myocardial gated-SPECT and coronary angiography. To evaluate myocardial ischaemia, we calculated the summed stress score, summed rest score and summed difference score indices. For the eLHR calculation, an anterior image was acquired, 4–6 min after radiotracer injection at stress (eLHR was defined as mean counts per pixel in the lung region of interest divided by the mean counts per pixel in the myocardial region of interest). Cardiovascular death and nonfatal myocardial infarction were considered as hard cardiac events, and late revascularization procedures as soft cardiac events. The Cox proportional hazards model in a stepwise method was used to determine the independent predictors for hard and soft cardiac events. Results During the follow-up period hard cardiac events occurred in 28 patients (10.1%) and soft cardiac events in 32 patients (11.6%). Implying multiple Cox regression analysis, eLHR was found to be a significant independent predictor for both soft and hard cardiac events. The hazard ratio (for a 0.1 unit increase) was 4.41 (95% CI 1.52–12.73, p =0.006) for soft cardiac events and 4.22 (95% CI 2.07–8.62, p