Incremental prognostic value of 99mTc-tetrofosmin early poststress pulmonary uptake. Determination of the optimal cut-off value.

Objectives: To evaluate the incremental prognostic value of (99m)Tc-tetrofosmin early poststress lung/heart ratio (eLHR) and to assess the optimal cut-off value.

Materials And Methods: We studied 503 patients (aged 61.3 years/SD = 8.6 years, 302 men) with stress/rest (99m)Tc-tetrofosmin myocardial gated-single photon emission computed tomography and coronary angiography. To evaluate myocardial ischemia, the summed stress score, summed rest score, and summed difference score indices were calculated. For the eLHR calculation, an anterior image was acquired 4-6 min after radiotracer injection at stress; eLHR was defined as the mean counts/pixel in the lung region of interest divided by the mean counts/pixel in the myocardial region of interest. The incremental prognostic value of eLHR was evaluated by a significant increase in the global χ(2) of the Cox proportional hazard model that included clinical, exercise, angiographic, and scintigraphic variables. Using the receiver operating characteristic analysis, the optimal cut-off of eLHR for the prediction of cardiac events was determined.

Results: During the follow-up period, hard cardiac events occurred in 50 (9.9%) and soft cardiac events in 61 (12.1%) patients. Receiver operating characteristic curve analysis showed that the optimal cut-off of eLHR for the prediction of cardiac events was 0.51, with a sensitivity of 78.4% and specificity of 72.2%. The area under the curve was 0.82 (95% confidence interval: 0.77-0.87). Multiple Cox regression analysis revealed that eLHR more than 0.51 (hazard ratio = 7.78; 95% confidence interval: 5.00-12.11) provided incremental prognostic value over clinical exercise testing and scintigraphic data for cardiac events.

Conclusion: A (99m)Tc-tetrofosmin eLHR value larger than 0.51 added incremental value to other variables for the prediction of cardiac events.