The Seattle Heart Failure Model (SHFM) is a validated prediction model that estimates the mortality in patients with chronic heart failure (CHF) using commonly obtained information, including clinical data, laboratory test results, medication use, and device implantation. In addition, cardiac iodine-123 meta-iodobenzylguanidine (MIBG) imaging provides prognostic information for patients with CHF. However, the long-term predictive value of combining the SHFM and cardiac MIBG imaging in patients with CHF has not been elucidated. To prospectively investigate whether cardiac iodine-123 MIBG imaging provides additional prognostic value to the SHFM in patients with CHF, we studied 106 outpatients with CHF who had radionuclide left ventricular ejection fraction < 40% (30 ± 8%). The SHFM score was obtained at enrollment, and the cardiac MIBG washout rate (WR) was calculated from anterior chest images obtained at 20 and 200 minutes after isotope injection. During a mean follow-up of 6.8 ± 3.5 years (range 0 to 13), 32 of 106 patients died from cardiac causes. A multivariate Cox analysis revealed that the WR (p = 0.0002) and SHFM score (p = 0.0091) were independent predictors of cardiac death. Kaplan-Meier analysis showed that patients with an abnormal WR (> 27%) had a significantly greater risk of cardiac death than did those with a normal WR for both those with a SHFM score of ≥ 1 (relative risk 3.3, 95% confidence interval 1.2 to 9.7, p = 0.01) and a SHFM score of ≤ 0 (relative risk 3.4, 95% confidence interval 1.2 to 9.6, p = 0.004). In conclusion, the cardiac MIBG WR provided additional prognostic information to the SHFM score for patients with CHF.