Left ventricular ejection fraction (EF) is used to assess patients with heart failure (HF); however, frequent measurements are not cost-effective. Impedance cardiography (ICG) is a low-cost, noninvasive test that measures systolic time intervals and may be a method for detecting impaired vs intact EF. This study evaluated the relationship between EF by echocardiography or gated nuclear ventriculography and systolic time ratio (STR) by ICG in outpatients with chronic HF. A retrospective chart review identified 52 patients with EF and STR measured within 2 weeks. There was an inverse correlation between STR and EF (r=-0.54; P<.001). The area under the receiver operating characteristic curve for STR to identify reduced EF was 0.86. An EF < or =50% and STR > or =0.50 demonstrated 93% sensitivity and 85% specificity. STR was able to distinguish intact (>50%) from impaired EF (< or =50%). STR by ICG has the potential to be a reliable method to monitor ventricular function in chronic HF.