We developed a risk factor-scaling score (RFSS) to select which patients supported by extracorporeal membrane oxygenation (ECMO) were suitable for ventricular assist device (VAD) implantation or heart transplantation (HTx). A total of 78 patients supported with ECMO for more than 48 h due to cardiac origin were included in this study. Patients were categorized into two groups based on the outcomes: the poor outcome group (n = 33) consisted of for those who later died or were later excluded from VAD or HTx; the favorable outcome group (n = 45) consisted of those who were weaned off ECMO finally and survived or were deemed suitable candidates for VAD or HTx. Seven risk factors were significant according to univariate analyses. Based on the regression coefficients of multivariate analysis, the RFSS was developed: (lung dysfunction x 7) + (systemic infection x 3) + (peak lactate > 3 mmole/L x 3) + (kidney dysfunction x 2) + (creatine kinase > 10,000 U/L x 1). Patients with an RFSS of 7 or more were be allocated to the poor outcome group. The RFSS was validated by another group of 30 patients with good correlation. The RFSS provides a way to predict which ECMO-supported patients are suitable candidates for VAD implantation or HTx.