Deteriorating ventricular function is a major concern after the Senning operation. A Doppler-derived non-geometric measurement, the so-called myocardial performance index, has been described for use in adults and children. We aimed to assess the utility of this index as a method for quantification of right ventricular function in patients in the late follow-up of the Senning procedure, and to correlate the right ventricular ejection fraction and the first derivative of right ventricular pressure as derived using echocardiography with the ejection fraction determined using magnetic resonance imaging. We studied 44 patients within a mean postoperative period of 15.3 years. We calculated the right ventricular myocardial performance index by pulsed wave Doppler interrogation of tricuspid inflow and aortic outflow, the ejection fraction by Simpson's rule, and the first derivative of right ventricular pressure by continuous wave Doppler from tricuspid regurgitation. Mean values of right ventricular myocardial performance index, ejection fraction, and the first derivative of right ventricular pressure were 0.50, 39 percent and 1,398 millimetres of mercury per second, respectively. A cut-off value of 0.47 for the right ventricle myocardial performance index was determined, with a sensitivity of 75 percent and a specificity of 62.5 percent. We found no correlation between ejection fraction and the first derivative of right ventricular pressure as estimated by echocardiography and the ejection fraction as shown by magnetic resonance imaging (r2 equal to 0.29 and 0.04 respectively). We concluded, first, that patients with preserved right ventricular function had values for the right ventricular myocardial performance index lower than 0.47, and second, that ejection fraction and the first derivative of right ventricular pressure as determined echocardiographically did not correlate with values derived using magnetic resonance imaging.