The development of tachycardia-induced cardiomyopathy (TIC) is related to the rate and duration of supraventricular tachycardia (SVT). Infants may be more susceptible to TIC because early symptoms might be unrecognized. Extracorporeal membrane oxygenation (ECMO) may improve outcome in patients with SVT and TIC; however, clinical predictors of infants who require ECMO support have not been determined. The purpose of this study was to identify predictors of the need for ECMO in infants with SVT and TIC. Sixteen infants <6 months of age who experienced resolution of TIC following control of arrhythmia were identified. Three patients (19%) required ECMO support. Comparisons were made between patients who required ECMO and those who did not. The groups were similar with respect to age at presentation, type of SVT, rate of SVT, and degree of ventricular dysfunction. However, patients requiring ECMO had increased median M-mode-derived left ventricular end diastolic dimension (LVED) z-score when compared to the medically managed patents (+2.8 vs. 0.0, P = 0.009). No patient in the medically managed group had an LVED z-score >2.3. Infants presenting with SVT and TIC with LVED z-score >2 are at increased risk for requiring ECMO support and early use of ECMO should be considered.