Echocardiography is the mainstay of preoperative arch imaging in infants with coarctation of the aorta. In simple coarctation, repair by way of sternotomy or thoracotomy is often determined by echocardiographic transverse arch measurements. The degree of arch hypoplasia that is prohibitive to repair by way of thoracotomy is unknown. Clinical predictors of recoarctation are also unknown. Demographic, echocardiographic (transverse arch and aortic measurements), operative, and postoperative data of infants <90 days old with simple coarctation repaired by way of thoracotomy between February 2005 and November 2011 were evaluated. Recoarctation was defined as surgical or catheter reintervention after hospital discharge. Eighty-four infants underwent coarctation repair at median age of 12 (range 1–85) days with median follow-up of 12.3 (range 0.5–71.9) months. The seven (8 %) infants with recoarctation underwent balloon angioplasty. In multivariable analysis, only greater postoperative Doppler peak velocity [1.13, confidence interval (CI) 1.04–1.23] and greater sinotubular junction z-score (hazard ratio 4.19, CI 1.47–11.95) independently predicted coarctation. Doppler peak velocity >2.12 m/s had sensitivity of 63 % and specificity of 83 % of predicting recoarctation, and ST junction z-score >−0.93 had sensitivity of 100 % and specificity of 58 %. No transverse arch dimensions were independently associated with recoarctation. Infants with transverse arch z-score as low as −2.8 underwent successful repair by way of thoracotomy. No clinical predictors were significant.