ObjectiveTo reveal the risk factors for delayed recovery and complications in infants with weight≤5.0 kg after surgical ventricular septal defect (VSD) closure.MethodsWe retrospectively reviewed a consecutive series of 86 patients with weight≤5.0 kg who were admitted to our institution for surgical VSD closure between January 2016 and July 2019, including 31 males and 55 females with an age of 17-266 (80.3±40.4) d and a weight of 2.5-5.0 (4.4±0.6) kg. The VSDs were divided into perimembranous (n=65, 75.6%), subaortic (n=17, 19.8%) and subaortic combined muscular types (n=4, 4.7%). Mechanical ventilation (MV) time≥24 h or ICU stay≥72 h were defined as delayed recovery. Death, sudden circulatory arrest, complete heart block requiring a permanent or temporary pacemaker implantation, neurological complications, reoperation (for residue shunt or valvular regurgitation), reintubation and diaphragmatic paralysis were considered as significant major adverse events.ResultsThere was no death, reoperation due to residual VSD or neurological complication. Totally 51 (59.3%) patients had MV timec≥24 h and 51 (59.3%) patients stayed in the ICU≥72 h. Two (2.3%) patients required temporary pacemaker and six (7.0%) patients required reintubation. During the follow-up of 3-36 (15.8±8.8) months, 1 patient died of pneumonia after discharge, 5 patients suffered mild tricuspid valve regurgitation and 1 patient suffered decreased left ventricular systolic function in the follow-up. No aortic valve injuries occurred.ConclusionFor patients whose weight≤5.0 kg, short-term results of surgical VSD closure are excellent. Low weight and age may prolong MV time; low birth weight and pulmonary hypertension may prolong ICU stay, but are not independent risk factors.