Data Extraction and Quality Assessment

Data were systematically extracted from the studies and independently compiled by two reviewers (Ling-Xi Liu and Fei Zhao) using a standardized electronic sheet and were cross-checked to reach a consensus. In cases of disagreement, a consensus was reached by discussion. Trial and patient characteristics were recorded, including the name of the first author, year of publication, country, case/control, study population, mean age or range, gender, weight, types of echocardiography, operative approach, type of occluder, and size and type of VSD. The outcomes of interest were the success rate, defined as the proportion of patients with no residual shunts and no need for conversion to COHS, and morbidity from intra- and post-operative complications, including arrhythmia, valvular regurgitation, residual shunts and others. The other events were clinical indicators, including the duration of the procedure, intensive care unit stay, hospital stay, total medical costs, and the number of transfused patients. VSDs were mainly classified according to the Anderson method^9,10, and included muscular VSD (mVSD), perimembranous VSD (pmVSD), doubly committed subarterial VSD (dcsVSD) and the special type of VSD. The latter was defined as the coexistence of multiple types of VSDs, including a patient with both a mVSD and a pmVSD¹¹ or an acquired VSD, such as a post-myocardial infarction VSD (pi-VSD)¹² and an iatrogenic VSD. Gender was reported as the proportion of females in the patient cohort. The surgical approach included three classes: median or subxiphoid sternotomy (the median approach), and the left and right intercostal space beside the sternum approach (left approach and right approach, respectively). If patients were lost to follow-up in the trial, we performed an intention-to-treat (ITT) analysis.

The quality assessment of all selected studies was independently performed by the two investigators (Yun-Han Jiang and Hua-Li Peng). All eligible randomized controlled trials were assessed using the Cochrane Risk of Bias assessment tool. This tool included the following items: allocation sequence generation, allocation concealment, participant masking, personnel and outcome assessors, completeness of outcome data, and selective outcome reporting. The Newcastle-Ottawa Scale (NOS) was used to assess the quality of the cohort studies and the case-control studies^13,14. For cohort studies, quality was evaluated based on three major components: selection of the study group (0–4 stars), quality of the adjustment for confounding variables (0–2 stars) and the assessment of outcome in the cohorts (0–3 stars). Case-control studies were also assessed based on three factors: selection of the case and controls (0–4 stars), comparability of the cases and controls (0–2 stars) and the ascertainment of exposure (0–3 stars). Furthermore, we chose an 18-item, validated quality appraisal tool to evaluate the methodological quality of the case series¹⁵. The quality assessments for each item were binary determinations of various aspects of the study, including the study objective; study population; intervention and co-intervention; outcome measures; statistical analysis; the results and conclusions; competing interests; and sources of support. The score of the assessment was the number of yes responses, and the score of acceptable quality was ≥14^15,16. Disagreements in the quality assessment were resolved through discussion.