3.1 Eligible studies and characteristics of studies
A total of 120 articles were identified, and 80 remained after title abstract screen and duplicate deletion. Altogether 71 articles were excluded for the following reasons: 33 articles were case reports, reviews or case series; 20 studies included no VSD patients; 12 studies performed no TVD procedure; 3 studies provided inadequate raw data for analysis; and 2 studies included insufficient patient population (Figure 1).
Only 9 studies were included after selection (Table 1), including 7 retrospective cohort studies, 1 respective cohort study and 1 prospective observational study. Quality assessment of included studies was summarized in Table 2. In the study led by Sasson11, patients were divided into three groups, group 1 included patients with no indication for TVD, group 2 for patients with indications for TVD and underwent TVD and group 3 for patients with indications for TVD but underwent non-TVD procedures. Our analysis took only group 2 and group 3 into consideration.