Right minithoracotomy versus median sternotomy for reoperative mitral valve surgery: a systematic review and meta-analysis of observational studies

Reoperative mitral valve surgery (MVS) through a median sternotomy (ST-MVS) can be particularly challenging due to dense adhesions and is known to carry a substantial risk of injuries to vascular structures. These injuries occur in 7-9% of cases and are associated with increased mortality rates. A valid alternative that could avoid the risks associated with redo ST-MVS is the right anterolateral minithoracotomy (MT-MVS) approach. The aim of this study was to quantify the effects of MT-MVS compared with those of ST-MVS on morbidity and mortality among patients who underwent prior cardiac surgery through a sternotomy. The MEDLINE and EMBASE databases were searched through 1 November 2017. Data regarding mortality, stroke, reoperation for bleeding and length of hospital stay were extracted and submitted to a meta-analysis using random effects modelling and the I2-test for heterogeneity. Six retrospective observational studies were included, enrolling a total of 777 patients. In a pooled analysis, MT-MVS demonstrated reduced mortality rates compared to a standard sternotomy [odds ratio (OR) 0.41, 95% confidence interval (CI) 0.18-0.96; P = 0.04]. MT-MVS was, moreover, associated with reduced length of hospital stay [difference between the means was -3.81, 95% CI -5.53 to -2.08; P < 0.0001) and reoperation for bleeding (OR 0.32, 95% CI 0.10-0.99; P = 0.0488). The incidence of stroke was similar (OR 1.51, 95% CI 0.65-3.54; P = 0.34), all in the absence of heterogeneity. In conclusion, reoperative minimally invasive MVS through a minithoracotomy is a safe alternative to standard sternotomy, with reduced mortality rates, length of hospital stay and reoperations for bleeding and a comparable risk of stroke. However, because the existing literature provided limited, low-quality evidence, more methodologically rigorous randomized controlled trials are needed.