Does full sternotomy have more significant impact than the cardiopulmonary bypass time in patients of mitral valve surgery?

Abstract

Background: Over the past decade, minimally invasive mitral valve surgery (MIMVS) has grown in popularity. Less invasive approaches to mitral valve surgery are increasingly used for improved cosmesis. We sought to compare these minimally invasive approaches fairly with conventional full sternotomy approaches by using propensity-matching methods. Methods: From January 2011 to January 2017, a total of 1120 isolated mitral valve operations were performed at our institution. Data were retrospectively collected on all patients, and a logistic regression model was created to predict selection to a minimally invasive versus conventional sternotomy approach. Propensity scores were then generated based on the regression model and matched pairs created using 1:1 nearest neighbor matching. There were 165 matched pairs in the analysis (sternotomy, n=165;MIMVS, n=165). Clinical outcomes included bypass and cross-clamp time, length of hospitalization, morbidity, and mortality. Patient details and follow-up outcomes were compared using multivariate, and Kaplan-Meier analyses. Results: The minimally invasive approach led to slightly longer cardiopulmonary bypass time (99±25 vs 88±17 min, p <0.001), and cross-clamp time (65±13 vs 49±11 min, p<0.001). Overall, no significant differences existed among major in-hospital complications between groups. There were no differences between the matched groups in 30-day mortality (1.2% vs 0.6%, p >0.05). However, Chest tube drainage was lower at 6 and 24 h after a minimally invasive approach (30±5 mL) and 120±20 mL than after conventional sternotomy 175±50 mL and 400±150 mL at these times (p<0.001). Transfusion was less frequent after minimally invasive surgery than after conventional surgery (15.7% vs 40.6%, p<0.001). Patients undergoing minimally invasive surgery spent less time on ventilation support (6.2±1.1 h vs 10.4±2.7, p<0.001). The multivariable regression analysis showed the full sternotomy was an independent risk factor for the propensity-adjusted likelihood of postoperative transfusion, re-exploration for bleeding, and postoperative ventilation support (p<0.05). But the duration of cardiopulmonary bypass time was not an independent risk factor. The mean duration of survival follow-up was 4.4±1.2 years. However, comparison of survival curves between the two groups revealed no significant difference (P=0.203). With regard to freedom from valve-related morbidity, there was no significant difference between groups (P=0.574). Conclusion: Within that portion of the spectrum of mitral valve surgery in which propensity matching was possible, minimally invasive mitral valve surgery has cosmetic, blood product use, and respiratory advantages over conventional surgery, and no apparent detriments. However, minimally invasive mitral valve surgery required a slightly longer cardiopulmonary bypass time and cross-clamp time. Minimally invasive mitral valve surgery represents a safe and effective surgical technique that we believe should be used more routinely in the surgical management of mitral valve disease. MIMVS provides equally durable midterm results as the standard sternotomy approach.