IJCS | Volume 33, Nº1, January / February 2019

30 Figure 2 - Pain intensity levels for patients undergoing minimally invasive cardiac surgery and median sternotomy on the third and seventh postoperative days. Box plot of pain intensity reported by the 34 patients (17 patients subjected to minimally invasive cardiac surgery, MI, and 17 to median sternotomy, MS) on the third (3 rd ) and seventh (7 th ) postoperative days. Squares, circles and triangles represent outliers. * p < 0.05 between groups (unpaired Student’s t-test) and within group (paired Student’s t-test). Silva et al. Minimally invasive surgery–pain investigation Int J Cardiovasc Sci. 2020;33(1):24-33 Original Article those subjected to MI procedure had less pain from the third PO day on and fewer sites of pain than the patients who underwent a sternal procedure. Our findings showed that a reduction in PI can lead to better recovery, indicated by shorter ICU and hospital stays as well as a diminished need for pain relief medications. In the 1990s, MI techniques were initially used in cardiac surgeries. 7,16–18 Meanwhile, Carpentier et al., 19 Chitwood et al., 20 Vanermen et al., 21 and Mohr et al., 22 established the MI approach for mitral valve surgery, and numerous studies started to report the feasibility, safety and efficacy of these procedures. 1–5 However, although many studies have evaluated the advantages of MI cardiac procedures, including pain sites and PI, in addition to hospital stay duration, 1–3,5,6,10,23 none of them performed a systematic comparison betweenMI andMS procedures regarding PO pain. In the current investigation, we studied patients with mitral valve disease and patients with septal defects, since these are among the most prevalent cardiovascular diseases among Brazilian adults 24 that can be addressed by either MI or MS procedure. The main surgical procedure was valve replacement followed by valve reconstruction, and the most common cause of valve dysfunction was inflammatory in both groups. The procedure time was longer in the MI group in comparison to the MS group, as reported in many other studies. 6,7,10,18,22,25–29 This difference was due to intrinsic characteristics of the MI procedure, which demands a femoral incision for echo-guided cannulation before the insertion of chest ports. Although a longer cardiopulmonary bypass and cross-clamp times may lead to higher mortality and morbidity, 30 Raja et al., 7 demonstrated that these adverse outcomes were not evident in the MI group. Differently from other studies on MI procedures, 28,31–33 we observed similar circulatory support and clamp times between the groups. These surgical variables are related to the complexity of the surgical procedure (mainly valve replacement) as well as the surgeon’s experience. In addition, the time for cardiopulmonary bypass could be reduced by percutaneous insertion of the cannula. Of note, the higher weight and body surface in the MS group was due to the exclusion criterion of a BMI greater than 32 kg/m 2 in the MI group. Despite this, we do not believe that BMI is directly related to PI in the POperiod, as we do not report any complication related to higher BMIs in this period.