Minimally invasive (MI) cardiac surgery is a safe procedure with similar mortality and morbidity, but better surgical outcomes compared with conventional sternotomy (MS) in some groups of patients.1^-4 The potential benefits of MI procedures include better stability of the sternum in the postoperative period, with implications on deep infection prevention, improvement of respiratory function, mobility and bleeding.5 The MI approach was introduced to reduce surgical trauma with better cosmetic results; this approach is currently applied to procedures including valve and septal defect surgeries.6^,7

Pain has been shown to be one of the primary sources of concern in surgical patients,8 even though it is expected in the postoperative (PO) period. Inadequate management of pain can have profound clinical (deep vein thrombosis, pulmonary embolism, coronary ischemia, myocardial infarction, pneumonia, and poor wound healing) and psychological (insomnia) implications that increase morbidity and mortality.8^,9

In the last few years, there has been a significant increase in knowledge about PO pain and tissue trauma that influence the choice for MI surgical procedures.1^,9 Although a median sternotomy (MS) remains the main access in cardiac surgeries, the intercostal access combined with a MI approach has been progressively used.2^,3^,5^,6^,10 Systematic assessment and treatment of pain is essential after cardiac surgery and can contribute to a faster recovery and rehabilitation of patients.11 Some studies have reported less PO pain and shorter in-hospital stays after a MI procedure,1^,3^,12^-14 but the literature lacks a comparative study between MS and MI procedures regarding pain intensity (PI). This prospective observational study aims to evaluate the PO thoracic PI by comparing patients subjected to a MI and MS procedures. We evaluated if patients with valve and septal defects subjected to MI procedure have less PO pain compared with those undergoing MS.

Demographic and clinical data, including the presence of cardiovascular risks factors in the study groups are described in Table 1. Most patients were women, and age was not different between the groups. Weight and BMI were different between the groups, probably due to the non-inclusion of patients with BMI > 32 kg/m2 in the MI group. The prevalence of comorbidities was not relevant, except for systemic arterial hypertension. Mitral valve insufficiency was the main diagnosis, followed by ostium secundum atrial septal defects, mitral valve stenosis, and ostium primum atrial septal defects.

Patients were subjected to mitral valve surgical repair or replacement (MS n = 11 and MI n = 9) or surgical closure of an atrial septal defect (MS-n = 6 and MI-n = 8). Procedures for mitral correction included bioprosthetic replacement (7 in the MS group and 8 in the MI group) and mitral valve repair (4 in the MS group and 1 in the MI group). Valve resection, valve reconstruction, and semi-rigid ring annuloplasty were the main procedure for mitral repair. In the MS group, one patient required a Neochord placement, and no patient was subjected to pulmonary vein isolation. Regarding the procedures for atrial septal defect closure, there were one suture closure and five patch closures in the MS group and three suture closures and five patch closures in the MI group.

Table 2 lists the PO data for the MS and MI groups. The MS procedure time was shorter than MI procedures. No difference was observed in mean aortic cross-clamping time or cardiopulmonary bypass time between the groups. Despite longer procedural times, MI patients needed less intensive care unit time for recovery in comparison with MS patients (Table 2). Mean hospital stay after the procedure was longer in the MS than in MI group. None of the patients had major complications, stroke or death after the surgery.

The PO pain evaluation indicated that most of the patients reported pain on the third PO day (MS = 94.1% and MI = 88.2%; p = 0.5410). On the seventh PO day, significantly more patients were free of pain in the MI group compared with the MS group (MS = 94.1% and MI = 64.7%; p = 0.0341). The patients in the MI group reported fewer pain sites than the patients in the MS group (Figure 1) on the third (MS = 3.2 ± 1.5; MI = 1.5 ± 1.2; p = 0.001) and seventh (MS = 3.1 ± 1.4; MI = 0.9 ± 0.9; p = 0.000) PO day.

Figure 1

The main sites of pain were those related to the surgical incision site. The upper area of the sternum (around the manubrium) was more painful for the MS group and the right submammary region was more painful for the MI group (Table 3). PI was different between the groups. The MS group had more intense pain than the MI group on the third PO day and on the seventh PO day. The MS group showed a mean of 5.3 ± 2.0 of maximal PO thoracic PI three days after the procedure, which was not significantly decreased on the seventh day after the surgical procedure (4.8 ± 2.2; p = 0.4931). The maximum PI reported by MI patients was significantly (p = 0.001) decreased from the third (3.0 ± 1.6) to the seventh PO day (1.2 ± 1.3). The comparison between groups demonstrated that the postoperative PI was higher and lasted longer in the MS group than in the MI group (p = 0.001) (Figure 2).

Figure 2

These data were in accordance with the medical necessity to control the symptoms. On the 3^rd PO day, all patients in the MS group and 16 patients in the MI group were receiving pain medications (p = 0.3052). On the 7^th PO day, 16 patients in the MS group and only six in the MI group were receiving pain medications (p = 0.0003).

The present study showed that, in patients undergoing surgical treatment for mitral valve and septal defects, 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 between MI and MS 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 adults24 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/m2 in the MI group. Despite this, we do not believe that BMI is directly related to PI in the PO period, as we do not report any complication related to higher BMIs in this period.

In addition, the number and sites of the incisions differed between the groups. The MS group had two thoracic incisions (main and chest tube incisions). The MI group had two incisions (thoracic and inguinal) and at least three right thoracic punctures. For the main incision, we used a wound protector for soft tissue34 to diminish intercostal retraction that could lead to nerve stimulation11^,35 during the procedure (e.g. valve replacement), which could be a cause of pain. We observed moderate to intense pain after both surgical approaches (MS and intercostal). According to the literature, at least 60% of the patients who underwent MS and MI procedures report moderate to severe pain in the early PO days.1 As expected, the main sites of pain were directly related to the surgical incision, i.e., the sternal wound for MS patients and the inframammary area for patients who underwent MI procedure, although the MS group also reported extra-wound pain sites (posterior thoracic area). Although MI procedure involves a higher number of incision/punctures, these patients did not report more pain sites as compared with those undergoing MS procedure.

Regarding PI, we observed that the most remarkable differences between the groups occurred on the seventh PO day. There were no significant differences in PI between the third and the seventh PO days in the MS group. This data agrees with the study by Mueller et al.,27 that indicated a slow reduction of thoracic pain following a sternal based procedure. On the other hand, there was a statistically significant reduction in PI from the third to the seventh PO days in the MI group. The presence of moderate to severe pain on the third PO day for both groups was in accordance with previous studies.1^,11^,23^,35^,36 Landrenaeu et al.,37 and Nagahiro et al.,38 compared conventional posterolateral thoracotomy with MI (video-assisted) thoracotomy procedures and verified that the MI approach promoted less postoperative PI. The advantages regarding PI and length of hospital stay for the MI procedures are well established1 and were corroborated in our study. In patients subjected to MI procedure, there was lower PO pain and need for pain medication, and shorter ICU and hospital stay (19 hours shorter and two and a half days shorter, respectively). It is worth mentioning that although the group differed in the presence of comorbidities, no PO complications related to these conditions were found in neither of the groups, such as hypertensive crisis or pulmonary complications.

This work resulted in important findings regarding PO pain, a symptom often overlooked by healthcare professionals dealing with cardiac surgery. Wildgaard et al.,11 noted that the strategies for PO pain control after thoracic procedures has evolved in the last years. However, inadequate pain management still affects the quality of life and postoperative outcomes of cardiac surgery patients,8^,9 whereas adequate pain control results in better rehabilitation after a cardiovascular surgical procedure. Thus, pain management is a challenging task, as it demands attention by health professionals in making correct decisions towards medications and PI ratings, considering patients’ pain tolerance and differences between protocols.

Despite all advances in the diagnosis and management of PO pain, accurate evaluation of this symptom is still very difficult, since the perception of pain and the response to pain medications vary widely between individuals. Also, the experience of the surgical team on MI procedures reduces possible complications of this type of surgery. A multicenter study involving larger number of patients should be performed to confirm the differences in PI reported in our study and to overcome the limitations of this study.

Patients subjected to a MI cardiac procedure reported lower PI and fewer pain sites from the third PO day on, and showed lower need for pain medication and shorter ICU stay when compared to those subjected to a MS procedure. Based on these results, our study reinforces the advantages of a MI procedure for valve surgery.