Background

Minimally invasive cardiac surgery has recently become more and more popular. Despite median sternotomy as the most common approach to the heart, alternative approaches, in particular minithoracotomy, are being used more and more often. The first procedures for congenital and acquired heart diseases via right-sided minithoracotomy were performed in the mid-90s [1—3]. Currently, new technologies of cardiopulmonary bypass, special surgical instruments and thoracoscopic assistance ensure more favorable outcomes after minimally invasive surgery. Right-sided minithoracotomy has a number of advantages compared to median sternotomy: reduced surgical trauma, preserved chest stability, reduced postoperative pain syndrome, accelerated postoperative recovery, reduced number of infectious complications and excellent cosmetic effect. However, there are some disadvantages too: higher duration of surgery, cardiopulmonary bypass and myocardial ischemia [4—7].

The purpose of this study was to evaluate the immediate results of heart valve repair through right-sided minithoracotomy in our center.

Material and methods

Patient characteristics

There were 41 interventions via right-sided minithoracotomy for the period from July 2017 to March 2020 in our department. The sample included 11 men (26.8%) and 30 women (73.2%). Age of patients ranged from 17 to 74 years (mean 49.5 ± 13.6 years). Mitral valve disease was diagnosed in 27 (65.9%) patients, atrial septal defect — 10 (24.4%) patients, myxoma — 2 (4.9%) patients, tricuspid valve disease — 1 (2.4%) patient, mitral valve disease with atrial septal defect — 1 (2.4%) patient. Preoperative characteristics of patients are summarized in Table 1. Left ventricular ejection fraction was normal (mean 63.7 ± 4.8% (range 55 — 75%)). Most patients had heart failure NYHA class III (56.1%). In 28 patients with mitral valve diseases, the etiological factors were as follows: connective tissue dysplasia — 18 (64.3%) cases, chronic rheumatic heart disease — 6 (21.4%) cases, secondary infective endocarditis in remission — 4 (14.3% ) case. Tricuspid valve disease was caused by secondary infective endocarditis in remission in a patient with connective tissue dysplasia. Euroscore II value ranged from 0.5 to 2.75% (mean 1.04 ± 0.5%), i.e. there was low surgical risk in all cases.

Table 1. Preoperative characteristics of patients

Note: BMI — body mass index, BSA — body surface area, CAD — coronary artery disease, COPD — chronic obstructive pulmonary disease, AF — atrial fibrillation, EDD — end-diastolic dimension, ESD — end-systolic dimension, LA — left atrium.

Statistical analysis

Statistical analysis was carried out using parametric and nonparametric methods. Accumulation, correction, systematization of initial data and visualization of results were performed in Microsoft Office Excel 2007 spreadsheets. Statistical analysis was carried out using the IBM SPSS Statistics v.23 software (IBM Corporation). In case of normal distribution, quantitative variables were pooled in variational series with calculation of mean (M) and standard deviations (SD).

Surgical features

Induction anesthesia was ensured in accordance with standard protocol and bilateral mechanical ventilation. The patient’s position was left posterior oblique under 20—30°. External defibrillator pads were used. Surgical field wrapping was preceded by marking of chest and inguinal incisions, jugular notch and xiphoid process (Fig. 1).

Fig. 1. Surgical team location.

A 5—6-cm skin incision was made under the right mammary gland. Then, soft tissues were displaced and thoracotomy was performed in the 4^th intercostal space after preliminary lung deflation. Simultaneously, we performed surgical approach to the right femoral vessels. Pericardiotomy and imposing of stay-sutures were followed by deployment of silicone Soft Tissue retractor and hard retractor. Flexible 5-mm thoracoscopic system can be used for visualization convenience. Optic visualization was ensured through the main incision. CPB was established in “femoral artery — femoral vein” scheme. Venous cannula positioning was controlled by transesophageal echocardiography. Chitwood aortic clamp was inserted through an additional 1-cm incision in the 5^th – 6^th intercostal space along the middle axillary line. Aortic cross-clamping was followed by non-selective antegrade cardioplegia through a cardioplegia cannula. Custodiol was used for heart valve surgery. In other cases, we applied blood cardioplegia. Blood cardioplegia was accompanied by normothermic perfusion, crystalloid cardioplegia — hypothermia 32°C. We used left atriotomy along the interatrial sulcus for mitral valve repair and right atriotomy along the interatrial sulcus in other cases. Stay-sutures were imposed on the atrial wall and a retractor was placed into the atrial cavity. Atrial drainage was performed through an atriotomy. Then, we performed the main surgical stage (Fig. 2).

Fig. 2. Surgical wound.

All knots were extracorporeal and tightened using a pusher. Cardioplegia cannula was removed on-pump with adequate hemostasis. All patients underwent fixation of myocardial electrodes to the right ventricular myocardium and pericardium. Pericardium was sutured using interrupted sutures. Pleural drainage was carried out through the aperture for aortic clamp.

Results

Surgical procedures are presented in Table 2. Mean time of surgery was — 265 ± 73 min (range 165 — 578 min), CPB — 121 ± 42 min (range 55 — 246 min), aortic cross-clamping — 89 ± 32 min (range 33 — 169 min).

Table 2. Surgical procedures

Note: LA — left atrium.

Mean blood loss was 592 ± 206 ml (range 300 — 1300 ml). Inotropic and vasopressor support in early postoperative period was required in 6 (14.6%) cases. Mean ICU-stay was 1.1 ± 0.4 days (range 1 — 3 days).

Fig. 3. Duration of mitral valve repair, cardiopulmonary bypass and myocardial ischemia depending on surgical experience.

Conversion of surgical approach was performed in 2 (4.9%) cases. The first one was a 36-year-old patient with mitral valve disease following connective tissue dysplasia. Intraoperative examination revealed thickened mitral leaflet, myxomatous changes and elongation of subvalvular structures. Mitral valve repair with a Carpentier-Edwards 32 mm annuloplasty ring was performed. Hydraulic test confirmed adequate valve closure. However, CPB weaning was followed by TEE data on severe mitral insufficiency due to A2 chord detachment. Median sternotomy was followed by mitral valve replacement with a Carbomedics Optiform 27 mm mechanical prosthesis. Time of surgery was 578 min, CPB — 210 + 74 min, aortic cross-clamping — 149 + 57 min. Postoperative period was complicated by right-sided pneumonia. The patient was discharged in 15 days after surgery. This was the second surgery through the minithoracotomy.

The second case of conversion was a 61-year-old patient with mitral valve disease and funnel chest. We decided to start surgery through the right-sided minithoracotomy with possible enlargement up to complete thoracotomy. Unfortunately, visualization of the atrium was unsatisfactory. Surgical approach was enlarged up to complete thoracotomy and mitral valve replacement with a Carbomedics Optiform 29 mm mechanical prosthesis was carried out. Surgery time was 407 min, CPB — 246 min, aortic cross-clamping — 169 min. Postoperative period was complicated by right-sided pneumonia and hydrothorax, that required pleural drainage. The patient was discharged in 11 days after surgery. This surgery through the minithoracotomy was the ninth. Characteristics of postoperative complications are presented in Table 3. Various postoperative complications occurred in 12 (29.3%) patients. There was no mortality. Mean postoperative hospital-stay was 6.5 ± 2.1 days (range 3 — 15 days).

Table 3. Postoperative complications

Note: LA — left atrium.

Postoperative scar 1 month later is shown in Fig. 4.

Fig. 4. Postoperative scar in 1 month after surgery.

Discussion

Various studies devoted to heart valve surgery through alternative approaches to median sternotomy have appeared since 1996 [1]. Navia J. and Cosgrove D. [8] reported a right parasternal approach. However, this method required resection of III-IV rib cartilages and ligation of the right internal thoracic artery. Loulmet D. et al. [9] described partial sternotomy with ligation of the right internal thoracic artery. We use the right-sided anterior minithoracotomy in the 4^th intercostal space proposed by Carpentier. In contrast to parasternal approach and partial sternotomy, this technique does not require resection of cartilages or ribs, as well as ligation of the right internal thoracic artery. Moreover, this approach preserves chest function. Another advantage is available fast conversion to thoracotomy. Despite small incision of 6—7 cm, exposure of mitral, tricuspid valves and interatrial septum is satisfactory. There is no excessive traction of ribs and chest tissues that reduces postoperative pain and improves quality of life [10].

Indications for heart valve surgery through a right-sided minithoracotomy in our study were the same as for traditional approach through a median sternotomy. According to various authors, contraindications for surgery through a right-sided minithoracotomy are peripheral artery disease with lesions of femoral and iliac arteries, previous chest irradiation, adhesions in the right pleural cavity, mitral annulus calcification, severe scoliosis and chest abnormalities [11, 12]. In our study, there were patients with scoliosis that impaired exposure and prolonged surgery. There was also a patient with a funnel chest deformity. An exposure was so unsatisfactory that conversion to thoracotomy was required. Thus, severe chest deformities require careful preoperative analysis due to possible contraindications for minimally invasive approach.

Endovascular treatment of ASD with occluders is currently preferred. However, surgery via minithoracotomy is an acceptable alternative in case of technical impossibility of endovascular procedure [13]. In our study, there was no at least one rim of ASD in all cases. Therefore, endovascular closure was accompanied by certain technical difficulties. However, surgery through minithoracotomy was effective even for ASD combined with partial abnormal drainage of pulmonary veins.

Resection of myxoma trough a right-sided minithoracotomy is largely limited by dimension and localization of tumor. Lee N. et al. [14] reported less time of CPB and aortic cross-clamping for sternotomy while postoperative blood loss and incidence of arrhythmias were less in the minithoracotomy group. Hospital-stay and mortality were similar. In our study, there were 2 cases of LA myxoma and no complications. Further follow-up is required, but early outcomes suggest minithoracotomy is a possible alternative to sternotomy.

Many authors describe a learning curve for surgery through minithoracotomy. The number of interventions required to master the technique varies and, apparently, depends on individual characteristics of surgeon. Mitral valve replacement is recommended at initial stages since this procedure is technically easier than mitral valve repair [15, 16]. According to our data, duration of surgery is gradually decreased over time. Further researches are required to estimate the length of learning curve.

Conclusion

Cardiac surgery through a right-sided minithoracotomy is safe and effective alternative to median sternotomy. This approach preserves chest stability, accelerated postoperative recovery and has an excellent cosmetic effect. Severe chest deformities require careful preoperative planning as relative contraindications for right-sided minithoracotomy. Unsatisfactory visualization can require conversion to complete thoracotomy. Accumulation of experience reduces duration of these procedures.

The authors declare no conflicts of interest.