Introduction

The aim of minimally or less invasive techniques in coronary artery bypass grafting (CABG) is to reduce surgical trauma and morbidity of cardiopulmonary bypass and thereby to shorten length of stay in the intensive care unit as well as total hospital length of stay [₁]. Access to the target coronary vessels by the new minimally invasive direct coronary artery bypass grafting (MIDCAB) techniques is gained via minithoracotomy [1,₂], ministernotomy [₃] and parasternal [₄] or subxiphoid incisions which are thought to cause less trauma to the patient than standard sternotomy. Rates of wound infections after MIDCAB cannot be estimated at present and exact techniques to treat these complications have not yet been reported.

Procedure

A 44 year old man was scheduled to undergo left internal mammary artery (LIMA) bypass grafting to the left anterior descending artery (LAD) via a left anterior fourth interspace minithoracotomy for an 80 % complex proximal LAD stenosis. A 12 cm skin incision was performed starting at the sternocostal junction of the fourth rib, extending over the rib and crossing an area about 2 cm below the left nipple. Subcutaneous tissue and the pectoralis major muscle were divided. After division of the intercostal muscles and opening of the pleura a standard rib spreader was inserted. The left lung was collapsed using a double lumen oral airway. Dissection of the left internal mammary artery was started at the sternal border of the minithoractotomy using electrocautery. To facilitate dissection the fourth rib was exarticulated from the sternocostal joint. Dissecetion of the IMA graft was carried out up to the cranial border of the second rib. The IMA dissection time was 85 min.

The pericardium was then opened to expose the LAD. The vessel was encircled proximally and distally to the planned anastomosis site by 3/0 Prolene sutures. After 5 min of ischemic preconditioning by occluding the target vessel and 5 minutes of reperfusion the LAD was incised and an anastomosis with the LIMA graft was performed on the beating, Esmolol treated heart. The LAD anastomotic time was 17 min. A 24 F chest tube was inserted. The fourth rib was reattached to the sternum using 0/8 PDS , two pericostal sutures were placed and the pectoralis major muscle was sutured in two layers. As the skin of the minithoracotomy incision appeared contused a 0,5 cm margin was excised together with subcutaneous fat. Povidone iodine solution was instilled locally and subcutaneous fat and skin closed using 0/0 Vicryl and a 3/0 Vicryl subcuticular running suture. Total operative time of the procedure was 220 min.

The patient was extubated 8 hours postoperatively and discharged from the intensive care unit after 20 hours. He was ambulated on the evening of the first postoperative day and received an oral diet at the same time. The chest tube was removed 48 hours postoperatively. There were no signs of myocardial ischemia on serial ECG recordings. The CK maximum was 469 U/l without a significant MB fraction, there was a slight temperature elevation to 37.8 °C during the ICU course. At discharge on the 5th postoperative day the minithoracotomy showed signs of contusion (slight hematoma and swelling). The patient was transferred to another hospital.

On the 10th postoperative day abscess formation was noted at the minithoracotomy site and the abscess was treated by incision and counterincision at the outside hospital. The patient was readmitted to our unit on the 19th postoperative day with two large wound defects extending onto the fouth rib (Fig. 1). Bacteriology findings were negative at re-admission and the wound edges showed clean granulation tissue. The patient was scheduled for repair of the defect using a pectoralis major muscle flap.

After radical debridement of soft tissue, necrotic as well as badly perfused parts of the fourth rib were removed. Access to the pectoralis major muscle was obtained through the presented incisions by elevating skinflaps from the prepectoral fascia, proceeding from the medial to the lateral border of the muscle. An additional 3 cm incision was placed in the anterior axillary fold for division of the muscle insertion. The insertion and the origin of the pectoralis major were completely divided and the muscle was transposed medially and caudally attached only to its vascular pedicle (thoracoacromial vessels). It was then sutured to the sternum and to the anterior layer of the rectus abdominis muscle sheath using 2/0 Vicryl. The wound was rinsed with Neomycin solution and three 14 F drains were inserted. Wound closure was performed using 3/0 Vicryl and 4/0 Prolene.

The drains were removed on the 3rd postoperative day. No further wound healing problems occurred and the patient recovered uneventfully.

Comment

Deep wound infection following coronary artery bypass grafting via sternotomy represents a serious postoperative problem and mortality rates are exceedingly high [₅]. One argument of introducing mini incisions in coronary artery bypass surgery was to reduce the risk of deep sternal wound infections. Our case shows that deep wound infection of a minithoracotomy approach might as well present as a serious surgical problem. The recent literature has not yet reported on infectious complications after MIDCAB procedures. We attribute the development of wound infection in our case to the long total operative time which can be explained by the fact that the case described was one of the first MIDCAB procedures performed at out department and that a learning phase was certainly present. Standard prepping and draping procedures as well as standard prophylactic antibiotic treatment were applied. Prolonged spreading of a small thoracotomy for nearly four hours might have caused contusion to the wound edges. We explain the postoperative CK elevation without a significant elevation of the MB fraction in part by mechanical damage to the great pectoralis muscle. Necrotic muscle might have been the basis development of infection after bacterial contamination. As special instruments for MIDCAB procedures are currently designed and commercially unavailable at present a standard rib spreader had to be used. Compression and reduced perfusion of the retracted tissue seem to be the major factors contributing to the unexpected postoperative course. As a consequence of the points discussed above we try to relax the rib spreader several times during MIDCAB procedures in order to avoid irreversible tissue damage.

Repair of chest wall defects by a pectoralis muscle flap [₆] is routinely performed at our institution and this was the reason why we chose this strategy. The case described might show that deep wound infections after MIDCAB procedures can be treated by radical debridement and defect coverage by a pectoralis major muscle flap. If infections after application of mini-incisions in coronary artery bypass surgery are less frequent and less life threatening than deep sternal wound infections after conventional coronary artery surgery needs to be demonstrated.