[ Scientific Activities - Actividades Científicas ]
Minimally invasive direct coronary artery bypass
vessel disease of the LAD.
Pr. Piet W Boonstra MD, PhD
Department of Thoracic and Cardiovascular Surgery
University Hospital of Groningen
Thoraxcentrum, University Hosp
|Indication to MIDCAB|
IntroductionMinimally invasive coronary direct artery bypass (MIDCAB) surgery is a procedure that avoids the use of open invasive surgery in favor of closed or local surgery causing less trauma than conventional coronary surgery and allowing shorter hospital stay.
Indication to MIDCAB
Minimal invasive coronary surgery via anterolateral
thoracotomy (MIDCAB) is especially suited for surgical revascularization of the left
anterior descending (LAD) and diagonal branches.
Some anatomic, morphologic and functional conditions are required to perform MIDCAB.
An adequate size and function of the left internal mammary artery (LIMA) is mandatory. Therefore, left subclavian artery stenosis is a contraindication.
There are also angiographic criteria related to the condition of the LAD. Diffuse calcification and intramyocardial course are contraindications for MIDCAB.
Chest wall deformities and previous traumas of the chest are relative contraindications as well as previous pleurodesis or severe pleural adhesions due to infectious diseases as tuberculosis.
Also previous pericarditis especially if presenting with sclerotic scaring and calcification may inhibit adequate exposure of coronary vessel. Conversely, pericardial scaring do not represent a contraindication in the case of reoperative coronary surgery. In fact, the danger of the reoperations is mainly hidden in the reopening of the sternum and in the manipulation of the heart and the old grafts [13-15]. If only the LAD needs to be revascularized and the LIMA has not been used previously, MIDCAB may become an alternative technique for reoperative coronary surgery [16,17]. The decreased motion of the heart due to the pericardial adhesions, makes the MIDCAB easier and thus attractive in these patients; re-sternotomy and cardiopulmonary bypass are not required thus reducing the risk.
Patients having an expected high complication rate of PTCA (with or without stent implantation) are considered eligible for MIDCAB either [18,19].
Beside cardiac and anatomic factors, the potential benefit for the patient by the avoidance of cardiopulmonary bypass may strongly influence the indication for a MIDCAB. Especially in patients with preexisting organ dysfunction, additional deterioration due to the adverse effects of cardiopulmonary bypass may be expected. Therefore, MIDCAB should be preferred in patients with chronic obstructive pulmonary disease, insulin-dependent diabetes mellitus, renal or liver insufficiency and previous cerebro-vascular accidents.
In case of coexisting malignancies and caogolupathies,
for which cardiopulmonary bypass might be critical, MIDCAB can be an attractive surgical
Additional cardiac dysfunctions as reduced left ventricular function, moderate valvular dysfunction, arrhythmia or unstable angina pectoris do not contraindicate MIDCAB and can be managed by adapting the anesthesiological regimen.
Central and peripheral cannulation carry an additional risk in case of extensive aortic or peripheral sclerosis and previous prosthetic grafting. In these cases MIDCAB may represent a valuable alternative.
Finally, young healthy patients whit a severe stenosis or occlusion of the LAD are ideal candidates for this type of surgery because they will benefit from the long term patency of the mammary artery conduit with a minimally invasive operation. In addition, in case of further progression of coronary artery disease with involvement of other coronary vessels, these patients can be re-operated through a midline sternotomy without the increased risks of a re-sternotomy.
Slide 1 and slide 2 summarize indication and contraindication to MIDCAB.
Several surgical devices specifically developed for
MIDCAB and coronary stabilizators are currently available.
Although surgical methods are still evolving, two general approaches of MIDCAB are currently used for the revascularization of the left anterior descending coronary artery with the left internal mammary artery.
The most prevalent approach for MIDCAB (open technique) is through a short (8-10 cm) left antero-lateral thoracotomy; the left internal mammary artery is harvested under direct vision and the mammary-to-coronary anastomosis is performed on the beating heart without cardiopulmonary bypass. This technique can be performed using conventional surgical instruments and video-scopic devices are not required. Single lung ventilation is preferred.
The second approach is video-thoracoscopic (closed technique), with multiple thoracic ports for the exposure and the manipulation of the left internal mammary artery; then the mammary-to-coronary anastomosis is performed under direct vision through a minimal (3-5cm) anterior thoracotomy on the beating heart without cardiopulmonary bypass [20-23]. The advantages of the closed technique are the possibility to obtain longer mammary pedicles than with the open technique and the possibility to avoid excessive stretching of the wound thus reducing postoperative pain. This technique must be performed using endosurgical instruments and video-scopic devices.
Open technique MIDCAB. A skin incision of approximately 8-10 cm is made halfway on an ideal line between the sternal notch and the lower left part of the chest (slide 3), usually corresponding to the fifth intercostal space . The medial edge of the incision is therefore 3 to 4 cm lateral to the mammary artery. Once the pleural cavity has been opened, the lung is deflated and the mammary artery is identified by palpation. At this moment (or later, according to the surgeons preference) the pericardium can be opened in order to inspect the target coronary artery and to find a proper site for the anastomosis, the overlying pericardial fat is dissected free, creating a flap that will be used at the end of the procedure to cover the mammary-to-coronary anastomosis. The use of the front lamp and optical magnification are recommended to provide an optimal visualization.
A specially adapted wound spreader is secured in place and gently opened in order to avoid rib fractures. The particular shape of the spreaders arms creates a visual tunnel toward the mammary artery, by retracting while pushing downward the sixth rib, at the same time retracting and pulling upward the fifth rib. The mammary artery is harvested as a pedicle from the 1st rib down to the 7th intercostal space, starting at the level of skin incision. The visualization of the distal part of the mammary pedicle is carried out by twisting (180 degrees) the wound spreader. After the mammary artery has been harvested, the wound spreader is replaced by another spreader that carries a coronary artery stabilizer (slide 4).
Then the heparin is given (100 IU/kg) and the mammary pedicle is divided. The target coronary artery is surrounded by two looping 5-0 polypropylene sutures, proximally and distally to the chosen site for the anastomosis. The stitches of the occluding suture should be as deep as possible, incorporating the thickest amount of tissue around the artery. This prevents the risk of damaging the coronary artery and provide a buttressing effect of the suture (slide 5). In order to test the tolerance to regional ischemia the coronary artery may be briefly occluded by means of the two looping sutures. The occluding sutures may also be used to produce short periods of coronary occlusion as a mean of ischemic preconditioning. Then the coronary stabilizator is adjusted and locked into place, centering the target coronary artery between the tines. The target coronary artery is opened longitudinally, the two looping sutures are pulled to provide an adequate hemostasis and the mammary-to-coronary anastomosis is performed with a running 7-0 or 8-0 polypropylene suture. After the anastomosis has been completed, the two looping sutures are cut and the coronary stabilizer is removed. In order to avoid kinking, the mammary pedicle is secured into place by means of two or three 5-0 polypropylene stitches, and the anastomosis may be covered with the flap of pericardial fat. No protamine is given at the end of the procedure unless excessive bleeding occurs .
The small thoracotomy wound is closed in layers and one
pleural drain is left in place.
Closed technique MIDCAB. Recently, the technical details of thoracoscopic harvesting of the internal mammary artery have been extensively reported [20-23]. This procedure is performed through multiple (4~5) thoracic ports and allows a complete dissection of the mammary from its origin at the subclavian artery to the 6th intercostal branches with transsection of all collateral branches.
The thoracoscopic instruments and the thoracoscope are introduced in the chest through three 15mm incision trocars at the level of different intercostal spaces, according to surgeons preference: 4th and 7th intercostal space; 4th and 6th intercostal space along the median axillary line and 5th intercostal space along the anterior axillary line; 3rd, 4th and 5th intercostal space along the posterior axillary line
This procedure enlarges the field of minimally invasive coronary artery bypass grafting techniques.
Clinical experience at the Groningen University Hospital
From January 1995 to January 1999 211 patients (male/female ratio, 174/37; mean age, 60±10) underwent primary MIDCAB according to the open technique in our Institute. In 209 patients a small left thoracotomy was performed, anastomosing the left internal mammary to the LAD; in 7 cases (3.3%) a sequential graft on the first diagonal branch and the LAD was performed. In 2 patients (0.9%) a right internal mammary was anastomosed to the right coronary artery via a small right anterolateral thoracotomy. The mean length of the mammary pedicles was 16±1 cm. The mean operative time was 87±25 minutes. The mean occlusion time of the coronary artery was 9±4 minutes (range 5-30 minutes). We recorded two in-hospital deaths (0.9%). In 5 patients (2.4%) MIDCAB was converted to a midline sternotomy and the anastomosis of the left LIMA was made after cardioplegic arrest. In 7 patients (3.3%) a perioperative myocardial infarction occurred. Mean postoperative ventilatory support was 8 ± 5 hours ranging from 0 to 32 hours. Mean postoperative bleeding was 264±330 ml and two patients (1.4%) required donor blood transfusions. Mean hospital stay was 4±1.9 days One reoperation for bleeding occurred. In 14 patients (6.6%) we recorded atrial fibrillation postoperatively (slide 6, slide 7).
MIDCAB opened a new era in the treatment of the isolated disease of the
LAD [6, 17-19, 20-23, 25]. In fact, along with the precise definition of the indication
for surgery, the evolution of basic technical concepts and the development of specific
surgical instruments have made MIDCAB easy and therefore widely accepted.
However, conventional coronary surgery with the use of cardiopulmonary bypass is an established and safe technique for the treatment of coronary artery disease and is currently the most frequently performed surgical procedure in industrialized countries. In addition, the avoidance of cardiopulmonary bypass and the use of a minimal surgical access may increase the technical difficulty of coronary surgery and some investigators have expressed caution concerning an excessive rate of anastomosis failure [26-30].
Prospective randomized clinical trials comparing MIDCAB to both coronary angioplasty and conventional coronary surgery in selected groups of patients are now going on to define which is the best treatment with coronary artery disease. The results of these ongoing studies will shed further light on this issue. (slide 8)
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Marco G. Lanfranconi, MD
Jan G. Grandjean, MD,PhD
Massimo A. Mariani, MD, PhD
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