Eur J Cardiothorac Surg 1998;14:S13-S19
© 1998 Elsevier Science NL
Less-invasive coronary artery bypass grafting: different techniques and approaches
A Diegeler*,
V Falk,
K Krähling,
M Matin,
Th Walther,
R Autschbach,
R Battelini,
F.W Mohr
Clinic of Cardiac Surgery, University of Leipzig, Heartcenter, Leipzig, Germany
* Corresponding author. Tel.: +49 341 8651421; fax: +49 341 8651452.
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Abstract
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Objective: The aim of this study was to compare four different techniques for less-invasive coronary artery bypass surgery with and without cardiopulmonary bypass (CPB) in terms of feasibility as well as in terms of the intra- and postoperative course. Methods: One hundred and fourteen patients were divided into four groups, according to the surgical technique. Group I: minithoracotomy, internal thoracic artery (ITA) harvesting and anastomosis under direct vision using cardiopulmonary bypass (CPB) on the fibrillating heart (n=31). Group II: sternotomy and beating heart without CPB (n=13). Group III: MIDCAB with CPB and cardioplegic cardiac arrest using endo-aortic balloon-occlusion, Port Access system (n=9). Group IV: MIDCAB on the beating heart without CPB (n=61). In total, 104 single and ten double graft procedures were performed using the radial artery T-graft technique in seven cases (groups III and IV). Results: Harvesting of the ITA graft took 41±16.2 min in group I and could be reduced to 31±8.3 min in group IV by the use of a specially-designed retractor. Complications were: death (n=1, group I), myocardial infarction, (n=1, group I), early occlusion of the graft (n=1, group IV), early stenosis of the anastomosis (n=2, groups I and IV), late stenosis of the anastomosis (n=1, group IV), thrombosis of the femoral vein (n=1, group III). Postoperative ventilation, ICU and hospital stay were similar among groups. Conclusions: Based on our results, the following strategy has been developed: MIDCAB without CPB is the preferred technique for one-vessel graft procedures to the left anterior descendens (LAD) or RCA. The Port Access system (with CPB) is reserved as a second option for young patients requiring multiple-vessel grafting to the left coronary circulation (LAD/CX) and as a backup to avoid conversion. Sternotomy and an off-pump technique is used for single-vessel or multiple-vessel graft procedures in selected patients (emergency procedure, acute myocardial infarction, in the very obese).
Key Words: Minimally-invasive direct coronary artery bypass • Minimally invasive • Less invasive • Coronary artery bypass
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1. Introduction
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Minimally-invasive, or rather less-invasive, surgical concepts have gained wide acceptance in many surgical fields. Recently cardiac surgeons have focused their interest on less- or minimally-invasive approaches for coronary artery bypass graft surgery [1–6, 10, 18]. Although Kolessov [9]performed the first internal thoracic artery bypass graft to the left anterior descending artery through a lateral thoracotomy on a beating heart as early as in 1964, cardiopulmonary bypass (CPB) soon became the golden standard in coronary bypass surgery. Since Benetti [1]and Pfister [13]published their results of a large series of coronary artery procedures without the support of CPB, several surgical groups began to perform coronary bypass anastomoses with different less-invasive approaches [2–5, 14, 18]. Parallel to this development a catheter-based system for cardioplegic arrest using a endo-aortic balloon-catheter (Port Access system, Heartport, Redwood City, CA) has been introduced and applied successfully for less-invasive CABG surgery with cardioplegic arrest [14–17].
Minimally (less) invasive direct coronary artery bypass (MIDCAB) was performed at our institution from March 1996. The main object of our program was to evaluate both the MIDCAB approach and the beating-heart technique, as well as to develop an algorithm to determine when to apply any of the techniques to guarantee the best result for the patient. This implies a maximum of safety while at the same time limiting the surgical trauma. We report the results of the first 114 patients. A decision tree was developed that takes into account the advantages of the different approaches to facilitate patient selection for each procedure.
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2. Materials and methods
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From March 1996 to April 1997, 114 patients undergoing less-invasive bypass procedures at the University of Leipzig were included in the study. Four different revascularization techniques were used. Group I: MIDCAB with CPB on the fibrillating heart (n=31). Group II: sternotomy without CPB on the beating heart. Group III: MIDCAB approach, CPB and cardioplegic arrest using the Port Access system. Group IV: MIDCAB approach without CPB on the beating heart.
Total intravenous anesthesia was performed using a standard protocol, which included right-sided single-lung ventilation for all MIDCAB procedures. To maintain a stable core temperature we used regional surface warming, that covered the right lateral body surface (Warm-TouchTM Malincroth Medical, Hennef, Germany).
2.1 Access
Two different types of left antero-lateral thoracotomy were performed throughout the study. In group I and in four patients of group III an anterior minithoracotomy through the fourth intercostal space was performed. After dissection of the fourth and fifth ribs from the sternal adjunct, the internal thoracic artery was harvested up to the first intercostal space under direct vision. After completion of the anastomosis the ribs were reconnected to the sternal adjunct using VicrylTM sutures (Ethicon, Sommerville, USA).
In group IV and in five patients of group III, the thoracotomy was performed more laterally, using a special retractor (CTS-CardioThoracic Systems, Cuportina, CA). Harvesting of the internal thoracic artery (ITA) graft was performed from a lateral view without resection or dissection of any part of the ribs. The most proximal anatomical structure visualized with this approach was the brachiochephalic vein.
2.2 Technique of distal anastomosis
2.2.1 Beating-heart technique without CPB
After sternotomy or lateral minithoracotomy and opening of the pericardium, the target coronary artery was identified and dissected from the surrounding tissue. To prevent bleeding from the coronary artery, it was snared proximally and distally by a soft vessel loop retractor (MediloopTM, Medipoint, Hamburg, Germany). in addition an airblower (Jostra, Hirrlingen, Germany) was used. Two differently-designed instruments were used for surface stabilization (CTS-CardioThoracic Systems or Autosuture, Elancourt, France) to immobilize the anastomotic site. After incision of the coronary artery, the anastomosis was performed by the usual parachute technique with a continued suture 8/0 ProleneTM (Ethicon). A reduction of the heart rate with Esmolol and Adenosine was only used in the first patients of group II, when surface stabilization was not yet available.
2.2.2 Cardioplegic arrest with the Port Access system (group III)
Cardiopulmonary bypass was employed by femoro–femoral cannulation. Using an endo-aortic balloon catheter system (Heartport, Redwood City, CA) as described elsewhere [16, 17], the aorta was occluded by a balloon and cardioplegia (Brettschneider HTK; Köhler, Alsbach-Hänlein, Germany) was delivered into the aortic root through the catheter.
2.3 Quality control
ITA graft flow was measured using a transit-time ultrasonic flow probe (CardioMed CM 4000, Norwegian) intra-operatively. Recently we introduced an endoscopic thermo-angiographic probe for patency control of the ITA-graft in MIDCAB procedures [6]. After discharge from ICU, angiography of the ITA graft was performed between the 2nd and 5th postoperative days. During follow-up, a second angiography was performed 6 months postoperatively.
Myocardial infarction was defined as more than 10% of the ratio of peak CK-MB to peak total CK on three consecutive samples together with the onset of a new Q-wave (Minnesota Code for pathologic Q-wave). All data were expressed as mean±SD.
2.4 Results
2.4.1 Demographics
Preoperative demographics were comparable for groups I–IV as depicted in Table 1
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2.4.2 Procedures
All patients in group I were operated on between March and November 1996. Duration for ITA graft harvesting was 40±6 min and considerably increased compared to group IV (30±3 min) when using a more lateral access and the CTS retractor. We started to combine limited access surgery (MIDCAB) and the beating-heart technique (group IV) in November 1996. Since that time, operation on the fibrillating heart was abandoned. A single graft procedure was performed in 104 patients, a double graft procedure in ten cases, in seven using the radial artery for a T-graft to the diagonal or intermedius branch and the ITA graft. Intraoperative data are listed in Table 2
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2.4.3 Complications and early follow up
Two patients of group I and six patients of group IV had to be converted to a standard sternotomy and CPB; CPB alone was necessary in two patients (femoro–femoral cannulation). Among these, conversion was necessary for anatomical reasons in six patients due to an intramyocardial running and/or diffuse diseased left anterior descendens (LAD). In one patient myocardial depression and arrhythmia occurred during ischemic preconditioning. In one patient a right ventricular injury due to a vessel loop which snared the proximal LAD could only be treated with the help of cardiopulmonary bypass.
There was one major complication in group I. Ventricular fibrillation occurred in a patient 10 h after the procedure without preceding signs of ischemia or myocardial dysfunction. Since patency of the graft could be confirmed during re-exploration, the reason for sudden onset of non-convertible ventricular fibrillation was unclear, with a questionable relation to the minimally-invasive technique. After CPB and reoperation, the patient died on postoperative-day 13, due to progressive cerebral edema. There was one early stenosis at the anastomotic site in group I and group IV, respectively. Both patients were re-operated using a conventional technique. All patients had patent grafts at postoperative angiographic control in group II and III respectively.
All radial artery T-grafts in group III and IV were patent on post-op angiography. One patient in group IV had a late graft stenosis at 4 months postoperatively. He was successfully treated by PTCA. There was one patient in group III with a thrombosis of the femoral vein after cannulation for CPB. Other intra- and postoperative complications are listed in Table 3
and Table 4
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3. Discussion
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The invasiveness of cardiac surgery is determined by the type of access, the use or non-use of extracorporeal circulation and the use of cardiac arrest. New techniques termed less- or minimally-invasive approaches have been introduced recently [3, 4, 15]. At present there is no agreement about the term `minimally-invasive'. Several groups are using different surgical techniques named minimally-invasive coronary bypass surgery depending on a limited approach, the off-pump technique or both. Following the goal of reduction of the surgical trauma in patients undergoing coronary bypass surgery, we prospectively evaluated a less-invasive approach to the heart avoiding the use of cardiopulmonary bypass.
3.1 Special considerations in anesthesia
Single-lung ventilation (right lung) was performed in all patients with a MIDCAB approach. Patients with severe obstructive lung disease or limited ventilation capacity should be excluded, as in this series. In all but one patient, single-lung ventilation was well tolerated. In terms of an early postoperative extubation, Kaliumchloracepat 20 mg combined with Clonidine 150 mg was used for premedication 1 h before surgery. Anesthesia was induced by a bolus application of Sufentanil and Propofol, was maintained by continued application of these drugs and was stopped during the closure of the chest. In terms of postoperative pain from the lateral thoracotomy, which is present in most of the patients, special anesthetic techniques for intercostal nerve blockade may be useful for early postoperative extubation. We used an intercostal application of Bupivacaine 0.5%. It is very important to avoid a reduction of core temperature below 35°C. With a warm airflow sheet to cover the right lateral surface of the body, core temperature could be kept above 35.3°C.
3.2 Surgical techniques
To minimize the negative effects on performance that are associated with the introduction of a new technique, we started our program with a limited access (MIDCAB), but still using cardiopulmonary bypass to perform the anastomosis on the fibrillating heart (group 1). In these first patients, the limited thoracotomy was performed by dissecting two ribs from their sternal connection. Although the ribs were reconnected to the sternum, two wound problems and prolonged postoperative pain in this group indicated a still traumatic approach. The more lateral MIDCAB approach, using the CTS retractor without rib dissection, is clearly less traumatic. In group IV we did not observe any severe wound-healing problem or prolonged postoperative pain.
In the beginning of our study we started with coronary bypass surgery on the beating heart without CPB (group II) but still using a sternotomy. Using this conventional access it was possible to perform grafts to the right coronary artery or to perform double-vessel grafting to the LAD, the RCA and even the diagonal or the intermedius branches. In addition, two emergency patients were operated on by this technique, one of whom had an acute occlusion of the LAD after failed PTCA, and another with acute myocardial infarction and severely impaired ventricular function.
3.3 Port Access system for cardioplegic arrest
We used the Port Access system for coronary bypass surgery (group III), having the advantage of the limited access and still the comfort to perform the anastomosis on an arrested heart and a bloodless surgical field. A complete cardioplegic cardiac arrest could be established in all of our patients. Placement of the endoclamp was technically more demanding compared to a conventional cross clamp technique but was safe in this study. Intraoperative monitoring by fluoroscopy and transesophageal echocardiography is essential [6]. In one of these patients, the coronary artery was running deep in epicardial fat and myocardial tissue but could be dissected under the condition of an arrested heart, which would have not been possible on the beating heart. After the first successful cases, the Port Access system was also used for two-vessel revascularization using the radial artery as a T-graft in four patients. All grafts were patent on postoperative angiogram. We feel that the safety of the anastomosis was not limited by the limited access in any patient. On the other hand, we were faced with intraoperative complications related to the `endoclamp' technique in patients who underwent minimally-invasive mitral valve surgery at our institution which is presented elsewhere [6]. The Port Access systems has its own risk profile and at present only limited experience is available. It has to be stressed that patient selection is crucial for the use of the Port Access system, since peripheral vascular disease, which may be associated with coronary artery disease, is an exclusion criteria.
3.3.1 Beating-heart technique and especially-designed instruments
Since especially-designed instruments were available for harvesting the ITA graft (CTS) and immobilization of the anastomosis (CTS/Autosuture), we combined the limited access with the beating-heart technique (group IV).
With the use of these instruments, the approach to the ITA as well as the technique of performing the anastomosis on the beating heart, improved considerably [2]. This resulted in shorter times, both for ITA graft harvesting and the performance of the anastomosis. In all patients, immobilization of the anastomotic site was achieved, so that a pharmacological reduction of the heart rate was not necessary to facilitate the technique, but may be used for myocardial protection during LAD occlusion. Since the beating-heart technique can be complicated by the onset of sudden myocardial depression or ventricular fibrillation we always have the heart–lung machine available in the operating room. Based on our experience with one patient, who did not tolerate occlusion of the LAD, we now perform 5 min of ischemic preconditioning, followed by reperfusion for another 5 min before we re-occlude the coronary artery to perform the anastomosis. Although the protective effect of ischemic preconditioning has not been confirmed yet [12], we think that intolerance to LAD occlusion would become obvious during this period and that unexpected myocardial depression or the onset of ventricular fibrillation during performance of anastomosis could thereby be avoided. This technique is mainly used in patients with a stenosis of less than 80%. In the presence of a totally or subtotally occluded LAD, additional distal occlusion is as a rule well tolerated. In patients with a stenosis below 80% the tolerance for LAD occlusion might be limited. Pharmacological reduction of heart rate and myocardial O2 consumption with Clonidine, Diltiazem or by betablockade may be helpful. However, further studies are necessary to outline the potential benefits under these special circumstances.
To achieve a bloodless field, snaring of the coronary artery is necessary in most of the patients. We used elastic vessel loops, connected to a rather big, but blunt, needle, to avoid the injury of the coronary artery or the septal branches of the LAD. Nevertheless, we had one injury of the right ventricle and we still see the potential risk associated with that maneuver. However recent studies indicate that snaring of the LAD is not harmful in terms of induction of stenosis [11].
3.4 Quality control
Graft patency and run-off should be detected by transient time ultrasound flow measurement or other techniques. In our institution thermal coronary angiography is routinely used for coronary artery surgery. Recently, endoscopic thermal coronary angiography has been applied in MIDCAB surgery [7]. If there are any doubts about the run-off of the graft, an intraoperative angiogram can be performed percutaneously via the femoral artery. Postoperative angiography should be performed in all patients to ensure patency of the graft and the quality of the anastomosis before discharge. We observed some minor stenoses at the anastomotic site, thus reangiography is recommended after another 6 months. One late stenosis (80%) at the anastomotic site, with the recurrence of mild angina symptoms, was observed. This stenosis was successfully treated by balloon angioplasty.
3.5 Flowchart and summary
The use of CPB can be associated with a systemic inflammatory response syndrome, cytokine release and clotting disorders [8]. In terms of a minimally-invasive procedure, CPB should be avoided whenever possible. Based on our initial experience with different less-invasive techniques for coronary artery bypass surgery, we have recently developed an algorithm for patient selection at our institution (Fig. 1
and Fig. 2
). For patients diagnosed with one-vessel disease of the LAD or RCA, ITA-to-LAD graft or right internal thoracic artery (RITA)-to-RCA graft is performed, using the MIDCAB approach without CPB. The Port Access system is only used as a back-up system to avoid conversion to a sternotomy in case of an intramyocardial running LAD or onset of left-ventricular dysfunction. In selected young patients, scheduled for a multiple-vessel graft to the left coronary circulation using the radial artery for a T-graft, the Port Access system could be an option to maintain limited access to the heart and in addition to achieve a safe anastomosis with a conventional technique on an arrested heart. However, using the CPB for a single vessel revascularization is some what invasive.
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Abstract
1. Introduction
