(Chest. 2005;127:47-52.)
© 2005
American College of Chest Physicians
Single-Vessel Revascularization With Minimally Invasive Direct Coronary Artery Bypass*
Minithoracotomy or Ministernotomy?
Hiroshi Niinami, MD, PhD;
Hidetsugu Ogasawara, MD;
Yuji Suda, MD and
Yasuo Takeuchi, MD
* From the Department of Cardiovascular Surgery, Daini Hospital, Tokyo Women’s Medical University, Tokyo, Japan.
Correspondence to: Hiroshi Niinami, MD, PhD, Associate Professor, Department of Cardiovascular Surgery, Daini Hospital, Tokyo Women’s Medical University, 2-1-10 Nishiogu, Arakawa-ku, Tokyo 116-8567, Japan; e-mail niinamca{at}dnh.twmu.ac.jp
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Abstract
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Study objectives: To compare the early outcome in patients who underwent off-pump single-vessel revascularization of the left anterior descending coronary artery (LAD) using two different approaches of minimally invasive direct coronary artery bypass grafting (MIDCAB): left anterior small thoracotomy (LAST) and lower ministernotomy.
Design: A retrospective analysis of the medical records on length of the skin incision, total operation time, duration of mechanical ventilation, blood transfusion rate, ICU stay, postoperative wound pain, and morbidities.
Patients: Thirty-two patients who underwent MIDCAB with the left internal thoracic artery to the LAD for single-vessel disease were studied. LAST was performed in 16 patients, and ministernotomy was performed in 16 patients. For the ministernotomy approach, the lower half of the sternum was split without transverse division, which we called the lower-end sternal splitting (LESS) approach. Postoperative pain was evaluated using a face-rating scale (scale, 1 to 6).
Results: There were no significant differences between the two groups in length of the skin incision, duration of mechanical ventilation, and ICU stay. Total operation time was shorter in the LESS group than in the LAST group (p < 0.05). No patients received a blood transfusion in either group. Atrial fibrillation developed in one patient in the LAST group and two patients in the LESS group. Early graft potency was 94% in the LAST group and 100% in the LESS group (p = 0.48). In the LAST group, subcutaneous emphysema developed in three patients and superficial wound dehiscence developed in two patients, but these complications were not observed in the LESS group (p < 0.05). Postoperative pain was significantly higher in the LAST group up to postoperative day 7 (p < 0.05).
Conclusions: Although LAST is the most commonly used approach for MIDCAB, wound complications and postoperative pain with this technique are not insignificant compared with the lower ministernotomy approach.
Key Words: beating heart • coronary artery bypass surgery • minimally invasive surgery
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Introduction
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The left anterior small thoracotomy (LAST) approach is the most well-recognized method used to perform minimally invasive direct coronary artery bypass grafting (MIDCAB) of the left internal thoracic artery (LITA) to the left anterior descending coronary artery (LAD).123 However, it is generally believed that the minithoracotomy approach is technically more demanding than the sternotomy approach, and thus can jeopardize the safe procurement of the LITA and the anastomosing procedure.45 However, the LAST approach is quite attractive in terms of preservation of chest stability and cosmetics compared with the conventional full sternotomy approach. With regard to cosmetics, there are several other less invasive approaches for MIDCAB, such as the ministernotomy approach.678
Recently, we developed a new ministernotomy approach for MIDCAB, namely, the lower-end sternal splitting (LESS) approach, which consists of a lower ministernotomy without transverse division of the sternum.9 The purpose of this study was to evaluate and compare our retrospective experience with the off-pump procedure via anterior minithoracotomy and lower ministernotomy in patients with single-vessel LAD disease with regard to early clinical outcomes, early graft patency, and wound-related problems.
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Materials and Methods
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In a retrospective single-institution review, we examined MIDCAB cases for isolated LAD disease performed between February 1998 and March 2001, comparing two different approaches (LAST vs LESS). The approach was not randomized.
The patient characteristics are shown in Table 1
. The patients in both groups were almost identical, except that the patients in the LAST group were younger than those in the LESS group. In both groups of patients, indications for surgery were as follows: (1) complete LAD occlusion, (2) complex lesions not considered suitable for percutaneous catheter interventions, (3) restenosis after previous percutaneous catheter interventions, and (4) the patient’s request for MIDCAB. In this study, patients who received other operative procedures, such as cholecystectomy or GI operation, at the same time or within 1 week after surgery were excluded. Also, patients with other coronary artery diseases were excluded, so that all patients had purely LAD single-vessel disease. Furthermore, patients with gastric ulcer and cholecystitis were excluded in order to avoid interference with postoperative wound pain.
Operative Techniques
For the LAST group (Fig 1
, top), the patient was placed in a 30° right lateral decubitus position, and the left hemithorax was entered through the fourth intercostal space without resection of a rib. The median length of the incision was 8 cm (range, 6 to 10 cm). The LITA was harvested under direct vision in all patients using a retractor (ThoraLift; United States Surgical Corporation; Norwalk, CT). After LITA preparation, diluted papaverine hydrochloride was applied externally. The pericardium was then opened, and a commercially available MIDCAB retractor and heart stabilizer (CAB Super-Slide Retractor; T. Koros Surgical Instruments Corporation; Moorpark, CA) were positioned. Heparin was administered (100 U/kg) to keep the activated clotting time at approximately 250 s. The anastomotic site of the LAD was chosen, and a 4-0 Prolene suture (Ethicon; Somerville, NJ) was passed around proximally to the anastomotic site of the coronary artery with the use of a snare with a Teflon felt pledget, except in cases of total occlusion. The LAD was opened longitudinally, and the proximal suture was snared gently for hemostasis. The LITA to LAD anastomosis was carried out using the 8–0 Prolene single parachute technique. Wound closure included reapproximation of the costal cartilages using 0 Vicryl pericostal interrupted sutures (Ethicon), as well as separate layer closures for the pectoralis muscles, deep dermal with 0 Vicryl sutures, and subcuticular layers with 3-0 Vicryl sutures. Subcutaneous drains were not utilized. A 24F single thoracotomy tube (Trocar Thoracic Catheter; Sherwood Medical; St. Louis, MO) was placed through a separate stab incision.
For the LESS group (Fig 1, bottom), the patient was placed in the supine position as for the conventional full sternotomy. A midline skin incision was made from the fourth intercostal space to the xiphisternum. The median length of the incision was 8 cm (range, 8 to 10 cm). The lower half of the sternum was then divided up to the third rib without division of the sternum. An ITA retractor (Rultract; Cleveland, OH) was used to harvest the LITA. After the LITA was harvested, a chest spreader, which was the same as the one used in the LAST group, was positioned and gently opened, spreading only the lower part of the sternum. The pericardium was opened up to the aortic root. Heparin was administered (100 U/kg) to keep the activated clotting time at approximately 250 s. The distal part of the LITA was then clipped and divided. A deep pericardial traction suture was placed on the left side for exposure of the LAD.10 As in the LAST approach, the stabilizer was then positioned and fixed on the LAD. The LITA to LAD revascularization was completed in the same manner as in the LAST group. After insertion of two 19-F drains (Blake Silicone Drain; Johnson & Johnson; Somerville, NJ) into the pericardial cavity and the substernal space, the lower sternotomy was closed with a combination of PDS codes and mersilene tape (Ethicon) or sternal wires (when sternal edge fractures occurred).
In both groups of patients, local myocardial ischemic preconditioning was performed with 3 min of LAD occlusion, followed by 3 min of reperfusion. Transesophageal echocardiography was used to monitor changes in wall motion in all cases. At the end of the procedure, heparin was not reversed, or a half dose of protamine was administered.
Postoperative ECG was performed, and serial samples of creatine phosphokinase (CK), and CK-MB were determined soon after surgery, and at 12 h, 24 h, and up to 48 h in all patients. Perioperative myocardial infarction was defined as either an increase in CK-MB enzyme levels > 50 IU/L or Q-wave formation in the postoperative ECG.
All patients received pain drugs regularly three times daily from postoperative day (POD) 1. If the patients suffered more pain in the interval between administration of the pain drugs, an indomethacin suppository was administered on an as-needed basis during the hospitalization period. Pain intensity was analyzed using the face-rating scale, which has a six-step approach and allows differentiation between no pain (score 1), trivial (score 2), mild (score 3), moderate (score 4), severe (score 5), and unbearable pain (score 6).1112 The face-rating scale was assessed by the nursing staff three times daily 1 h after administration of pain drugs during hospitalization. The pain experienced each day was calculated as the mean of the three measurements.
Postoperative angiography was performed within 1 month after surgery in all patients in both groups. All anastomoses were reviewed and classified as described by FitzGibbon et al.13 After hospital discharge, each patient was seen at our outpatient clinic every month to assess postoperative wound problems and recurrent angina.
Statistical Analysis
All data were analyzed. Statistical analysis was performed using a statistical software package (StatView, version 5.0; SAS Institute; Cary, NC). Continuous data were analyzed using the unpaired Student t test, and categorical data using the 
2 test or Fisher exact test as appropriate. Data are expressed as mean ± 1 SD unless otherwise indicated. Between-group differences with p < 0.05 were regarded as significant.
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Results
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The operative data for the two groups are listed in Table 2
. No patients required conversion to the full sternotomy or cardiopulmonary bypass (CPB) in either group. There was no early mortality in either group of patients. There were no significant differences in the length of skin incision, duration of mechanical ventilation, and ICU stay between the two groups. However, total operation time was slightly shorter in the LESS group than in the LAST group (p < 0.0465). No patients received a blood transfusion in either group. Atrial fibrillation developed in one patient in the LAST group and two patients in the LESS group within 1 week postoperatively. No patients had perioperative myocardial infarction, and the peak CK-MB averaged 9.6 ± 3.2 IU/L in the LAST group and 7.9 ± 4.6 IU/L in the LESS group (p = 0.3726). However, the peak activity of CK was significantly higher in the LAST group compared to the LESS group (974 ± 287 IU/L vs 232 ± 112 IU/L, p < 0.0001).
According to the early postoperative coronary angiogram, grade A was confirmed in 14 patients (87.5%), grade B was confirmed in 1 patient, and grade O was confirmed in 1 patient in the LAST group, and grade A was confirmed in 16 patients (100%) in the LESS group. Overall early graft patency therefore was 94% in the LAST group and 100% in the LESS group (p = 0.48). The grade B patient underwent successful percutaneous coronary angioplasty in the LITA, and another patient in grade O underwent successful percutaneous coronary angioplasty in the LAD. Subcutaneous emphysema developed in three patients in the LAST group, and two patients had superficial wound dehiscence. Superficial dehiscence was resolved with simple debridement and healing by second intention (ie, healing by granulation after suppuration). However, these complications were not observed in the LESS group (p = 0.0434).
Postoperative pain data are summarized in Table 3
. The mean postoperative pain scores up to POD 7 were significantly lower in the LESS group than in the LAST group (p < 0.0001).
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Discussion
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The LAST approach for MIDCAB is the most frequently employed technique for single-vessel revascularization of the LAD using the LITA. Despite widespread acceptance of this technique, concern has been shown about technical problems when harvesting the LITA, graft patency, perioperative complications, and postoperative pain. Several studies14151617 have compared MIDCAB using the LAST approach and the conventional full sternotomy regarding these concerns. Ng et al14 reported significantly higher wound complications in patients who underwent off-pump coronary artery bypass with the LAST approach compared to the full sternotomy approach. Detter et al18 reported that the LAST approach for MIDCAB tended to have a higher risk of conversion to CPB compared to the full sternotomy approach for off-pump coronary artery bypass. Nevertheless, the LAST approach is quite attractive from the cosmetic point of view. However, in this regard, other minimally invasive approaches exist, such as the lower ministernotomy approach.678 We have been employing the lower ministernotomy approach without transverse division of the sternum, which we call the LESS approach for MIDCAB, since 1999.9 The reason why we developed the LESS approach was initially because the LAST approach is generally limited to LAD single-vessel revascularization. Through the LESS approach, not only the LAD but also the right coronary artery can be revascularized with the same incision. We have performed up to three bypasses with this approach. After the introduction of this approach, we believed that it was easy to perform the MIDCAB operation, so that we shifted the approach for LAD single-vessel revascularization from the LAST to the LESS for MIDCAB. The results obtained from this study were almost identical for the two different approaches in terms of mortality and major morbidities. However, our study demonstrated some differences between the two approaches. First, LITA graft harvesting through a limited thoracotomy is technically more demanding than ministernotomy as demonstrated by the lengthy surgery and tendency for a worse graft patency. We believe that during LITA harvesting, even with a limited incision, surgeons feel more familiar with the ministernotomy rather than the minithoracotomy approach, since it is almost identical to the conventional full sternotomy approach. Moreover, the length of the LITA with the LESS approach is much longer than with the LAST approach, since with the LESS approach, we can take down the LITA distally to its bifurcation, but with the LAST approach, it is taken up to the fifth intercostal space. This fact makes it easier to graft the LITA to even the distal LAD with the LESS approach. Furthermore, the exposure of the anterior surface of the heart with the LESS approach is almost the same as with the conventional full sternotomy approach, so that identification of the LAD and the localization of the optimal part of the target vessel for the anastomosis is easier. In contrast, with the LAST approach there is a risk of damaging the LITA during harvesting, since this is a technically demanding procedure for harvesting the LITA, and a learning curve exists.16
Secondly, postoperative wound complications are not insignificant with the LAST approach. In our study, since the number of patients was small, no serious infections occurred in either group of patients. However, superficial wound dehiscence developed in two patients (12.5%) in the LAST group. Ng et al14 reported significantly higher wound complications in patients with the LAST approach, compared to the conventional full sternotomy approach (9.1% vs 1.1%, p < 0.005). They suspected that the difference in morbidity between LAST and median sternotomy could be due to the lack of collateral blood supply to the intercostal muscle. In fact, this might be well correlated to the significantly higher peak CK levels for the LAST approach.
Regarding postoperative wound pain, our results indicated that after the LAST approach for MIDCAB, irritation of the intercostal nerves during the first week, postoperatively, caused pain of higher intensity than did the LESS approach. Some studies1517 have demonstrated that the LAST approach causes significantly more pain in the early postoperative period than the conventional full sternotomy approach. We have not compared patients with the LESS approach and the full sternotomy approach. However, our impression was also that patients with the LESS approach showed a lower threshold of pain early postoperatively than did those with the full sternotomy approach. Strain caused by mobilization causes bony friction of the sternum in patients with a full sternotomy. When the patients moved their arms, they suffered intense pain due to friction of the split manubrium sterni because of the sternoclavicular joints. We believe that with our approach, patients should have less pain than with full sternotomy, since the manubrium sterni is intact. There are several methods to minimize the postoperative pain that occurs with the LAST approach. Bucerius et al19 introduced endoscopic internal thoracic artery (ITA) dissection using a robotic telemanipulation system for the LAST approach to minimize postoperative pain. They revealed the superiority of this technique compared to the conventional ITA takedown for the LAST approach in terms of postoperative pain. However, mastering this technique is time-consuming and also, at present, the price of the system prohibits widespread use. In order to avoid rib traction, Cohn et al20 used interposition of the right inferior epigastric artery (RIEA) graft between the side of the intact LITA and LAD as the "H" graft, which also reduced postoperative pain. However, they stated potential disadvantages, including the second incision for the RIEA and second anastomosis for attachment of the proximal RIEA to the LITA. Furthermore, the potential for diversion of significant LITA flow to noncoronary vascular beds can be represented some variant of a "steal" syndrome. In this regard, the LESS approach is a simpler method for performing MIDCAB.
One of the concerns when performing coronary artery revascularization without CPB with impaired visualization through limited surgical access is an unfavorable coronary anatomy, in which case the patients need CPB. In this study, we did not encounter any patients who required conversion to full sternotomy or to CPB, probably due to proper patient selection. We believe that the major key to a successful MIDCAB procedure could be the suitable selection of patients. However, if patients need conversion to full sternotomy, with the LESS approach the incision can be easily and rapidly extended to a full sternotomy, in contrast to the LAST approach, which requires an additional incision. Compared to the standard ministernotomy approach that requires transverse division of the sternum, the sternal retractor in the LESS approach can be applied without sternal instability after conversion. The incidence of upper sternal edge fractures with the LESS approach is approximately 20%. Some fractures occurred during the ITA takedown, and others while spreading the CAB Super-Slide Retractor. Fortunately, these fractures occurred in localized areas, and at the time of the chest closure, the sternum was rejoined easily, as it fitted like a key in a key hole. With regard to the sternal closure, in patients in whom sternal fractures did not occur, a combination of PDS codes and Mersilene tapes instead of the conventional steel wires was used. The reason for using these nonsteel wire materials for sternal closure was that with the LESS approach, after the anastomosis, when the retractor is taken out, the sternum rejoined by itself, since the manubrium sterni was intact. Therefore, the materials used should be strong enough to close the body of the sternum. When sternal fractures occurred, conventional stainless steel wires were used. These patients have been followed up at our outpatient clinic, and no patient has had sternal instability. One of the advantages of using these materials is that they cannot be visualized on the postoperative chest radiograph.
The limitation of this study is that it was a retrospective study with a small sample size. However, the preoperative patient characteristics (Table 1) were remarkably similar in the two study groups except for patient age. The fact that the patients in the LAST group were relatively younger may have influenced postoperative wound pain.
Although both approaches for MIDCAB showed good results with no hospital mortality, low early morbidities, no blood transfusion, and comparable angiographic results despite the challenging techniques, the LAST approach showed more wound-related complications, including postoperative wound pain, compared with the LESS approach. We believe that the lower ministernotomy approach for MIDCAB is preferable from the standpoint of safety and comfort for both patients and surgeons in the treatment of LAD single-vessel disease compared with the LAST approach.
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Footnotes
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Abbreviations: CK = creatine phosphokinase; CPB = cardiopulmonary bypass; ITA = internal thoracic artery; LAD = left anterior descending coronary artery; LAST = left anterior small thoracotomy; LESS = lower-end sternal splitting; LITA = left internal thoracic artery; MIDCAB = minimally invasive direct coronary artery bypass grafting; POD = postoperative day; RIEA = right inferior epigastric artery
Received for publication March 8, 2004.
Accepted for publication July 28, 2004.
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Abstract
Introduction
