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Multivessel minimally invasive coronary artery bypass grafting, performed chiefly with left internal thoracic artery and saphenous vein grafts through a left anterolateral thoracotomy, has recently emerged as an alternative to conventional coronary artery bypass grafting. The present study involves our initial experience with respect to early postoperative and angiographic outcomes after total arterial multivessel off-pump minimally invasive coronary artery bypass grafting with bilateral internal thoracic arteries.
Methods
A total of 88 consecutive patients undergoing total arterial off-pump minimally invasive coronary artery bypass grafting with bilateral internal thoracic arteries without ascending aortic manipulation were included in this study. Bilateral internal thoracic arteries were harvested under direct vision through a left anterolateral thoracotomy and used as Y or in situ grafts. Multivessel grafting was performed off pump. Postoperative graft assessment was performed in 51 patients.
Results
The mean age of patients was 67.1 ± 7.2 years, and 79 patients (89.8%) were male. The mean body mass index and ejection fraction were 26.7 ± 2.7 kg/m2 and 57.6% ± 6.6%, respectively, and 40 patients (45.5%) had left main disease. No intraoperative conversions to cardiopulmonary bypass or sternotomy occurred. A total of 209 distal anastomoses (mean 2.4 ± 0.5) were performed, with 57 patients undergoing double, 29 patients undergoing triple, and 2 patients undergoing quadruple coronary artery bypass grafting. There was no in-hospital mortality, and 5 patients underwent reexploration for bleeding. No patient had stroke or chest wound infections. Predischarge coronary angiography revealed an overall graft patency rate of 96.8%.
Conclusions
Off-pump minimally invasive coronary artery bypass grafting using total arterial revascularization with bilateral internal thoracic arteries is a feasible and safe operation that is associated with excellent short-term outcomes and early graft patency. Future studies should focus on improving the generalizability and reproducibility of this technique.
Off-pump minimally invasive CABG with bilateral ITAs can be performed with low postoperative complication rates and good angiographic outcomes, thus promising good long-term results in selected patients. Left coronary tree revascularization with this approach and PCI of the right coronary system could be a good option for hybrid coronary revascularization in the future.
See Commentaries on pages 1120, 1121, and 1122.
Although the widespread adoption of minimally invasive cardiac surgical (MICS) procedures has been predominantly observed in valvular heart and single vessel coronary artery bypass grafting (CABG),
The first report about the feasibility, safety, and applicability of MICS-CABG performed through a left anterolateral minithoracotomy without endoscopic or robotic assistance was published 10 years ago.
However, such surgeries are most commonly performed with a left internal thoracic artery (ITA) and saphenous veins with the use of aortic clamping for proximal anastomoses, which can potentially result in higher rates of midterm vein graft failures and perioperative stroke.
Several retrospective studies have shown that the use of bilateral ITAs is associated with improved survival and freedom from reoperations/reinterventions, and the benefit seems to increase in the second decade after surgery.
The use of composite arterial grafts and off-pump techniques avoids ascending aortic manipulation, which could prevent or at least reduce perioperative stroke rates.
ART Investigators Randomized trial to compare bilateral vs. single internal mammary coronary artery bypass grafting: 1-year results of the Arterial Revascularisation Trial (ART).
Therefore, a CABG operation with the use of bilateral ITAs as in situ or composite grafts through a minimally invasive sternal-sparing approach would resolve sternal wound problems and could reduce perioperative stroke rates and achieve excellent long-term outcomes, in addition to offering other known benefits of MICS.
Review of a 13-year single-center experience with minimally invasive direct coronary artery bypass as the primary surgical treatment of coronary artery disease.
in our institute, we developed the technique of performing multivessel CABG with bilateral ITAs through a left anterolateral minithoracotomy for selected patients. The aim of the present study was to assess the early mortality and major postoperative complications such as myocardial infarction, stroke, wound infections, and renal and respiratory insufficiency, and evaluate the angiographic patency of grafts performed with this technique.
Materials and Methods
A total of 88 consecutive patients who underwent off-pump MICS-CABG between February 2015 and March 2019 at our institution were included in this retrospective study. Of these, the majority of the surgeries (n = 79) were performed from June 2017 onward, comprising 3.5% of all primary isolated CABG procedures (n = 2253) at our center during this time period. Demographic, intraoperative, and outcome data of all patients were collected prospectively and entered into a computerized database. Patients who underwent MIDCAB procedures (single vessel bypass operations involving an anastomosis between the left ITA and the left anterior descending artery [LAD] through a left anterior small thoracotomy) were not included in the current series. Additionally, patients who underwent conventional CABG due to intolerance to single-lung ventilation after induction of anesthesia before skin incision were excluded.
The study was approved by our institutional review board. Because this was a retrospective study, individual patient informed consent was waived.
Patient Selection
All patients with an indication for isolated surgical revascularization are potential candidates for a MICS-CABG approach. However, preferable candidates are those with a body mass index (BMI) less than 30 kg/m2, cardiothoracic-ratio (CTR) less than 50%, left ventricular ejection fraction (LVEF) greater than 45%, and left ventricular end-diastolic internal diameter less than 55 mm. Patient selection criteria are comprehensively described in the Appendix E1. The preoperative assessment protocol includes a thorough history, airway examination, x-ray chest, electrocardiography, transthoracic echocardiography, carotid Doppler, and pulmonary function tests. Baseline investigations include a full blood count, blood glucose levels, serum electrolytes, renal and liver function tests, and a complete coagulation profile.
Surgical Procedure
Surgery is performed with a double-lumen endotracheal tube inserted under bronchoscopic guidance. A detailed anesthesia protocol is provided in the Appendix E1.
Intraoperative transesophageal echocardiography is mandatory to monitor volume status, cardiac performance, atrioventricular valve function for new-onset regurgitation. or severe right ventricular outflow tract obstruction that can occur during subluxation of the heart. Transeosphageal echocardiography also facilitates safe insertion and placement of femoral venous and arterial cannulas, should cardiopulmonary bypass be required.
The operation is performed through a 7- to 8-cm incision through the left fourth or fifth intercostal spaces, between the midclavicular and anterior axillary lines. The left ITA harvest is performed using the Thoratrak (Medtronic, Minneapolis, Minn) rib spreader pulled cephalad by the Rultract Skyhook (Rultract, Cleveland, Ohio) or the IMAGate sternal wire lift (Geister Medizintechnik GmbH, Tuttlingen, Germany) retractor (Figure 1, A), along with long-shafted instruments and electrocautery blade (Figure 1, B). Thereafter, the right ITA is exposed by a subxyphoid hook that is pulled up by an angulated bar fixed to the operating table (Fehling Surgical Instruments Inc, Karlstein, Germany), thereby increasing the space within the anterior mediastinum (Figure 1, C). Rightward dissection within the anterior mediastinum leads to the exposure of the right ITA, which is then harvested by direct vision in a skeletonized fashion (Figure 1, D).
Figure 1A, Thoratrak (Medtronic, Minneapolis, Minn) rib spreader (black arrow) is inserted through the fifth intercostal space. The upper blade is pulled cephalad and anteriorly by hooking it on to a pulley system called the Rultract Skyhook retractor (Rultract, Cleveland, Ohio) (yellow hatched arrow). Rib spreading and upward pull on the upper blade (shown by the direction of the hatched arrow) help elevate the upper part of the thoracic cage facilitating the harvest of the LITA. B, Black arrow shows the bifurcation at the distal end of the LITA, which is harvested in a skeletonized fashion. C, Black arrow shows the proximal end of the LITA, which can be harvested up to and further proximal to the SCV if required. D, Sub-xyphoid hook is inserted through a 1-cm subxyphoid incision (black arrow) and pulled cephalad (yellow hatched arrow) through its connection with an angulated bar (white hatched arrow). This maneuver lifts the lower third of the sternum, thus increasing space in the lower anterior mediastinum to facilitate the harvest of the RITA. E, RITA and vein (yellow hatched and black arrows) are visualized clearly after placing a green sponge in right pleura. F, RITA is harvested in a skeletonized fashion. Yellow double arrow shows the lower third of the RITA, which can be harvested, if required.
The pericardium is then opened over the ascending aorta and the main pulmonary artery. After heparinization, the Y-anastomosis between the left and the right ITAs is constructed at the level of the pulmonary valve using the foot pods of the Octopus Nuvo (Medtronic) epicardial tissue stabilizer as a stable platform (Figure 2, A). Thereafter, the pericardium is further opened toward the apex exposing the LAD. After stabilization with the Octopus Nuvo, an end-to-side anastomosis is performed between the left ITA and the LAD with 7-0 or 8-0 polypropylene (Figure 2, B). Thereafter, the high lateral wall vessels such as the diagonal branches, the intermediate and proximal obtuse marginal arteries are exposed with an armless Starfish (Medtronic) apical positioner with a thick ligature tied to its neck. The right ITA is anastomosed to 1 or more of these vessels in an end-to-side or side-to-side fashion using the Octopus Nuvo stabilizer (Figure 2, C and D). Visualization of all anastomoses is facilitated by use of an intracoronary shunt and a blower-mister.
Figure 2A, LITA (white arrow) is fixed on to a platform (yellow arrow) created by covering the pods of the Octopus Nuvo with a finger glove. B, Completed Y-anastomosis (black arrow) between the LITA (black hatched arrow) and the RITA (yellow arrow) seen on the platform in a magnified view. C, Black arrow shows a completed LITA-LAD anastomosis. D, Black arrow shows a completed RITA–intermediate artery sequential anastomosis. An atraumatic silastic tape that is made occlusive with clips (yellow arrow) is used to temporarily occlude the coronary target proximal to the site of the anastomosis to facilitate its construction. E, Positioning of the heart for the left circumflex artery anastomosis is facilitated by the Starfish (yellow arrow shows one of the pods) that pulls the heart anteriorly and to the right and the Octopus Nuvo (black arrow) that stabilizes the target vessel (black hatched arrow).
All grafts are assessed intraoperatively using Transit Time Flow Measurement (Medistim). Thereafter, the heart is placed back into its normal position and the pericardium is partially closed taking precautions to prevent graft kinking or compression. Bilateral pleural drains are inserted, and the left lung is gradually reinflated under direct vision. The thoracotomy wound is closed in layers after administration of intramuscular bupivacaine (Figure 3). Further detailed steps of the procedure are outlined in the Appendix E1.
All patients receive acetylsalicylic acid and clopidogrel postoperatively.
Twelve-lead electrocardiograms and cardiac enzymes (creatinine kinase [CK]/CK-MB isoenzyme] levels) are routinely assessed. Coronary angiography (CA) or computed tomography (CT) of the coronary system was electively performed as a measure of quality control in patients operated during the early part of this series and only in presence of evidence of ischemia (Appendix E1) in the latter part of the series. A standard pain control protocol is followed for all cardiac surgical patients (Table E1) with the aim to maintain pain levels below 4 on the pain scale (Figure E1). Patients with persistent pain levels 4 or greater at rest or 5 or greater on mobilization are given patient-controlled analgesia.
Follow-up
Follow-up was performed by personal or phone contact with patients and family members, with supplemental information supplied by family physicians and referring cardiologists. The closing interval was between January and April 2019.
Outcome and Explanatory Variables
The main focus of the current series was procedure safety and efficacy including in-hospital and 30-day mortality, perioperative MI, stroke, deep chest wound infections, and angiographic bypass patency, as well as overall short-term survival and freedom from major cerebral and cardiovascular events. Important explanatory variables are defined in the Appendix E1.
Statistical Methods
The data were imported into SPSS version 17.0 (IBM Corp, New York, NY) for description and analysis. Categoric variables are expressed as frequencies and percentages. Normal distribution of measurements was verified by Q–Q plots. Normally distributed continuous variables are expressed as mean ± standard deviation. In case of non-normally distributed/skew data, the median with interquartile ranges (IQRs) is reported. Variables that had a univariable P value less than .2 or those judged to be clinically important were submitted to a binary forward stepwise conditional regression model to determine the independent predictors of respiratory complications, which are expressed as odds ratios and 95% confidence intervals (CIs). The mean length of surgery (Figure 4) for various time periods of the study was compared using a 1-way analysis of variance with the post hoc Dunnett's test for multiple comparisons. The graph was created using SigmaPlot, version 12.0 (Systat Software, Inc, San Jose, Calif).
Figure 4Box plot demonstrating total OR time over 4 years. The upper and lower borders of the red boxes represent the IQR of OR time equal to the difference between the 75th and 25th percentiles. The middle horizontal line represents the median. The upper and lower whiskers (green) represent the maximum and minimum values of nonoutliers.
The demographic characteristics of patients undergoing MICS-CABG are depicted in Table 1. Ages of patients ranged between 33 and 84 years with a median of 67 years (IQR, 61.0-74.0). The majority of patients were men. The median BMI was 26.4 kg/m2 (IQR, 24-29) with 11 patients having a BMI 31.0 kg/m2 or greater. The CTR, defined as the ratio of maximal horizontal cardiac diameter to maximal horizontal thoracic diameter (inner edge of ribs/edge of pleura on CXR) × 100, ranged between 37% and 57% with a median of 47% (IQR, 44.0-49.8). Only 16 patients had a CTR greater than 50%. Most patients had a good LVEF, with only 4 patients having LVEF 40% or less. The left ventricular internal dimension in diastole ranged between 32 and 64 mm, and was greater than 55 mm in 7 patients only. The overall risk profile of patients was relatively low, as depicted by the mean European System for Cardiac Operative Risk Evaluation.
Table 1Preoperative patient characteristics
Preoperative variables
n = 88
Age, y (mean ± SD)
67.1 ± 7.2
Female %, [n]
10.2 [9]
Diabetes mellitus %, [n]
35.2 [31]
Hypertension %, [n]
93.1 [82]
Hyperlipidemia %, [n]
90.9 [80]
Body mass index (mean ± SD)
26.7 ± 2.7
Preoperative myocardial infarction %, [n]
19.3 [17]
Left ventricular ejection fraction (%) (mean ± SD)
57.6 ± 6.6
Left ventricular end-diastolic diameter (mm) (mean ± SD)
47.6 ± 4.1
Cardiothoracic ratio (%) (mean ± SD)
46.7 ± 3.4
Coronary artery disease %, [n]
Left main disease
45.5 [40]
2-vessel disease
47.7 [42]
3-vessel disease
52.3 [46]
Chronic obstructive pulmonary disease %, [n]
10.2 [9]
Serum creatinine levels (mean ± SD)
1.0 ± 0.2
Peripheral vascular disease %, [n]
18.2 [16]
Stroke %, [n]
3.4 [3]
Previous PCI %, [n]
28.4 [25]
Timing of surgery %, [n]
Elective
96.6 [85]
Urgent
3.4 [3]
Logistic euroSCORE (mean ± SD)
2.7 ± 1.5
SD, Standard deviation; PCI, percutaneous coronary intervention; euroSCORE, European System for Cardiac Operative Risk Evaluation.
Intraoperative details are listed in Table 2. All patients underwent revascularization with 2 ITAs. A Y-anastomosis between the left and right ITAs was performed in all but 1 patient, in whom in situ ITAs were used. No other conduits (radial artery or vein) were used, either as primary conduits or interposition or extension grafts, in any of the patients during the primary operation. The aorta was not manipulated in any patient. A total of 209 distal anastomoses were performed, of which 33 were sequential. Incomplete revascularization was observed in 8 patients. Of these, 4 patients were planned for hybrid procedures and underwent postoperative percutaneous coronary intervention (PCI) of the right coronary artery, 3 patients had an occluded right coronary artery that was too small and diffusely diseased to warrant a bypass graft, and 1 patient had a diseased circumflex artery with small branches (0.75 mm) who also underwent postoperative PCI. Therefore, at discharge only 3 patients (3.4%) had incomplete revascularization. The mean length of surgery gradually decreased over time (Figure 4). The insignificant increase in length of surgery observed in the second half of 2018 was due to the performance of two 4-vessel CABG surgeries that lasted longer than 2- and 3-vessel CABGs.
Table 2Intraoperative parameters
Intraoperative parameters
n = 88
No. of distal anastomoses
Total [n]
209
Mean ± SD
2.4 ± 0.5
No. of sequential anastomoses [n]
33
No. of bypass grafts %, [n]
2-vessel CABG
64.8 [57]
3-vessel CABG
32.9 [29]
4-vessel CABG
2.3 [2]
Territories grafted %, [n]
Left anterior descending artery territory
98.9 [87]
Circumflex territory
32.9 [76]
Right coronary artery territory
10.2 [9]
Incomplete revascularization %, [n]
9.1 [8]
Conversion to on-pump CABG
0.0 [0]
Conversion to sternotomy
0.0 [0]
Length of surgery (min) (mean ± SD)
283 ± 49
SD, Standard deviation; CABG, coronary artery bypass grafting.
No patient died in the hospital. However, 1 patient experienced a sudden cardiac arrest on the floor on postoperative day 4. She was resuscitated and placed on extracorporeal membrane oxygenation for 5 days, after which she was successfully weaned. She received a tracheotomy and was then transferred to a neurologic rehabilitation center where she died on postoperative day 19.
Other postoperative complications are presented in Table 3. Postoperative CK-MB levels ranged between 16 and 128 IU/L, with a median of 33.5 IU/L (IQR, 26-48.8). Only 1 patient had a perioperative myocardial infarction. The average erythrocyte transfusion rate of 3.3/patient transfused was skewed, because the patient with postoperative extracorporeal membrane oxygenation required a total of 18 units of packed red cells. Apart from new-onset atrial fibrillation, respiratory complications were the commonest postoperative adverse events. Length of surgery was found to be the only independent predictor of respiratory complications (odds ratio, 1.02; 95% CI, 1.008-1.034; P = .002) on multivariable analysis.
Table 3Postoperative outcomes and angiographic results
Postoperative outcomes
n = 88
In-hospital mortality
0.0 [0]
30-d mortality %, [n]
1.1 [1]
Low cardiac output syndrome %, [n]
1.1 [1]
Extracorporeal membrane oxygenation %, [n]
1.1 [1]
Myocardial infarction %, [n]
1.1 [1]
Creatine kinase–MB fraction (IU/L)
42.8 ± 18.8
Planned coronary angiography results
% (Total No. of anastomoses examined/No. of occluded or stenotic grafts/anastomoses)
Overall graft patency
96.8 [124/4]
Left ITA patency
96.4 [56/2]
Right ITA patency
97.2 [71/2]
Bypass revision %, [n]
3.4 [3]
Reexploration for bleeding %, [n]
5.7 [5]
Perioperative transfusion
30.7 [27]
No. of units
3.3
Stroke
0.0 [0]
New dialysis %, [n]
1.1 [1]
Respiratory complications %, [n]
13.6 [12]
Respiratory insufficiency %, [n]
7.9 [7]
Respiratory failure %, [n]
5.7 [5]
New-onset atrial fibrillation %, [n]
14.8 [13]
Chest wound infections %, [n]
Superficial
0.0 [0]
Deep
0.0 [0]
Patient-controlled analgesia %, [n]
3.4 [3]
Hospital stay (d) (mean ± SD)
9.3 ± 3.5
ITA, Internal thoracic artery; SD, standard deviation.
Planned postoperative CA was performed in 49 patients. We stopped performing postoperative coronary imaging after the 55th patient, because we were convinced by then that the operation could be effectively performed. Overall, 2 patients refused CA, 2 did not receive any postoperative imaging because of renal insufficiency, and 2 agreed to undergo CT- CA. Coronary imaging revealed 1 twisted right ITA (patient 1), 1 spastic (patient 6), 1 occluded left ITA (patient 34) due to thrombus formation, and one 70% anastomotic stenosis (patient 7) of a total of 124 anastomoses that were examined. It resulted in an overall patency rate of 96.8%. These patients had only shown a gradual increase in serial CK-MB levels without other evidence of MI. Patients 1 and 6 underwent repeat CABG through a sternotomy, and patient 34 underwent excision of the thrombotic segment of the left ITA followed by an end-to-end anastomosis through the same thoracotomy incision. Patient 7 was conservatively managed as the native vessel was small in caliber and had diffuse disease. Furthermore, 1 right ITA graft demonstrated spasm that resolved after infusion of nitroglycerine. Of the remaining 33 patients who were not planned for routine postoperative imaging, 2 required CA. One angiogram was normal, and 1, which was from the patient with extracorporeal membrane oxygenation, revealed a twisted right ITA between the intermediate and obtuse marginal anastomoses. The native vessel flow was not affected and was treated with PCI.
Follow-up
Follow-up time ranged from 6 days to 4.2 years, with a mean of 10.5 ± 9.2 months. Overall, 6 patients were lost to follow-up, resulting in completeness of follow-up of 93.2%. One patient died of sepsis after dialysis after 305 days. The patient was dialysis-dependent before MICS-CABG surgery. One patient underwent PCI of the left ITA-LAD anastomosis 6 months after surgery due to recurrence of angina. The predischarge CA was normal in this patient.
Discussion
The results of our study demonstrate that off-pump MICS-CABG with bilateral ITAs can be performed safely with good procedural outcomes that are comparable to those achieved through a median sternotomy. The reported early mortality for patients undergoing MICS-CABG ranges between 0% and 1.6%,
which matches well with that in our series (1.1%). We recently reported a 30-day mortality of 0.7% in approximately 1200 patients undergoing off-pump CABG with bilateral ITAs, which is reflective of the experience with this technique in our institution.
One would expect that the average number of grafts and the rate of completeness of revascularization would be lower in patients undergoing MICS-CABG, especially when performed off-pump.
The average number of grafts ranges between 2.1 and 3.1 in various reports because of patient selection. It would be inappropriate to compare the average number of grafts with other studies involving conventional CABG, because our patient selection bias resulted in a large proportion of our cohort to consist of patients with 2-vessel disease. Of the 8 patients with incomplete revascularization in our series, 4 underwent PCI of the right coronary artery as part of a planned hybrid procedure. Therefore, our true incomplete revascularization rate was only 4.5%, which was primarily due to nongraftable targets that rarely affect patient outcomes and prognosis.
The most notable outcome of our study was that no patient developed perioperative stroke or chest wound infection. Stroke, which is a major drawback of CABG,
Analysis of stroke occurring in the SYNTAX trial comparing coronary artery bypass surgery and percutaneous coronary intervention in the treatment of complex coronary artery disease.
DOORS Study Group On-pump versus off-pump coronary artery bypass surgery in elderly patients: results from the Danish on-pump versus off-pump randomization study.
Anaortic off-pump versus clampless off-pump using the PAS-Port device versus conventional coronary artery bypass grafting: mid-term results from a matched propensity score analysis of 5422 unselected patients.
The relatively low incidence of new-onset atrial fibrillation (14.8%) could have been an additional factor in preventing stroke in our patients, because atrial fibrillation has been known to be a predictor of perioperative stroke.
Furthermore, all patients in the current series received dual antiplatelet therapy with aspirin and clopidogrel after surgery, which could have helped in countering the hypercoagulability that is often observed after off-pump CABG.
Warm ischemia provokes inflammation and regional hypercoagulability within the heart during off-pump coronary artery bypass: a possible target for serine protease inhibition.
MICS-CABG totally eliminates sternal wound complications, which has traditionally been the key deterrent for use of bilateral ITAs through a sternotomy. CABG with bilateral ITAs is associated with greater deep sternal wound infection rates compared with that with single ITA.
ART Investigators Randomized trial to compare bilateral vs. single internal mammary coronary artery bypass grafting: 1-year results of the Arterial Revascularisation Trial (ART).
Pedicled and skeletonized single and bilateral internal thoracic artery grafts and the incidence of sternal wound complications: Insights from the Arterial Revascularization Trial.
Therefore, MICS-CABG confers an even greater benefit with respect to postoperative wound complication rates when bilateral ITAs are used. Superficial and deep chest wound infections affecting the thoracotomy site are rare, as was the case in our study.
Despite the good postoperative outcomes after MICS-CABG in the current series, there are 2 caveats that should be taken into consideration. The first one is that this operation is associated with a steep learning curve for the whole surgical team. Use of special ventilator maneuvers, adaptability to limited vision, space and restricted movements during surgery, and familiarization with unconventional equipment and instrumentation are unique to this procedure, and can generate errors. Most graft or anastomotic complications occurred during the initial period of our experience. Of 5 patients with positive postoperative CA, 3 occurred in the first 7 cases. The duration of surgery also gradually decreased from 6 hours to less than 4 hours with increasing experience, similar to that reported by Une and colleagues.
They did not observe significant differences in major adverse cerebral and cardiovascular events between the early and late phases of their study, which was similar to our series and could probably be due to the large experience of the surgeons in performing conventional off-pump CABG. Therefore, it is mandatory that surgeons have or acquire adequate experience in performing composite bilateral ITA grafting off-pump through a sternotomy approach before performing this operation through a minimally invasive access.
The second caveat is that good clinical outcomes can be partly due to favorable patient selection (Figure 5). Patients with severe COPD, interstitial lung disease, or severe pulmonary hypertension should be avoided, because they are unlikely to tolerate single-lung ventilation. Only 9% of patients had COPD in the current study. The majority of patients in the present series were nonobese with a BMI less than 30 kg/m2. Morbid obesity should be considered a contraindication for this procedure.
Figure 5The study includes 88 patients, who underwent multivessel MICS-CABG with bilateral ITAs. The patients were highly selected predominantly on the basis of the CTR measured on chest x-rays, LVEF, and left ventricular end-diastolic internal diameter on echocardiography and a suitable coronary anatomy and targets on CA. The majority of patients received a Y-graft configuration constructed with the in situ left and free right ITAs. Routine postoperative CA revealed an overall patency of 97%. Good wound cosmesis was one of the benefits of this approach. CTR, Cardiothoracic ratio; LAD, left anterior descending; LCx, left circumflex; CA, coronary angiography; RITA, right internal thoracic artery; LITA, left internal thoracic artery.
The CTR provides a good estimation of the relationship between the size of the heart and the thoracic cavity volume. The majority of patients in our series had a CTR less than 50%, which makes it easier to subluxate the heart without producing hemodynamic instability. Likewise, patients with left ventricular internal dimension in diastole less than 50 mm and good left ventricular function are generally more suitable for this operation.
Assessment of graft function before discharge is essential, because the margin of error while performing MICS-CABG is small. To the best of our knowledge, our group is the first to report on immediate postoperative angiographic outcomes after MICS-CABG surgery. Overall patency was 96.7% among the patients who underwent planned CA (Figure 5). We observed that competitive flow in the LAD was responsible for irreversible spasm in 1 left ITA between the Y- and LAD anastomosis. Another patient developed a thrombus in the left ITA approximately 1 cm proximal to the Y-anastomosis most likely due to the administration of excessive procoagulants for postoperative bleeding. At revision, there was no evidence of injury or dissection in the left ITA, so that the thrombosed segment was resected and an end-end anastomosis was performed with good flow measurements.
An important technical aspect that should be addressed during this operation is careful placement of the heart back into its position after grafting is complete. Our series had 2 patients with twisted right ITAs that were diagnosed on postoperative CA, despite adequate flow measurements. It occurs in patients in whom the heart needs to be forced back into its original position. In such cases, it is wise to recheck the lie of the graft to the lateral wall to rule out a twist, kink, or torque.
The 6-month angiographic patency study by Ruel and colleagues
reported an overall angiographic patency rate of 91% in patients who received MICS-CABG. We believe that there is a high likelihood that our patency rates will remain stable over time, considering the lone use of bilateral ITAs and the corrective measures already taken in patients with abnormal angiograms. Furthermore, only 1 patient has undergone repeat revascularization (PCI) for recurrent angina pectoris at a mean follow-up of 10.5 months. No other adverse events or recurrence of angina was recorded at follow-up of other patients.
Two other facets of MICS-CABG surgery need mention. First, patients are maintained on single-lung ventilation for prolonged periods of time, most commonly extending for virtually the entire duration of surgery. The length of surgery was found to be an independent predictor for the development of postoperative respiratory complications in our series. Therefore, careful patient selection is extremely important to avoid prolonged operative times, especially during the initial phase of a surgeon’s learning curve. Respiratory failure rates in our patients (5.7%) were consistent with those reported by McGinn and colleagues
in their series of 450 patients undergoing MICS-CABG (5.8%). Lung-protective ventilation is important in prevention of significant lung injury. The second facet is occurrence of greater postoperative pain that may be associated with rib spreading. Only 3 patients in our series required patient-controlled analgesia, which is commonly offered to patients who have severe unrelenting pain that is not responsive to opioid analgesics. This could be due to gradual spreading of the ribs during ITA harvest and prevention of rib fractures, which can be achieved by splitting the pectoralis major muscle well beyond the ends of the skin incision. Additionally, bupivacaine is injected into the intercostal spaces superior and inferior to the incision.
Study Limitations
Our study is a retrospective analysis of select patients who underwent a relatively new procedure. It also included the learning curve of the operating surgeon and the entire surgical team, which had a large experience in off-pump CABG and MIDCAB procedures before development of this operation. Therefore, these results can neither be extrapolated to patients undergoing conventional CABG or MICS-CABG with different grafts and configurations nor to other surgical units. Furthermore, our study has a short follow-up and is thereby unable to shed light on the long-term outcomes. However, performance of a quality check of the bypass grafts through postoperative CA helped us to ensure quality control and should lead to good long-term outcomes.
Conclusions
Off-pump MICS-CABG with bilateral ITAs is feasible and can be safely and effectively performed with excellent short-term results in selected patient populations. It has the potential to eliminate the risk of perioperative stroke and chest wound infections despite the use of bilateral ITAs. Good postoperative angiographic results are an assurance for promising long-term results (Figure 5). Our study demonstrates that CABG can now be performed in a minimally invasive manner with the best available conduits (Figure 5). Combining off-pump MICS-CABG with bilateral ITAs for the left coronary tree with PCI of the right coronary system when possible could be a good option for selected patients suitable for hybrid coronary revascularization in the future.
Table E1Postoperative pain management protocol in our institution
Time period
Basic protocol
Medication PRN for sudden-onset sharp pain (pain score ≥4 at rest or ≥5 on mobilization) or prevention before chest tube removal/physiotherapy
Day of surgery
4 × 1 g metamizole (1 g/2 mL) or Paracetamol 4 × 1 g, and Piritramid boluses (0.025 mg/kg) IV
0.025 mg/kg piritramid IV or 1 20 mg tablet of morphine sulphate Inform the floor doctor if no reduction in pain after 2 doses Inform pain nurse or consultant anesthesiologist on call if pain score continues to remain ≥4 at rest or ≥5 on mobilization Consider patient-controlled analgesia
In case of allergy to or contraindications for the use of metamizole, patients receive paracetamol with acetylsalicylic acid. All other patients receive 3× 500 mg ibuprofen per day.
or paracetamol 4 × 0.5-1g, and oxycodon 10-(20) mg PO 2× day
In case of allergy to or contraindications for the use of metamizole, patients receive paracetamol with acetylsalicylic acid. All other patients receive 3× 500 mg ibuprofen per day.
or paracetamol 4× 0.5-1 g
PRN, Pro re nata; IV, intravenous; POD, postoperative day; PO, per os.
∗ In case of allergy to or contraindications for the use of metamizole, patients receive paracetamol with acetylsalicylic acid. All other patients receive 3× 500 mg ibuprofen per day.
All patients with an indication for isolated surgical revascularization are potential candidates for a MICS-CABG approach. However, patients are carefully selected predominantly based on the BMI, CTR, LVEF, left ventricular end-diastolic internal diameter (LVID [d]) and the coronary anatomy with the intention of performing the procedure without cardiopulmonary bypass. Preferable candidates are those with a BMI less than 30 kg/m2, CTR less than 50%, LVEF greater than 45% and LVID [d] less than 55 mm. Patients requiring isolated left-sided coronary revascularization are ideal candidates for MICS-CABG. Right coronary artery revascularization is possible, but technically more challenging. Patients with severe obesity, COPD (forced expiratory volume in 1 second < 50%-80% of the predicted value or PaO2 <60 mm Hg and PaCO2 >55 mm Hg on room air), severe chest deformities, highly stenotic or occluded left subclavian artery, or those requiring emergency CABG or having diffusely diseased or calcified coronary targets or deep intramuscular vessels are also not considered for this approach at the present time. MICS-CABG is also avoided in patients with a contraindication for intraoperative transesophageal echocardiography.
The preoperative assessment protocol includes a thorough history, airway examination, x-ray chest, electrocardiography, transthoracic echocardiography, a carotid Doppler, and pulmonary function tests. Baseline investigations include a full blood count, blood glucose levels, serum electrolytes, renal and liver function tests, and a complete coagulation profile.
Anesthesia
Anesthesia is induced with fentanyl and propofol. Rocuronium or atracurium is used as a paralytic agent to facilitate orotracheal intubation. A 35-41F left-sided double-lumen endotracheal tube is used for 1-lung ventilation. Fiber-optic bronchoscopy is performed to confirm its position in supine und in right semi-lateral position. Ultrasound-guided arterial and central venous catheter insertion is performed. Anesthesia is maintained with a combination of sevoflurane/remifentanil or sufentanil, and depth of anesthesia is monitored with Narcotrend (Monitor Technick, Bad Bramstedt, Germany). Muscle relaxants are administered as necessary at the discretion of the anesthesiologist. Patients are ventilated with a tidal volume of 6 mL/kg of the predicted body weight. Positive end-expiratory pressure is set at 5 to 8 cm H2O, but the Pplateau-pressure is not allowed to exceed 25 cm H2O, and respiratory rate is adjusted to maintain a PaCO2 less than 5.8 kPa. Peak inspiratory and driving pressures are also considered for optimizing ventilation and recruitment maneuvers. FiO2 was adjusted between 60% and 100% to maintain a SpO2 greater than 92%.
Surgical Technique
The patient is positioned in a 30° right lateral decubitus position, with the right arm positioned laterally at the level of the posterior axillary line so as to have access to the anterolateral chest wall. The lower body is placed more flat to facilitate access for femoral cannulation in the event of conversion from off- to on-pump CABG or venous conduit harvest. During the early phase of our experience, the left femoral vein and artery were prepared for cannulation through a small 2-cm groin incision, a precautionary step that is not performed any more.
A 7- to 8-cm incision is made in the left fifth intercostal space, between the midclavicular and anterior axillary lines. A Thoratrak (Medtronic) rib spreader is inserted and gradually pulled cephalad and toward the left by using a Rultract Skyhook (Rultract) or the IMAGate Sternal wire lift (Geister Medizintechnik GmbH) retractor (Figure 1, A). The left ITA is harvested by direct vision in a skeletonized fashion from the left the subclavian vein to the bifurcation with the help of long-shafted instruments and electrocautery blade (Figure 1, B). The left ITA is transected at its distal end after intravenous administration of 5000 units of heparin. Thereafter, a hook is inserted into the anterior mediastinum under the xyphoid process through a 1-cm subxyphoid incision and connected to an angulated bar, which is fixed to the operating table, with a blade guide and coupling rider (Fehling Surgical Instruments Inc, Karlstein, Germany) and progressively pulled cephalad so that the lower third of the sternum is pulled anteriorly, thereby increasing the space within the thorax to facilitate harvest of the right ITA (Figure 1, C). Thereafter, dissection within the anterior mediastinum is continued toward the right pleura, which is opened completely. A laparotomy sponge is inserted into the right pleura to keep the right lung away from the right ITA. Additionally, 3 to 4 stay sutures are placed into the pericardial fat along the right cardiac border and pulled out through a puncture wound in the left chest wall, which is made as posteriorly as possible. This maneuver depresses the heart posteriorly and helps in further increasing the space within the thorax. The right ITA can now be visualized clearly and is harvested by direct vision in a skeletonized fashion (Figure 1, D). The length of the right ITA depends on the number and location of the coronary targets that have to be grafted on the lateral, posterior and inferior walls of the heart. Nonetheless, it is possible to harvest the entire length of the right ITA of from the right the subclavian vein to the bifurcation. The remaining dose of Heparin is administered and the right ITA is transected proximally and distally for use as a free graft.
The pericardium is then opened in a graded fashion. It is first opened from the ascending aorta superiorly to about 3 to 4 cm inferior to the main pulmonary artery. The Y-anastomosis between the left and the right ITAs is constructed at the level of the pulmonary valve. A 5-mm incision is made 1 or 2 intercostal spaces inferior to the thoracotomy to allow introduction of an Octopus NS (Medtronic) epicardial tissue stabilizer. Its foot pods, which are covered with a finger glove, are positioned at the level of the pulmonary valve just lateral to the main pulmonary artery and used as a stable platform to construct the Y-anastomosis (Figure 2, A). The site on the left ITA where the anastomosis has to be performed is fixed to the finger glove with a couple of 6-0 polypropylene sutures, after which, an end-to-side anastomosis is performed with 8-0 polypropylene. Thereafter, the pericardium is further opened toward the apex till the LAD is adequately exposed. The anastomotic site is stabilized with the Octopus NS and an end-to-side anastomosis is performed between the left ITA and the LAD with 7-0 or 8-0 polypropylene (Figure 2, B). Visualization is facilitated by use of an intracoronary shunt and a blower-mister. Thereafter, the high lateral wall vessels such as the diagonal branches of the LAD, the intermediate and proximal obtuse marginal arteries are similarly grafted. The right ITA is anastomosed to one or more of these vessels in an end-to-side or side-to-side fashion using the stabilizer (Figure 2, C).
Further extension of the pericardiotomy around the apex of the heart up to the level of the left phrenic nerve and the additional utilization of a heart positioner enables mobilization of the heart for grafting distal vessels on the posterolateral wall such as the distal obtuse marginal or circumflex or posterolateral ventricular arteries and the posterior descending artery. The head of a Starfish (Medtronic) apical positioner with a thick ligature tied to its neck is placed on the apex of the heart. The ligature helps in maneuvering the apex of the heart into various positions that help securing the vessel to be grafted as close to the thoracotomy as possible, without causing hemodynamic instability. The apex is pulled toward and under the medial end of the thoracotomy incision for the distal obtuse marginal and circumflex arteries and toward the left shoulder for the posterior descending and distal right coronary arteries. The anastomotic sites on the target vessels have to be further stabilized with the Octopus Nuvo stabilizer (Figure 2, D). The anastomoses between the right ITA and the coronary vessels are then performed in a routine manner.
All grafts are assessed intraoperatively using Transit Time Flow Measurement (Medistim). Approximately 75% of the calculated dose of protamine is then administered. Thereafter, the heart is placed back into its normal position and the pericardium is partially closed over the lower third of the heart, taking precautions to prevent graft kinking or compression. The anterolateral surface of the heart is covered with redundant pericardial fat, which prevents displacement of the grafts after inflation of the left lung. Left and right pleural drains are inserted into the thorax through insertion sites of the Octopus Nuvo and subxyphoid hook, respectively. The left lung is gradually reinflated under direct vision and the ribs are approximated with a 2-0 polydioxanone suture. Intramuscular bupivacaine is administered in 1or 2 intercostal spaces superior and inferior to the thoracotomy. The pectoralis major muscle is approximated with No. 2 polyglactin 910. The subcutaneous tissues and skin are closed in layers (Figure 3).
Evidence of Postoperative Ischemia
Presence of elevated CK-MB levels greater than 5× normal upper limit (normal values <24.6 IU/L) or new ST-segment changes on electrocardiography and new regional wall motion abnormalities on postoperative echocardiogram, or greater than 1 episode of ventricular tachycardia or ventricular fibrillation, sudden cardiac arrest, or unexpected or unexplained hemodynamic compromise.
Definitions of Explanatory Variables
The cardiothoracic ratio was defined as the ratio of maximal horizontal cardiac diameter to maximal horizontal thoracic diameter (inner edge of ribs/edge of pleura on chest x-ray) × 100. Perioperative stroke was defined as the development of new focal or global neurologic deficit, either permanent or transient, in the perioperative period, diagnosed clinically and confirmed by computed tomography brain scans. Incomplete revascularization was recorded when the ratio of the number of vessels grafted to those that could be grafted was less than 1. It was also noted for patients planned for future PCI. Grafts or anastomoses were considered suboptimal if they demonstrated greater than 50% stenosis or occlusion on postoperative CA. Respiratory complications included respiratory insufficiency and respiratory failure. Respiratory insufficiency was defined as the need for noninvasive ventilation for a total period of less than 72 hours at any time during the postoperative hospital stay. Respiratory failure was defined as a cumulative requirement for intubation and ventilation for 72 hours or more at any time during the postoperative hospital stay.
References
Davierwala P.M.
Seeburger J.
Pfannmueller B.
Garbade J.
Misfeld M.
Borger M.A.
et al.
Minimally invasive mitral valve surgery: “The Leipzig experience”.
Randomized trial to compare bilateral vs. single internal mammary coronary artery bypass grafting: 1-year results of the Arterial Revascularisation Trial (ART).
Review of a 13-year single-center experience with minimally invasive direct coronary artery bypass as the primary surgical treatment of coronary artery disease.
Analysis of stroke occurring in the SYNTAX trial comparing coronary artery bypass surgery and percutaneous coronary intervention in the treatment of complex coronary artery disease.
Anaortic off-pump versus clampless off-pump using the PAS-Port device versus conventional coronary artery bypass grafting: mid-term results from a matched propensity score analysis of 5422 unselected patients.
Warm ischemia provokes inflammation and regional hypercoagulability within the heart during off-pump coronary artery bypass: a possible target for serine protease inhibition.
Pedicled and skeletonized single and bilateral internal thoracic artery grafts and the incidence of sternal wound complications: Insights from the Arterial Revascularization Trial.
With the introduction of off-pump coronary bypass surgery by Buffolo and Benetti,1,2 a variety of incisions and techniques have evolved,3 aimed at decreasing morbidity and mortality while increasing longevity. Median sternotomy and on-pump revascularization continues to be the most widely used technique. Morbidity of postoperative pain, stroke, sternal wound infection, and long-term durability of multivessel bypass remain a concern. A combination of off-pump and minimally invasive approaches that avoid median sternotomy, particularly in the setting bilateral internal thoracic artery (BITA) harvesting, has evolved during the last 20 years.
The sternotomy remains the most common approach for most cardiac surgical procedures, allowing for excellent exposure, predictability, and a high degree of surgical control. When adopting a minimally invasive approach, a central principle is that the results achieved must be, at minimum, the same as the conventional counterpart. If this can be achieved, then the minimally invasive approach can be considered better. However, it must also be recognized that as invasiveness decreases, complexity increases, and control over the procedure is necessarily diminished.
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