|Year : 2018 | Volume
| Issue : 3 | Page : 90-96
Comparison of left internal mammary harvesting techniques for coronary artery bypass grafting: A prospective study
Sarvesh Kumar1, Vijayant Devenraj1, Akshyaya Pradhan2, Vivek Tewarson1, Sushil Singh K1, BB Kushwaha3
1 Department of Cardiothoracic and Vascular Surgery, King George's Medical University, Lucknow, Uttar Pradesh, India
2 Deparment of Cardiology, KG Medical University, Lucknow, Uttar Pradesh, India
3 Department of Anesthesiology, King George's Medical University, Lucknow, Uttar Pradesh, India
|Date of Web Publication||12-Sep-2018|
Dr. Vijayant Devenraj
Department of Cardiothoracic and Vascular Surgery, King George's Medical University, Lucknow - 226 003, Uttar Pradesh
Source of Support: None, Conflict of Interest: None
Introduction: Left internal mammary artery (LIMA) is the most common arterial conduit used for patients undergoing coronary artery bypass grafting (CABG) surgery. Maintaining pleural integrity during harvesting has been documented to have better patient outcomes. Hence, we evaluated postoperative outcomes using two different LIMA harvesting techniques, one with intact pleura and other with pleura opened.
Methods: In this prospective study, we recruited a total of 110 patients undergoing CABG. Based on the pleural being intact or opened, the patients were divided in two groups. In Group 1, LIMA was harvested with pleura intact (extra-pleural approach) while in Group 2, LIMA was harvested with pleura being opened (intrapleural / pleurotomy). The primary objective was to evaluate the impact on various post-operative parameters like total ventilatory time, mediastinal drainage, need for Blood transfusions, post operative deterioration of lung function , post operative pain scores and duration hospital stay.
Results: Out of 110 patients undergoing CABG, LIMA was harvested by extra-pleural approach in sixty-six while in the rest forty-four pleurotomy was needed. The baseline demographic attributes of patients were similar in both groups. The post operative parameters such as ventilatory time, blood loss, need for blood transfusions, and prolonged hospital stay were found to be significantly higher in the group with intrapleural LIMA harvest technique (P <0.05). Pulmonary complications like pleural effusion, atelectasis were more frequent with in the intrapleural harvest as compared to extra-pleural harvest technique.(P <0.001). Post operative pain scores as evaluated by NRS scale were also significantly higher after intrapleural harvest (P <0.001).
Conclusions: Harvesting of LIMA for CABG extrapleurally has significant post-operative benefits and faster recovery compared to pleurotomy and intraplueral approach.
Keywords: Atelectasis, coronary artery bypass surgery, extrapleural harvest, left internal mammary artery, pleural effusion, pulmonary function test
|How to cite this article:|
Kumar S, Devenraj V, Pradhan A, Tewarson V, SushilS, Kushwaha B. Comparison of left internal mammary harvesting techniques for coronary artery bypass grafting: A prospective study. Heart India 2018;6:90-6
|How to cite this URL:|
Kumar S, Devenraj V, Pradhan A, Tewarson V, SushilS, Kushwaha B. Comparison of left internal mammary harvesting techniques for coronary artery bypass grafting: A prospective study. Heart India [serial online] 2018 [cited 2019 Jun 25];6:90-6. Available from: http://www.heartindia.net/text.asp?2018/6/3/90/241069
| Introduction|| |
The incidence of coronary artery disease has seen a constant upward trend in the past two decades and coronary artery bypass grafting (CABG) remains the mainstay of treatment in many anatomical subsets. The use of arterial grafts for CABG has resulted in long-term survival benefit and an increase in myocardial ischemia free period postoperatively. Left internal mammary artery (LIMA) is the most widely used arterial graft worldwide. Various surgical techniques have been developed to harvest LIMA from its bed to be used as arterial conduit for CABG. The most common technique is using electrocautery for dissection of LIMA and clipping of intercostal arterial side branches. The other newer technique is endoscopic harvesting of LIMA, which is less often used. In both the techniques, the LIMA can be harvested without opening of pleura (extrapleural harvesting) and with opening of pleura (pleurotomy or intrapleural harvest). Intrapleural LIMA harvesting with opening of the pleural cavity and subsequent placement of intercostal drainage tube has been demonstrated to increase postoperative pain and impairment of pulmonary function with increased respiratory complications such as atelectasis and pleural effusions., Surgical technique to harvest LIMA extrapleurally is technically more demanding for the surgeon due to intimate anatomical relations of pleura and internal mammary artery. At the same time, LIMA harvested extrapleurally with intact pleura have been reported to have reduced postoperative pain and pulmonary complications.,
Therefore, in our study, we have compared and analyzed the postoperative outcomes of the two LIMA harvesting techniques (pleura intact-extrapleural harvest versus opening of pleura-intrapleural harvest) in patients undergoing CABG with LIMA arterial conduit.
| Patients and Methods|| |
This study was conducted in the Department of Cardiothoracic and Vascular Surgery, King George's Medical University, Lucknow, India. It was a prospective study and included 110 patients who underwent CABG surgery from November 2011 to October 2013. Institutional ethics committee clearance was obtained before initiation of the study.
All patients were operated by the same surgeon and team. All patients were de novo cardiac surgery patients undergoing isolated CABG. These patients had their antiplatelet drugs discontinued at least 4 days preoperatively. Routine baseline investigations and pulmonary function test (PFT) were done preoperatively.
In our study, we aimed for extrapleural LIMA harvest in all cases. Among these, patients in whom LIMA could not be harvested extrapleurally due to various reasons such as adherent pleura and intimate anatomical relations and the pleura had to be opened, we harvested LIMA intrapleurally. Hence, based on the pleural integrity, the study patients were divided into two groups. In Group 1, LIMA was harvested extrapleurally (pleura intact) and comprised of 66 patients. In Group 2, LIMA was harvested intrapleurally (pleurotomy) and comprised of 44 patients.
We excluded patients with severe chronic obstructive/restrictive pulmonary disease, skeletal rib cage abnormalities, and emergency CABG surgeries.
General anesthesia was induced for all the patients. Following midline sternotomy and before heparinization, LIMA dissection and harvesting was performed. Meticulous care was taken to preserve the integrity of the pleura during LIMA harvesting and when LIMA was harvested without opening pleura (extrapleurally) these formed Group 1. Cases in which the pleural had to be opened and the LIMA was harvested intrapleurally formed the second group, that is, Group 2. Electrocautery was used for dissection and hemoclips were used for side branch occlusions in all the patients and LIMA was harvested as a pedicle. Heparin was administered in a weight-based regimen after harvesting LIMA. At the end of the surgery, after all desired coronary vessels were grafted, heparin reversal with protamine was initiated. A retrosternal and retrocardiac mediastinal drain was left in situ in all the patients of extrapleural LIMA harvest. In patients with intrapleural LIMA harvest, an additional chest tube drain was placed into the left hemithorax.
Collection and evaluation of data
Patients demographic data were recorded. Pre- and postoperative laboratory investigations, PFTs, and arterial blood gas (ABG) analysis were recorded. Postoperative ventilator requirement, ionotropic requirement, total chest (mediastinal) drainage for assessing blood loss, packed red blood cell (PRBC) transfusions units, respiratory complications such as pleural effusion and atelectasis, Intensive Care Unit and hospital stay duration, and wound infection were recorded in data sheets.
PFT was done preoperatively for the initial assessment and on the 5th postoperative day (POD), when most of the patients became fully mobilized and their hemodynamic parameters stabilized. Forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC), and FEV1/FVC ratio were the analyzed parameters in PFT.
POD values of partial oxygen pressure (PaO2), partial carbon dioxide pressure (PaCO2), and oxygen (O2) saturation at room air were recorded from ABG analysis for comparison on the 5th POD.
Preoperative, the 1st and 4th POD chest radiographs were reviewed by the same radiologist, who was unaware of the purpose of the study. Preoperative and 4th POD films included standard posteroanterior and lateral views, whereas 1st POD film were single anteroposterior views taken at the bedside after extubation. Left lower lobe atelectasis and pleural effusion were assessed after removal of chest tubes on the 4th POD.
Numeric Rating Scale (NRS-11) was used as a rating parameter to study postoperative pain quality and intensity on a scale of 0–10. Pain was defined as follows: No pain (0), mild (1-3), moderate (4-6), and severe (7-10). Pain assessment was done at the 5th POD and on 15th POD as outdoor patient in follow-up.
Statistical tools employed
The statistical analysis was done using Statistical Package for the Social Sciences Version 15.0 (SPSS Inc., Chicago, IL, USA). The values were represented in number (%) and mean ± standard deviation (SD) The following statistical formulas were used: mean, SD, Student's t-test, and paired t-test.
| Results|| |
Out of 110 patients undergoing CABG, LIMA was harvested by extrapleural approach in 66 (Group 1) while in the rest 44, pleurotomy was needed (Group 2). Baseline demographic features were similar in both groups [Table 1]. The age of patients ranged from 35 to 72 years with mean age >50 years in both the groups. The mean age of the patients in Group 1 was 56.1 ± 8.0 years and 56.6 ± 8.8 years in Group 2. Majority of the patients were males, 86.4% in former and 77.27% in latter. Mean body mass index (BMI) of patients in Group 1 was comparable to that of Group 2 (23.2 ± 2.9 vs. 22.5 ± 2.4 kg/m2), respectively.
|Table 1: Baseline demographic profiles of patients who underwent extrapleural harvest and intrapleural harvest of the left internal mammary artery|
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The New York Heart Association (NYHA) class at presentation was significantly higher in Group 2 compared to Group 1. Almost 60% of patients in extrapleural harvest group presented with NYHA Class II while the rest were in NYHA Class III. The situation was almost reversed in intrapleural harvest group with 61% in NYHA Class III. Interestingly, none of the patients in either group were in Class I or Class IV. More patients in Group 2 were suffering from diabetes mellitus although the difference was not statistically significant. Majority of Group 1 patients (62.1%) and almost half (47.7%) of Group 2 patients had normal LVEF. Although of note, number of patients with moderately reduced and poor LVEF was nonsignificantly higher in Group 2. Preoperatively, there was no statistically significant difference between two groups for any of the parameters regarding and pulmonary functions.
Majority of the patients (n = 42; 63.63%) in Group 1 required 6–12 h ventilatory support with the mean 6.3 ± 2.05 h, but in Group 2, most of the patients (n = 30; 68.18%) required ventilatory support for >12 h with the mean of 12.5 ± 3.2 h. The difference of mean duration of ventilatory support in two groups was statistically significant (P < 0.001); [Table 2].
|Table 2: Comparison of postoperative outcomes between extrapleural and intrapleural harvesting approach|
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Most of the patients (n = 46; 69.69%) in Group 1 required <6 h inotropic support with a mean duration of 4.2 ± 5.13 h. On the other hand, in Group 2, 26 patients (45.5%) required >6 h ionotropic support with a mean of 7.3 ± 5.2 h. Although this difference was clearly apparent, it was not found to be statistically significant (P = 0.23).
The mean blood loss (measured by mediastinal drainage) in Group 1 was significantly lower in comparison to Group 2 (245.2 ± 101.36 ml vs. 620.2 ± 229.89 ml; P < 0.001). As a corollary, there was also a significant difference between the blood transfusion PRBC requirement in the two groups was significant. While the majority of patients in Group 1 required 1 unit of PRBC with a mean value of 0.24 ± 0.53 units, those in Group 2 required 2 units of PRBC with a mean value of 1.25 ± 1.18 units PRBCs. The mean duration of hospital was also significantly prolonged with extrapleural harvest vis-à-vis an intrapleural approach (6.2 ± 1.26 days vs. 9.9 ± 1.40 days; P = 0.01). Majority of patients (69.69%) in the first group had a hospital stay of <6 days in comparison to Group 2 where the majority of patients (n = 38; 86.36%) had a hospital stay of >6 days.
The postoperative chest X-ray on day 4 revealed that there were 8 (12.3%) patients in Group 1 who had pleural effusion in comparison to 16 (36.3%) patients in Group 2 [Figure 1]. Similarly, while 9 (13.6%) patients of Group 1 had atelectasis of left lower lobe in comparison 20 (45.4%) patients in Group 2. Both the differences were found to be significant statistically (P < 0.05) [Table 3]. However, there was no statistically significant difference between the two groups with relation to wound infection and all-cause mortality.
|Figure 1: Comparison of postoperative complications between extrapleural harvest and intrapleural harvest cohorts. (# - results were statistically significant; P < 0.05)|
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|Table 3: Comparison of postoperative pulmonary function parameters between both groups|
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On the 5th POD, in Group 1, the mean PaO2, PaCO2, and O2 saturation were 88.2 ± 5.40, 36.5 ± 2.29, and 98.0 ± 1.05 in comparison to 63.1 ± 2.57, 41.2 ± 3.01, and 95.9 ± 1.26 in Group 2, respectively. The mean FVC, FEV1, and FEV1/FVC values were 2.0 ± 0.30, 1.6 ± 0.23, and 78.3 ± 3.93 in former while the values in latter stood at 1.7 ± 0.25, 1.3 ± 0.19 and 75.5 ± 6.21, respectively. Hence, for various pulmonary function parameters such as PaO2, FVC, FEV1, and FEV1/FVC ratio, the mean values with extrapleural approach were significantly higher and better as compared to that an intrapleural approach [Table 3].
At POD 5, majority of patients in Group 1 had a moderate pain using an NRS-11 scale with a mean of value of 5.6 ± 0.94 in comparison to Group 2 which had a severe pain score with a mean of 6.6 ± 0.50 (P < 0.001). By the 15th POD, most of the patients (n = 60; 90.90%) in Group 1 had moved to mild pain zone in comparison Group 2 where majority of patients (n = 37; 84.0%) were still languishing in moderate pain zone (mean pain scores − 2.5 ± 0.73 vs. 4.8 ± 0.59; P < 0.001); [Figure 2] and [Table 4].
|Figure 2: (a and b) Hybrid Doughnut chart showing the percentage of patients in various numeric rating scale-11 pain score ranges in at 5th postoperative day (left panel) and 15th postoperative day (right panel). The inner circle displays the results from the extrapleural group while the outer circle represents the intrapleural group|
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|Table 4: Comparison of mean postoperative pain scores by numeric rating scale-11 scale at two different time frames in both groups|
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| Discussion|| |
The present study was a 2-year prospective study and included 110 patients of elective CABG in whom LIMA was harvested as conduit for left anterior descending coronary artery grafting. We demonstrated that extrapleural harvest of LIMA whenever feasible leads to significant decline in postoperative complications along with added advantage of shorter hospital stay and diminished postoperative pain.
The patients demographics such as age, sex, BMI, comorbid conditions such as diabetes mellitus and baseline LVEF were equally matched in both groups except for the preoperative NYHA class which was higher in intrapleural group. All the postoperative variables such as pleural collection, atelectasis, ventilatory time, mediastinal drainage, blood transfusion requirement (PRBC), PFT parameters, pain score, hospital stay, and all-cause mortality were higher with an intrapleural approach.
Previous studies had demonstrated a significant decrease in respiratory complications in the patients who had LIMA harvested extrapleurally.,, This was aptly reflected in our study where the differences between the ventilatory time of both groups were found to be statistically significant. Others studies have also reported the higher use of inotropic agents during recovery in patients in whom pleura had been opened., Although our results mirrored these trends, we could not achieve statistical significance.
With respect to postoperative blood loss measured by total mediastinal drainage and subsequent need for blood or component transfusion, the extrapleural approach emerges as a clear winner over intrapleural (pleura open) group. This has been shown by prior researchers and affirmed by our group.,,, The difference is striking in our project with majority of patients having minor blood loss (<300 ml) and not requiring any PRBC transfusion with an extrapleural approach. This will definitely translate into diminished postoperative morbidity and mortality following CABG.
Pulmonary complications are also a cause of concern following CABG and most of the data support benefits of an intact pleura during LIMA Harvest.,,,,, Our results concur with the existing data with a statistically significant decline in pleural effusion and atelectasis with an intact pleural approach.
ABG analysis in the study also favored an extrapleural harvest technique. Current literature also supports such an approach with demonstrable benefits in PaO2, PaCO2, and O2 saturation in patients undergoing extrapleural harvesting of LIMA.,,
Assessment of pulmonary function on the 5th POD demonstrated clearly visible advantages of all parameters, namely, FVC, FEV1, and FEV1/FVC ratio. There was no difference in preoperative PFT's assessment as previously alluded too. It has been shown that a possible mechanism for decline in FEV1 and FVC in intrapleural harvesting of LIMA group is related to higher incidence of pleural effusion and atelectasis. Postoperative pain was found to be an important factor for decrease in PFT in either group because of trauma to chest wall.
NRS-11 was used in this study as a rating parameter to study postoperative pain quality and intensity on a scale of 0–10. The mean scores were significantly lower with extrapleural group in early postoperative period (day 5) and benefits were sustained in the late postoperative period (Day 15). Interestingly, the bull's eye plot revealed that at all points of time percentage of patients in lower (NRS-11) pain zones was higher with extrapleural approach vis-à-vis the intrapleural cohort. A correlation between preservation of pleural integrity during IMA harvesting for positive beneficial effect to decreased postoperative pain has been postulated and aptly demonstrated in the present research.
Longer hospital stays in patients whose pleura has been opened during LIMA harvesting leads to additional burden on hospital resources with increased morbidity., This was also observed in the current cohorts despite no significant correlation with the mortality or wound infection with either techniques.
| Conclusion|| |
Harvesting of LIMA for CABG with intact pleura (extrapleurally) has significant postoperative benefits for patients resulting in decreased ventilatory time, reduced pain, blood loss, and blood transfusions with better lung function parameters and faster recovery compared to patients with pleurotomy and intrapleural harvest technique for LIMA. Harvesting of LIMA extrapleurally should be a preferred technique for all patients undergoing CABG with LIMA arterial graft.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2]
[Table 1], [Table 2], [Table 3], [Table 4]