Sternal Blood Flow Research Articles

Incidence and Risk Factors for Surgical Site Infection Following Coronary Artery Bypass Graft Procedures

Background: Deep and organ-space surgical site infections (SSIs) are serious complications of coronary artery bypass graft (CABG) procedures. It is unclear whether the use of bilateral versus single internal mammary artery (BIMA vs SIMA) and surgical approach to internal mammary artery (IMA) harvest (pedicled vs skeletonized) are independent risk factors for SSI. The use of BIMA grafting redirects blood flow away from the sternum to the heart and may increase SSI risk due to lower tissue perfusion. A skeletonized approach to graft harvest, wherein the IMA is dissected free of surrounding tissue to preserve collateral sternal blood flow, may decrease SSI risk as compared to a pedicled approach in which the IMA is mobilized within a tissue pedicle. We describe the incidence and potential risk factors for post-CABG SSI in an academic tertiary-care center performing ~500 IMA procedures annually. Methods: Data were abstracted on adult patients who underwent a CABG procedure using at least 1 IMA graft between July 2017 and June 2020. Additional data on potential risk factors for SSI were obtained electronically from hospital data marts and the Division of Cardiac Surgery database, including demographics, comorbidities, number of arterial grafts, surgical approach, surgeon, and discharge location. Using standard NHSN definitions, infection control practitioners identified post-CABG deep and organ-space SSIs. Patient and procedure characteristics were evaluated as potential risk factors for deep and organ-space SSI using the Fisher exact test. Results: Of 1,591 CABG procedures performed during the study period, 1,244 (78.2%) were performed using a SIMA technique and 347 (21.8%) were performed using a BIMA technique. The overall post-CABG SSI incidence was 1.2 per 100 procedures, with 1.0 SSIs per 100 SIMA procedures and 1.7 SSIs per 100 BIMA procedures. Table 1 demonstrates an increase over time in proportion of CABG procedures performed using SIMA and skeletonized IMA grafts. We also observed a decrease in overall SSI incidence over this period. See Table 2 for univariate predictors of post-CABG SSI. Conclusions: Female sex, BMI ≥40, age ≥75 years, diabetes, and discharge to a rehabilitation setting were associated with development of post-CABG SSI. Although the overall incidence of deep and organ-space SSI in our cohort was very low, making it difficult to draw conclusions about potentially modifiable risk factors, an increase in the use of SIMA and skeletonized grafts appears to be accompanied by a decrease in SSI incidence. More data from our institution and others are needed to determine the significance of this trend.Funding: NoDisclosures: None

Measuring arterial oxygen saturation from an intraosseous photoplethysmographic signal derived from the sternum

Photoplethysmography performed on the peripheral extremities or the earlobes cannot always provide sufficiently rapid and accurate calculation of arterial oxygen saturation. The purpose of this study was to evaluate a novel photoplethysmography prototype to be fixed over the sternum. Our hypotheses were that arterial oxygen saturation can be determined from an intraosseous photoplethysmography signal from the sternum and that such monitoring detects hypoxemia faster than pulse oximetry at standard sites. Sixteen healthy male volunteers were subjected to incremental hypoxemia using different gas mixtures with decreasing oxygen content. The sternal probe was calibrated using arterial haemoglobin CO-oximetry (SaO2%). Sternal probe readings (SRHO2%) were then compared to SaO2% at various degrees of hypoxia. The time to detect hypoxemia was compared to measurements from standard finger and ear pulse oximeters. A significant association from individual regression between SRHO2% and SaO2% was found (r2 0.97), Spearman R ranged between 0.71 and 0.92 for the different inhaled gas mixtures. Limits of agreement according to Bland–Altman plots had a increased interval with decreasing arterial oxygen saturation. The sternal probe detected hypoxemia 28.7 s faster than a finger probe (95% CI 20.0-37.4 s, p < 0.001) and 6.6 s faster than an ear probe (95% CI 5.3–8.7 s, p < 0.001). In an experimental setting, arterial oxygen saturation could be determined using the photoplethysmography signal obtained from sternal blood flow after calibration with CO-oximetry. This method detected hypoxemia significantly faster than pulse oximetry performed on the finger or the ear.

Invited Commentary

The authors of this study [1Rubens F.D. Chen L. Bourke M. Assessment of the association of bilateral internal thoracic artery skeletonization and sternal wound infection after coronary artery bypass grafting.Ann Thorac Surg. 2016; 101: 1677-1683Abstract Full Text Full Text PDF Scopus (25) Google Scholar] have again verified the safety of bilateral internal thoracic arterial (BITA) grafting in patients requiring coronary revascularization. Their sizeable experience involving a large cohort of patients comparing skeletonized pedicle harvesting with traditional pedicle harvesting techniques demonstrated equivalent rates of sternal infections and other related complications. Over time, arterial conduit use has become the standard of care, relegated to hallowed evidence-based acceptance in appropriately selected patients. However, despite the universal acceptance of single arterial grafting, ElBardissi and colleagues [2ElBardissi A.W. Aranki S.F. Sheng S. O’Brien S.M. Greenberg C.C. Gammie J.S. Trends in isolated coronary artery bypass grafting: an analysis of the Society of Thoracic Surgeons adult cardiac surgery database.J Thorac Cardiovasc Surg. 2012; 143: 273-281Abstract Full Text Full Text PDF PubMed Scopus (345) Google Scholar] revealed that only 4% to 12% of surgical revascularization procedures use BITA; clearly, evidence-based practice is rarely translated into routine clinical practice outside of reporting centers. Previous guidelines supporting arterial grafting with BITA conduits were often dependent on the severity of the native vessel disease; these studies often discouraged the use of BITA when the stenosis was not critical (<90%) [3Hillis L.D. Smith P.K. Anderson J.L. et al.American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines2011 ACCF/AHA guideline for coronary artery bypass graft surgery: executive summary: a report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines.J Thorac Cardiovasc Surg. 2012; 143: 4-34Abstract Full Text Full Text PDF PubMed Scopus (186) Google Scholar]. In regards to sternal complications, Dorman and coworkers [4Dorman M.J. Kurlansky P.A. Traad E.A. Galbut D.L. Zucker M. Ebra G. Bilateral internal mammary artery grafting enhances survival in diabetic patients a 30-year follow-up of propensity score–matched cohorts.Circulation. 2012; 126: 2935-2942Crossref PubMed Scopus (123) Google Scholar] addressed the effects of diabetes in a high-volume center with extensive BITA use. An even earlier large-scale, multicenter randomized arterial revascularization trial (ART) compared revascularization using BITA for the two most important left-sided target arteries with single internal thoracic artery (ITA) coupled with a combination of radial arteries or venous conduits for the remaining graft sites. This study demonstrated equivalent low 30-day (1%) and 1-year (2.5%) mortality rates, as well as similar rates of stroke and myocardial infarction, and the need for repeat revascularization for BITA grafting compared with the more traditional single ITA grafting strategy. Of note in this study was the increased incidence of sternal wound healing complications requiring reconstruction (1.9% versus 0.6%) in BITA patients compared with single ITA use, especially in diabetic patients. Although this randomized trial used a variety of ITA harvesting techniques, the results suggested that skeletonization of the ITA during harvesting may yield fewer sternal complications [5Taggart D.P. Altman D.G. Gray A.M. et al.ART InvestigatorsRandomized trial to compare bilateral vs. single internal mammary coronary artery bypass grafting: 1-year results of the Arterial Revascularisation Trial (ART).Eur Heart J. 2010; 31: 2470-2481Crossref PubMed Scopus (303) Google Scholar]. It is clear that skeletonization affords the surgeon increased arterial conduit length, creating the potential for multiple grafts of the left coronary circulation with a longer left ITA, as well as improving the distal reach of the right coronary arterial target sites with a skeletonized right ITA. Importantly, the known risk factors for suspected increased sternal complications from BITA use (increased body mass index, diabetes, peripheral vascular disease, female sex, and preoperative anemia) are more related to full sternotomy itself, instead of ITA harvesting, and were not significantly different in this report. Bilateral ITA utilization strategies for complex coronary revascularization has clearly demonstrated safety, diminished future interventions, improved graft longevity, and increased patient survival rates. The current report provides further evidence that harvesting techniques matter; hopefully studies like these will prevail over the continued reluctance to commit to more arterial grafting among the cardiac surgery community. The authors are to be congratulated for their excellent results, as well as advancing our understanding of this important topic. Assessment of the Association of Bilateral Internal Thoracic Artery Skeletonization and Sternal Wound Infection After Coronary Artery Bypass GraftingThe Annals of Thoracic SurgeryVol. 101Issue 5PreviewSkeletonization is a technique of bilateral internal thoracic artery (BITA) harvest that preserves sternal blood flow. We sought to identify the relationship of skeletonization and sternal wound infection in a population undergoing BITA harvest. Full-Text PDF

Assessment of the Association of Bilateral Internal Thoracic Artery Skeletonization and Sternal Wound Infection After Coronary Artery Bypass Grafting

Skeletonization is a technique of bilateral internal thoracic artery (BITA) harvest that preserves sternal blood flow. We sought to identify the relationship of skeletonization and sternal wound infection in a population undergoing BITA harvest. Demographics and outcomes were recorded from patients undergoing coronary artery bypass graft surgery with BITA using either skeletonized (n= 531) or nonskeletonized (n= 970) techniques. The primary outcome was total infection. Propensity scores analysis as well as univariable and multivariable analysis was performed to determine the effect of skeletonization in the total cohort and in each sex. Although patients undergoing skeletonized BITA had a lower body mass index, they were significantly older, with a higher proportion of women, diabetes mellitus, urgent or emergent surgery, renal failure, vascular and lung disease, and lower preoperative hemoglobin. There was a significant effect of skeletonization in decreasing total infection incidence (odds ratio [OR] 0.606, 95% confidence interval [CI]: 0.383 to 0.959, p= 0.032). The effect of skeletonization on total infection in men was more prominent (OR 0.466, 95% CI: 0.290 to 0.870), whereas there was no effect in women (OR 0.887, 95% CI: 0.441 to 1.786). Multivariable analysis confirmed that skeletonization was protective (OR 0.606, 95% CI: 0.383 to 0.957, p= 0.032). Other factors associated included being female (OR 3.327, 95% CI: 2.080 to 5.322, p < 0.001), insulin-dependent diabetes mellitus (OR 2.638, 95% CI: 1.506 to 4.624, p= 0.001), peripheral vascular disease (OR 2.101, 95% CI: 1.247 to 3.539, p= 0.005), increased body mass index (OR 1.100, 95% CI: 1.054 to 1.149, p < 0.001), and decreased preoperative hemoglobin (OR 0.984, 95% CI: 0.972 to 0.997, p= 0.013). Skeletonization is associated with a significant protective effect with regard to sternal infection after coronary artery bypass graft surgery with BITA. Being female is a major risk factor for infection, and the risk is not modified significantly with a strategy of skeletonization in women.

68. Bilateral internal mammary artery in coronary artery bypass grafting and the risk of sternal wound infection in diabetic patients

Background Coronary artery bypass grafting is superior to percutaneous interventions in diabetic patients with multi-vessel coronary disease. The use of bilateral internal mammary arteries may lead to better long-term survival, but the risk of postoperative deep sternal wound infection has limited its use in diabetic patients. However, studies have reported conflicting results. Methods MEDLINE, EMBASE, World of Science, and the Cochrane library were searched for studies comparing the incidence of deep sternal wound infection in diabetic patients undergoing either (LITA) or BITA harvest. We used random effect models to compare risk ratios within groups. Results One randomized controlled trial and 10 observational studies (126,235 diabetic patients: 122,465 LITA, 3770 BITA) met inclusion criteria. Deep sternal wound infection occurred in 3.1% and 1.6% for the BITA and LITA cohorts, respectively. The risk ratio for deep sternal wound infection development was 1.71 (1.37–2.14) for BITA compared with LITA. Patients who underwent skeletonized BITA harvest had a similar risk of deep sternal wound infection compared with LITA (0.9 [0.42–2.09]), although pedicled harvest demonstrated increased risk (1.77 [1.4–2.23]). Early mortality was comparable in the LITA cohort (2.5%) and the BITA cohort (2.3%; p = 0.8). Conclusions The risk of sternal wound infection can be minimized in diabetic patients undergoing CABG by performing ITA harvested in a skeletonized manner with meticulous attention to preserving sternal blood flow. Pedicled harvest is to be discouraged when utilizing both ITA owing to a significant increase in the risk of sternal wound infection.

Bilateral Internal Thoracic Artery Harvest and Deep Sternal Wound Infection in Diabetic Patients

Coronary artery bypass graft surgery is superior to percutaneous intervention in diabetic patients with multivessel disease. The use of bilateral internal thoracic arteries (BITA) may provide better long-term graft patency, but the risk of postoperative deep sternal wound infection has limited its use in diabetic patients. However, studies have reported conflicting results, and require systematic evaluation. MEDLINE, EMBASE, World of Science, and the Cochrane library were searched for randomized controlled trials and observational studies comparing the incidence of deep sternal wound infection in diabetic patients undergoing either left internal thoracic artery (LITA) or BITA harvest. We used random effect models to compare risk ratios within groups. One randomized controlled trial and 10 observational studies (126,235 diabetic patients: 122,465 LITA, 3,770 BITA) met inclusion criteria. Deep sternal wound infection occurred in 3.1% and 1.6% for the BITA and LITA cohorts, respectively. The risk ratio for deep sternal wound infection development was 1.71 (1.37 to 2.14) for BITA compared with LITA. Patients who underwent skeletonized BITA harvest had a similar risk of deep sternal wound infection compared with LITA (0.9 [0.42 to 2.09]), although pedicled harvest demonstrated increased risk (1.77 [1.4 to 2.23]). Early mortality was comparable in the LITA cohort (2.5%) and the BITA cohort (2.3%; p = 0.8). The risk of deep sternal wound infection can be minimized in diabetic patients undergoing coronary artery bypass graft surgery by performing ITA harvested in a skeletonized manner with meticulous attention to preserving sternal blood flow. Pedicled harvest is to be discouraged when utilizing both ITA owing to a significant increase in the risk of postoperative deep sternal wound infection.

Decreasing sternum microcirculation after harvesting the internal thoracic artery

The effect of harvesting the internal thoracic artery (ITA) on blood supply to the sternum is not completely understood. Using a novel laser Doppler flow meter, we evaluated changes in sternum microcirculation prior to and after ITA harvesting. Forty-six patients (37 males, 69.4 ± 7.9 years) scheduled for coronary artery bypass grafting were enrolled into the study and divided into skeletonized (n = 23) and pedicled (n = 23) groups of patients with a left ITA. All right ITA were harvested using the skeletonized method. Sternal blood flow was measured presternally and retrosternally in the upper, middle, and lower sternal parts with a novel laser Doppler flow meter that measures blood flow at 1-mm depth using a 780-nm laser. Following median sternotomy, blood flow was measured before and after ITA harvesting. In all patients (46 left and 16 right ITA cases), the middle part of the retrosternal microcirculation deteriorated (middle: pre- 2.71 ± 1.49, post- 2.43 ± 1.01 ml min(-1)100 g(-1); p < 0.05), while blood flow of other parts did not change. In patients with left ITA divided into skeletonized and pedicled groups, although middle retrosternal blood flow decreased after harvesting in both groups, there was no difference in deterioration between the groups. In patients with right ITA, the middle and lower retrosternal blood flow also deteriorated. The degree of sternal microcirculation damage after ITA harvesting is not different between skeletonized and pedicled group patients, suggesting that skeletonization is not advantageous for maintaining sternal microcirculation.

Skeletonization of the internal thoracic artery for coronary artery bypass grafting

Multiple cohort studies have shown that long-term outcomes after coronary surgery can be markedly improved when bilateral internal thoracic arteries (BITA) are used for revascularization. Applying this strategy is challenging, however, as a large proportion of patients suffer from comorbidities such as diabetes, and sternal devascularization with BITA may increase the risk of complications. Skeletonization is a technique of internal thoracic artery (ITA) harvest that has been proposed to reduce chest wall ischemia and thus minimize these problems. Evidence is presented from animal and human studies which confirm that skeletonization preserves sternal blood flow. When meticulously completed, skeletonization is not associated with vessel wall damage. Intrapatient comparisons have conclusively demonstrated that skeletonization minimizes chest wall pain and discomfort. Many studies have confirmed that, when this strategy is used for BITA, the incidence of sternal wound infection approximates that seen with single ITA use, even in diabetic patients on insulin. Finally, there is no evidence in the current literature to suggest that skeletonization jeopardizes ITA patency. The strategy of skeletonization is an advance that will facilitate complete arterial revascularization in high-risk patients whose surgery has previously been limited to saphenous vein conduits. Theoretical concerns challenging this approach should be tested long-term in a randomized clinical trial in patients undergoing BITA revascularization.

Near-infrared spectroscopy for noninvasive evaluation of chest wall ischemia immediately after left internal thoracic artery harvesting

The conclusions remain controversial about whether the sternal blood flow is preserved or diminished after internal thoracic artery (ITA) harvesting for coronary artery bypass grafting (CABG), especially in diabetic patients. We investigated the blood supply of the chest wall noninvasively using near-infrared spectroscopy (NIRS) immediately after CABG. The study group comprised 30 patients who underwent CABG using a skeletonized left ITA through median sternotomy. As a control group, three nondiabetic patients undergoing valve surgery through median sternotomy were also included. On arrival of the patient in the intensive care unit immediately after surgery, two reflectance sensors were placed on the bilateral parasternal regions at the fourth intercostal space to record regional oxygen saturation (rSO(2)) and hemoglobin index (HbI) continuously approximately for 17 h. The differences in right and left values (R-L rSO(2) and R-L HbI) were significantly greater in the diabetic patients than in the nondiabetic patients (3.74% +/- 2.47% vs. 1.98% +/- 1.67 %, p = 0.036; and 0.28 +/- 0.19 vs. 0.13 +/- 0.13, p = 0.020). The R-L HbI was significantly greater in the on-pump patients than in the off-pump patients, although there was no significant difference in R-L rSO(2). Both R-L rSO(2) and R-L HbI were similar among the control, nondiabetic, and off-pump patients. The technique of NIRS enables noninvasive, continuous monitoring of chest wall perfusion immediately after ITA harvesting. Our study using NIRS showed a decrease in blood flow and oxygen metabolism of the hemisternum after LITA harvest in diabetic CABG patients.

Sternal Nourishment in Various Conditions of Vascularization

Early changes in sternal perfusion were studied after midline sternotomy and different methods of mammary artery (MA) harvesting. Our observations were made in the swine model after midline sternotomy. In group 1 (6 animals), after unilateral skeletonized MA harvesting, (99m)Tc particles were injected intravenously. In group 2 (7 animals), after unilateral mammary artery and vein harvesting (semiskeletonized technique), (99m)Tc particles were injected intravenously. In group 3 (5 animals), after skeletonized bilateral MA harvesting, 99mTc particles were injected into the intercostal musculature lateral to the sternal border. In groups 1 to 3, sternal samples were analyzed using gamma counting. In group 4 (6 animals), unilateral skeletonized MA harvesting was performed. In group 5 (5 animals), the MA was harvested unilaterally using the semiskeletonized technique. In groups 4 and 5, sternal blood flow was assessed using thermography. Data were collected in all groups for 5 hours postoperatively. Both radioactive and thermographic flow measurements showed a statistically significant decrease in sternal blood flow on the side of harvested mammary vessels, regardless of harvesting technique. Radioactivity of the devascularized hemisterni on the side of intramuscular particle injection was substantially higher than in the contralateral half, confirming the role of diffusion in sternal nourishment. The distal sternal segments were least perfused by the MA. There is an acute reduction of sternal perfusion during the early postoperative period, even if collaterals are preserved by skeletonized MA harvesting. Diffusion plays an important role in sternal nourishment, particularly of the xiphoid, and even more so after MA harvesting.

Changes in Sternal Blood Flow after Different Methods of Internal Thoracic Artery Harvesting

The study was designed to assess the early changes in sternal perfusion after midline sternotomy and different (skeletonized versus semiskeletonized) techniques of internal thoracic artery (ITA) harvesting. The experiments were performed in the swine model. After midline sternotomy, ITA harvesting (skeletonized technique) was performed unilaterally in Group I (6 animals). The ITA and the internal thoracic vein (ITV) were harvested (semiskeletonized technique) in Group II (5 animals). The contralateral sternal half served as a control. Using a thermographic camera with a 0.06 degrees C sensitivity, sternal perfusion was assessed 2 and 5 hours after surgery. Midline sternotomy alone did not affect sternal blood flow. A statistically significant ( p < 0.05) reduction in perfusion of the involved sternal half in comparison to the control side was detected at 2 and 5 hours after surgery. The degree of perfusion deficit was not related to the harvesting technique. Skeletonized and semiskeletonized ITA harvesting techniques caused a similar acute reduction in sternal perfusion during the early postoperative period and this effect lasted for at least 5 hours.

Sternal blood flow during coronary artery bypass surgery – An experimental study using laser doppler flowmetry

Sternal blood flow during coronary artery bypass surgery – An experimental study using laser doppler flowmetry

Sternal blood flow during mobilization of the internal thoracic arteries

A laser Doppler tissue perfusion monitor was used to measure sternal blood flow before, during, and after mobilization of the internal thoracic arteries in 24 patients undergoing coronary artery bypass grafting. To minimize chest wall injury, a narrow pedicle was mobilized. Bilateral flow data were available from 15 of the 24 patients. Analysis of these 39 studies showed no significant reduction of sternal blood flow as a consequence of mobilization of the internal thoracic arteries except in 2 patients who were both diabetic and obese.

The effects of different techniques of internal mammary artery harvesting on sternal blood flow

We investigated chest wall blood flow in a canine model to determine if the technique used to harvest the mammary artery has a differential effect on residual chest wall blood flow. Eight dogs underwent bilateral internal mammary artery mobilization; one artery was harvested as a pedicle and the other was harvested as a skeletonized vessel. Residual blood flow to the chest wall distribution of each artery was measured with radioactive microspheres. Chest wall blood flow was significantly decreased from preharvest levels after internal mammary artery mobilization regardless of the technique used. Tissue blood flows decreased to 46.9%, 22.1%, and 41.2% of baseline values for the manubrium (p < 0.01), sternum (p < 0.001), and ribs (p < 0.05), respectively. Residual sternal blood flow on the side of the skeletonized vessel was significantly greater than on the side of the pedicle graft (2.60 +/- 0.68 versus 1.27 +/- 0.27 cm3/min/100 gm, p < 0.001). We conclude that minimization of tissue mobilization during internal mammary artery harvesting may reduce sternal devascularization. This finding may have clinical significance with respect to lowering the incidence of sternal wound complications in coronary bypass surgery using the internal mammary artery as a bypass conduit.

Effect of Internal Mammary Artery Mobilization on Sternal Blood Flow

Use of the internal mammary artery as a conduit for coronary artery bypass has enhanced this procedure in terms of prolonged graft patency. An earlier warning that use of both arteries would devascularize the sternum was based on postmortem radiologic imaging. This was complemented by a subsequent animal study employing isotopic microspheres. In the present clinical study, laser Doppler flowmetry was adapted to identify changes in blood supply to the left half of the divided manubrium sternum during separation of the left internal mammary artery from its chest wall attachment. Our finding of continued blood flow after this event suggests that complete devascularization of the sternum does not take place. Quality of sternal bone and surrounding tissues and clinical indications should remain as factors influencing use of one or both internal mammary arteries.