Harvesting, routing, and anastomosing the left internal mammary artery graft

Thymus fat as an attractive source of angiogenic factors in elderly subjects with myocardial ischemia

Aging negatively affects angiogenesis which is found to be linked to declined vascular endothelial growth factor (VEGF) production. Adult human thymus degenerates into fat tissue (thymus adipose tissue (TAT)). Recently, we described that TAT from cardiomyopathy ischemic subjects has angiogenic properties. The goal of our study was to analyze whether aging could also impair angiogenic properties in TAT as in other adipose tissue such as subcutaneous (subcutaneous adipose tissue (SAT)). SAT and TAT specimens were obtained from 35 patients undergoing cardiac surgery, making these tissues readily available as a prime source of adipose tissue. Patients were separated into two age-dependent groups; middle-aged (n = 18) and elderly (n = 17). Angiogenic, endothelial, and adipogenic expression markers were analyzed in both tissues from each group and correlations were examined between these parameters and also with age. There were no significant differences in subjects from either group in clinical or biological variables. Angiogenic markers VEGF-A, B, C, and D and adipogenic parameters, peroxisome proliferator-activated receptors (PPARγ2), FABP4, and ADRP showed elevated expression levels in TAT from elderly patients compared to the middle-aged group, while in SAT, expression levels of these isoforms were significantly decreased in elderly patients. VEGF-R1, VEGF-R2, VEGF-R3, Thy1, CD31, CD29, and VLA1 showed increased levels in TAT from the elderly compared to the middle-aged, while in SAT these levels displayed a decline with aging. Also, in TAT, angiogenic and endothelial parameters exhibited strong positive correlations with age. TAT appears to be the most appropriate source of angiogenic and endothelial factors in elderly cardiomyopathy subjects compared to SAT.

Reoperative off-pump coronary artery bypass grafting: current outcomes, concerns and controversies

Increasing numbers of patients have undergone coronary artery bypass grafting in the last four decades. As a result, the incidence of reoperative coronary artery bypass grafting is rising. Reoperative procedures pose several technical difficulties and are associated with increased operative risks, which exceed those of the initial revascularization. As the incidence of reoperative procedures is increasing so is the experience of reoperative coronary artery bypass grafting, with the resultant evolution of several alternative strategies to lower the operative risks. These strategies include alternative techniques for re-entry, strict avoidance of graft manipulation to minimize the risk of graft atheroembolism, and modification of the method of myocardial protection, depending on the status of the native coronary circulation and the patency of venous or arterial grafts. Off-pump coronary artery bypass grafting is one such technique that, through the avoidance of inherent risks of cardiopulmonary bypass, has the potential to reduce the morbidity associated with reoperative coronary artery bypass grafting. This article evaluates the current outcomes of reoperative off-pump coronary artery bypass grafting, and highlights the concerns and controversies associated with this strategy.

VEGF gene expression in adult human thymus fat: a correlative study with hypoxic induced factor and cyclooxygenase-2

It is well known that the adult human thymus degenerates into fat tissue; however, it has never been considered as a potential source of angiogenic factors. Recently, we have described that this fat (TAT) produces angiogenic factors and induces human endothelial cell proliferation and migration, indicating its potential angiogenic properties.

Design

Adult thymus fat and subcutaneous adipose tissue specimens were obtained from 28 patients undergoing cardiac surgery, making this tissue readily available as a prime source of adipose tissue. We focused our investigation on determining VEGF gene expression and characterizing the different genes, mediators of inflammation and adipogenesis, and which are known to play a relevant role in angiogenesis regulation.

Results

We found that VEGF-A was the isoform most expressed in TAT. This expression was accompanied by an upregulation of HIF-1α, COX-2 and HO-1 proteins, and by increased HIF-1 DNA binding activity, compared to SAT. Furthermore, we observed that TAT contains a high percentage of mature adipocytes, 0.25% of macrophage cells, 15% of endothelial cells and a very low percentage of thymocyte cells, suggesting the cellular variability of TAT, which could explain the differences in gene expression observed in TAT. Subsequently, we showed that the expression of genes known as adipogenic mediators, including PPARγ1/γ2, FABP-4 and adiponectin was similar in both TAT and SAT. Moreover the expression of these latter genes presented a significantly positive correlation with VEGF, suggesting the potential association between VEGF and the generation of adipose tissue in adult thymus.

Conclusion

Here we suggest that this fat has a potential angiogenic function related to ongoing adipogenesis, which substitutes immune functions within the adult thymus. The expression of VEGF seems to be associated with COX-2, HO-1 and adipogenesis related genes, suggesting the importance that this new fat has acquired in research in relation to adipogenesis and angiogenesis.

Angiogenic properties of adult human thymus fat

The endogenous proangiogenic properties of adipose tissue are well recognized. Although the adult human thymus has long been known to degenerate into fat tissue, it has never been considered as a potential source of angiogenic factors. We have investigated the expression of diverse angiogenic factors, including vascular endothelial growth factor A and B, angiopoietin 1, and tyrosine-protein kinase receptor-2 (an angiopoietin receptor), and then analyzed their physiological role on endothelial cell migration and proliferation, two relevant events in angiogenesis. The detection of the gene and protein expression of the various proteins has been performed by immunohistochemistry, Western blotting, and quantitative real-time polymerase chain reaction. We show, for the first time, that adult thymus fat produces a variety of angiogenic factors and induces the proliferation and migration of human umbilical cord endothelial cells. Based on these findings, we suggest that this fat has a potential angiogenic function that might affect thymic function and ongoing adipogenesis within the thymus.

Do you need to clamp a patent left internal thoracic artery-left anterior descending graft in reoperative cardiac surgery?

BACKGROUND

Dogma suggests optimal myocardial protection in cardiac surgery after prior coronary artery bypass graft surgery (CABG) with patent left internal thoracic artery (LITA) pedicle graft requires clamping the graft. However, we hypothesized that leaving a patent LITA-left anterior descending (LAD) graft unclamped would not affect mortality from reoperative cardiac surgery.

METHODS

Data were collected on reoperative cardiac surgery patients with prior LITA-LAD grafts from July 1995 through June 2006 at our institution. With the LITA unclamped, myocardial protection was obtained initially with antegrade cardioplegia followed by regular, retrograde cardioplegia boluses and systemic hypothermia. The Society of Thoracic Surgeons National Database definitions were employed. The primary outcome was perioperative mortality. Variables were evaluated for association with mortality by bivariate and multivariate analyses.

RESULTS

In all, 206 reoperations were identified involving patients with a patent LITA-LAD graft. Of these, 118 (57%) did not have their LITA pedicle clamped compared with 88 (43%) who did. There were 15 nonsurvivors (7%): 8 of 188 (6.8%) in the unclamped group and 7 of 88 (8.0%) in the clamped group (p = 0.750). Nonsurvivors had more renal failure (p = 0.007), congestive heart failure (p = 0.017), and longer perfusion times (p = 0.010). When controlling for independently associated variables for mortality, namely, perfusion time (odds ratio 1.014 per minute; 95% confidence interval: 1.004 to 1.023; p = 0.004) and renal failure (odds ratio 4.146; 95% confidence interval: 1.280 to 13.427; p = 0.018), an unclamped LITA did not result in any increased mortality (odds ratio 1.370; 95% confidence interval: 0.448 to 4.191). Importantly, the process of dissecting out the LITA resulted in 7 graft injuries, 2 of which significantly altered the operation.

CONCLUSIONS

In cardiac surgery after CABG, leaving the LITA graft unclamped did not change mortality but may reduce the risk of patent graft injury, which may alter an operation.

Technique of Lung Retraction During Internal Mammary Artery Harvesting

We describe a novel technique for lung retraction during dissection of the internal mammary artery for its use in coronary artery bypass grafting. The lung is retracted using the blades of the Octopus (Medtronic Inc, Minneapolis, MN) suction stabilizer, without the suction connected. This technique can be used when the internal mammary artery is harvested by widely opening the pleura or by the extrapleural approach. This technique makes mammary artery dissection easy, and it can be used for harvesting internal mammary arteries bilaterally. The method described is simple, causes no impairment in gas exchange, and offers no additional expense, because the same stabilizer would be used later for the off-pump coronary artery bypass surgery.

Injury to a patent left internal thoracic artery graft at coronary reoperation

BACKGROUND

The purpose of this study was to determine the prevalence, outcome, and operative strategies for patients having injury to a patent left internal thoracic artery (LITA) graft to the left anterior descending coronary artery (LAD) at coronary reoperation.

METHODS

Of 655 patients with a patent LITA graft to the LAD undergoing coronary reoperation from 1986 to 1997, 35 (5.3%) sustained intraoperative injury to the LITA graft.

RESULTS

Strategies to restore flow to the LAD included new saphenous vein graft to the LAD in 15 patients, saphenous vein graft to the LITA stump in 7, saphenous vein graft to the LAD and repair of the LITA graft in 6, and other strategies in 7. All or part of the LITA graft to the LAD was salvaged in 20 patients (57%). Fourteen patients (40%) sustained perioperative myocardial infarction, and 3 patients died (8.6%). The 3 patients who died all had stenosis or thrombosis of the graft to the LAD documented at autopsy.

CONCLUSIONS

We conclude that (1) the prevalence of injury to a patent LITA graft is 5.3%; (2) a variety of techniques can be used to restore blood flow to the LAD; and (3) ineffective revascularization of the LAD in this situation is associated with operative mortality. At primary coronary artery bypass grafting, the LITA pedicle should be positioned in the left chest away from the posterior sternal table; this strategy may minimize the risk of LITA graft injury at coronary reoperation.

A technique to protect the left internal thoracic artery

The natural tendency of the harvested in-situ left internal thoracic artery is to assume a position near the anterior midline of the mediastinum, adjacent to the posterior sternal table. This repositioning of the left internal thoracic artery makes sternal reentry for redo myocardial revascularization (or other open cardiac procedures) hazardous. A technique of posterior and lateral repositioning of the mobilized in-situ left internal thoracic artery by creating a thymic flap and a pleuromediastinal groove is presented.

Impact of pleurotomy, continuous positive airway pressure, and fluid balance during cardiopulmonary bypass on lung mechanics and oxygenation

OBJECTIVE

To determine effects of surgical pleurotomy, continuous positive airway pressure, and fluid balance during cardiopulmonary bypass (CPB) on lung mechanical properties and indices of oxygenation.

DESIGN

Prospective, descriptive, and interventional study.

SETTING

Cardiothoracic service at a major university referral center.

PARTICIPANTS

Eighteen anesthetized-paralyzed patients undergoing elective coronary artery bypass grafting requiring CPB.

INTERVENTIONS

During CPB, continuous positive airway pressure (CPAP) was applied to nine patients, in nine others, no CPAP was applied.

MEASUREMENTS AND MAIN RESULTS

From measurements of airway and esophageal pressures and flow, lung resistance and elastance were determined before sternotomy and after sternal reapproximation. Measurements were made during forced ventilation over a physiologic range of tidal volumes and frequencies, and frequency and volume dependences of lung resistance and elastance were additionally identified. In all patients, lung resistance and elastance increased after CPB, consistent with models of pulmonary edema. Multiple regression analysis showed that these increases were relatively less in patients with intact pleurae (p < 0.05) or net negative fluid balance (p < 0.05); however, no difference in these increases was noted between patients receiving CPAP and those receiving no CPAP. Increases in lung resistance were positively correlated to net fluid balance, and negatively correlated to frequency and tidal volume (p < 0.05). Increases in lung elastance were positively correlated to tidal volume (p < 0.05). Absolute change in alveolar-arterial oxygen gradient was negatively correlated with net fluid balance, whereas percentage change was positively correlated to changes in lung elastance (p < 0.05).

CONCLUSIONS

These findings suggest that pleurotomy before CPB and positive fluid balance during CPB enhance postbypass pulmonary edema and/or atelectasis, as demonstrated by acute changes in respiratory mechanics and indices of oxygenation. Low levels of CPAP applied during CPB did not significantly change either mechanical properties or oxygenation.

Technique to protect the internal mammary artery pedicle

A simple technique to protect the internal mammary artery pedicle from injury in reoperative sternotomies is described. It consists of a pericardial window created by two pericardial flaps with displacement of the mammary pedicle away from the midline.

Histological study of the internal mammary artery with emphasis on its suitability as a coronary artery bypass graft

The internal mammary, musculophrenic, and superior epigastric arteries were unilaterally harvested from 11 individuals (aged 49 to 83 years; mean age, 67 years) and were examined histologically at 1-cm intervals. In 2 individuals the media of the entire internal mammary artery was elastic, whereas in the other 9 individuals we observed an alternating histological pattern in the media of the internal mammary artery, that of the proximal and distal segments being elastomuscular and that of the mid segment being elastic. In 4 of the latter 9 individuals the distal 10% to 20% of the media of the internal mammary artery was muscular with rare elastic lamellae. The media of the first 1 to 2 cm of the musculophrenic and superior epigastric arteries was elastomuscular or muscular with rare elastic lamellae, whereas more distally the media was purely muscular. The degree of intimal hyperplasia was significantly greater in arterial segments with a purely muscular media (25.6%) than in those with elastic (16.7%), elastomuscular (15.3%), and muscular (with rare elastic lamellae) (17.5%) types of media (p < 0.01). The mean cross-sectional luminal area of the elastic segment (1.9 mm2) and proximal and distal elastomuscular segments (1.9 and 1.2 mm2, respectively) of the internal mammary artery was significantly greater than that of the muscular segments of the musculophrenic artery (0.9 mm2) and the superior epigastric artery (0.7 mm2) (p < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Radiographic pulmonary abnormalities after different types of cardiac surgery

One aim of this study was to determine the incidence of new radiographic pulmonary abnormalities during hospitalization after cardiac surgery. Another aim was to determine if such abnormalities are more common among patients who had left internal mammary artery (LIMA) grafting. The predictive value of radiographic abnormalities for clinically important pulmonary morbidity was also determined. The anteroposterior chest radiographs of 152 patients obtained by portable equipment were evaluated to determine the incidence of new postoperative radiographic pulmonary abnormalities such as atelectasis, consolidation, infiltrate, and pleural effusion. Clinically important pulmonary morbidity was defined as a delay in tracheal extubation or discharge from the hospital because of a pulmonary reason. Among the 89 patients who had LIMA grafting and left pleurotomy, there was an 88% incidence of left-sided pulmonary abnormalities; a 73% incidence of left-sided atelectasis; and a 55% incidence of left-sided effusion. Among the 63 patients who had saphenous vein grafting only and/or valvular surgery, the respective incidences were 68%, 54%, and 35%, which were lower (P less than or equal to 0.05) than those in the patients who had LIMA grafting. There was no significant difference in abnormalities between the saphenous vein grafting and the valvular surgery groups. The 35% incidence of left-sided pleural effusion when LIMA grafting and pleurotomy were not performed was unexpectedly high. There was no association between radiographic abnormalities and age, the duration of cardiopulmonary bypass, and the duration of aortic occlusion, indicating that cardiopulmonary bypass was not a primary etiology of these radiographic abnormalities.(ABSTRACT TRUNCATED AT 250 WORDS)

Selective and adjustable pericardial flap to protect internal mammary artery grafts

We describe the surgical technique of a localized and adjustable pericardial flap to protect internal mammary artery grafts. This flap allows selective pulmonary retraction, maintains pleural integrity, and saves most of the pericardium for later closure. This technique has proved to be simple and highly effective. We have used it in 80 patients and have not had any related complications.

Pleuropulmonary morbidity: internal thoracic artery versus saphenous vein graft

Although use of the internal thoracic artery (ITA) for coronary artery bypass grafting results in superior graft patency and improved patient survival, our initial clinical observations suggested an increased incidence of pleuropulmonary morbidity with its use. One hundred consecutive patients with left ITA grafts were studied prospectively and compared with a consecutive retrospective group of 100 patients undergoing coronary artery bypass grafting with saphenous vein grafts only. Preoperative, postoperative day (POD) 2, POD 6, and postoperative week 8 chest roentgenograms were analyzed for atelectasis and effusion. Postoperative left lower lobe atelectasis was common in both groups on both POD 2 (saphenous vein, 43%, versus ITA, 53%; not significant) and POD 6 (saphenous vein, 40%, versus ITA, 41%; not significant). There was a significantly higher incidence of pleural effusion on POD 6 in the ITA group (84% versus 47%; p less than 0.05) but most of these were small. There was more chest tube drainage (1,413 versus 1,028 mL; p less than 0.01) and a greater need for secondary thoracostomy or thoracentesis (4% versus 0%) in the ITA group. The left pleural space was opened in 67 of the 100 ITA patients but pleurotomy did not appear to influence postoperative morbidity. We conclude that use of the internal thoracic artery for coronary artery bypass grafting results in a small but significant increase in pleuropulmonary morbidity.

Retrophrenic location of the internal mammary artery graft

A technique of locating the internal mammary artery behind the phrenic nerve is described, which extends the application of internal mammary artery grafting to the lateral wall of the left ventricle. The technique also facilitates the performance of the posterolateral anastomosis between the internal mammary and circumflex coronary arteries.

Internal mammary artery grafts: the shortest route to the coronary arteries

Inadequate length can limit the use of the internal mammary artery (IMA) for coronary revascularization. By following the shortest route from its origin to the recipient coronary artery, IMA use can be maximized. Seven cadavers were studied to determine that shortest route for the left and right IMAs. The shortest route for the left IMA to the left anterior descending coronary, diagonal, and circumflex coronary arteries was through the pericardium (p less than or equal to 0.01). For the right IMA, the significantly shortest routes were across the anterior heart for the left anterior descending and diagonal arteries, through the right pericardium for the right coronary artery or posterior descending artery, and through the pericardium and transverse sinus for the circumflex artery. Thus, any coronary artery can be reached with an in situ IMA, and the route through the pericardium is markedly shorter to ipsilateral coronary arteries.

Delayed pleuropulmonary complications following coronary artery revascularization with the internal mammary artery

We have seen four cases of delayed postoperative pleuro-pulmonary complications associated with use of the internal mammary artery (IMA) conduit. In each case the left IMA was used as a bypass conduit to the left anterior descending (LAD) coronary artery. In two of the instances the complications were life-threatening to the patients. Each patient was left with symptomatic residual roentgenographic changes. The IMA is becoming the graft of choice for coronary artery revascularization. The potential for delayed pleuropulmonary complications associated with use of this graft is not well recognized.