An update on internal mammary artery grafting for coronary artery disease

Neovascularization of Thymoma From Left Internal Mammary Artery Bypass Graft

We present the case of a type AB thymoma in a 69-year-old man with previous coronary artery bypass grafting (CABG) in whom angiography revealed a left internal mammary artery graft supplying blood flow to a thymic neoplasm, which simultaneously occluded the graft. This required a redo sternotomy, lysis of pericardial adhesions, complete thymectomy, and redo one vessel off-pump CABG. This case seeks to sensitize physicians to the possibility of coronary adverse events in patients with a previous CABG in the setting of management of mediastinal neoplasms, and it presents the novel findings on cardiac imaging associated with this case.

Long-Term (≥10 Years) Safety of Percutaneous Treatment of Unprotected Left Main Stenosis With Drug-Eluting Stents

Percutaneous coronary intervention (PCI) of unprotected left main disease (ULM) with drug-eluting stents (DES) is hampered by lack of information on long-term (≥10 years) safety data. All patients treated with PCI on ULM in 9 international centers with at least 10 years follow-up were enrolled. Baseline and procedural features were recorded. Repeat PCI (re-PCI) on ULM at 10 years was the primary end point. Secondary end points included major adverse cardiac events and its components (cardiac and noncardiac death, myocardial infarction, re-PCI not on ULM, and stent thrombosis). Sensitivity analysis was performed according to the presence of isolated ULM disease: 284 patients were enrolled. A total of 70 patients (21%) performed a re-PCI on ULM, 39 in the first year, and 31 between 1 and 10 years (only 5 overall performed for acute coronary syndrome). Patients with re-PCI on ULM did not show differences in baseline and procedural features, or experience higher rates of cardiovascular death (12% vs 11%, p 0.65), myocardial infarction (11% vs 6%, p 0.56), or of re-PCI on non-ULM disease (31% vs 27%, p 0.76) compared with those without re-PCI on ULM. At Kaplan-Meier analysis, patients with PCI in other coronary vessels were at higher risk of major adverse cardiac events, driven by target vessel revascularization (20.4% vs 32.9%, p 0.009), as confirmed at multivariate analysis (stenosis other than LM; hazard ratio 2, 1.4 to 2.7, all CI 95%). In conclusion, despite of using first-generation stents, PCI on ULM is safe, with low rates of recurrent events due to index revascularization. Progression of atherosclerotic lesions on other coronary vessels represents the only independent predictive factor for prognosis.

Why is the mammary artery so special and what protects it from atherosclerosis?

The internal mammary artery (IMA) grafts have been associated with long-term patency and improved survival as compared to saphenous vein grafts (SVGs). Early failure of IMA is attributed to poor surgical technique and less with thrombosis. Similarly, bypass surgery especially with the use of IMA has also been shown to be superior at 1-year as well as over five years compared to percutaneous procedures, including the use of drug-eluting stents for the treatment of coronary artery disease. The superiority of IMAs over SVGs can be attributed to its striking resistance to the development of atherosclerosis. Structurally its endothelial layer shows fewer fenestrations, lower intercellular junction permeability, greater anti-thrombotic molecules such as heparin sulfate and tissue plasminogen activator, and higher endothelial nitric oxide production, which are some of the unique ways that make the IMA impervious to the transfer of lipoproteins, which are responsible for the development of atherosclerosis. A better comprehension of the molecular resistance to the generation of adhesion molecules that are involved in the transfer of inflammatory cells into the arterial wall that also induce smooth muscle cell proliferation is needed. This basic understanding is crucial to championing the use of IMA as the first line of defense for the treatment of coronary artery disease.

Low-level-laser irradiation induces photorelaxation in coronary arteries and overcomes vasospasm of internal thoracic arteries

BACKGROUND AND OBJECTIVE

As low-level laser irradiation (LLLI) seems to induce vasodilation besides many other known biological effects, LLLI has been increasingly used in therapy of medical conditions with various irradiation parameters. The aim of this study was to investigate the effect of LLLI on photorelaxation of human coronary and internal thoracic arteries (ITA).

MATERIALS AND METHODS

Thirty vessel segments of ITA used for routine coronary artery bypass grafting as well as left anterior descending coronary arteries (LAD) of patients undergoing cardiac transplantation were cut into 4-mm rings stored in a modified Krebs-Henseleit solution and evaluated in a myograph. Both types of vessel segments were irradiated by a semiconductor non-thermal GaAs diode laser operating at a wavelength of 680 nm. After precontraction with thromboxane agonist U44619, respective relaxation responses were evaluated and compared to pharmacological dilatation induced by substance P.

RESULTS

Mean pharmacological vasodilation by substance P was 22.6 ± 3.3%, 12.8 ± 1.4%, and 20.4 ± 3.2% in macroscopic healthy LAD, LAD with atheromatous plaque, and ITA, respectively. Average photorelaxation induced by LLLI was 16.5 ± 2.0%, 1.9 ± 1.7%, and 6.8 ± 4.7%, accordingly. Vasodilatatory responses induced either by substance P or administration of LLLI were significantly decreased in LAD with atheromatous plaque (P < 0.0001). Vasospasms of ITA segments occurring during experiments could be abandoned when LLLI was administered.

CONCLUSION

Macroscopic healthy LAD exposed to LLLI revealed significant photorelaxation. With the administration of LLLI, 73% of the maximal obtainable effect by an endothelium-dependent vasodilator could be reached. Furthermore, LLLI has the potential to overcome vasospasms of ITA.

Computerized tomography may underestimate the patency of internal thoracic artery composite grafts

BACKGROUND

Multidetector-row computerized tomography (MDCT) has been regarded as useful for noninvasive assessment of the bypass grafts after coronary artery bypass grafting (CABG), but there have been few reports validating its accuracy in assessment of composite arterial graft patency.

METHODS

In 108 patients who underwent CABG with a Y-composite graft made of bilateral internal thoracic arteries (ITAs), early postoperative (mean interval, 4.9 months) MDCT findings were compared with the findings of subsequent conventional coronary angiography (19 patients, mean 4.7 months after initial MDCT) or later MDCT (89 patients, mean 31.0 months after surgery). A total of 248 grafts with 409 distal anastomoses (mean 3.8/patient) were assessed.

RESULTS

In the early MDCT, the left ITA was patent in 94.4%. The right ITA with multiple sequential anastomoses was completely patent in 73.8% and partially patent in 21.4%. Discrepancy of findings between early computed tomography (CT) and later imaging studies was found in 18 patients (16.7%). Fourteen (42.4%, 4 left and 10 right ITAs) among the 33 initially nonvisualized grafts showed improved patency in later MDCT or conventional angiogram. The positive predictive value of the early MDCT for ITA composite graft occlusion was calculated at 57.6% or lower, whereas the negative predictive value was 97.8% or higher.

CONCLUSIONS

For a composite graft made of bilateral ITAs, especially for those with multiple sequential anastomoses, MDCT may reflect only the functional patency and underestimate the actual anatomic patency.

Wide sternal retraction may impede internal mammary artery graft flow and reduce myocardial function during off-pump coronary artery bypass grafting: presentation of two cases

The internal mammary artery (IMA) is routinely used for grafting of the left anterior descending coronary artery (LAD), providing good flow to the anterior left ventricle (LV) wall. Impeded IMA-to-LAD flow may result in myocardial ischaemia and haemodynamic deterioration. From a study population, we describe two incidents where myocardial ischaemia was observed during off-pump coronary artery bypass surgery (CABG), with a confirmed reduction in the IMA-to-LAD flow in one patient. In patient no. 1, normal IMA flow was assessed by transit-time flow measurement after a complete IMA-to-LAD anastomosis. The anterior LV wall thickening was monitored continuously by epicardial ultrasonic transducers. Normal wall thickening was confirmed after IMA grafting. During a wide sternal opening for circumflex grafting the anterior wall motion displayed an ischaemic pattern, with reduced systolic and increased post-systolic wall thickening. IMA flow was reduced simultaneously. When easing the sternal opening, IMA flow normalized, as did the motion pattern in the anterior LV wall. In patient no. 2, similar changes in wall thickening occurred during a wide sternal opening after IMA-to-LAD grafting. When easing the retractor, the wall thickening normalized. It is important for the surgeon to be aware of this possible cause of myocardial ischaemia, with a risk of subsequent haemodynamic deterioration. This may not only be of great importance during off-pump CABG, but can also be significant for successful weaning from the cardiopulmonary bypass machine.

Chest wall reconstruction of severe mediastinitis with intercostal artery-based pedicled vertical rectus abdominis muscle flap with oblique-designed skin pedicle

Recurrent poststernotomy mediastinitis has significant morbidity and mortality. Reconstructive treatment begins with pectoral muscle or omental flaps. When these options are unavailable or inadequate, surgeons resort to internal mammary artery-based vertical rectus abdominis muscle flap. If the internal mammary artery is harvested for coronary artery bypass grafting, surgeons are reluctant to use the muscle for pedicled flap because of the elevated risks. However, recent reports suggest that if enough time passes for intercostal artery collaterals to develop, they would support the viability of the flap. Moreover, recent improvements in defining flap microvasculature and proposed surgical techniques have enabled us to further refine the procedure. Although it appears that the intercostal artery-based pedicled vertical rectus abdominis muscle flap with oblique-designed skin pedicle is safe and effective for chest wall reconstruction, potential for failure remains elevated until sample size accumulates.

Identification of omentin mRNA in human epicardial adipose tissue: comparison to omentin in subcutaneous, internal mammary artery periadventitial and visceral abdominal depots

OBJECTIVE

The purpose of this study was to determine the relative distribution of omentin and visfatin mRNA in human epicardial, peri-internal mammary, upper thoracic, upper abdominal and leg vein subcutaneous adipose tissue as well as the distribution of omentin in the nonfat cells and adipocytes of human omental adipose tissue.

BACKGROUND

Omentin is found in human omentum but not subcutaneous fat. Omentin and visfatin are considered markers of visceral abdominal fat.

RESEARCH DESIGN AND METHODS

The mRNA content of omentin and visfatin was measured by qRT-PCR analysis of fat samples removed from humans undergoing cardiac or bariatric surgery.

RESULTS

Omentin mRNA in internal mammary fat was 3.5%, that in the upper thoracic subcutaneous fat was 4.7% while that in the other subcutaneous fat depots was less than 1% of omentin in epicardial fat. The distribution of visfatin mRNA did not vary between the five depots. Omentin mRNA was preferentially expressed in the nonfat cells of omental adipose tissue since the omentin mRNA content of isolated adipocytes was 9% of that in nonfat cells, and similar results were seen for visfatin. The amount of omentin mRNA in differentiated adipocytes was 0.3% and that of visfatin 4% of that in nonfat cells. The amount of omentin mRNA in preadipocytes was virtually undetectable while that of visfatin was 3% of that in freshly isolated nonfat cells from omental adipose tissue.

CONCLUSION

Omentin mRNA is predominantly found in epicardial and omental human fat whereas visfatin mRNA is found to the same extent in epicardial, subcutaneous and omental fat.

Cardiac procedures in patients with a body mass index exceeding 45: outcomes and long-term results

BACKGROUND

Obesity has become a public health crisis. Although prior studies in obese patients undergoing cardiac surgical procedures have shown variable effects on outcomes, data are limited for extremely obese patients (body mass index [BMI] > or = 45). We undertook this study to evaluate outcomes in this cohort.

METHODS

A retrospective analysis was performed on 14,571 patients in our database who underwent cardiac operations from 1992 to 2005. Patient demographics, comorbidities, and outcomes were recorded. A univariate analysis between two groups: BMI 21 to 34.9 and BMI 45 or more was performed. Logistic regression models were used to identify independent risk factors for 30-day mortality. Long-term follow-up of the extreme obese group was achieved.

RESULTS

We identified 128 extreme obese patients, and 480 patients with a BMI of 21.0 to 34.9 were randomly selected for comparison. Univariate analysis showed significant differences in age, gender, and multiple comorbidities, as well as in cardiopulmonary bypass and cross-clamp times, operative procedure, and transfusion requirements. Extreme obese patients had a higher incidence of infection, acute renal failure, and 30-day mortality. Logistic regression analysis showed BMI, preoperative renal insufficiency, and transfusion status to be independent risk factors for 30-day mortality. Follow-up data did not reveal significant functional improvements. Long-term survival was 33.6% at 12 years.

CONCLUSIONS

Extreme obese patients undergoing cardiac surgical procedures have higher perioperative morbidity and mortality compared with a lower BMI group. BMI and preoperative renal insufficiency increase mortality in both groups, whereas transfusion does so only in the extreme obese. These patients can realize acceptable outcomes from cardiac procedures, but continue to suffer from the comorbidities of obesity.

Outcomes of coronary artery bypass graft surgery

This review article summarizes the major studies that have investigated the outcomes of coronary artery bypass graft surgery (CABG). The article includes a review of the literature in the areas of: history of CABG; indications for CABG; and measurement of quality of life following CABG, including prolongation of life, physical functioning (ie, relief from angina and dyspnea, physical activity, as well as complications of surgery and re-hospitalization), psychological functioning, and social functioning. Overall, the literature demonstrates that the outcomes of CABG have historically been measured in terms of mortality and morbidity; however, it has now been well recognized that adjustment to CABG is a multidimensional phenomenon that is not fully explained by medical factors. Therefore, in addition to studying mortality and morbidity outcomes following CABG many recent studies have identified that it is important to investigate various physical, psychological, and social variables that have a significant impact on post-operative adjustment to CABG.