Arterial grafts for coronary artery bypass grafting: biological characteristics, functional classification, and clinical choice

Coronary Artery Bypass Surgery to Treat Anomalous Origin of Coronary Arteries in Adults: A Systematic Review

OBJECTIVE

To review the available literature on the use of coronary artery bypass grafting (CABG) as a treatment option for anomalous origin of coronary artery in adults.

METHODS

A systematic literature search was performed in March 2023 (including Ovid MEDLINE, Ovid Embase, and the Cochrane Library databases) to identify studies reporting the use of CABG in adult patients with anomalous origin of coronary artery.

RESULTS

A total of 31 studies and 62 patients were included, 32 patients (52%) were women, and the mean age was 45.1±16.1 years. The most common coronary anomaly was the right coronary artery arising from the left coronary sinus in 26 patients (42%), followed by an anomalous left coronary artery from the pulmonary artery in 23 patients (37%). A total of 65 conduits were used in 61 patients, and 1 case report did not report conduit type. Reported grafts included saphenous vein (23 of 65 [35.4%]), left internal thoracic artery (15 of 65 [23.1%]), right internal thoracic artery (23 of 65 [35.4%]), and radial artery (2 of 65 [3.1%]); right gastroepiploic artery and basilic vein were used once (1.5%) each. Ligation of the native coronary artery was performed in 42 (67.7%) patients. Patient follow-up was available in 19 studies with a mean of 31.2 months. Only 1 operative mortality was reported.

CONCLUSIONS

Based on the limited available data, CABG can be performed with good early results. Use of arterial conduits and ligation of the native coronary artery may improve long-term graft patency.

Acute Mechanical Consequences of Vessel-Specific Coronary Bypass Combinations

PURPOSE

Premature coronary artery bypass graft (CABG) failure has been linked to geometric, mechanical, and compositional discrepancies between host and graft tissues. Acute hemodynamic disturbances and the introduction of wall stress gradients trigger a myriad of mechanobiological processes at the anastomosis that can be associated with restenosis and graft failure. Although the origins of coronary artery disease dictate the anastomotic target, an opportunity exists for graft-vessel optimization through rationale graft selection.

METHODS

Here we explored the four distinct regions of the left (L) and right (R) ITA (1 = proximal, 2 = submuscular, 3 = middle, 4 = distal), and four common target vessels in the coronary circulation including the proximal and distal left anterior descending (PLAD & DLAD), right coronary (RCA), and left circumflex (LCX) arteries. Benchtop biaxial mechanical data was used to acquire constitutive model parameters of these tissues and enable vessel-specific computational models to elucidate the mechanical consequences of 32 unique graft-target combinations.

RESULTS

Simulations revealed the maximum principal wall stresses for the PLAD, RCA, and LCX occurred when anastomosed with LITA1, and the maximum flow-induced shear stress occurred with LITA4. The DLAD, on the other hand, reached stress maximums when anastomosed to LITA4. Using a normalized objective function of simulation output variables, we found LITA2 to be the best graft choice for both LADs, RITA3 for the RCA, and LITA3 for the LCX.

CONCLUSION

Although mechanical compatibility is just one of many factors determining bypass graft outcomes, our data suggests improvements can be made to the grafting process through vessel-specific regional optimization.

Antispastic Effect of Fasudil and Cocktail of Fasudil and Nitroglycerin in Internal Thoracic Artery

BACKGROUND

Spasm of arterial grafts in coronary artery bypass grafting is a clinical problem and can occasionally be lethal. Perioperative spasm in the internal thoracic artery (ITA) and coronary arteries occurs in 0.43% of patients. This study aimed to investigate the antispastic effect of a RhoA/Rho-kinase (Rho-associated coiled-coil-containing protein kinase [ROCK]) inhibitor (fasudil) with and without nitroglycerin in combination in the ITA.

METHODS

Isolated human ITA rings taken from 68 patients who were undergoing coronary bypass were studied in a myograph. Cumulative concentration-relaxation curves for fasudil (-9 to -3.5 log M) were established in the ITA, which was precontracted with potassium chloride or U46619. The inhibitory effect of fasudil (-6.3 or -5.3 log M) or fasudil in combination with nitroglycerin were also tested. The ROCK2 protein was measured by Western blot.

RESULTS

Fasudil caused similar relaxation in ITA rings contracted by potassium chloride or U46619. Pretreatment with -5.3 log M fasudil significantly depressed contraction induced by potassium chloride (P = .004 vs control; P = .017 vs -6.3 log M) and U46619 (P = .010 vs control; P = .041 vs. -6.3 log M). Fasudil in combination with nitroglycerin had more effect and more rapid and sustained relaxation than either vasodilator alone. Fasudil caused a decrease of ROCK2 protein content (P = .014).

CONCLUSIONS

Fasudil fully relaxes some vasoconstrictor-induced contraction and decreases ROCK2 protein content in the ITA. The combination of fasudil and nitroglycerin has a superior effect than either vasodilator alone. The new cocktail solution composed of fasudil and nitroglycerin (pH 7.4) has effective antispastic action and may prove to be a new antispastic method for arterial conduits during coronary bypass surgery.

The effect of erector spinae plane block on arterial grafts in coronary artery bypass grafting

Background

This study aims to evaluate the sympathectomy effects of erector spinae plane block on the diameters and cross-sectional areas of the left and right internal mammary arteries and of the radial arteries.

Methods

This prospective study included a total of 25 patients (14 males, 11 females; median age: 67 years; range, 23 to 75 years) who underwent erector spinae plane block categorized as the American Society of Anesthesiologists Class III and underwent off-pump coronary artery bypass grafting between June 01, 2020 and March 01, 2021. The effects of erector spinae plane block on the diameters and cross-sectional areas of the left and right internal mammary arteries and radial arteries were assessed using ultrasonography images taken both before and 45 min after the procedure, from the third, fourth, and fifth intercostal spaces for the left and right internal mammary arteries and from 3 cm proximal to the wrist for the radial arteries.

Results

The diameters and cross-sectional areas of the left and right internal mammary arteries and radial arteries significantly increased compared to baseline values after the erector spinae plane block (p<0.05). There was no significant difference in the pre- and post-procedural heart rate and mean arterial pressure values (p>0.05).

Conclusion

The bilateral erector spinae plane block, which was performed at the T5 level, provided vasodilatation of the left and right internal mammary arteries and radial arteries without causing any significant difference in the heart rate and mean arterial pressure. These findings indicate that the sympathetic block produced by the erector spinae plane block may facilitate better surgical conditions by preventing arterial spasms. Thus, bilateral erector spinae plane block may be a promising technique to achieve regional anesthesia for off-pump coronary artery bypass grafting.

Left Internal Mammary Artery as an Endocrine Organ: Insights Into Graft Biology and Long-term Impact Following Coronary Artery Bypass Grafting

The left internal mammary artery (LIMA) is considered the criterion standard vessel for use in coronary artery bypass grafting. In recent decades, countless studies have documented its superiority over other arterial and venous coronary artery bypass grafting conduits, although the full mechanisms for this superiority remain unknown. A growing body of literature has unveiled the importance of extracellular vesicles known as exosomes in cardiovascular signaling and various pathologic states. In this review, we briefly compare the clinical longevity of the LIMA relative to other conduits, explore the effects of varying grafting techniques on clinical and angiographic outcomes, and provide physiologic insights into graft function on a cellular and molecular level. Finally, we explore exosome signaling as it pertains to atherosclerosis in support of the LIMA as an "endocrine organ."

Brachial Plexus Block for Removal of Retained Radial Artery Sheath

In this case, we present a lesser-known application of regional anesthesia, specifically, managing a patient with vasospasm and retained radial artery (RA) vascular sheath after coronary angiography. Providing an ultrasound-guided supraclavicular block, in combination with general anesthesia, allowed the proceduralist to remove the retained sheath after several hours of failed treatment and manipulation. Severe arterial spasm was alleviated by eliciting a sympathectomy, along with analgesia of the right upper extremity, and maintaining this post-procedure. The block optimized arterial flow through the RA post-intervention and helped manage the patients' pain from manipulation.

Small-diameter artery decellularization: Effects of anionic detergent concentration and treatment duration on porcine internal thoracic arteries

Engineered replacement materials have tremendous potential for vascular applications where over 400,000 damaged and diseased blood vessels are replaced annually in the United States alone. Unlike large diameter blood vessels, which are effectively replaced by synthetic materials, prosthetic small-diameter vessels are prone to early failure, restenosis, and reintervention surgery. We investigated the differential response of varying 0%-6% sodium dodecyl sulfate and sodium deoxycholate anionic detergent concentrations after 24 and 72 h in the presence of DNase using biochemical, histological, and biaxial mechanical analyses to optimize the decellularization process for xenogeneic vascular tissue sources, specifically the porcine internal thoracic artery (ITA). Detergent concentrations greater than 1% were successful at removing cytoplasmic and cell surface proteins but not DNA content after 24 h. A progressive increase in porosity and decrease in glycosaminoglycan (GAG) content was observed with detergent concentration. Augmented porosity was likely due to the removal of both cells and GAGs and could influence recellularization strategies. The treatment duration on the other hand, significantly improved decellularization by reducing DNA content to trace amounts after 72 h. Prolonged treatment times reduced laminin content and influenced the vessel's mechanical behavior in terms of altered circumferential stress and stretch while further increasing porosity. Collectively, DNase with 1% detergent for 72 h provided an effective and efficient decellularization strategy to be employed in the preparation of porcine ITAs as bypass graft scaffolding materials with minor biomechanical and histological penalties.

Comparative Evaluation on Impacts of Fibronectin, Heparin-Chitosan, and Albumin Coating of Bacterial Nanocellulose Small-Diameter Vascular Grafts on Endothelialization In Vitro

In this study, we contrast the impacts of surface coating bacterial nanocellulose small-diameter vascular grafts (BNC-SDVGs) with human albumin, fibronectin, or heparin–chitosan upon endothelialization with human saphenous vein endothelial cells (VEC) or endothelial progenitor cells (EPC) in vitro. In one scenario, coated grafts were cut into 2D circular patches for static colonization of a defined inner surface area; in another scenario, they were mounted on a customized bioreactor and subsequently perfused for cell seeding. We evaluated the colonization by emerging metabolic activity and the preservation of endothelial functionality by water soluble tetrazolium salts (WST-1), acetylated low-density lipoprotein (AcLDL) uptake assays, and immune fluorescence staining. Uncoated BNC scaffolds served as controls. The fibronectin coating significantly promoted adhesion and growth of VECs and EPCs, while albumin only promoted adhesion of VECs, but here, the cells were functionally impaired as indicated by missing AcLDL uptake. The heparin–chitosan coating led to significantly improved adhesion of EPCs, but not VECs. In summary, both fibronectin and heparin–chitosan coatings could beneficially impact the endothelialization of BNC-SDVGs and might therefore represent promising approaches to help improve the longevity and reduce the thrombogenicity of BNC-SDVGs in the future.

Longitudinal histomechanical heterogeneity of the internal thoracic artery

The internal thoracic artery (ITA) is the principal choice for coronary artery bypass grafting (CABG) due to its mechanical compatibility, histological composition, anti-thrombogenic lumen, and single anastomotic junction. Originating at the subclavian artery, traversing the thoracic cavity, and terminating at the superior epigastric and musculophrenic bifurcation, bilateral ITAs follow a protracted circuitous pathway. The physiological hemodynamics, anatomical configuration, and perivascular changes that occur throughout this length influence the tissue's microstructure and gross mechanical properties. Since histomechanics play a major role in premature graft failure we used inflation-extension testing to quantify the regional material and biaxial mechanical properties at four distinct locations along the left (L) and right (R) ITA and fit the results to a structurally-motivated constitutive model. Our comparative analysis of 44 vessel segments revealed a significant increase in the amount of collagen but not smooth muscle and a significant decrease in elastin and elastic lamellae present with distance from the heart. A subsequent decrease in the total deformation energy and isotropic contribution to the strain energy was present in the LITA but not RITA. Circumferential stress and compliance generally decreased along the length of the LITA while axial stress increased in the RITA. When comparing RITAs to LITAs, some morphological and histological differences were found in proximal sections while distal sections revealed differences predominantly in compliance and axial stress. Overall, this information can be used to better guide graft selection, graft preparation, and xenograft-based tissue-engineering strategies for CABG.

Comparison of Outcomes and Frequency of Graft Failure With Use of Free Versus In Situ Internal Mammary Artery Bypass Conduits (from the PREVENT IV Trial)

Although in situ internal mammary artery (is-IMA) grafting remains the most frequent conduit in coronary artery bypass grafting (CABG), circumstances may necessitate free grafting of the IMA (f-IMA), though differences in outcomes have not been fully characterized. The purpose of this study was to compare clinical and angiographic outcomes of is-IMA versus f-IMA coronary bypass grafts in patients who underwent elective CABG surgery. In 1,829 patients in the angiographic cohort of PREVENT IV, 1,572 (85.9%) had at least 1 IMA graft; of these, 34 (2.2%) patients had at least 1 f-IMA graft and 1,538 (97.8%) had at least 1 is-IMA graft without additional f-IMA grafts. Characteristics of patients, procedure, and grafts/targets were compared between cohorts. Primary endpoints included death, myocardial infarction, and revascularization, as well as incidence of graft failure (stenosis >75%) on angiography at 12-18 months postoperatively. Patients receiving is-IMA grafts were more often of white race and higher weight. Aortic cross-clamp time was shorter in the f-IMA cohort (39.5 vs 57.0 min, p = 0.04), but duration of bypass was similar (93.5 vs 100.0 minutes, p = 0.793). Of the in situ grafts, 97.3% were via the left internal mammary artery (LIMA), 86.6% were of good quality, and the left anterior descending (LAD) was bypassed in 88.2%. This compares with free grafts, which were via the LIMA in 68.0%, of good quality in 96.1%, and bypassed the LAD in 58.8% and first obtuse marginal (OM1) in 23.5%. Rates of death, myocardial infarction, and revascularization were similar between groups. The rate of graft failure was higher in f-IMA grafts (23.3%) compared with is-IMA grafts (8.5%; p < 0.01). Although clinical outcomes were similar with use of free versus in situ IMA grafts, higher rates of graft failure were encountered with use of the f-IMA graft. In conclusion, in situ grafts should be the preferred conduit for patients who undergo CABG surgery.

Role of botulinum neurotoxin-A in cerebral revascularization graft vasospasm prevention: current state of knowledge

Graft stenosis and occlusion remain formidable complications in cerebral revascularization procedures, which can lead to significant morbidity and mortality. Graft vasospasm can result in early postoperative graft stenosis and occlusion and is believed to be at least partially mediated through adrenergic pathways. Despite various published treatment protocols, there is no single effective spasmolytic agent. Multiple factors, including anatomical and physiological variability in revascularization conduits, patient age, and comorbidities, have been associated with graft vasospasm pathogenesis and response to spasmolytics. The ideal spasmolytic agent thus likely needs to target multiple pathways to exert a generalizable therapeutic effect. Botulinum toxin (BTX)-A is a powerful neurotoxin widely used in clinical practice for the treatment of a variety of spastic conditions. Although its commonly described paradigm of cholinergic neural transmission blockade has been widely accepted, evidence for other mechanisms of action including inhibition of adrenergic transmission have been described in animal studies. Recently, the first pilot study demonstrating clinical use of BTX-A for cerebral revascularization graft spasm prevention has been reported. In this review, the mechanistic basis and potential future clinical role of BTX-A in graft vasospasm prevention is discussed.

An innovative panel to assess endothelial integrity of pedicled and skeletonized internal thoracic artery used as aortocoronary bypass graft: a randomized comparative histologic and immunohistochemical study

Background

Optimal preservation of endothelial integrity of the vessels used as aortocoronary grafts is a crucial determinant of long-term clinical success of coronary artery bypass grafting (CABG). The purpose of this study was to evaluate an impact of two common techniques to harvest left internal thoracic artery (LITA) on endothelial integrity.

Methods

One hundred twenty consecutive patients (84 males and 36 females) with a mean age of 64.9±8.8 years undergoing CABG were randomized to receive pedicled (group P; n=60) or skeletonized (group S; n=60) LITA grafts. During surgery LITA was harvested by the same experienced cardiac surgeon. The most peripheral surplus segments of LITA were obtained and then analysed histologically under light microscope. Additionally, endothelial expression of CD31, CD34, CD133 and nitric oxide synthase (eNOS) were evaluated by means of immunohistochemistry.

Results

In both groups, no cases of major arterial wall damage such as disruption, dissection, thrombosis or subadventitial hematoma were noted on LITA cross sections. Immunohistochemical assessment of protein expression revealed no differences in endothelial expression of CD133, CD34 antigens (markers of regeneration potential) and eNOS (indicating preserved functional integrity) between studied groups. Contrary to them, endothelial immunoreactivity of CD31, a marker of the morphological integrity of the endothelium, was revealed to be stronger in group P.

Conclusions

The skeletonized method of LITA harvesting may be associated with worse preservation of morphological integrity of endothelium but without compromising functional integrity and potential for tissue regeneration.

Conduits Used in Coronary Artery Bypass Grafting: A Review of Morphological Studies

There is a significant variety of vascular conduits options for coronary bypass surgery. Adequate graft selection is the most important factor for the success of the intervention. To ensure durability, permeability, and bypass function, there must be a morphological similarity between the graft and the coronary artery. The objective of this review was to analyze the morphological characteristics of the grafts that are most commonly used in coronary bypass surgery and the coronary arteries that are most frequently occluded. We included clinical information regarding the characteristics that determine the behavior of the grafts and its permeability over time. Currently, the internal thoracic artery is the standard choice for bypass surgery because of the morphological characteristics of the wall that makes less prone to developing atherosclerosis and hyperplasia. The radial and right gastroepiploic arteries are the following second and third best options, respectively. The ulnar artery is the preferred choice when other conduits are not feasible.

Contemporary use of arterial and venous conduits in coronary artery bypass grafting: anatomical, functional and clinical aspects

Although the benefits of using the left internal mammary artery to bypass the left anterior descending artery (LAD) have been extensively ascertained, freedom from major cardiovascular events and survival after coronary artery bypass grafting (CABG) also correlate with the completeness of revascularisation. Hence, careful selection of the second-best graft conduit is crucial for CABG success. The more widespread use of saphenous vein grafts contrasts with the well-known long-term efficacy of multiple arterial grafting, which struggles to emerge as the procedure of choice due to concerns over increased technical difficulties and higher risk of postoperative complications. Conduit choice is at the discretion of the operator instead of being discussed by the heart team, where cardiologists are not usually engaged in such decisions due to a hypothetical lack of technical knowledge. Furthermore, according to the ESC/EACTS guidelines, traditional CABG remains the gold standard for multi-vessel coronary artery disease with complex LAD stenosis, but hybrid procedures using percutaneous coronary intervention for non-LAD targets could combine the best of two worlds. With the aim of raising the cardiologist's awareness of the surgical treatment options, we provide a comprehensive overview of the anatomical, functional and clinical aspects guiding the decision-making process in CABG strategy.

The descending branch of the lateral circumflex femoral artery as an alternative conduit for coronary artery bypass grafting: Experience from an anatomical, radiological and histological study

The descending branch of the lateral circumflex femoral artery (DBLCFA) has been suggested as an option for use in coronary artery bypass grafting (CABG). Our aim was to combine radiological examination, surgical and anatomical preparation, and histological assessment of the DBLCFA to map its variability and to assess the benefits of this conduit in cardiac surgery. The pelvic and femoral arteries were examined by CT angiography (CTA) in 100 patients (aged 68.3 ± 9.3 years) to assess the variability of the DBLCFA. Anatomical dissections were performed on 20 cadavers. In 15 patients, an autologous DBLCFA was implanted during CABG. In 35 samples, possible atherosclerotic lesions were examined histologically. The length of the potential DBLCFA conduits measured by CTA was 9.3 ± 2.9 cm, without correlating with the length of the thigh. Anatomical variations that would prevent the DBLCFA from being used in CABG were found in 27 out of 100 patients. Except for focal thickening of the intima, eccentric hypertrophy of the intima was found in three out of 35 samples. No inflammatory infiltration, foam cells, atheroma, or calcifications were found histologically. The DBLCFA is not to be used routinely or in preference to other grafts of choice. However, owing to its moderate variability, sufficient length, caliber, and rare atherosclerosis, it can be used in the absence of other suitable grafts as an alternative conduit implanted as a composite Y-graft end-to-side to the internal thoracic artery in patients without diabetic angiopathy, neuropathy or peripheral artery disease who are undergoing extensive or repeat coronary revascularization. Clin. Anat. 29:779-788, 2016. © 2016 Wiley Periodicals, Inc.

Effects of intraoperative diltiazem infusion on flow changes in arterial and venous grafts in coronary artery bypass graft surgery

Objective

This study aimed to show the effects of intra-operative diltiazem infusion on flow in arterial and venous grafts in coronary artery bypass graft surgery.

Methods

Hundred fourty patients with a total of 361 grafts [205 (57%) arterial and 156 (43%) venous] underwent isolated coronary surgery. All the grafts were measured by intraoperative transit time flow meter intra-operatively. Group A (n=70) consisted of patients who received diltiazem infusion (dose of 2.5 microgram/kg/min), and Group B (n=70) didn't receive diltiazem infusion.

Results

Mean graft flow values of left internal mammary artery were 53 ml/min in Group A and 40 ml/min in Group B (P<0.001). Pulsatility index (PI) values of left internal mammary artery for Group A and Group B were 2.6 and 3.0 respectively (P<0.001). No statistically significant difference was found between venous graft parameters.

Conclusion

We recommend an effect of diltiazem infusion in increasing graft flows in coronary artery bypass graft operations.

Arterial segments as microvascular interposition grafts in venous anastomosis in digital replantations

Introduction:

Microvascular anastomosis is a crucial procedure in replantation surgeries. Venous insufficiency is one of the most consistent cause of failure or re-exploration in these surgeries necessitating the use of venous grafts.

Materials and Methods:

We discuss our study of 9 such replantation surgeries executed in calendar year 2013-2014, including a double finger replantation done in the same patient having total amputation of 4 fingers of the same (right) hand, in which an arterial segment was used as a microvascular interposition graft for venous anastomosis. Out of these 9 surgeries, 3 were re-exploration procedures for venous compromise and 6 were successful primary replantations.

Results:

In all, 8 replants were successful and one failed due to arterial compromise.

Discussion:

In our experience and extensive review of the previously available literature, we would like to portray the advantages of arterial segments as microvascular grafts in replant surgeries. Specifically, in a crush amputation injury for which the use of a vascular interposition graft is being contemplated. If any other digit is also amputated and is unsuitable for replantation, it can act as a potential donor site to harvest the arterial segment. However, when dealing with single finger amputation, the surgeon must be confident about the single digital arterial anastomosis, before harvesting the second digital artery as a microvascular graft.

Conclusion:

In our study, we found the use of arterial grafts in microvascular anastomosis of veins advantageous, as arterial segments have better ability to resist spasm due to environmental changes, better pressure tolerance as compared to venous segments, and provide an appropriate calibre match and ease of harvest in the same operative field.

Potassium induced contraction of the internal thoracic artery in vitro is time related: the potential consequences in the analysis of the mechanism of the spasm after coronary artery bypass grafting and in the analysis of the results of in vitro studies

The aim of the present study was to examine how, under in vitro conditions, the human left internal thoracic artery (LITA) reacts to contractile agonist:potassium chloride (KCL) as a function of time, as well as to examine whether a change in the LITA reactivity can correlate with the occurrence of the refractory vascular spasm (RVS). Distal segments of LITA obtained from 33 patients aged 38–73, at the time of routine coronary artery surgical revascularization (CABG). Contractile response to 80 mmol K⁺ was recorded under isometric conditions. In 16 (48,5 %) LITA segments, contractile reaction to K⁺ after experiments ranging 1–10 h were registered. No contractile response even after 10 h of incubation was observed in 17 (51.5 %) LITA segments. Between 120 and 300 min after the beginning of the experiment, the reaction was maximum and amounted up to 300 % control reaction, then decreased. First, with respect to in vitro research isolated by LITA rings, while analyzing the results of the research, one should take into consideration the possibility that during the research, the functional state of the tissues changes and in particular its sensitivity to depolarization of the cell membrane. Second, the change in the sensitivity to depolarization of the cell membrane of the smooth muscles’ LITA might be the potential mechanism causing the occurrence of the postoperative spasm after the CABG treatment.

Endothelium-dependent vasoactivity of the human internal mammary artery

Coronary artery disease is recognized as a major health problem worldwide, particularly because of the associated morbidity and mortality. Coronary artery bypass grafting has been an established mainstay in the treatment of this disease for almost half a century and is arguably the most intensively studied surgical procedure ever undertaken. Because of its unique properties, the human internal mammary artery has long been considered the best graft to use in this type of surgery. Previous studies have shown several advantages of this graft compared with others, that is, lower incidence of atherosclerosis. However, few comparative studies on the reactivity of this artery have been published. Moreover, these studies usually focus on isolated cardiovascular risk factors rather than combined risk factors. In fact, patients who require coronary revascularization usually present multiple risk factors, which can interfere with several pathways of regulation of vascular function, namely endothelial function. Several diseases and cardiovascular risk factors have been shown to interfere with endothelial function, promoting the production of vasoconstrictors, inhibiting the production of vasodilators, or both, and thus eventually leading to endothelial dysfunction. Therefore, it is of great interest to study the endothelial function, particularly of the human internal mammary artery, in the presence of combined cardiovascular risk factors and concomitant diseases. Many techniques have been developed to assess the endothelial function, in particular, studies on isolated arteries, as well as spectroscopic, electrochemical, and immunological methods, among others.

Expression of growth arrest-specific protein 6 and Axl molecules in the left internal mammary artery of patients undergoing coronary artery bypass grafting

AIMS

Studies have demonstrated that using a left internal mammary artery (LIMA) graft yields excellent long-term results in coronary artery bypass grafting (CABG). The growth arrest-specific 6 (Gas6) gene and its receptor, Axl, are crucial in vascular haemostasis and atherosclerosis. The objective of this study was to determine the expression of Gas6 and Axl molecules in the aorta and LIMA in patients undergoing CABG.

METHODS

Plasma and tissue specimens were collected from 19 patients undergoing elective CABG. The expression of the Gas6 and Axl in the injured aorta and LIMA was examined using reverse transcription PCR (RT-PCR), real-time RT-PCR, western blot and immunohistochemical staining.

RESULTS

In CABG patients, the mRNA, immunoreactivity and protein expressions of the Gas6 and Axl were considerably higher in the LIMA than those in the aorta. Further analysis revealed that the expression of the Gas6 positively correlated with that of Axl in the LIMA and aorta. The plasma Gas6 level was considerably and positively correlated with the expression of Gas6 protein in the LIMA and aorta.

CONCLUSIONS

The present study discovered that the higher expression of Gas6/Axl pathway components in the LIMA compared with that in the aorta may partly explain the less frequent atherosclerotic events involving the LIMA compared with other arteries. Moreover, Gas6 may play a critical and protective role in human vascular biology.

Coronary artery bypass grafting: Part 1--the evolution over the first 50 years

Surgical treatment for angina pectoris was first proposed in 1899. Decades of experimental surgery for coronary artery disease finally led to the introduction of coronary artery bypass grafting (CABG) in 1964. Now that we are approaching 50 years of CABG experience, it is appropriate to summarize the advancement of CABG into a procedure that is safe and efficient. This review provides a historical recapitulation of experimental surgery, the evolution of the surgical techniques and the utilization of CABG. Furthermore, data on contemporary clinical outcomes are discussed.

Suxiao jiuxin pill induces potent relaxation and inhibition on contraction in human artery and the mechanism

Suxiao Jiuxin Pill, a compound Chinese traditional medicine with main components of tetramethylpyrazine and borneol, is widely used for antiangina treatment in China but its pharmacological effect on human blood vessels is unknown. We investigated the effect and possible mechanism of SJP in the human internal mammary artery (IMA, n = 78) taken from patients undergoing coronary surgery. SJP caused full relaxation in KCl- (99.4 ± 10.5%, n = 6) and U46619- (99.9 ± 5.6%, n = 6) contracted IMA. Pretreatment of IMA with plasma concentrations of SJP (1 mg/mL), calculated from the plasma concentration of its major component borneol, significantly depressed the maximal contraction to KCl (from 35.8 ± 6.0 mN to 12.6 ± 5.6 mN, P = 0.03) and U46619 (from 19.4 ± 2.9 mN to 5.7 ± 2.4 mN, P = 0.007) while SJP at 10 mg/mL abolished the subsequent contraction. Endothelium denudation and inhibition of eNOS significantly altered the SJP-induced relaxation without changes of eNOS expression. We conclude that SJP has a potent inhibitory effect on the vasoconstriction mediated by a variety of vasoconstrictors in human arteries. The vasorelaxation involves both endothelium-dependent and -independent mechanisms. Thus, the effect of SJP on human arteries demonstrated in this study may prove to be particularly important in vasorelaxing therapy in cardiovascular disease.

Endoscopic radial artery harvesting does not compromise graft patency for coronary artery bypass graft: a meta analysis of 2782 patients

BACKGROUND

Endoscopic radial artery harvesting is a favourable harvesting technique which provides excellent cosmetic result and low incidence of incision related complications, however the impact of this technique on graft quality is less well-explained. We sought to evaluate the impact of harvesting technique on graft patency and relevant clinical outcomes in patients undergoing coronary artery bypass graft (CABG).

METHOD

A systematic literature search was conducted to identify publications containing comparisons between different sampling skills in CABG, data was extracted and analysed with Revman, Downs and Black score was applied to evaluate the methodological quality of included studies.

RESULT

Ten studies containing 2782 patients were undertaken, the quality was generally acceptable. Pooled analysis results indicate endoscopic radial artery harvesting was associated with a lower incidence of wound infection and a similar incidence of haematoma formation compared with open harvesting. The difference in graft patency and all-cause mortality was insignificant between two cohorts.

CONCLUSION

Endoscopic radial artery harvesting is a safe technique and provides equivalent graft patency as compared with open harvesting, further investigation is required to confirm the aforementioned conclusion and evaluate the impact of harvesting technique on hand sensory and motor function.

Radial artery as graft for coronary artery bypass surgery: Advantages and disadvantages for its usage focused on structural and biological characteristics

Radial artery (RA) is the most popular arterial graft after the left internal thoracic artery in both low- and high-risk patients undergoing coronary artery bypass grafting. Various arterial grafts such as the right internal thoracic artery, the right gastroepiploic artery, and the inferior epigastric artery have also gained ground over the past 30 years because of the intimal hyperplasia and atherosclerosis of the saphenous vein leading to late graft occlusion. In this review article we would like to present the utility of the RA as a graft, focused mainly on its structural and biological characteristics.

Potent vasodilatory effect of fasudil on radial artery graft in coronary artery bypass operations

BACKGROUND

The radial artery (RA) is a useful conduit for coronary artery bypass grafting (CABG) but is susceptible to vasospasm during harvesting. We evaluated the usefulness of fasudil, a Rho kinase inhibitor, in dilating the RA graft and increasing graft free flow (GFF) compared with the conventional graft-dilating agents papaverine and verapamil-nitroglycerin (VG).

METHODS

Between June 2012 and January 2013, 45 patients with ischemic heart disease who underwent isolated CABG using the RA were enrolled and randomly assigned to fasudil (n = 15), papaverine (n = 15), or VG (n = 15). Fasudil (2.67 mmol/L), papaverine (1.0 mmol/L) mixed with heparinized blood, or VG (30 μmol/L each of verapamil and nitroglycerin) was injected intraluminally into the RA graft after harvesting. Main outcome measures were RA GFF, hemodynamic changes, and histopathologic examination of the RA.

RESULTS

In the fasudil group, GFF increased significantly (p < 0.001) from 36.8 ± 20.4 at baseline to 148.0 ± 88.3 mL/min after injection. GFF increased significantly (p < 0.001) from 36.0 ± 19.0 to 72.3 ± 36.7 mL/min in the papaverine group and increased significantly (p < 0.001) from 39.5 ± 23.3 to 64.3 ± 29.9 mL/min in the VG group. The GFF was significantly higher (p = 0.001) in fasudil-treated RA than in papaverine- or VG-treated RA. Histopathologically, RA graft diameter was markedly increased after fasudil injection, and the structure of the multiple elastic lamellae was intact. Blood pressure did not change significantly after drug injection in all groups.

CONCLUSIONS

Fasudil exhibited a very potent vasodilatory effect on the RA compared with conventional papaverine or VG, resulting in increased GFF. This agent is useful for dilating RA grafts in CABG.

Total arterial coronary revascularization-patient selection, stenoses, conduits, targets

Graft patency determines prognosis in coronary artery bypass grafting (CABG). Numerous reports over the past 20 years have documented superior patencies and prognosis when multiple arterial grafts are used, yet less than 10% of CABG have multiple arterial grafts. Several conduits have been proposed, with varying degrees of success. Saphenous vein grafts (SVG) begin to fail with intimal hypertrophy and then atheroma after 5 years, with patency rates of 50% to 60% at 10 years, and <30% at 15 years. In contrast, left internal thoracic artery (LITA) patency is >95% at 10 years and >90% at 20 years. The radial artery is extremely versatile and can reach all territories, but is muscular and vulnerable to spasm and competitive flow. Similarly, the right gastroepiploic artery is also muscular, and is best suited to the posterior descending coronary artery, especially in reoperations and is also affected by competitive flow. In addition, bilateral internal thoracic artery grafting (BITA) grafts and total arterial revascularization (TACR) can be performed with identical perioperative mortality (1%) and perioperative morbidity to LITA + SVG. Importantly, survival is superior-85% to 90% at 10 years versus 75% to 80% respectively. BITA/TACR patients also suffer fewer late cardiac events and reoperations, with superior results for older patients, those requiring urgent surgery, diabetics, patients with renal dysfunction and in reoperations. Contraindications to BITA include obesity, insulin dependent diabetics, and severe chronic obstructive airways disease. As such, arterial grafts have better patencies and clinical results. BITA/TACR is often underutilized, but can be achieved in the majority of patients. Opportunities exist to enhance BITA/TACR use in CABG to the potential benefit of our patients.

Arterial grafts: clinical classification and pharmacological management

In comparison with standard saphenous vein grafts, use of the internal mammary artery (IMA) as a coronary artery bypass graft has achieved superior long-term results. This is related to the differences in the biological characteristics between the venous and arterial grafts. However, even arterial grafts are not uniform in their biological characteristics. The variation in the perioperative behavior of the grafts and in their long-term patency may be related to different characteristics. These factors should be taken into account in the use of arterial grafts, some of which are subjected to more active pharmacological intervention during and after the operation to obtain satisfactory results. To better understand the biological behavior of the grafts, their common features and their differences, a clinical classification may be useful for a practicing surgeon. Based on experimental studies of their vasoreactivity combined with anatomical, physiological and embryological considerations, we have proposed a functional classification for arterial grafts that may be useful clinically. Our classification suggests that there are three types of arterial grafts: Type I-somatic arteries; Type II-splanchnic arteries; and Type III-limb arteries. Type I arteries have enhanced endothelial function and release more nitric oxide and other relaxing factors. Type II arteries, such as the gastro-epiploic artery, and Type III arteries, such as the radial artery (RA), have higher pharmacological reactivity to vasoconstrictors. This classification explains why the IMA has the best long-term patency. Because Type II and III arteries are prone to spasms due to higher contractility, they require more active pharmacological interventions. Furthermore, the harvesting technique of the conduits, including the saphenous vein and IMA, are described and discussed in this article. Prevention of spasms using two cocktails of medications (verapamil + nitroglycerin and nicardipine + nitroglycerin) during harvesting of the conduits is described. These solutions have been demonstrated to be clinically effective.

Mediastinitis after coronary artery bypass grafting increases the incidence of left internal mammary artery obstruction

Mediastinitis after coronary artery bypass grafting (CABG) gives a longstanding chronic inflammation and has a detrimental negative effect on long-term survival. For this reason, we aimed to study the effect of mediastinitis on graft patency after CABG. The epidemiologic design was of an exposed (mediastinitis, n = 41) versus non-exposed (non-mediastinitis, controls, n = 41) cohort with two endpoints: (i) obstruction of saphenous vein grafts (SVG) and (ii) obstruction of the internal mammary artery (IMA) grafts. The graft patency was evaluated with coronary CT-angiography examination at a median follow-up of 2·7 years. The number of occluded SVG in the mediastinitis group was 18·9% versus 15·5% in the control group. Using generalized estimating equations model with exchangeable matrix, and confounding effect of ischaemic time and patients age, we found no significant association between presence of mediastinitis and SVG obstruction [rate ratio (RR) = 0·96, 95% CI (0·52-2·67), P = 0·697]. The number of occluded IMA grafts was 10·5% in the mediastinitis group and 2·4% in the control group. Using the Poisson regression model, we estimated RR = 5·48, 95% CI (1·43-21·0) and P = 0·013. There was a significant association between mediastinitis and IMA graft obstruction, when controlling for the confounding effect of ischaemic time, body mass index, presence of diabetes mellitus and the number of diseased vessels. Presence of mediastinitis increases the risk of IMA graft obstruction. This may confirm the importance of inflammation as a major contributor to the pathogenesis of atherosclerosis and explain the negative effect of mediastinitis on a long-term survival.

Cell-permeant peptide inhibitors of vasospasm and intimal hyperplasia

Outcomes from vein graft bypass are limited by graft failure, leading causes of which include intimal hyperplasia and vasospasm. Intimal hyperplasia remains the most common cause of graft failure, but no therapeutic modalities have been shown to prevent intimal hyperplasia in humans. The small heat shock proteins are a class of naturally occurring proteins in vascular smooth muscle. These proteins have an integral role in maintenance of vascular tone and in cellular defense against various stressors. Transduction domains have enabled intracellular therapeutic delivery of peptide analogs of heat shock proteins, as well as peptide inhibitors of the kinases that phosphorylate these proteins. These cell-permeant peptides have been shown to prevent vasospasm and intimal hyperplasia in vitro. Since vascular bypass using vein grafts is analogous to autologous organ transplantation, ex vivo treatment of the vein graft with cell-permeant peptide inhibitors of vasospasm and intimal hyperplasia prior to implantation provides a unique opportunity for targeted treatment of the graft to improve patency.

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.

Role of TRPC3 channel in human internal mammary artery

BACKGROUND AND AIMS

Intracellular calcium regulation in endothelial cells depends on transient receptor potential channels (TRPs). Canonical TRPs (TRPCs) are now recognized as the most important Ca(2+)-permeable cation channels in vascular endothelium and TRPC3 channel is reported to play a role in vasodilation in animal vessels. However, little is known about the role of TRPCs in human arteries. We therefore tested the hypothesis that TRPCs play a role in human arteries.

METHODS

Cumulative concentration-relaxation curves to acetylcholine (-11 to -4.5 log M) were established in the human internal mammary artery (IMA) rings (n = 42) taken from 28 patients undergoing coronary artery bypass grafting in precontraction induced by U46619 (-8 log M) in the absence or presence of SKF96365 (10 μmol/L) or Pyr3 (3 μmol/L). Protein expressions of TRPC3 were determined by Western blot and immunohistochemistry staining.

RESULTS

The maximal relaxation induced by acetylcholine was significantly attenuated by the nonspecific cation channels inhibitor, SKF96365 (48.2 ± 3.7 vs. 66.0 ± 0.9% in control, p <0.01) or the selective TRPC3 blocker, Pyr3 (58.4 ± 2.3% vs. 67.7 ± 1.1% in control, p <0.01). Protein expression of TRPC3 was detected in human IMA.

CONCLUSIONS

TRPC3 exists and plays a role in the acetylcholine-induced endothelium-dependent relaxation in the human IMA. This study suggests that TRPC3 may be a potential new target in endothelial protection in patients with endothelial dysfunction such as in patients with coronary artery disease in order to improve the long-term patency of the grafting vessels.

Histological comparison of the candidate arteries for bypass grafting of the posterior interventricular artery

This study evaluated five vessels as potential candidates for coronary artery bypass grafting at the posterior interventricular artery (PIVA) blockage site. We used light microscopy and digital image analysis of H&E and Van Gieson's-stained slides to investigate luminal diameter, arterial wall thickness, and relative muscularity and elasticity of candidate vessels. Results from our sample indicate that the inferior epigastric artery (IEA) may be the preferred graft to the PIVA based on overall similarities in these measurements. Other arteries provided a favorable match based on a single measurement, but the IEA agreed most consistently with the PIVA. When choosing a vessel to bypass blockage at the PIVA, cardiothoracic surgeons should be aware of the many favorable features of the IEA.

Endothelium-dependent vasoconstriction in isolated vessel grafts: a novel mechanism of vasospasm?

BACKGROUND

YC-1 (3-(5'-hydroxymethyl-2'furyl)-1-benzyl-indazole) is an allosteric activator of soluble guanylyl cyclase (sGC) and a vasodilator. This study describes a paradoxical action of YC-1 in isolated vessels of patients with coronary artery disease (CAD) that appears to trigger an endothelium-dependent vasoconstrictor pathway present in vessels with endothelial dysfunction.

METHODS

Effects of YC-1 on the tensions of isolated vessels were investigated in an organ bath. Vasoconstrictors released from the vessels were quantified through enzyme-linked immunosorbent assay.

RESULTS

YC-1 elicited long-lasting constriction in saphenous veins and radial arteries from patients with CAD, but not in human umbilical veins. The half-maximal effective dose was 1.0 μmol/L. Constriction was attenuated by nifedipine (an L-type Ca(2+)-channel blocker), bosentan (an endothelin [ET](A)/ET(B) inhibitor), BQ-788 (N-[(cis-2,6-Dimethyl-1-piperidinyl)carbonyl]-4-methyl-L-leucyl-1-(methoxycarbonyl)-D-tryptophyl-D-norleucine; an ET(B) inhibitor), and by denuding, but not by ODQ (1H-(1,2,4)oxadiazolo[4,3-a]quinoxalin-1-one; an inhibitor of sGC), BQ-123 (cyclo(-D-Trp-D-Asp-Pro-D-Val-Leu); an ET(A) inhibitor), or phosphoramidon (an endothelin converting enzyme inhibitor). Indomethacin (an inhibitor of cyclooxygenase-1 and -2) and SQ29,548 ([1S-[1α,2α(Z),3α,4α]]-7-[3-[[2-[(phenylamino)carbonyl]hydrazino]methyl]-7-oxabicyclo[2.2.1]hept-2-yl]-5-heptenoic acid; a thromboxane receptor antagonist) suppressed YC-1-induced constriction, whereas DFU (5,5-dimethyl-3-(3-fluorophenyl)-4-(4-methylsulfonyl)phenyl-2(5H)-furanone; a cyclooxygenase-2 inhibitor) had no effect. Rings of saphenous vein released significantly more endothelin-1 in the presence than in the absence of YC-1.

CONCLUSIONS

YC-1-induced vasoconstriction demonstrates the existence of an endothelium-dependent vasoconstrictor pathway in the blood vessels of patients with CAD that to date has been described only in animal models of hypertension. Patients with CAD who have elevated plasma levels of endothelin-1 are thus prone to endothelium-dependent vasoconstriction, which may also play a role in vasospasm in vascular grafts.

Vascular reactivity in human arteries: from experimental study to clinical application

The principal function of VSM cells in mature animals is contraction. The endothelium is now recognized to elaborate various vasoactive factors and to play a critical part in regulation of vascular tone. Many circulating mediators and hormones have effects on vascular tone that are mediated via multiple receptors. Vasoactive agents also exert their effects on tissues by acting on one or more processes in the contraction–relaxation cycle in VSM. In humans,systemic, pulmonary, and various organ circulation(s) are maintained by an intricate and complex cardiovascular system. We expect future studies to clarify the sophisticated but complex mechanisms of VSM in humans.

DYNAMIC MECHANICAL PROPERTIES OF ARTERIAL AND VENOUS GRAFTS USED IN CORONARY BYPASS SURGERY

In this work we studied the frequency dependence of the dynamic mechanical characteristic s of saphenous vein (SV) and internal mammary artery (IMA) grafts. Rectangular longitudinal strips from 14 patients were tested under cyclic uniaxial tensile loading in the frequency range of 0.1–20 Hz, at 37°C in wet conditions. The dynamic mechanical parameters (the storage modulus ES and the hysteresis ratio h (loading/loop area)) together with the collagen phase modulus EH were computed as a function of frequency. The results showed that in all graft types ES and EH varied with frequency in the range 0.5–10 Hz, presenting a maximum in the neighboring of 1 Hz. The hysteresis ratio h was increased in the frequency range 1–20 Hz. It seems from the results that the physical resonance frequency of the components of the tissue responsible for their elastic behavior may lay in the range around 1 Hz, while that for the viscous behavior in the range of 20 Hz or more. Early clinical outcomes of both grafting were studied in parallel. In a one-year postoperative period the follow-up (clinical examination, electrocardiography, echocardiography and stress test) did not reveal any sign of graft occlusion or severe stenosis except one perioperative infraction but without any correlation to the graft quality.

The right internal thoracic artery: the forgotten conduit--5,766 patients and 991 angiograms

BACKGROUND

The right internal thoracic artery (RITA) is biologically identical to the left ITA, yet is rarely used in coronary artery bypass graft surgery (CABG). We examined the results and long-term patency of RITA grafts.

METHODS

Between 1986 and 2008, 991 consecutive RITA graft angiograms for postoperative cardiac symptoms were evaluated by two independent observers. Grafts were considered nonpatent if they had a greater than 80% stenosis, string sign, or total occlusion. Patency was examined over time by coronary territory, whether in situ or free RITA, and compared with other conduits. Clinical results were collected prospectively and by the National Death Index.

RESULTS

A total of 5,766 patients had a RITA graft as part of a bilateral ITA CABG procedure. Operative mortality was 1.1%; deep sternal infection 1.5%. Of 7,780 coronary conduits studied, 991 RITA conduits were examined; a mean of 100±60 months postoperatively (1 to 288 months). Overall ten-year RITA patency was 90%. The RITA graft patency to the left anterior descending artery (LAD; n=149) was 95% at 10 years and 90% at 15 years. Ten-year RITA patency to the circumflex marginal (Cx; n=436) was 91%, right coronary artery (n=199) was 84% (p<0.001), and posterior descending artery (n=207) was 86%. Ten-year RITA and LITA patencies to the LAD were identical (95% vs 96%) and to the Cx (91% vs 89%), respectively. In situ RITA (n=450) and free RITA (n=541) had similar ten-year patencies (89% vs 91%; p=0.44). The RITA patency was always better than the radial artery (p<0.01) and saphenous vein grafts (p<0.001). Atheromatous changes were not seen in the RITA angiograms. Ten-year survival of patients with RITA and LITA for triple-vessel coronary disease was 89%.

CONCLUSIONS

Late patencies of RITA are excellent, equivalent to the LITA for identical territories, always better than radial arteries and saphenous vein grafts, and remain free of atheroma. Use of RITA in addition to LITA is associated with excellent survival in triple-vessel coronary disease. More extensive use of the RITA in CABG is recommended.