Trace amine-induced vasoconstriction of human mammary artery and saphenous vein.

Sympathomimetic amines, including ß-phenylethylamine (PEA), constrict animal blood vessels but their mechanism of action is not now thought to be through α-adrenoceptors and release of noradrenaline but via trace amine-associated receptors (TAARs). This information is not available for human blood vessels. Functional studies were therefore performed on human arteries and veins to establish whether they constrict to PEA and whether any constrictions are adrenoceptor-mediated. Isolated internal mammary artery or saphenous vein rings were set up in Kreb's-bicarbonate solution at 37 ± 0.5 °C gassed with O2:CO2 (95:5) under class 2 containment. Isometric contractions were measured and cumulative concentration-response curves for PEA or the α-adrenoceptor agonist, phenylephrine were established. PEA showed concentration-related contractions. The maximum was significantly greater in arteries (1.53 ± 0.31 g, n = 9) than veins (0.55 ± 0.18 g, n = 10), but not when plotted as % of KCl contractions. PEA showed slowly developing contractions plateauing at 17,3 ± 3.7 min in mammary artery. The reference α-adrenoceptor agonist, phenylephrine, exhibited more rapid onset (peak 5.0 ± 1.2 min) but non-sustained contractions. In saphenous veins, PEA (62.8 ± 10.7%) and phenylephrine (61.4 ± 9.7%, n = 4) displayed the same maximum, but phenylephrine was more potent. The α1-adrenoceptor antagonist, prazosin (1 µM), blocked phenylephrine contractions of mammary arteries but not PEA contractions in either vessel. PEA causes substantial vasoconstriction of human saphenous vein and mammary artery, which explains its vasopressor actions. This response, however, was not mediated via α1-adrenoceptors, but likely due to TAARs. The classification of PEA as a sympathomimetic amine on human blood vessels is therefore no longer valid and requires revision.

Internal mammary artery: the primary conduit for surgical revascularization.

Internal mammary artery, by far, is the gold standard and first conduit for surgical revascularization especially when it comes to bypassing a lesion in the left anterior descending coronary artery. Several factors behind using this artery have been established, including but not limited to, the anatomical location, the course and flow, the elastic nature of the artery as well as the physiological characteristics that make this conduit to yield excellent long-term patency rates. This review aims to thoroughly examine current literature and establish the facts behind using this conduit in our daily surgical revascularization practice.

Minimally invasive multivessel coronary bypass surgery: Angiographic patency data.

OBJECTIVE: Minimally invasive multivessel coronary artery bypass grafting (MIM CABG) has demonstrated its safety, effectiveness and high rate of reproducibility. However, minithoracotomy CABG is still rarely performed. In this study, we retrospectively analyze the CT-angiographic graft patency rates for the patients subjected to this operation. METHODS: A total of 245 patients were subjected to MIM CABG by a left minithoracotomy approach between 2014 and 2018. The left internal thoracic artery (LITA) harvesting, proximal, and distal anastomoses were performed under direct vision. The patients then underwent 128-slice computed tomography coronary angiography (CTA). The angiographic results were obtained for 127 (51.8%) patients (the follow-up period of 31.1 ± 7.8 months, from 15 to 45 months). Of the total patients, 204 (83.2%) were followed clinically during the time period from 12 to 56 months. RESULTS: Complete revascularization was performed for all the patients. The mean number of grafts was 2.6 ± 0.5. The perioperative mortality was 0.4% (1 patient). There were two conversions to sternotomy (0.8%), four reopenings for bleeding (1.6%), three myocardial infarctions (1.2%), and one stroke (0.4%). Twenty-two patients (9.0%) received transfusions. The long-term mortality was 4.4% (nine patients). Three patients (1.5%) suffered from a stroke during the follow-up period. For five patients (2.4%), repeat revascularization was necessary. For the examined patients, the overall graft patency rate was 89.8%, the LITA graft patency rate was 98.4%, the radial artery patency was 100%, and the saphenous vein graft patency was 84.0%. CONCLUSIONS: MIM CABG allows complete surgical revascularization with excellent clinical outcomes and promising angiographic graft patency rates.

The influence of hemodynamics on graft patency prediction model based on support vector machine.

In the existing patency prediction model of coronary artery bypass grafting (CABG), the characteristics are based on graft flow, but no researchers selected hemodynamic factors as the characteristics. The purpose of this paper is to study whether the introduction of hemodynamic factors will affect the performance of the prediction model. Transit time flow-meter (TTFM) waveforms and 1-year postoperative patency results were obtained from 50 internal mammary arterial grafts (LIMA) and 82 saphenous venous grafts (SVG) in 60 patients. Taking TTFM waveforms as the boundary conditions, the CABG ideal models were constructed to obtain hemodynamic factors in grafts. Based on clinical characteristics and combination of clinical and hemodynamic characteristics, patency prediction models based on support vector machine (SVM) were constructed respectively. For LIMA, after the introduction of hemodynamic factors, the accuracy, sensitivity and specificity of the prediction model increased from 70.35%, 50% and 74.17% to 78.02%, 70% and 78.89%, respectively. For SVG, the accuracy, sensitivity and specificity of the prediction model increased from 63.24%, 40% and 76.91% to 74.41%, 60.1% and 82.73%, respectively. The performance of the prediction model can be improved by introducing hemodynamic factors into the characteristics of the model. The accuracy, sensitivity and specificity of the prediction results are higher with the addition of hemodynamic characteristics.

Beyond patency: Functional assessment of adequacy using internal mammary artery grafting to the left anterior descending artery.

INTRODUCTION: Arterial graft physiology influences the long-term outcome of coronary artery bypass grafting (CABG). We studied factors that can affect the overall resistance to flow using internal mammary artery grafting to the left anterior descending artery. METHODS: This was a prospective, nonrandomized observational study of 100 consecutive patients who underwent elective on-pump isolated or combined valve surgery and CABG. Coronary stenoses were assessed using conventional and quantitative coronary angiography assessment. The flow and pulsatility index (PI) of the grafts were assessed by transit-time flowmetry during cardioplegic arrest and at the end of the operation. Fractional polynomials were used to explore linearity, followed by multivariable regression analysis. RESULTS: Univariate analysis demonstrated higher flows at the end of the operation in patients who had higher flows with the cross-clamp on (P < .001), in males (P = .004), in patients with a low PI at the end of the operation (P = .04), and in patients with a larger size of the recipient artery (P = .005). Multivariable regression analysis showed that the graft flow at the end of the operation was significantly associated with the mean flow with the cross-clamp on (P < .001), sex (P = .003), and PI at the end of the operation (P = .003). Concomitant valve surgery did not influence flows. Male patients had 18 mL/min higher flow. CONCLUSIONS: The graft flow at the end of the operation can be determined by the flow with the cross-clamp on, the PI with the cross-clamp off and coronary artery. We reported differences in the graft flows between sexes, and for first the time, we introduced the concepts of "adequate flow" and "resistance-to-forward-flow" for patent coronary grafts.

Intraoperative graft flow profiles in coronary artery bypass surgery: A meta-analysis.

BACKGROUND: Conduits used in coronary artery bypass artery grafting (CABG) have different properties and flow profiles. We compared intraoperative mean graft flow (MGF) between arterial and venous conduits, off-pump CABG (OPCABG) and on-pump CABG (ONCABG) procedures, skeletonized and pedicled internal mammary artery (IMA) grafts, and pulsatility index (PI) between OPCABG and ONCABG, in pairwise meta-analyses. METHODS: Following a systematic literature search, all studies comparing MGF in arterial and venous grafts, were included. The primary endpoint was comparison of pooled MGF between arterial and venous grafts. Secondary endpoints were comparisons of pooled MGF in OPCABG vs ONCABG, anastomosed skeletonized vs pedicled IMA grafts, free skeletonized vs pedicled IMA grafts and PI in OPCABG versus ONCABG. RESULTS: A total of 25 studies with 4443 patients were included. Compared with venous grafts, arterial grafts had lower MGF (standardized mean difference [SMD], -0.28; 95% confidence interval [CI, -0.34; -0.22]; P < .001). OPCABG was associated with significantly lower MGF compared to ONCABG (SMD, -0.29; 95%CI, -0.50; -0.08]; P = .01). No differences were found in MGF between skeletonized vs pedicled IMA after anastomosis (SMD, 0.32; 95%CI [-0.08; 0.71]; P = .11) or in free flow (SMD, 0.76; 95%CI [-0.14; 1.65]; P = .10). No difference was found in PI between OPCABG and ONCABG. At meta-regression, age was associated with higher MGF, while OPCABG was associated with lower MGF. CONCLUSIONS: Intraoperative flow of venous conduits is higher than that of arterial grafts. Compared to OPCABG surgery, graft flow is higher in ONCABG. In skeletonized and pedicled IMA conduits, no difference in flow profiles was found.

Characterisation of vasodilatory responses in the presence of the CGRP receptor antibody erenumab in human isolated arteries.

BACKGROUND: Migraine is associated with activation of the trigeminovascular system, release of calcitonin gene-related peptide (CGRP) and dilation of dural arteries. Novel treatments target calcitonin gene-related peptide or its receptor, which are present in all vascular beds, raising cardiovascular concerns. Erenumab is a human CGRP-receptor antibody approved for the prophylactic treatment of migraine. METHODS: We characterised the relaxant responses to CGRP in the absence and presence of erenumab (1 µM) in isolated human middle meningeal, internal mammary and (proximal and distal) coronary arteries. Furthermore, in human internal mammary arteries from cardiovascularly-compromised patients, we assessed the pharmacological specificity of erenumab by investigating whether the vasodilatory responses to acetylcholine, sodium nitroprusside, pituitary adenylate cyclase activating polypeptide-38 (PACAP), vasoactive intestinal peptide and nicardipine, along with the vasoconstrictor responses to dihydroergotamine, were modified by erenumab. RESULTS: Calcitonin gene-related peptide induced concentration-dependent vasodilatory responses in all vessels studied that were significantly antagonised by erenumab. In human internal mammary arteries from cardiovascularly-compromised patients, the responses to acetylcholine, sodium nitroprusside, PACAP, vasoactive intestinal peptide, nicardipine and dihydroergotamine were unaffected by erenumab. CONCLUSION: Erenumab inhibits calcitonin gene-related peptide-induced vasodilatory responses in human middle meningeal arteries, human internal mammary arteries and human coronary arteries. Moreover, erenumab shows functional specificity as no interaction was observed with the relaxant responses to several vasodilators, nor the dihydroergotamine-dependent vasoconstrictor responses.

EPA:DHA 6:1 is a superior omega-3 PUFAs formulation attenuating platelets-induced contractile responses in porcine coronary and human internal mammary artery by targeting the serotonin pathway via an increased endothelial formation of nitric oxide.

At arterial sites of endothelial denudation and dysfunction, activated platelets contribute to vascular injury through the release of potent contracting factors such as serotonin (5-HT). This study evaluated whether omega-3 polyunsaturated fatty acids (PUFAs), known to protect the vascular system, are able to prevent platelets-induced contractile responses in isolated arteries and, if so, to investigate the underlying mechanism and the importance of the omega-3 PUFAs formulation. Porcine coronary arteries (PCA), human internal mammary arteries (IMA) and washed human platelets were prepared and vascular reactivity was studied in organ chambers. In PCA rings, aggregating platelets caused concentration-dependent contractions that were significantly inhibited by the 5-HT2A receptor antagonist ketanserin, and by EPA:DHA 6:1 but not EPA:DHA 1:1 at 0.4% v/v. EPA:DHA 6:1 also prevented the 5-HT-induced contractions but affected only slightly those to the thromboxane A2 analogue U46619. The inhibitory effect of EPA:DHA 6:1 on platelets-induced contractions was not observed in rings without endothelium, and prevented by an eNOS inhibitor but not by inhibitors of endothelium-dependent hyperpolarization. In IMA rings, EPA:DHA 6:1 but not EPA:DHA 1:1 at 0.4% v/v significantly prevented the 5-HT-induced contraction, and induced greater endothelium-dependent relaxations than bradykinin and acetylcholine sensitive to an eNOS inhibitor. EPA:DHA 6:1 strongly inhibits platelets- and 5-HT-induced contractions in PCA rings and those to 5-HT in IMA rings most likely through an increased endothelial formation of NO. These findings suggest that the omega-3 PUFAs EPA:DHA 6:1 formulation may be of interest to prevent platelets-induced vascular injury at arterial sites of endothelial dysfunction.

Propofol-Induced Vasodilation in Human Internal Mammary Artery: Role of Potassium Channels.

OBJECTIVES: The aim of this study was to investigate the vascular effects and mechanisms of propofol in the human internal mammary artery (IMA). DESIGN: In vitro experimental study. SETTING: The study was conducted in the research laboratory of a pharmacology department. PARTICIPANTS: IMA segments were obtained from 52 patients undergoing coronary artery bypass surgery. INTERVENTIONS: The IMA rings were suspended in isolated organ baths, and the changes in the tension were isometrically recorded. The antagonistic effect of propofol (1 µM, 10 µM, and 100 µM) on contractions induced by potassium chloride (45 mM), phenylephrine (1 µM), 5-hydroxytryptamine (30 µM), and calcium chloride (10 µM-10 mM) was investigated. The relaxations induced by propofol also were tested in the presence of the nitric oxide synthase inhibitor, nitro-L-arginine methyl ester (100 mM); the cyclooxygenase inhibitor, indomethacin (10 mM); and the potassium ion channel inhibitors, tetraethylammonium (1 mM), iberiotoxin (20 nM), glibenclamide (10 µM), 4-aminopyridine (1 mM), and barium chloride (30 µM). MEASUREMENTS AND MAIN RESULTS: Propofol caused a significant concentration-dependent vasorelaxation, which was endothelium independent. It inhibited the contractions induced by potassium chloride, phenylephrine, 5-hydroxytryptamine, and calcium chloride (p < 0.001), but it did not affect the basal tension. Propofol-induced relaxation was significantly inhibited by iberiotoxin and tetraethylammonium (p < 0.001); however, it was not affected by 4-aminopyridine, glibenclamide, and barium chloride. CONCLUSION: This study clearly reveals that propofol relaxes the IMA, and propofol-induced vasodilation may be related to large conductance calcium ion-activated potassium ion channel activation. Propofol use in coronary artery bypass surgery can be valuable via its favorable vasodilator effect to overcome perioperative vasospasm of IMA.

MDMA modulates 5-HT1-mediated contractile response of the human internal thoracic artery in vitro.

3,4-Methylenedioxymethamphetamine (MDMA or "ecstasy") is a popular recreational drug of abuse. In addition to its characteristic psychotropic effects, important cardiovascular effects have been described such as increased blood pressure and heart rate. MDMA was previously shown to behave as a partial agonist on 5-hydroxytryptamine (5-HT) receptors in the human internal thoracic artery in vitro, involving the 5-HT2A subtype. Here, we studied the interaction of MDMA (400, 800 and 1600 µM) with the following 5-HT receptor agonists: 5-carboxamidotryptamine (5-CT, full agonist for the 5-HT1, 5-HT2, 5-HT5, 5-HT6 and 5-HT7 receptors) and sumatriptan (selective 5-HT1B/1D receptors agonist). The results showed the ability of MDMA to influence the concentration-dependent response of 5-CT (97.3% of maximal reduction for 1600 µM of MDMA) and sumatriptan (72.43% of maximal reduction for 1600 µM of MDMA). The lower concentration of MDMA (400 µM) produced a significant potentiation of the response to sumatriptan thus suggesting an interaction of MDMA with the activation of 5-HT receptors, namely of the 5-HT1 subtype, in the peripheral vasculature. Together our results further support the importance of the affinity of MDMA to 5-HT receptors in the vascular effects of this drug.

Mechanisms Responsible for Serotonin Vascular Reactivity Sex Differences in the Internal Mammary Artery.

BACKGROUND: The increased adverse cardiac events in women undergoing coronary artery bypass grafting are multifactorial and may include clinical, psychosocial, and biological factors. Potential contributing biological factors could include vascular hyperreactivity of the internal mammary artery (IMA) to endogenous vasoconstrictors in women, resulting in a predilection to myocardial ischemia. This study evaluated sex differences in serotonin and thromboxane A2 dependent vasoconstriction in human isolated IMA, with the mechanistic role of (1) the endothelium, (2) nitric oxide (NO), (3) prostaglandins, and (4) receptor activity investigated for any observed sex difference. METHODS AND RESULTS: Viable isolated human IMA segments were obtained from 116 patients (44 women [mean age, 66.8±12.2 years] and 72 men [mean age, 66.6±10.4 years]) undergoing coronary artery bypass grafting. Cumulative concentration-response curves for serotonin and thromboxane A2 mimetic, U46619, were determined and revealed an increased sensitivity to serotonin but not U46619 in women. This sex difference to serotonin was further assessed by the following: (1) endothelial denudation, (2) endothelial NO synthase inhibition and NO quantification using electron paramagnetic resonance, (3) cyclooxygenase inhibition and prostaglandin metabolite quantification using mass spectrometry, and (4) quantification of receptor activity status. The female hyperreactivity to serotonin was (1) abolished by endothelial denudation; (2) unaffected by NO synthase inhibition, with no difference in electron paramagnetic resonance-assessed NO levels; (3) abolished by cyclooxygenase inhibition (quantification of prostaglandins in IMA revealed a trend towards reduced 6-keto prostaglandin F1α in female IMA; P=0.08); and (4) unrelated to receptor activity. CONCLUSIONS: These data indicate that female IMAs are hyperreactive to serotonin but not U46619, with the former attributable to an endothelium-dependent cyclooxygenase pathway.

Current status of intra-operative graft assessment: Should it be the standard of care for coronary artery bypass graft surgery?

The "Achilles heel" of coronary artery bypass graft (CABG) surgery is graft patency. While long-term patency is determined by the type of conduit and the progression of graft and native vessel disease, short-term patency is affected by intra-operative technical issues. Transit-time flow measurements and epicardial ultrasound have been shown to accurately assess intra-operative graft patency. This review will examine the evidence to support the premise that intra-operative graft assessment is essential in determining graft patency and should be the standard of care when performing CABG surgery.

Diabetes Mellitus Induces Hyperreactivity of 5-Hydroxytryptamine (5-HT)-Induced Constriction in Human Internal Thoracic Artery and Is Associated with Increase in the Membrane Protein Level of 5-HT2A Receptor.

Studies indicate that 5-hydroxytryptamine (5-HT) released from activated platelets in coronary artery bypass grafting (CABG) induces 5-HT2A receptor-mediated graft spasm. We previously reported that 5-HT-induced constriction of human endothelium-denuded saphenous vein (SV) was significantly augmented in patients with diabetes mellitus (DM) than in patients without DM (non-DM), without changes in the levels of the membrane-bound 5-HT2A receptor of their smooth muscle cells. Although the internal thoracic artery (ITA) is the key graft conduit for CABG, the effect of DM on the ITA graft spasm is still unclear. Therefore, in this study, we investigated the effect of DM on 5-HT-induced vasoconstriction and the level of membrane-bound 5-HT2A receptor in ITA grafts. 5-HT-induced constriction of the isolated human endothelial-denuded ITA was significantly higher in patients with DM than in patients without DM. In addition, the level of the 5-HT2A receptor in the membrane fraction of human ITA smooth muscle cells was significantly higher in patients with DM than in those without DM. These results demonstrate that DM is a risk factor for CABG in both venous and arterial conduits, and that it differentially affects the level of the membrane-bound 5-HT2A receptor in the venous and arterial smooth muscle cells.

Internal mammary artery flow in different racial groups of Pakistan.

OBJECTIVE: To find out any differences in free flow of internal mammary artery among different ethnic groups. METHODS: This observational, cross-sectional study was conducted at the Civil Hospital, Karachi, from January 2013 to December 2015, and comprised patients who underwent coronary artery bypass grafting. The participants were divided into 5 groups, i.e. Sindhi, Muslim migrants from India, Punjabi, Pathan and Balochi patients. Free flow of internal mammary artery was measured immediately after harvesting within a syringe, and its flow was measured in 30 seconds. SPSS 18 was used for data analysis. RESULTS: Of the 158 patients, 44(27.8%) were Sindhi, 33(20.9%) Punjabi, 8(5%) Baloch, 21(13.3%) Pathan and 52(32.9%) were migrants. The overall mean age was 52±8 years and the mean flow was 11.6±9.6ml per 30 seconds. The flow was 9.3±6 ml, 10±8ml, 13±11ml, 17±14ml and 15±13 ml in 30 seconds among migrants, Sindhi, Punjabi, Pathan and Baloch patients, respectively, with significant higher flow in Pathan patients compared to Sindhi and migrant patients (p<0.05). A flow of less than 5ml/30 sec was mostly found in migrants or Sindhi subjects 30/40(75%), and flow more than 30ml/ 30 seconds was found mostly in Baloch or Pathan patients 4/8(50%). Low flow internal mammary artery, which was used on left anterior descending artery, showed significantly higher need of inotropic support as compared to high flow internal mammary artery (p=0.004), more low cardiac output syndrome (p=0.022) and more use of intra-aortic balloon pump (p=0.028). CONCLUSIONS: Internal mammary artery flow was higher in Pathan and Baloch patients and low in migrants and Sindhis.

Inhibition of microsomal PGE synthase-1 reduces human vascular tone by increasing PGI2 : a safer alternative to COX-2 inhibition.

BACKGROUND AND PURPOSE: The side effects of cyclooxygenase-2 (COX-2) inhibitors on the cardiovascular system could be associated with reduced prostaglandin (PG)I2 synthesis. Microsomal PGE synthase-1 (mPGES-1) catalyses the formation of PGE2 from COX-derived PGH2 . This enzyme is induced under inflammatory conditions and constitutes an attractive target for novel anti-inflammatory drugs. However, it is not known whether mPGES-1 inhibitors could be devoid of cardiovascular side effects. The aim of this study was to compare, in vitro, the effects of mPGES-1 and COX-2 inhibitors on vascular tone in human blood vessels. EXPERIMENTAL APPROACH: The vascular tone and prostanoid release from internal mammary artery (IMA) and saphenous vein (SV) incubated for 30 min with inhibitors of mPGES-1 or COX-2 were investigated under normal and inflammatory conditions. KEY RESULTS: In inflammatory conditions, mPGES-1 and COX-2 proteins were more expressed, and increased levels of PGE2 and PGI2 were released. COX-2 and NOS inhibitors increased noradrenaline induced vascular contractions in IMA under inflammatory conditions while no effect was observed in SV. Interestingly, the mPGES-1 inhibitor significantly reduced (30-40%) noradrenaline-induced contractions in both vessels. This effect was reversed by an IP (PGI2 receptor) antagonist but not modified by NOS inhibition. Moreover, PGI2 release was increased with the mPGES-1 inhibitor and decreased with the COX-2 inhibitor, while both inhibitors reduced PGE2 release. CONCLUSIONS AND IMPLICATIONS: In contrast to COX-2 inhibition, inhibition of mPGES-1 reduced vasoconstriction by increasing PGI2 synthesis. Targeting mPGES-1 could provide a lower risk of cardiovascular side effects, compared with those of the COX-2 inhibitors. LINKED ARTICLES: This article is part of a themed section on Targeting Inflammation to Reduce Cardiovascular Disease Risk. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.22/issuetoc and http://onlinelibrary.wiley.com/doi/10.1111/bcp.v82.4/issuetoc.

Studying the blood pressures of antegrade and retrograde internal mammary vessels: Do they really work as recipient vessels?

BACKGROUND: The proximal ends of internal mammary (IM) vessels are now the most common recipient vessels for breast reconstruction. On the other hand, bilateral deep inferior epigastric artery perforator (DIEP) flaps are often needed according to the territory and the volume required for reconstruction. The usefulness of retrograde IM vessels as second recipients has recently been reported, but there are very few quantitative studies on the hydrodynamics of the retrograde IM vessels. Because the flow is dependent on the pressure differential, the blood pressures of the antegrade IM artery (AIMA), antegrade IM vein (AIMV), retrograde IM artery (RIMA), retrograde IM vein (RIMV), and recirculated intraflap vein (FV) were investigated to solve this question and to confirm the reliability and usefulness of the retrograde IM vessels. METHODS: Ten free flap breast reconstructions were included in this study. The IM vessels were exposed, and the pressures were measured. After recirculation, the FV pressures were measured when the flap was not ischemic or congestive. Systemic blood pressure was also recorded during the whole measurement period. RESULTS: The AIMA and RIMA pressures were 70.4 ± 8.2 mmHg and 54.0 ± 8.6 mmHg (p = 0.000003), respectively, while the systemic pressure was 65.1 ± 10.0 mmHg. The AIMV pressure was always smaller than the RIMV pressure; the mean AIMV pressure was 5.3 ± 1.6 mmHg. In addition, the FV pressure was greater (p = 0.03) than the RIMV pressure (17.7 ± 9.9 mmHg), while the RIMV pressure was 8.7 ± 2.0 mmHg. CONCLUSIONS: Both the RIMA and RIMV are useful and reliable as second recipients for bipedicled free flap transfers. This is a great benefit because it would provide two recipients in one surgical site and would be especially useful in thin patients or patients with previous abdominal scars requiring double pedicled DIEP flaps. LEVEL OF EVIDENCE: Therapeutic Study, Level IV.

Application of omentum as an in vivo bioreactor for regeneration of decellularized human internal mammary artery.

This study investigates the extent of cell seeding as well as lumen patency in acellular Internal mammary artery (IMA) scaffolds that have been re-cellularized by omentum as a natural bioreactor. Sixteen Virgin female Wistar rats were selected for implantation of acellular scaffold in omentum. Following laparotomy omentum was retracted to the outside of the abdomen and the more vascularized portion of it was selected for the experiment. The scaffold was wrapped by omentum and placed between two layers of rectus muscles that have been previously dissected. Samples were taken from scaffolds at 2 and 3 months for histopathological evaluation. All the grafts were explanted at 2 and 3 months and the lumens were completely patent compared to the native scaffold. The histology of implanted IMA after 2 and 3 months showed progressive recellularization especially by smooth muscle cells over the media layer. CD 34 staining was positive adjacent to the grafts which showed well angiogenesis. Trichrome and Movat's Pentachrome staining showed normal collagen formation in the inner media layer. Promising results obtained from the introduced protocol for in vivo recellularization, including patent lumen and proper cell seeding, encourages application of the mentioned technique for experimental vascular graft application. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 2685-2693, 2017.

Endothelium-dependent vasorelaxant effect of procyanidin B2 on human internal mammary artery.

The aim of the present study was to investigate and characterize vasorelaxant effect of procyanidin B2 on human internal mammary artery (HIMA) as one of the mechanisms of its protective effect against vascular risk. Procyanidin B2 induced strong concentration-dependent relaxation of HIMA rings pre-contracted by phenylephrine. Pretreatment with L-NAME, a NO synthase inhibitor, hydroxocobalamin, a NO scavenger, and ODQ, an inhibitor of soluble guanylate cyclase, significantly inhibited procyanidin B2-induced relaxation of HIMA, while indomethacin, a cyclooxygenase inhibitor, considerably reduced effects of low concentrations. Among K+ channel blockers, iberiotoxin, a selective blocker of large conductance Ca2+-activated K+ channels (BKCa), abolished procyanidin B2-induced relaxation, glibenclamide, a selective ATP-sensitive K+(KATP) channels blocker, induced partial inhibition, while 4-aminopyridine, a blocker of voltage-gated K+(KV) channels, and TRAM-34, an inhibitor of intermediate-conductance Ca2+-activated K+(IKCa) channels, slightly reduced maximal relaxation of HIMA. Further, procyanidin B2 relaxed contraction induced by phenylephrine in Ca2+-free Krebs solution, but had no effect on contraction induced by caffeine. Finally, thapsigargin, a sarcoplasmic reticulum Ca2+-ATPase inhibitor, significantly reduced relaxation of HIMA produced by procyanidin B2. These results demonstrate that procyanidin B2 produces endothelium-dependent relaxation of HIMA pre-contracted by phenylephrine. This effect is primarily the result of an increased NO synthesis and secretion by endothelial cells and partially of prostacyclin, although it involves activation of BKCa and KATP, as well as KV and IKCa channels in high concentrations of procyanidin B2.

Intraoperative Analysis of Flow Dynamics in Arteriovenous Composite Y Grafts.

Objective: Composite graft of left internal thoracic artery and great saphenous vein in revascularization of the left coronary system is a technique well described in literature. The aim of this study is to analyze blood flow dynamics in this configuration of composite graft especially in what concerns left internal thoracic artery's adaptability and influence of great saphenous vein segment on left internal thoracic artery's flow. Methods: Revascularization of left coronary system with composite graft, with left internal thoracic artery revascularizing the anterior interventricular artery and a great saphenous vein segment, anastomosed to the left internal thoracic artery, revascularizing another branch of the left coronary system, was performed in 23 patients. Blood flow was evaluated by transit time flowmetry in all segments of the composite graft (left internal thoracic artery proximal segment, left internal thoracic artery distal segment and great saphenous vein segment). Measures were performed in baseline condition and after dobutamine-induced stress, without and with non-traumatic temporary clamping of the distal segments of the composite graft. Results: Pharmacological stress resulted in increase of blood flow values in the analyzed segments (P<0.05). Non-traumatic temporary clamping of great saphenous vein segment did not result in statistically significant changes in the flow of left internal thoracic artery distal segment, both in baseline condition and under pharmacological stress. Similarly, non-traumatic temporary clamping of left internal thoracic artery distal segment did not result in statistically significant changes in great saphenous vein segment flow. Conclusion: Composite grafts with left internal thoracic artery and great saphenous vein for revascularization of left coronary system, resulted in blood flow dynamics with physiological adaptability, both at rest and after pharmacological stress, according to demand. Presence of great saphenous vein segment did not alter physiological blood flow dynamics in distal segment of left internal thoracic artery.

Intraoperative analysis of flow dynamics in arteriovenous composite y grafts

Abstract Objective: Composite graft of left internal thoracic artery and great saphenous vein in revascularization of the left coronary system is a technique well described in literature. The aim of this study is to analyze blood flow dynamics in this configuration of composite graft especially in what concerns left internal thoracic artery's adaptability and influence of great saphenous vein segment on left internal thoracic artery's flow. Methods: Revascularization of left coronary system with composite graft, with left internal thoracic artery revascularizing the anterior interventricular artery and a great saphenous vein segment, anastomosed to the left internal thoracic artery, revascularizing another branch of the left coronary system, was performed in 23 patients. Blood flow was evaluated by transit time flowmetry in all segments of the composite graft (left internal thoracic artery proximal segment, left internal thoracic artery distal segment and great saphenous vein segment). Measures were performed in baseline condition and after dobutamine-induced stress, without and with non-traumatic temporary clamping of the distal segments of the composite graft. Results: Pharmacological stress resulted in increase of blood flow values in the analyzed segments (P<0.05). Non-traumatic temporary clamping of great saphenous vein segment did not result in statistically significant changes in the flow of left internal thoracic artery distal segment, both in baseline condition and under pharmacological stress. Similarly, non-traumatic temporary clamping of left internal thoracic artery distal segment did not result in statistically significant changes in great saphenous vein segment flow. Conclusion: Composite grafts with left internal thoracic artery and great saphenous vein for revascularization of left coronary system, resulted in blood flow dynamics with physiological adaptability, both at rest and after pharmacological stress, according to demand. Presence of great saphenous vein segment did not alter physiological blood flow dynamics in distal segment of left internal thoracic artery.