Bypass Arteries Research Articles

Polyvinyl Alcohol Sponges to Facilitate Cerebral Bypass Surgery: Technical Note

The standard way of isolating bypass vessels from surrounding structures during cerebral bypass surgery has been to use a rubber dam or neurosurgical patty. Here, the use of polyvinyl alcohol (PVA) sponges is described as a possible upgrade from these traditional bypass dams. PVA sponges were used to isolate bypass arteries from surrounding tissues during microvascular anastomosis in 25 patients undergoing bypass surgery at our institution. There were no adverse events related to the use of PVA for microvascular anastomosis. PVA sponges offered some specific advantages when compared with rubber and cottonoid dams. Although preliminary, our experience using PVA sponges during microvascular anastomosis suggests some of their properties can facilitate cerebral bypass surgery.

WHY STEAL FROM ONE WHEN YOU CAN STEAL FROM TWO: A UNIQUE CASE OF CLASSIC SUBCLAVIAN STEAL SYNDROME WITH CONCOMITANT CORONARY SUBCLAVIAN STEAL SYNDROME IN THE POST CORONARY BYPASS PATIENT

Subclavian steal syndrome (SSS) involving both vertebral and bypass arteries in the post-CABG patient is poorly described in the literature. Cases of coronary subclavian steal syndrome (CSSS) in the post-CABG patient traditionally require repeat open thoracic surgery or percutaneous intervention via

Operative cooperation of the intra-extra cranial bypass operation of the intracranial giant aneurysms

Objective To explore the operative cooperation of the intra-extra cranial bypass operation of the intracranial giant aneurysms. Methods A retrospective analysis of 7 patients who had intracranial giant aneurysm and received the intra-extra cranial bypass operation from October 2014 to June 2016. All preoperative and intraoperative nursing points of operative cooperation were analyzed. Results The post-operative digital subtraction angiographies of 7 patients without any perioperative nursing complications showed enough flow in the bypass arteries. Conclusions Operative multi-incision managing, positive temperature intervening, special instruments using and thrombosis preventing play very important roles in the nursing points of the successful operative cooperation. Key words: Intra-extra cranial bypass operation; Operative cooperation; Nursing points

Isolated Human Pulmonary Artery Structure and Function Pre- and Post-Cardiopulmonary Bypass Surgery.

BackgroundPulmonary dysfunction is a known complication after cardiac surgery using cardiopulmonary bypass, ranging from subclinical functional changes to prolonged postoperative ventilation, acute lung injury, and acute respiratory distress syndrome. Whether human pulmonary arterial function is compromised is unknown. The aim of the present study was to compare the structure and function of isolated and cannulated human pulmonary arteries obtained from lung biopsies after the chest was opened (pre–cardiopulmonary bypass) to those obtained at the end of cardiopulmonary bypass (post–cardiopulmonary bypass) from patients undergoing coronary artery bypass graft surgery.Methods and ResultsPre‐ and post–cardiopulmonary bypass lung biopsies were received from 12 patients undergoing elective surgery. Intralobular small arteries were dissected, cannulated, pressurized, and imaged using confocal microscopy. Functionally, the thromboxane mimetic U46619 produced concentration‐dependent vasoconstriction in 100% and 75% of pre‐ and post–cardiopulmonary bypass arteries, respectively. The endothelium‐dependent agonist bradykinin stimulated vasodilation in 45% and 33% of arteries pre‐ and post–cardiopulmonary bypass, respectively. Structurally, in most arteries smooth muscle cells aligned circumferentially; live cell viability revealed that although 100% of smooth muscle and 90% of endothelial cells from pre–cardiopulmonary bypass biopsies had intact membranes and were considered viable, only 60% and 58%, respectively, were viable from post–cardiopulmonary bypass biopsies.ConclusionsWe successfully investigated isolated pulmonary artery structure and function in fresh lung biopsies from patients undergoing heart surgery. Pulmonary artery contractile tone and endothelium‐dependent dilation were significantly reduced in post–cardiopulmonary bypass biopsies. The decreased functional responses were associated with reduced cell viability.Clinical Trial Registration URL: http://www.isrctn.com/ISRCTN34428459. Unique identifier: ISRCTN 34428459.

MAP-Kinase Activated Protein Kinase 2 Links Endothelial Activation and Monocyte/macrophage Recruitment in Arteriogenesis.

Arteriogenesis, the growth of natural bypass arteries, is triggered by hemodynamic forces within vessels and requires a balanced inflammatory response, involving induction of the chemokine MCP-1 and recruitment of leukocytes. However, little is known how these processes are coordinated. The MAP-kinase-activated-proteinkinase-2 (MK2) is a critical regulator of inflammatory processes and might represent an important link between cytokine production and cell recruitment during postnatal arteriogenesis. Therefore, the present study investigated the functional role of MK2 during postnatal arteriogenesis. In a mouse model of hindlimb ischemia (HLI) MK2-deficiency (MK2KO) significantly impaired ischemic blood flow recovery and growth of collateral arteries as well as perivascular recruitment of mononuclear cells and macrophages. This was accompanied by induction of endothelial MCP-1 expression in wildtype (WT) but not in MK2KO collateral arteries. Following HLI, MK2 activation rapidly occured in the endothelium of growing WT arteries in vivo. In vitro, inflammatory cytokines and cyclic stretch activated MK2 in endothelial cells, which was required for stretch- and cytokine-induced release of MCP-1. In addition, a monocyte cell autonomous function of MK2 was uncovered potentially regulating MCP-1-dependent monocyte recruitment to vessels: MCP-1 stimulation of WT monocytes induced MK2 activation and monocyte migration in vitro. The latter was reduced in MK2KO monocytes, while in vivo MK2 was activated in monocytes recruited to collateral arteries. In conclusion, MK2 regulates postnatal arteriogenesis by controlling vascular recruitment of monocytes/macrophages in a dual manner: regulation of endothelial MCP-1 expression in response to hemodynamic and inflammatory forces as well as MCP-1 dependent monocyte migration.

CT perfusion assessment of Moyamoya syndrome before and after direct revascularization (superficial temporal artery to middle cerebral artery bypass).

To evaluate the utility of CT perfusion (CTP) for the assessment of superficial temporal artery-middle cerebral artery (STA-MCA) anastomosis in patients with Moyamoya syndrome (MMS). Twenty-four consecutive MMS patients, who underwent unilateral STA-MCA bypass surgery, received CTP before and after surgery. The relative perfusion parameter values of surgical hemispheres before treatment were compared with post-treatment values. All patients underwent CT angiography (CTA) before and after surgery in order to confirm the patency of bypass. The follow-up CTA after surgery clearly demonstrated 20 (20/24, 83.3 %) bypass arteries, whereas four (16.7 %) bypass arteries were occluded or very small. Postoperative rMTT and rTTP values (P < 0.05) of the surgical side were significantly lower than pre-operation. In patients (n = 20) with bypass patency, postoperative rCBF, rMTT and rTTP values (P < 0.05) of the surgical side were significantly improved. However, the differences of all parameters were not significant (P > 0.05) in the patients (n = 4) without bypass patency after revascularization. This study demonstrates that CTP can provide a crucial quantitative assessment of cerebral haemodynamic changes in MMS before and after STA-MCA anastomosis. Twenty-four MMS patients undergoing STA-MCA bypass received CTP pre- and post-surgery. Cerebral haemodynamics improved on the surgical side post-surgery on CTP maps. rCBF might have a better correlation with patency of the bypass artery. CTP can evaluate cerebral perfusion changes in MMS patients after cerebral revascularization.

Adult Moyamoya disease: 320-Multidetector row CT for evaluation of revascularization in STA–MCA bypasses surgery

PurposeTo evaluate the utility of 320-multidetector row whole-brain computed tomography perfusion (WBCTP) and whole-head subtracted dynamic angiography (WHSDCTA) for assessing the revascularization of blood flow after superficial temporal artery (STA) to middle cerebral artery (MCA) bypass surgery in adults with Moyamoya disease (MD) in the short and long term. Patients and methods320-multidetector row WBCTP and WHSDCTA were applied in 20 patients with MD before and after surgery (for an average of 3 days and 3 months). The bypass arteries were investigated using WHSDCTA and compared with DSA. The regions of interests (ROIs) in the surgical and mirror sides of the cerebral cortex were drawn on a Vitrea Workstation. Cerebral blood volume (CBV), time to peak (TTP), cerebral blood flow (CBF), mean transit time (MTT), and delay time were recorded. Preoperative and postoperative perfusion parameters in the MCA distribution were compared using the paired t-test. ResultsWHSDCTA could clearly demonstrate 24 bypass arteries in 26 arteries for 20 patients, results which were in accordance with the results of digital subtraction angiography (DSA). When comparing preoperative values to those within 3 days after surgery, only TTP and delay time were significantly different (P<0.05). Values of CBV, TTP, CBF, delay time, and MTT 3 months after surgery were significantly different (P<0.05) from those of preoperative perfusion. ConclusionThese data suggest that 320-multidetector row WBCTP and WHSDCTA can be used to evaluate the revascularization of blood flow after STA–MCA bypass surgery in patients with MD in the short and long term.

Posterior circulation revascularization to manage vertebrobasilar occlusion

Objective To discuss the technique and effect of posterior circulation revascularization to manage vertebrobasilar occlusion. Methods Nine patients with vertebrobasilar occlusion were treated by using occipital artery ⁃ posterior inferior cerebellar artery bypass, superficial temporal artery ⁃ superior cerebellar artery bypass, superficial temporal artery⁃posterior cerebral artery bypass and occipital artery⁃ vertebral artery bypass with radial artery graft. Results Intraoperative indocyanine green angiography showed all the bypass arteries were patent. Postoperative DSA or CTA showed bypass arteries patent in 8 patients, among whom seven patients got obvious improvement on MR or CT perfusion. One patient died of heart failure on the 15th day postoperative. During the follow⁃up of eight patients, no stroke reoccurred, four patients got back to nearly normal life. Conclusion Most of the patients with vertebrobasilar occlusion could benefit from the posterior circulation revascularization, which should be confirmed by randomized controlled clinical trials in the future. DOI：10.3969/j.issn.1672⁃6731.2012.03.021

Assessment of cerebral perfusion from bypass arteries using magnetic resonance regional perfusion imaging in patients with moyamoya disease

The purpose of this study was to evaluate whether cerebral perfusion from bypassed arteries can be demonstrated on regional perfusion imaging (RPI) using arterial spin labeling. We then compared cerebral perfusion on RPI and digital subtraction angiography (DSA) in moyamoya patients who underwent extracranial-intracranial bypass surgery. We performed RPI using a 3-T magnetic resonance scanner and DSA studies in 11 moyamoya patients treated by bypass surgery. For RPI we placed a selective labeling slab on the bypassed external carotid artery. Two neuroradiologists determined the extent and location of the cerebral perfusion from bypass arteries in the middle cerebral artery territories on RPI and DSA. Kappa analysis was used to assess the interobserver agreement with respect to the extent and location of the cerebral perfusion and to evaluate the intermodality agreement between RPI and DSA. Interobserver agreement for the extent of cerebral perfusion on RPI was very good (kappa=0.89), with excellent location (kappa=1.00). Intermodality agreement for the extent of perfusion was very good (kappa=0.89), with good location (kappa=0.74). RPI is useful for evaluating cerebral perfusion from bypass arteries in moyamoya patients.

Biomechanical Regulation of Endothelium-dependent Events Critical for Adaptive Remodeling

Alterations in hemodynamic shear stress acting on the vascular endothelium are critical for adaptive arterial remodeling. The molecular mechanisms regulating this process, however, remain largely uncharacterized. Here, we sought to define the responses evoked in endothelial cells exposed to shear stress waveforms characteristic of coronary collateral vessels and the subsequent paracrine effects on smooth muscle cells. A lumped parameter model of the human coronary collateral circulation was used to simulate normal and adaptive remodeling coronary collateral shear stress waveforms. These waveforms were then applied to cultured human endothelial cells (EC), and the resulting differences in EC gene expression were assessed by genome-wide transcriptional profiling to identify genes distinctly regulated by collateral flow. Analysis of these transcriptional programs identified several genes to be differentially regulated by collateral flow, including genes important for endothelium-smooth muscle interactions. In particular, the transcription factor KLF2 was up-regulated by the adaptive remodeling coronary collateral waveform, and several of its downstream targets displayed the expected modulation, including the down-regulation of connective tissue growth factor. To assess the effect of endothelial KLF2 expression on smooth muscle cell migration, a three-dimensional microfluidic assay was developed. Using this three-dimensional system, we showed that KLF2-expressing EC co-cultured with SMC significantly reduce SMC migration compared with control EC and that this reduction can be rescued by the addition of exogenous connective tissue growth factor. Collectively, these results demonstrate that collateral flow evokes distinct EC gene expression profiles and functional phenotypes that subsequently influence vascular events important for adaptive remodeling.

Congenital Atresia of the Left Main Coronary Artery Associated With Patent Ductus Arteriosus and Aortic Regurgitation

Congenital left main coronary artery (LMCA) atresia is a rare anomaly and surgical revascularization is recommended once the diagnosis is confirmed. In some cases, LMCA atresia will coexist with other cardiac anomalies, mostly in pediatric patients. A 32-year-old woman had congenital LMCA atresia associated with patent ductus arteriosus (PDA), aortic regurgitation (AR), and moderate pulmonary hypertension. The PDA and AR were repaired surgically and the patient's symptoms improved. Coronary revascularization was not performed because the LCA was supplied by 2 large conus arteries, as "naturally occurring" bypass arteries. The patient remained asymptomatic at the 2.5-year follow-up visit. Given the positive outcome in this patient, surgical repair of the associated cardiac defect without coronary revascularization may be a reasonable approach for patients with congenital LMCA atresia, in which the left coronary arterial tree is supplied by other "naturally occurring" bypass arteries.

Investigation of the Chemical Differences between Native and Bypass Coronary Artery Plaques from the Same Heart Using Cross Polarization Magic Angle Spinning Nuclear Magnetic Resonance (CP/MAS-NMR)

The plaque deposits in bypass arteries and native arteries from the same heart have been studied using solid state cross polarization nuclear magnetic resonance (CP/MAS NMR). Both 13C and 31P signals were observed. The samples are of interest because plaque in native arteries may have deposited during the lifetime of the patient. However, plaque in the bypass occurred since bypass surgery. It has been observed that the mature plaque in native arteries was more calcified than that in bypass arteries, especially if the latter had not matured to become significant in size. Results showed that the concentrations of carboxylate carbons present in cholesterol esters were similar in native and bypass arteries. However, the areas of the 13C peaks of the carboxylate compared to the sum of areas of all other 13C arteries indicated that the carboxylate was attached to five or six other carbons. From this we can calculate that the carboxylate to other carbon ratio in the remainder must be 1:4 or 1:3. This indicates large quantities of other organic compounds in the deposits. Studies of 31P showed that phosphorus existed primarily as hydroxyapatite in the crystalline native plaque. However, a large proportion existed as organic phosphorus in the bypass plaque. In addition, we studied the interactions of calcium with homocysteine and cholesterol. Calcium-homocysteine and cholesterol-homocysteine precipitates were characterized using 13C solid state NMR. Results showed that calcium appeared to interact with sulphur in the homocysteine which seemed to form dimers and polymers.

High resolution three-dimensional visualization and characterization of coronary atherosclerosis in vitro by synchrotron radiation x-ray microtomography and highly localized x-ray diffraction

Human atherosclerotic plaques in both native and bypass arteries have been visualized using microtomography to provide additional information on the nature of coronary artery disease. Plaques contained within arteries removed from three white males aged 51, 55 and 70 are imaged in three-dimensions with monochromatic synchrotron x-ray radiation. Fields of view are 658 × 658 × 517 voxels, with cubic voxels ranging from 12 to 13 µm on a side. X-ray energies range from 11 to 15 keV (bandpass approximately 10 eV). At lower energies, high local absorption tends to generate reconstruction artefacts, while at higher energies the arterial wall is scarcely visible. At all energies, calcifications are clearly visible and differences are observed between plaques in native arteries (lifetime accumulations) versus bypass arteries (plaques developing in the interval between the heart bypass operation and the autopsy). In order to characterize coronary calcification, a micro-focused, 50 µm2, 25 keV x-ray beam was used to acquire powder diffraction data from selected calcifications. Also, large calcifications were removed from the native arteries and imaged with 25 keV x-ray energy. Calcifications are composed of hydroxyapatite crystallites and an amorphous phase. In summary, native calcifications are larger and have a higher fraction of hydroxyapatite than calcifications from the bypass arteries.

Morphology and patency of Gore-Tex wrapped internal mammary artery bypass-evaluation with helical CT

Objective: To determine the patency of coronary internal mammary artery bypass (IMAB) with CT-angiography (CTA) and to evaluate the morphology of a covering Gore-tex IMAB-sleeve (PIMAS) used to protect the bypass at possible reoperation. Materials and Methods: Sixty-five patients with IMAB wrapped with PIMAS (67 grafts) were prospectively investigated by CTA for bypass patency and sleeve morphology 6 months postoperatively with a standardised radiological and clinical protocol. Results: All patent bypass arteries (62/62) were identified by CTA as open. In the remaining five cases, CTA revealed a bypass occlusion, which could be proven by coronary angiography in two cases (two patients refused angiography, one bypass was open angiographically). Morphology of the PIMAS could be imaged exactly in all cases. Sleeve implantation did not lead to adverse effects in terms of bypass occlusion or compression. In four patients, additional clinically relevant information were achieved. Conclusion: PIMAS implantation proved to be a safe procedure with good short-term results. CTA is a valuable method to exclude occlusion of sleeved IMA bypasses. Depiction of the wrapped IMAB by CTA supplies important information for preparing strategy in case of reoperation.