A Novel Smart Assistance System for Blood Vessel Approaching: A Technical Report Based on Oximetry.

In clinical practice, the catheter has to be placed at an accurate position during anesthesia administration. However, effectively guiding the catheter to the accurate position in deeper tissues can be difficult for an inexperienced practitioner. We aimed to address the current issues associated with catheter placement using a novel smart assistance system for blood vessel catheter placement. We used a hollow introducer needle embedded with dual wavelength (690 and 850 nm) optical fibers to advance the tip into the subclavian vessels in anesthetized piglets. The results showed average optical density changes, and the difference between the absorption spectra and hemoglobin concentrations of different tissue components effectively identified different tissues (p < 0.05). The radial basis function neural network (RBFNN) technique was applied to distinguish tissue components (the F-measure value and accuracy were 93.02% and 94%, respectively). Finally, animal experiments were designed to validate the performance of the proposed system. Using this system based on oximetry, we easily navigated the needle tip to the target vessel. Based on the experimental results, the proposed system could effectively distinguish different tissue layers of the animals.

Hemodynamic consequences of TEVAR with in situ double fenestrations of left carotid artery and left subclavian artery.

The aortic major branches after thoracic endovascular aortic repair (TEVAR) could be preserved by in situ fenestration (ISF). This study aims to explore the hemodynamic consequences of ISF-TEVAR with double fenestrations. Two patients with aortic dissection and aneurysm, respectively, were treated by ISF-TEVAR and both the left carotid artery (LCA) and left subclavian artery (LSA) were reconstructed by fenestration technique. The blood was considered a non-Newtonian fluid and the Windkessel model was adopted at the aortic outlets. Simulations were performed in two postoperative models to analyze the effects of the double fenestration stents on the hemodynamics. The postoperative wall pressure of the LCA and LSA is relatively low and the pressure difference between the inner and outer walls of the protruding segment of the LSA stent is found. Acceleration occurs when blood flows around the fenestration stents and the shear-thinning rheological behavior is observed at the aortic arch. Moreover, regions susceptible to thrombosis are identified and the surface exposed to high relative residence time is located at the aortic arch after the LSA stent. The presence of the double fenestration stents has a profound impact on the postoperative hemodynamics, and the aortic arch and rebuilt branches should be closely watched during follow-up.

Computational fluid dynamics simulation of the right subclavian artery cannulation.

OBJECTIVE: The purpose of this study was to evaluate the efficacy of right subclavian artery cannulation using computational fluid dynamics. METHODS: Patient-specific models of the aortic arch were made with 4 patterns (1: normal aorta, 2: ascending aorta aneurysm, 3: distal arch aneurysm, 4: bovine arch) based on the computed tomography images. Right subclavian artery and ascending aorta cannulation models were created to simulate the physiologic pulsatile flow. Perfusion flow through the arterial cannula was set to 2.50 L/min (50% flow), 3.75 L/min (75% flow), and 5.0 L/min (100%), respectively, and a 3-dimensional movie was made of 1 cardiac cycle to evaluate the blood flow. RESULTS: In both 50% and 75% flow simulation with right subclavian artery cannulation, the blood streamline from the right subclavian artery produced retrograde flow of the brachiocephalic artery and antegrade flow of the right common carotid artery throughout the cardiac cycle in all cases. Right subclavian artery flow deflected ascending aorta flow to the descending aorta. Left-side supra-aortic branches were perfused by blood flow from both the right subclavian artery cannula and the aortic valve. The ascending aortic cannulation model showed that blood flow from the aortic valve reached all 3 supra-aortic vessels in systole. CONCLUSIONS: Right subclavian artery cannulation was cerebroprotective, especially on the right side.

Hemodynamic analysis of outflow grafting positions of a ventricular assist device using closed-loop multiscale CFD simulations: Preliminary results.

Subclavian arteries are a possible alternate location for left ventricular assist device (LVAD) outflow grafts due to easier surgical access and application in high risk patients. As vascular blood flow mechanics strongly influence the clinical outcome, insights into the hemodynamics during LVAD support can be used to evaluate different grafting locations. In this study, the feasibility of left and right subclavian artery (SA) grafting was investigated for the HeartWare HVAD with a numerical multiscale model. A 3-D CFD model of the aortic arch was coupled to a lumped parameter model of the cardiovascular system under LVAD support. Grafts in the left and right SA were placed at three different anastomoses angles (90°, 60° and 30°). Additionally, standard grafting of the ascending and descending aorta was modelled. Full support LVAD (5l/min) and partial support LVAD (3l/min) in co-pulsation and counter-pulsation mode were analysed. The grafting positions were investigated regarding coronary and cerebral perfusion. Furthermore, the influence of the anastomosis angle on wall shear stress (WSS) was evaluated. Grafting of left or right subclavian arteries has similar hemodynamic performance in comparison to standard cannula positions. Angularity change of the graft anastomosis from 90° to 30° slightly increases the coronary and cerebral blood flow by 6-9% while significantly reduces the WSS by 35%. Cannulation of the SA is a feasible anastomosis location for the HVAD in the investigated vessel geometry.

Left Subclavian Artery Perfusion During the Norwood Operation for Interrupted Aortic Arch With Aortic Atresia.

The combination of aortic atresia and interrupted aortic arch is a rare condition. We describe a case of Norwood operation for this defect, in which a collateral artery from the descending aorta supplied coronary perfusion. The devised cardiopulmonary bypass technique is discussed, in which the left subclavian artery perfusion was utilized in addition to the cannulation to the descending aorta to secure the cerebral perfusion.

Endovascular repair of thoracic aortic aneurysm associated with right-sided aortic arch: report of two cases.

Right-sided aortic arch (RAA) is a rare congenital disorder. We describe herein two cases of thoracic aortic aneurysm with a right aortic arch and right-sided descending aorta treated with thoracic endovascular aortic repair (TEVAR). In one case, a 70-year-old man with Edwards type 1 RAA underwent TEVAR using a Relay stent-graft (Bolton Medical, Barcelona, Spain). In another case, a 72-year-old woman with Edwards type 3 RAA underwent TEVAR using a Kawasumi Najuta stent-graft (Kawasumi Laboratories, Inc., Tokyo, Japan) with the "buffalo horn chimney technique", our original method for left subclavian artery flow preservation. The postoperative courses were uneventful. Postoperative computed tomography showed complete exclusion of the aneurysm without endoleakage. Compared to conventional open surgical repair, TEVAR is challenging in patients with a RAA and right-sided descending aorta. However, our results showed that TEVAR might be feasible and a treatment option even in a patient with a RAA and right-sided descending aorta.

Investigation of hemodynamics in an in vitro system simulating left ventricular support through the right subclavian artery using 4-dimensional flow magnetic resonance imaging.

OBJECTIVES: Left ventricular assist devices are an important treatment option for patients with heart failure alter the hemodynamics in the heart and great vessels. Because in vivo magnetic resonance studies of patients with ventricular assist devices are not possible, in vitro models represent an important tool to investigate flow alterations caused by these systems. By using an in vitro magnetic resonance-compatible model that mimics physiologic conditions as close as possible, this work investigated the flow characteristics using 4-dimensional flow-sensitive magnetic resonance imaging of a left ventricular assist device with outflow via the right subclavian artery as commonly used in cardiothoracic surgery in the recent past. METHODS: An in vitro model was developed consisting of an aorta with its supra-aortic branches connected to a left ventricular assist device simulating the pulsatile flow of the native failing heart. A second left ventricular assist device supplied the aorta with continuous flow via the right subclavian artery. Four-dimensional flow-sensitive magnetic resonance imaging was performed for different flow rates of the left ventricular assist device simulating the native heart and the left ventricular assist device providing the continuous flow. Flow characteristics were qualitatively and quantitatively evaluated in the entire vessel system. RESULTS: Flow characteristics inside the aorta and its upper branching vessels revealed that the right subclavian artery and the right carotid artery were solely supported by the continuous-flow left ventricular assist device for all flow rates. The flow rates in the brain-supplying arteries are only marginally affected by different operating conditions. The qualitative analysis revealed only minor effects on the flow characteristics, such as weakly pronounced vortex flow caused by the retrograde flow via the brachiocephalic artery. CONCLUSIONS: The results indicate that, despite the massive alterations in natural hemodynamics due to the retrograde flow via the right subclavian and brachiocephalic arteries, there are no drastic consequences on the flow in the brain-feeding arteries and the flow characteristics in the ascending and descending aortas. It may be beneficial to adjust the operating condition of the left ventricular assist device to the residual function of the failing heart.

Biaxial mechanical properties of the human thoracic and abdominal aorta, common carotid, subclavian, renal and common iliac arteries.

The biomechanics of large- and medium-sized arteries influence the pathophysiology of arterial disease and the response to therapeutic interventions. However, a comprehensive comparative analysis of human arterial biaxial mechanical properties has not yet been reported. Planar biaxial extension was used to establish the passive mechanical properties of human thoracic (TA, [Formula: see text]) and abdominal (AA, [Formula: see text]) aorta, common carotid (CCA, [Formula: see text]), subclavian (SA, [Formula: see text]), renal (RA, [Formula: see text]) and common iliac (CIA, [Formula: see text]) arteries from 11 deceased subjects ([Formula: see text] years old). Histological evaluation determined the structure of each specimen. Experimental data were used to determine constitutive parameters for a structurally motivated nonlinear anisotropic constitutive model. All arteries demonstrated appreciable anisotropy and large nonlinear deformations. Most CCA, SA, TA, AA and CIA specimens were stiffer longitudinally, while most RAs were stiffer circumferentially. A switch in anisotropy was occasionally demonstrated for all arteries. The CCA was the most compliant, least anisotropic and least frequently diseased of all arteries, while the CIA and AA were the stiffest and the most diseased. The severity of atherosclerosis correlated with age, but was not affected by laterality. Elastin fibers in the aorta, SA and CCA were uniformly and mostly circumferentially distributed throughout the media, while in the RA and CIA, elastin was primarily axially aligned and concentrated in the external elastic lamina. Constitutive modeling provided good fits to the experimental data for most arteries. Biomechanical and architectural features of major arteries differ depending on location and functional environment. A better understanding of localized arterial mechanical properties may support the development of site-specific treatment modalities for arterial disease.

[Hemodynamic features assessment in submental and facial arteries in patients with early atherosclerotic disease of brachycephalic arteries].

By ultrasonicduplex scanning nature estimated haemodynamics in the arteriessubmentalis and facial of patients with early signs of atherosclerotic changes in the brakhiotsefalarteries and periodontal pathology of different stages - for perfection of prophylaxis of periodontal diseases by the means of investigation of prophylaxis vascular diseases. It was established, that influence of risk factors is more important than the age of patients.

Anatomic and flow dynamic considerations for safe right axillary artery cannulation.

OBJECTIVES: Neuroprotection is of paramount interest in cardiac surgery. Right axillary artery cannulation is well established in aortic surgery because it significantly improves survival and outcome, but malperfusion of the right brain after direct cannulation has been reported. Anatomically, 4 vessel segments are potentially amenable for cannulation of the subclavian and axillary arteries. Clinical studies vary widely in dissection sites and cannulation techniques. We investigated critical flow dynamics in the right brain caused by arterial inflow after direct cannulation and specified cannulation positions that provide optimal cerebral perfusion. METHODS: Distances from the lateral margin of the axillary artery and the subclavian artery to the origin of the vertebral artery were measured in 14 human corpses by a flexible ruler. We calculated the hemodynamics within the vertebral artery, depending on different positions of the cannula tip, in a computer-calculated model. RESULTS: The mean distance from the axillary artery to the vertebral artery was 8.5 cm, and the mean distance from the subclavian artery to the vertebral artery was 6.7 cm. Computed flow calculations demonstrated reversed flow in the vertebral artery when the cannula tip was positioned too close to its orifice. To ensure safe supra-aortic flow, a cannula can be inserted securely up to 6.0 cm into the axillary artery and 4.2 cm into the subclavian artery. CONCLUSIONS: Direct cannulation of the right axillary artery can lead to cerebral malperfusion, caused by an obstruction of the vertebral artery's orifice by the arterial cannula or a subclavian steal phenomenon due to flow reversal. The safety of direct axillary artery cannulation can be improved by a well-considered dissecting site and insertion length of the cannula.

Altered maternal left ventricular contractility and function during normal pregnancy.

OBJECTIVES: To evaluate maternal left ventricular (LV) systolic and diastolic function during normal pregnancy by non-invasive measures of LV contractility incorporating loading conditions. METHODS: Sixty-five women were examined using echocardiography, including tissue Doppler and two-dimensional speckle tracking, and subclavian artery pulse trace recordings at gestational weeks 14-16, 22-24 and 36, and at 6 months postpartum. RESULTS: The mean ± SD age of the women was 32.0 ± 4.6 years. Cardiac output and LV end-diastolic volume were on average 20% and 23% higher, respectively, during pregnancy, compared to that at 6 months postpartum (both, P < 0.01). LV ejection fraction, global peak systolic strain and rate-corrected LV velocity of circumferential fiber shortening (Vcfc) were 11%, 6% and 6% lower, respectively, at 36 weeks' gestation compared to at 6 months postpartum (all, P < 0.01). Afterload, measured as LV end-systolic wall stress (ESWS) increased by 10% between 14-16 and 36 weeks' gestation (P < 0.01). Analysis of the relationship between Vcfc and ESWS revealed that LV contractility was lower during pregnancy than at 6 months postpartum. Changes in diastolic function were demonstrated by 11% lower mitral early diastolic (E) wave velocity, 8% lower tissue Doppler early diastolic velocity (e') and 13% higher left atrial area (all P < 0.01) during pregnancy. Tissue Doppler E/e' remained unaltered (P = 0.78). CONCLUSIONS: During normal pregnancy, LV contractility is lower than it is at 6 months postpartum. This is associated with increased LV and left atrial area, whereas filling pressures are unchanged. These findings suggest that pregnancy exerts a larger load on the cardiovascular system than previously assumed.

Subclavian flap aortoplasty and preservation of left upper extremity circulation using an interposition graft.

OBJECTIVES: To introduce a surgical technique to maintain left upper limb blood flow after subclavian flap aortoplasty (SFA). METHODS: Five patients (9 to 23 months of age) with a diagnosis of long-segment aortic coarctation underwent conventional SFA. A Gore-tex graft was interposed between the stump and the proximal descending aorta to maintain perfusion of subclavian artery. RESULTS: All patients had a patent Gore-tex graft and normal blood flow of the subclavian artery and left upper limb. One patient expired and four others were discharged with a mean follow-up of 48 months. On follow-up all patients had normal development of the left upper limb and no signs of limb ischemia. Echo findings revealed normal arch flow with normal flow in the Gore-tex graft and left upper extremity. CONCLUSIONS: Interposing a Gore-tex graft between the subclavian artery stump and proximal descending aorta concomitant with SFA can be safely performed in infants with long-segment aortic coarctation, with preservation of left upper extremity circulation.

Systemic arterial response and ventriculo-arterial interaction during normal pregnancy.

BACKGROUND: During normal pregnancy (NP), cardiac output (CO) increases, and blood pressure and systemic vascular resistance are reduced. We wanted to evaluate systemic arterial properties and interaction between the left ventricle (LV) and systemic arteries during NP. The role of systemic arteries and their interaction with LV-function in this hemodynamic response, lack description. METHODS: We used noninvasive methods to study 65 healthy women (32 ± 5 years) with NP repeatedly at gestational weeks 14-16, 22-24, 36, and 6 months postpartum (PP). Aortic root pressure and flow were obtained by calibrated right subclavian artery pulse traces and aortic annular Doppler flow recordings. Arterial properties were described by estimates of total arterial compliance (C), proximal aortic stiffness (characteristic impedance (Z(0))), arterial elastance (Ea), and peripheral arterial resistance (R). Ventriculo-arterial coupling (VAC) was characterized by the ratio between arterial (E(a)I) and LV (E(LV)I) elastance index. RESULTS: During NP, CO increased by 20% due to increased heart rate and stroke volume. Mean arterial pressure was reduced by 10% (P < 0.001) as compared to 6 months PP. R was reduced by 5% (P < 0.01), Z(0) trended lower and C higher. E(a)I decreased (P < 0.01) and E(LV)I was reduced to a higher extent resulting in 29% increase of E(a)I/E(LV)I during NP (P < 0.01). CONCLUSIONS: During NP there is an increase in CO, and decrease in blood pressure and R whereas central aortic properties are less altered. The increased VAC index (E(a)I/E(LV)I) during NP indicates a decrease in LV-function not fully compensated for by vascular adaptation.

A bicarotid trunk in association with an aberrant right subclavian artery. Report of two cases, clinical impact, and review of the literature.

A combination of an aberrant right subclavian artery (ARSA) and a bicarotid trunk (BCT) appears in up to 2.5% of the population. The aim of this study is to report the higher total and male incidence of this variation in the literature and to summarise its clinical impact, providing useful knowledge to anatomists, radiologists, cardiologists, and vascular and thoracic surgeons in order to avoid diagnostic pitfalls and therapeutic complications. A total of 72 (43 female and 29 male) Greek Caucasian formalin-embalmed cadavers were studied. The international literature was reviewed along with the dissection archives of the Department of Anatomy from 1986 to 2009. Two male cadavers were found to have an ARSA combined with a BCT (incidence: total 2.78%, males 6.9%, females 0%). Both aortic arches consisted of three branches: (1) the BCT, (2) the left subclavian artery, and (3) the ARSA. The common carotids followed a normal route to the neck; the ARSA passed between the trachea and the oesophagus in the first case and behind the oesophagus in the second case, and was accompanied by a non-recurrent laryngeal nerve. In the second cadaver the ARSA formed a sharp angle (kinking/buckling) on its route to the right arm. The ARSA is associated with several congenital cardiovascular anomalies and some chromosomal and other syndromes. It is occasionaly responsible for causing dysphagia, dyspnoea, or acute ischaemia to the right upper limb, and it may present as a superior mediastinal mass in cases of aneurysm formation.

Correlation between morphometry of the suprascapular notch and anthropometric measurements of the scapula.

The concept of the study was to find the correlation between the morphometry of the suprascapular notch and basic anthropometric measurements of the human scapula. The measurements of the human scapulae included: morphological length and width, maximal width and length projection of scapular spine, length of acromion, and maximal length of the coracoid process. The glenoid cavity was measured in two perpendicular directions to evaluate its width and length. The width-length scapular and glenoid cavity indexes were calculated for every bone. In addition to standard anthropometric measurements two other measurements were defined and evaluated for every suprascapular notch: maximal depth (MD) and superior transverse diameter (STD). The superior transverse suprascapular ligament was completely ossified in 7% of cases. Ten (11.6%) scapulae had a discrete notch. In the studied material, in 21 (24.4%) scapulae the MD was longer than the STD. Two (2.3%) scapulae had equal maximal depth and superior transverse diameter. In 47 (57.7%) scapulae the superior transverse diameter was longer than the maximal depth. There was no statistically significant difference between anthropometric measurements in the group with higher MD and the group with higher STD. The maximal depth of the suprascapular notch negatively correlated with the scapular width-length index. The maximal depth of the scapular notch correlated with the morphological length of the scapulae.

The relationship between aortic baroreceptor activity and arterial pressure is not monotonic.

Previous reports indicate that when aortic pressure (AP) falls below the threshold (P (th)) for baroreceptor sensitivity, activity in the aortic depressor nerve (ADN) may increase. To quantify and explain this anomalous behaviour, we analysed curves describing the relationship of baroreceptor fibre activity in rabbit left ADN to AP. Data were obtained in anaesthetised New Zealand White rabbits. Occlusion and release of cuffs around the inferior vena cava and descending aorta generated AP ramps (25-140 mmHg). Response curves were obtained for 173 fibres in 26 animals. Thirty percent of curves had a nadir (J-shaped curve), and in 40% activity was always present. In fibres showing activity below P (th), firing was predominantly diastolic, switching to systolic firing at P (th). The unusual behaviour of a substantial fraction of aortic baroreceptors below P (th) accounts for the J-shaped response curve of the whole ADN. We suggest that fibres that fire during diastole at pressures below P (th) may have sensory endings close to the origin of the left subclavian artery. As a consequence of this anatomical location, low pressures can impose strain on these receptors, which is then relieved by the systolic pulse.

Perioperative implications of retrograde flow in both the subclavian arteries in an adult undergoing surgical repair of coarctation of aorta.

During surgical repair of coarctation of aorta (CoA), management of spinal cord ischemia and prevention of paraplegia is an important issue. The risk factors for paraplegia include level and duration of aortic-clamping, clamping of left subclavian artery (SCA), intraoperative temperature, variability of collateral circulation to the spinal cord, cerebrospinal fluid pressure, upper body arterial pressure, and aortic pressure beyond the aortic clamp. A short clamp time (<30 min), and distal aortic pressure>60 mmHg, minimizes the risks of spinal cord injury. In an adult patient during surgical repair of CoA, the arterial pressure in the femoral artery remained around 45 mmHg and repair took 83 min of aortic-clamping. Neurological assessment on regaining consciousness showed no deficit of lower limbs. Aortic root angiogram had shown retrograde filling of both SCAs. A unique situation in which clamping of SCAs would increase flow to the spinal cord as their clamping would stop stealing of blood and aortic-clamping proximal to CoA will further increase collateral flow; because of these reasons, the patient tolerated prolonged aortic-clamping despite low distal aortic pressure without neurological deficit. However, aortic-clamping increased left ventricular after-load and the patient developed worsening of mitral regurgitation and pulmonary hypertension during aortic clamping.

Flow analysis of ventricular assist device inflow and outflow cannula positioning using a naturally shaped ventricle and aortic branch.

Tip geometry and placement of rotary blood pump inflow and outflow cannulae influence the dynamics of flow within the ventricle and aortic branch. Cannulation, therefore, directly influences the potential for thrombus formation and end-organ perfusion during ventricular assist device (VAD) support or cardiopulmonary bypass (CPB). The purpose of this study was to investigate the effect of various inflow/outflow cannula tip geometries and positions on ventricular and greater vessel flow patterns to evaluate ventricular washout and impact on cerebral perfusion. Transparent models of a dilated cardiomyopathic ventricle and an aortic branch were reconstructed from magnetic resonance imaging data to allow flow measurements using particle image velocimetry (PIV). The contractile function of the failing ventricle was reproduced pneumatically, and supported with a rotary pump. Flow patterns were visualized around VAD inflow cannulae, with various tip geometries placed in three positions in the ventricle. The outflow cannula was placed in the subclavian artery and at several positions in the aorta. Flow patterns were measured using PIV and used to validate an aortic flow computational fluid dynamic study. The PIV technique indicated that locating the inflow tip in the left ventricular outflow tract improved complete ventricular washout while the tip geometry had a smaller influence. However, side holes in the inflow cannula improved washout in all cases. The PIV results confirmed that the positioning and orientation of the outflow cannula in the aortic branch had a high impact on the flow pattern in the vessels, with a negative blood flow in the right carotid artery observed in some cases. Cannula placement within the ventricle had a high influence on chamber washout. The positioning of the outflow cannula directly influences the flow through the greater vessels, and may be responsible for the occasional reduction in cerebral perfusion seen in clinical CPB.

A mouse model of ischemic spinal cord injury with delayed paralysis caused by aortic cross-clamping.

BACKGROUND: Spinal cord ischemia and paralysis are devastating perioperative complications that can accompany open or endovascular repair surgery for aortic aneurysms. Here, we report on the development of a new mouse model of spinal cord ischemia with delayed paralysis induced by cross-clamping the descending aorta. METHODS: Transient aortic occlusion was produced in mice by cross-clamping the descending aorta through a lateral thoracotomy. To establish an optimal surgical procedure with limited mortality, variable cross-clamp times and core temperatures were tested between experiments. RESULTS: The onset of paresis or paralysis and postsurgical mortality varied as a function of cross-clamp time and core temperature that was maintained during the period of cross-clamp. Using optimal surgical parameters (7.5-min cross-clamp duration at 33°C core temperature), the onset of paralysis is delayed 24-36 h after reperfusion, and more than 95% of mice survive through 9 weeks after surgery. These mice are further stratified into two groups, 70% (n = 19/27) of mice developing severe hind limb paralysis and the remaining mice showing mild, though still permanent, behavioral deficits. CONCLUSION: This new model should prove useful as a preclinical tool for screening neuroprotective therapeutics and for defining the basic biologic mechanisms that cause delayed paralysis and neurodegeneration after transient spinal cord ischemia.