Outflow Vessels Research Articles

Vessel outflow sensitivity to composition

The vessel composition is important when considering vessel outflow because changes in composition change the density and potentially more importantly change the shape and location of the boundary of the two-phase envelope. The influence on the phase boundary can be significant on vessel outflow as the liquid phase density is typically two orders of magnitude larger than the gas phase density for pressures and temperatures remote from the thermodynamic critical point. In this article two issues are addressed, outflow sensitivity to composition of hydrocarbon systems with a large component of methane, and outflow from systems where a petroleum fraction representation of composition is used. It is shown that approximating multi-component systems with a large methane content by methane can result in significant discrepancies in the predicted mass flow rate and vessel pressure. When a vessels composition is characterised by petroleum fractions, and the Kesler–Lee equations are used to predict thermodynamic properties, the predicted outflow is almost comparable to the predicted outflow calculated using a mole fraction representation of composition.

Recommended standards for reports dealing with arteriovenous hemodialysis accesses

The incidence rate of treated end-stage renal disease in the united states is 180 per million and continues to rise at a rate of 7.8% per year. Arteriovenous hemodialysis access (AV access) creation and maintenance are two of the most difficult issues associated with the management of patients on hemodialysis. The 1-year complication rate of a primary prosthetic AV access for hemodialysis ranges from 33% to 99%. Various investigators report on patency and complications of AV access. However, it is rather difficult to compare outcomes because of the wide variety of access materials, configurations, locations, risk factors, and quality of inflow and outflow vessels. Although there have been reporting standards for dialysis access endovascular interventions and for central venous access placement, standards regarding surgical access placement and its revision are lacking. The "Dialysis Outcome Quality Initiative," published by the National Kidney Foundation, provides recommendations for optimal clinical practices aimed at improving dialysis outcome and patient survival. This reporting standards document is not meant to be a "practice guidelines" or "best practices" document. Rather, the purpose of this document is to provide standardized definitions related to AV access procedures and to recommend reporting standards for patency and complications, to be used by surgeons, nephrologists, and interventional radiologists, that will permit meaningful comparisons among AV access procedures. The terms, definitions, and categories featured in this article have been approved by the Committee on Reporting Standards of the Society for Vascular Surgery and the American Association for Vascular Surgery and should be observed in preparing manuscripts on AV accesses for submission to the Journal Of Vascular Surgery.

Hepatectomy by preliminary ligation of the inflow and outflow vessels to the diseased side without dissection of the hepatic hilus

Hepatectomy by preliminary ligation of the inflow and outflow vessels to the diseased side without dissection of the hepatic hilus

The structure and function of the helical heart and its buttress wrapping. II. Interface between unfolded myocardial band and evolution of primitive heart.

The unfolded myocardial band containing a central fold, extending between the pulmonary artery and aorta, has been used to explain the intact or wrapped cardiac structure, composed of a basal and apical loop forming a buttress and helix, connected to the outflow vessels of both ventricles. The interface between this simple structure, and embryologic development of the primitive heart evolving from a singular tube, into a dual pumping chamber with separate left and right sides, must be explained. The objective is to suggest that a simple and integrated triple figure-eight spiral band, with three S-shaped helixes and their apices may correlate the conventional embryologic development of the primitive heart (bulbus cordis, ventricle, and arterial outflow vessels), with the three stages of spatial orientation of the myocardial band (basal and apical loops), which extends between dual ventricular outflow vessels, in the sequence defined by the unwrapped myocardial band.

The endoleak problem in endoluminal therapy

Endovascular treatment of aortic aneurysms with stent grafts was performed increasingly in recent years. The most frequent complication after endovascular therapy of aortic aneurysms is an endoleak. In case of a persistent endoleak, diameter of the aneurysm is increasing with a high risk of aneurysm ruptur. Diagnostic tools are spiral computed tomography and angiography. Spiral computed tomography is the most sensitive method for the diagnosis of an endoleak ad should be performed with a biphasic acquisition. In- and outflow of sidebranches can be identified correctly with selective angiography in 86%. Perigraft endoleaks should be treated in any case. Patent side branches generally are observed over a period of 6 months. After 6 months approximately half of these endoleaks are thrombosed. Is there an increasing of the diameter of the aneurysm or any changing in the morphology of the aneurysm there is an indication for embolisation of these sidebranches of the aneurysmal sac. Preinterventional embolisation of patent sidebranches is under discussion. Type I endoleaks can be managed by additional stent-graft implantation or coil embolisation. In case of type II endoleaks in- ad outflow vessels should be embolised with coils. Therapy of type III endoleak is performed mostly by additional stent-graft placement. The total incidence of secondary interventions in the Eurostar-study was nearly 10% per year.

Hemodynamic evaluation of rectal varices by endoscopic color Doppler ultrasonography

Background: Rectal varices are an infrequent but potentially serious cause of hematochezia. In this paper, the hemodynamics of rectal varices using endoscopic color Doppler ultrasonography (ECDUS) are evaluated.Method: This study consisted of six rectal variceal patients who had F2 type of the rectum, and four of the six had a positive red color sign. We monitored the color flow images of rectal varices.Results: Color flow images of rectal varices were obtained in all six patients. Color flow images of inflow and outflow vessels of rectal varices were obtained in all six patients. We performed endoscopic injection sclerotherapy (EIS) on three of the six patients. After EIS, ECDUS revealed the disappearance of the variceal blood flow in one case, and the decrease of blood flow in two cases.Conclusion: The technique of ECDUS is a useful modality for detecting rectal varices on color flow images and for evaluating the therapeutic effects of EIS.

Patency and limb salvage after infrainguinal bypass with severely compromised ("blind") outflow.

Infrainguinal graft patency and limb salvage are adversely affected by severely compromised outflow. Retrospective review of all infrainguinal bypass procedures performed at a single institution during a 5-year period. University teaching hospital. Two hundred seventy-four patients underwent infrainguinal bypass for limb salvage (351 grafts in 307 limbs). All infrainguinal bypasses originated from a femoral artery. The distal anastomosis in 279 grafts was located in an artery with at least 1 patent outflow vessel with anatomically normal end-artery runoff (Society for Vascular Surgery/International Society for Cardiovascular Surgery ad hoc committee runoff score, 1-9). The distal anastomosis of 72 grafts was located in an artery with only collateral outflow ("blind bypass"; runoff score, 10). Perioperative morbidity and mortality, primary-assisted and secondary graft patency, limb salvage, and survival. All data are presented as mean +/- SEM. Patients undergoing blind bypass were older (age, 70 +/- 2 vs. 66 +/- 1 years; P <.05) and had a higher incidence of hypertension (90% vs 70%; P <.05) and end-stage renal disease (24% vs. 13%; P <.05). Comparing patients undergoing blind bypass to bypass with at least 1 patent outflow vessel, there were no differences in the use of nonautogenous conduits (50% vs 59%; P =.21) or postoperative warfarin (30% vs 32%; P =.69), or in perioperative mortality rates (2.7% vs 3.2%; P =.79). After a median follow-up of 13 months (range, 0-60 months), 2-year secondary graft patency for the entire group was 63% +/- 4%. The secondary patency rate of blind bypass grafts was no different from that of grafts with at least 1 patent outflow vessel (67% +/- 7% vs. 64% +/- 4%; P was not significant). However, the 2-year limb salvage rate in limbs with blind outflow was significantly worse than in limbs with at least 1 patent outflow vessel (67% +/- 7% vs. 76% +/- 3%; P =.04). Acceptable long-term patency rates can be achieved in infrainguinal bypass grafts with blind outflow, although blind outflow remains a marker for subsequent limb loss in the chronically ischemic leg.

Endovascular management of visceral artery aneurysm.

To retrospectively review our experience with visceral artery aneurysms (VAAs) treated with percutaneous coil embolization techniques. Patient records were retrospectively reviewed between 1988 and 1998 for VAA cases treated with catheter-based techniques. Nine patients (5 women; mean age 64 +/- 11 years) with 12 (8 false and 4 true) VAAs were identified. The majority (67%) of these patients presented with symptoms of aneurysm rupture. The etiology of the aneurysm was iatrogenic in 4, pancreatitis in 4, and idiopathic in 4. Ten cases involved the hepatic artery; the other 2 aneurysmal arteries were the middle colic and the gastroduodenal. Selective and superselective catheter techniques were used to obtain access to the VAA. A variety of microcoils were delivered to entirely fill saccular aneurysms, whereas fusiform aneurysms were thrombosed by occluding the inflow and outflow vessels. Aneurysm exclusion was achieved in 9 (75%) of the 12 cases. The 3 technical failures resulted from the inability to cannulate the aneurysm neck. Coil embolization of the neck of the aneurysm sac did not result in occlusion of the native vessel, with a single exception. No procedure-related complications or deaths were noted. All patients remained symptom free during a mean follow-up of 46.0 +/- 29.6 months. Percutaneous transcatheter coil embolotherapy is an effective alternative to open surgery for the management of VAAs. This therapy may decrease the morbidity and mortality associated with an open surgical procedure in patients with ruptured aneurysms and pseudoaneurysms, selectively thrombosing the aneurysm while preserving flow in the native vessel.

Trauma Centers Bleeding Dollars With Balance Sheets in the Red

In Texas, trauma centers lose, on average, $20 million each year. In California, losses total at least $400 million for the state’s major trauma centers, and the California Medical Association is calling for a $300 million infusion of cash into the state’s trauma system just to maintain the services. “Trauma care in Texas is imperiled,” claims Amir Rubin, chief operations officer at Hermann Hospital in Houston. “Texas’ trauma centers are currently delivering the highest levels of critical services to all Texans around the clock, regardless of HMO plan restrictions, regardless of insurance status. These trauma centers however, cannot sustain losses year after year and remain viable.” In Texas, where motorists rack up the highest number of annual motor vehicle accidents (3901 in 1999), trauma centers often mean the difference between life and death for accident victims, who make up the majority of their patients. However, according to a survey of the state’s Level I and II trauma centers by Mr Rubin, most centers are losing large amounts of money. Trauma in the uninsured population accounts for much of the increase during the past decade, according to Mr Rubin’s study. Twenty-one percent of Texans are without health insurance, he reported, with 31% of the population of Harris County (which includes Houston) and 25% of Dallas County uninsured. During the past year, the volume of trauma increased 5.4%, with concurrent increases in operating losses. At the same time, the federal government cut the funding that goes into state Disproportionate Share Payments. These payments were designed to help defray deficiencies between Medicaid payments and the cost of delivering Medicaid and indigent care (for which there is no reimbursement). Payments to private, nonprofit trauma centers declined 23% and those to public, district facilities dropped 11%. “The survey results reveal not only a bleak financial …

Inferior mesenteric artery as outflow vessel in endoleaks after abdominal aortic stent-graft implantation: 36-month follow-up CT study.

The aim of this study was to determine the role of the inferior mesenteric artery (IMA) as an outflow vessel in endoleaks after abdominal aortic stent-graft implantation. Forty consecutive patients in whom abdominal aortic aneurysms (AAA) had been treated with stent-graft implantation were evaluated retrospectively. Spiral-CT examinations and angiographies up to 36 months after implantation were analyzed. In 29 (73%) of the 40 patients the IMA was perfused prior to implantation. In 5 (17%) of these 29 cases, the artery remained perfused after stent-graft insertion. In all 5 cases, endoleaks were detected; however, in none of these cases was the IMA the sole cause. In 3 of these 5 cases, angiography showed antegrade flow in the IMA. Implantation of extension stent grafts caused thrombosis of the aneurysmal sac and the IMA. There were no secondary endoleaks caused by the IMA at the 36-month follow-up examinations. The majority of IMAs which are patent prior to intervention occlude after successful stent-graft insertion. In cases with leaks and angiographically proven antegrade flow in the IMA, implantation of extension stent grafts is a therapeutic alternative to embolization. In this study, the IMA was not responsible for secondary endoleaks.

Subhepatic Inferior Vena Cava Resection with Left Renal Vein Reimplantation to a Large Ascending Lumbar Collateral

A 6-year-old girl, postnephrectomy for a Wilms tumor, demonstrated a recurrence involving the liver and inferior vena cava by ultrasound. Reoperation for removal of the recurrence required further resection and a bypass using an ascending lumbar collateral as an outflow vessel.

Suggested treatment protocol for improving patency of femoral-infrapopliteal cryopreserved saphenous vein allografts

Purpose: Cryopreserved saphenous vein allografts are used for femoral-infrapopliteal bypass graft purposes when adequate autogenous vein is unavailable. Anticoagulation, immunosuppression therapy, or both have been suggested means for improving allograft patency. Immunosuppression has significant cost and morbidity and has produced variable results. Our successful treatment of luminal surface hypercoagulability associated with certain endovascular procedures prompted the use of an anticoagulation protocol prospectively to improve graft patency and limb salvage for patients receiving femoral-infrapopliteal cryopreserved saphenous vein allografts. Methods: Between September 1995 and October 1999, 24 patients (15 men and nine women) were enrolled in a prospective clinical trial for salvage of 26 severely ischemic lower limbs with femoral-infrapopliteal cryopreserved saphenous vein allograft bypass grafts. All patients were treated with a protocol (aspirin, low-dose heparin, low molecular weight dextran 40, dipyridamole, and warfarin), and no immunosuppressive agents were used. The cryopreserved saphenous vein allografts were matched to patients by ABO and Rh compatibility. Indications for revascularization were ischemic rest pain (n = 8), nonhealing ulcer (n = 13), or focal gangrene (n = 5), and no usable autogenous vein was available. Follow-up ranged from 2 to 35 months (mean, 19 months). We studied the location and type of outflow anastomosis, specific outflow vessel, morbidity, death, secondary procedures (digital/transmetatarsal amputation), and complications related to the treatment protocol. Life table analyses of primary graft patency and limb salvage were compared with other current reported data. Results: Primary graft patency with Kaplan-Meier life table analysis was 96% at 6 months, 87% at 12 months, and 82% at 18 and 24 months. There were no reoperations for acute graft occlusion. One graft underwent late segmental aneurysmal degeneration and rupture. There were no procedure-related deaths or bleeding complications. During late follow-up, anticoagulation was discontinued in three patients (12%) because of gastrointestinal bleeding. Limb salvage was 88% at 6 months and 80% at 12, 18, and 24 months. Patients returned to ambulatory status that was limited only by their other comorbidities. Conclusion: Femoral-infrapopliteal bypass graft for limb salvage with a cryopreserved saphenous vein allograft can be an acceptable alternative when autogenous vein is not available. Our treatment protocol substantially improved allograft patency and limb salvage when compared with current published data. (J Vasc Surg 2000;32:731-8.)

Multiple Pancreaticoduodenal Aneurysms: Treatment with Superior Mesenteric Artery Stent-Graft Placement and Distal Embolization

Abbreviations: IAPDA 5 inferior anterior pancreaticoduodenal artery, IPPDA 5 inferior posterior pancreaticoduodenal artery, PDA 5 pancreaticoduodenal artery, SMA 5 superior mesenteric artery DURING the last decade, transluminal placement of endovascular grafts has evolved as an alternative to open surgical repair of aortic (1– 4), peripheral (5–7), and visceral artery aneurysms (8,9), as well as traumatic vascular injuries (10,11). Transcatheter embolization is an established technique in the treatment of visceral artery aneurysms (12,13), including those arising from peripancreatic vessels (14–17). We report a unique case in which multiple pancreaticoduodenal artery (PDA) aneurysms were treated by percutaneous placement of a graftcovered stent in the superior mesenteric artery (SMA) combined with transcatheter embolization of the outflow vessel.

Ventricular motion during the ejection phase: a computational analysis.

In the present paper, the study of the ventricular motion during systole was addressed by means of a computational model of ventricular ejection. In particular, the implications of ventricular motion on blood acceleration and velocity measurements at the valvular plane (VP) were evaluated. An algorithm was developed to assess the force exchange between the ventricle and the surrounding tissue, i.e., the inflow and outflow vessels of the heart. The algorithm, based on the momentum equation for a transitory flowing system, was used in a fluid-structure model of the ventricle that includes the contractile behavior of the fibers and the viscous and inertial forces of the intraventricular fluid. The model calculates the ventricular center of mass motion, the VP motion, and intraventricular pressure gradients. Results indicate that the motion of the ventricle affects the noninvasive estimation of the transvalvular pressure gradient using Doppler ultrasound. The VP motion can lead to an underestimation equal to 12.4 +/- 6.6%.

Angiography of Leaks After Endovascular Repair of Infrarenal Aortic Aneurysms

We examined whether leaks that persist after stent grafting are associated with outflow arteries. Selective angiography was performed in 21 patients with persistent leaks after undergoing endovascular repair of infrarenal aneurysms of the abdominal aorta. Late leaks occurred in five patients whose prostheses were originally sealed. Before angiography, the size and position of leaks were determined with CT and color Doppler sonography. Superselective angiography was successful in 19 of 21 patients. In two patients, angiography was performed over the afferent artery supplying the leak. We found one outflow artery at the site of the leak in 10 patients (47%); two outflow arteries in five (23.8%); and as many as five outflow arteries in three (14%). Angiography overlooked outflow arteries in three patients (14%). The lumbar and inferior mesenteric, urethral, and testicular arteries were identified as outflow arteries. Other than feeder arteries, persistent leaks are associated with outflow vessels that contribute to the patency of leaks.

Embolotherapy of Persistent Endoleaks after Endovascular Repair of Abdominal Aortic Aneurysm with the Ancure-Endovascular Technologies Endograft System

Endoleak is a potential complication after endovascular repair of abdominal aortic aneurysm (AAA). It may result in continued growth of the aneurysm and potentially result in aneurysm rupture. The authors present their experience with embolotherapy in patients with persistent perigraft flow treated with the Ancure-Endovascular Technologies endograft system. Between February 1996 and August 1998, 54 patients underwent successful repair of AAA with use of the Ancure system. All underwent operative angiography and discharge computed tomography (CT). Follow-up included CT at 6, 12, and 24 months, and CT was also performed at 3 months if an endoleak was present on the discharge CT. Persistent endoleak was defined as perigraft flow still present on the 6-month CT. Seven of 21 initial endoleaks persisted at 6 months. Six patients returned for embolization of the perigraft space and outflow vessels including lumbar arteries and the inferior mesenteric artery (IMA). Five of the six patients had leaks from the proximal (n = 1) or distal attachment sites (n = 4) of the Ancure system with outflow into lumbar arteries and/or the IMA; one leak was caused by retrograde IMA flow. The six patients underwent nine embolization procedures with only one minor complication. Follow-up CT showed complete resolution of endoleak and decrease in size of the aneurysm sac in all patients. Although endoleak is commonly seen initially with the Ancure system, persistent leak occurred in 13% of the patients in the study. Persistent flow in most patients arises from a graft attachment site combined with patent outflow vessels such as the IMA or lumbar arteries. Persistent endoleaks can be effectively and safely embolized with use of a combination of coil embolization of the perigraft space and embolization of outflow vessels. Such intervention resulted in a decrease in size of the aneurysm sac.

Effects of temperature and physical activity on blood flow shunts and intracardiac mixing in the toad Bufo marinus.

Blood flow in systemic (.Qsys) and pulmocutaneous (.Qpul) arteries was measured as a function of body temperature (10 degrees, 20 degrees, and 30 degrees C) at rest and following enforced physical activity in conscious, adult cane toads (Bufo marinus). Arterial and mixed venous hemoglobin concentration (CHb) and total oxygen content (Co2, tot) were measured in a separate group under identical conditions. Heart rate (fH) and total flow (.Qtot) increased significantly (P<0.001) with elevated temperature and with activity, whereas stroke volume (VS) increased (P<0.001) only with activity. .Qtot ranged about 10-fold, from 10 degrees C (rest) to 30 degrees C (activity); increases in both fH and VS contributed to the increase in .Qtot. The overall distribution of blood to the pulmocutaneous circuit (net L-R shunt) increased with both temperature and activity and was significantly correlated with .Qtot. These data indicate that blood flow distribution in toads is a direct function of cardiac output, and this is linked to relative changes in resistance in the major outflow vessels. Arterial O2 saturation (Sa) was high (mean=93%) in all conditions except activity at 30 degrees C, when it decreased to 74% and contributed to a decrease in the arteriovenous O2 difference. Venous O2 saturation (Sv) was high at rest (76%) and dropped significantly during activity to about 30% at all temperatures. Intracardiac arterial-venous mixing (systemic mixing index) showed the strongest correlation with variation in fH with minimal mixing (17%) occurring at about 50 beats min-1. The most mixing occurred at the lowest fH (13 beats min-1) and at the highest fH (103 beats min-1). The results indicate that the heart of a 0.25-kg toad becomes more efficient from an oxygen transport perspective from low fH to 50 beats min-1 and then less efficient at higher fH, contributing to an uncoupling of blood flow and metabolic rates at these high rates.

MR angiography of run-off vessels.

Magnetic resonance angiography has taken a huge step forward since the introduction of contrast-enhanced MR angiography using gadolinium chelates. The more conventional MR angiographic techniques, such as time-of-flight and phase-contrast MR angiography, have been ousted by contrast-enhanced MR angiography in most vascular areas. However, in imaging the lower extremities, the major obstacle is the length of the vascular tree. In order to cover the entire peripheral vasculature, at least two to three fields of view are required. Using contrast-enhanced MR angiography, the best results are obtained if the vessels of interest are imaged during passage of a bolus of contrast material. Vessel-to-background contrast in subsequent acquisitions using subsequent injections of contrast material is hampered by recirculation and leakage of previously injected gadolinium, enhancing both the venous system and surrounding tissue. To overcome this problem several research groups have come up with various solutions. The three main strategies employed can be classified as either bolus catch, bolus chase, or bolus track techniques. The purpose of this article is to explain working mechanisms of the three bolus imaging strategies for imaging both inflow and outflow vessels of the lower extremities, to show their advantages and disadvantages, and to review results described in the literature in imaging patients using these techniques.

Venous sac embolization of pulmonary arteriovenous malformation: preliminary experience using interlocking detachable coils.

To evaluate the indication and advantages of venous sac embolization of pulmonary arteriovenous malformations (PAVMs) using interlocking detachable coils (IDCs). We performed percutaneous embolization in 12 PAVMs in four patients using IDCs, initially placed in the venous sac or at the feeding artery to prevent systemic migration of additional coils. We placed the IDCs in the venous sac in PAVMs with the following vascular architecture: the draining vein was larger than the feeding arteries and both vessels were interposed with the venous sac or there were short feeding arteries. Complete occlusion was achieved in all 12 PAVMs without significant complications. We deployed IDCs in the venous sac in eight PAVMs and in the feeding artery in four. Venous sac embolization may be beneficial in PAVMs with large out-flow vessels or short feeding arteries. IDCs are suitable for this procedure.

Connexin 43 Expression Reflects Neural Crest Patterns during Cardiovascular Development

We used transgenic mice in which the promoter sequence for connexin 43 linked to a lacZ reporter was expressed in neural crest but not myocardial cells to document the pattern of cardiac neural crest cells in the caudal pharyngeal arches and cardiac outflow tract. Expression of lacZ was strikingly similar to that of cardiac neural crest cells in quail–chick chimeras. By using this transgenic mouse line to compare cardiac neural crest involvement in cardiac outflow septation and aortic arch artery development in mouse and chick, we were able to note differences and similarities in their cardiovascular development. Similar to neural crest cells in the chick, lacZ-positive cells formed a sheath around the persisting aortic arch arteries, comprised the aorticopulmonary septation complex, were located at the site of final fusion of the conal cushions, and populated the cardiac ganglia. In quail–chick chimeras generated for this study, neural crest cells entered the outflow tract by two pathways, submyocardially and subendocardially. In the mouse only the subendocardial population of lacZ-positive cells could be seen as the cells entered the outflow tract. In addition lacZ-positive cells completely surrounded the aortic sac prior to septation, while in the chick, neural crest cells were scattered around the aortic sac with the bulk of cells distributed in the bridging portion of the aorticopulmonary septation complex. In the chick, submyocardial populations of neural crest cells assembled on opposite sides of the aortic sac and entered the conotruncal ridges. Even though the aortic sac in the mouse was initially surrounded by lacZ-positive cells, the two outflow vessels that resulted from its septation showed differential lacZ expression. The ascending aorta was invested by lacZ-positive cells while the pulmonary trunk was devoid of lacZ staining. In the chick, both of these vessels were invested by neural crest cells, but the cells arrived secondarily by displacement from the aortic arch arteries during vessel elongation. This may indicate a difference in derivation of the pulmonary trunk in the mouse or a difference in distribution of cardiac neural crest cells. An independent mouse neural crest marker is needed to confirm whether the differences are indeed due to species differences in cardiovascular and/or neural crest development. Nevertheless, with the differences noted, we believe that this mouse model faithfully represents the location of cardiac neural crest cells. The similarities in location of lacZ-expressing cells in the mouse to that of cardiac neural crest cells in the chick suggest that this mouse is a good model for studying mammalian cardiac neural crest and that the mammalian cardiac neural crest performs functions similar to those shown for chick.