Repair of an autotransplant renal artery aneurysm: case report and literature review

We report the successful repair of a renal artery aneurysm involving the autotransplanted kidney of a 25-year-old hypertensive woman. The risk factors for renal artery aneurysm rupture, and the relationships between hypertension and renal artery aneurysms are presented.

Femoral and popliteal arteries: reanalysis of results of balloon angioplasty

The author presents an alternative statistical analysis of the results of the University of Toronto series of percutaneous transluminal angioplasty (PTA) of the femoral and popliteal arteries (n = 254). After recalculation of the data with the Kaplan-Meier method, the postprocedure success rate ranged from 88.8% +/- 2.0 at 1 month to 35.7% +/- 4.8 at 6 years. With Cox multiple regression analysis, the type of femoropopliteal lesion and the runoff were the variables that were useful to predict late results. For stenoses with good runoff, the success rate was 53% at 5 years; with poor runoff, 31% at 5 years. For occlusions with good runoff, the success rate was 36% at 5 years; with poor runoff, 16% at 5 years. In initially successful cases, ongoing clinical success at 1, 3, and 5 years was better in patients with good runoff at the time of PTA than in those with poor runoff. Now that more recent studies have documented improved technical success in femoropopliteal PTA, a comparative study of the relative safety, long-term clinical efficacy, and cumulative cost of PTA versus surgery seems warranted.

Computer simulation of blood flow patterns in arteries of various geometries

The purpose of this study is to illustrate the application of computer simulation to the study of blood flow through arteries and to demonstrate the relationship between geometry of the vessels and local flow patterns. A finite element computer program was developed to simulate steady and pulsatile blood flow by solving the continuity and Navier-Stokes equations. The accuracy of the computational method has been confirmed by comparing the numeric results to analytic solutions and to published experimental data from physical models. The results are presented as plots of the velocity vectors, streamlines, and pressure contours. The computational model has been applied to illustrate flow patterns in the following situations: pulsatile flow in a cylindric artery and an artery with an axisymmetric stenosis, steady flow in cylindric arteries with stenoses of varying severity and with different flow rates, steady flow in an artery containing a fusiform aneurysm, steady flow in a two-dimensional model of a symmetric Y-shaped bifurcation, and steady flow in a two-dimensional model of the carotid bifurcation. Regions that are commonly associated with arterial disease often coincide with zones of reversed or stagnant flow. In conclusion, the versatility and feasibility of computational simulation of blood flow is illustrated by this study. Although this mathematic model is a simplification of the real flow phenomena, it yields results that provide useful insights into the understanding of local blood flow patterns for a variety of complex geometries.

Cerebral blood flow velocities by transcranial Doppler during parabolic flight

Microgravity is produced for 20 to 30 seconds in NASA's KC-135 aircraft at the end of a 2 G pullup for each of 40 parabolas per flight. Continuous transcranial Doppler ultrasound, arterial blood pressure, and acceleration levels were recorded for 12 male and 8 female healthy subjects without known cardiovascular or cerebrovascular disease. Recordings were made throughout 10 parabolas per subject in each of the supine, sitting, and standing postures. The data were digitized for off-line analysis using Fast Fourier Transform and other signal processing methods. A phase lag in changes to transcranial Doppler waveforms from the onset of acceleration was more pronounced in the standing position than in the sitting position. There was less of a phase lag in the supine position. These ultrasound changes preceded the more delayed variations in arterial blood pressure. The KC-135 provides a unique short-term environment that allows measurement of the human response to variations in acceleration but limits physiological monitoring of responses to a steady state of microgravity.

Descending thoracic aortofemoral bypass as an alternative for aortoiliac revascularization

We performed descending thoracic aorta to femoral bypass in six selected patients over the past four years. An alternative inflow source was selected because the standard transabdominal approach was contraindicated or considered hazardous. The inflow consisted of a single Dacron tube from the descending thoracic aorta to the left groin, and a femorofemoral bypass to the right groin. There was no operative mortality or major morbidity related to the surgical procedure. After an average follow-up of 17.1 months (range 6 to 23 months), all thoracofemoral grafts remained patent. One patient had repeated occlusions of the femorofemoral graft related to right lower extremity outflow disease, while the remaining five crossover grafts are patent. One patient died 22 months postoperatively from a myocardial infarct, with a patent bypass. Although this series represents a small group of patients, we feel that descending thoracic aortofemoral bypass offers excellent inflow and reliable patency, and is a good alternative when reoperation on the abdominal aorta is undesirable. This procedure may also be considered for conversion of an axillofemoral bypass that has failed repeatedly.

Suggested standards for reporting on arterial aneurysms. Subcommittee on Reporting Standards for Arterial Aneurysms, Ad Hoc Committee on Reporting Standards, Society for Vascular Surgery and North American Chapter, International Society for Cardiovascular Surgery

The literature on arterial aneurysms is subject to potential misinterpretation because of inconsistencies in reporting standards. The joint councils of the Society for Vascular Surgery and the North American Chapter of the International Society for Cardiovascular Surgery appointed an ad hoc committee to address this issue. This communication, prepared in response to the need for standardized reporting, defines and classifies arterial aneurysms and recommends standards for describing the causes, manifestations, treatment, and outcome criteria that are important when publishing data on aneurysmal disease.

Steady and pulsatile flow fields in an end-to-side arterial anastomosis model

We investigated the flow field within a rigid-walled in vitro model of an end-to-side 45 degree anastomosis in an attempt to identify possible hemodynamic factors that may contribute to the pathogenesis of distal anastomotic intimal hyperplasia. A high-resolution photochromic tracer technique was used to visualize the flow in orthogonal planes and to determine the axial wall shear stress profiles for both steady and pulsatile flows over a range of physiologically relevant conditions. The flow field showed qualitative similarities to those seen in curved vessel: rapidly moving fluid from the graft section affects the bed of the host vessel, that is, the wall opposite the anastomosis, eventually advancing down the host vessel in a spiraling motion. A small mobile separation zone was noted at the toe of the anastomosis. Comparison of wall shear stress profiles with previously reported preferential sites for the development of intimal hyperplasia supported a low wall shear stress and/or flow separation pathogenesis hypothesis. One notable exception was the bed of the host artery that appeared to be subjected to a complex hemodynamic environment.

Detailed visualization of pulsatile flow fields produced by modelled arterial stenoses

A multiple trace photochromic method was used to visualize the pulsatile flow field created by modelled arterial stenoses of 38% and 65% area reductions. Using flow parameters similar to those of a medium sized artery in man, the flow patterns at seven axial locations in relation to the stenosis were simultaneously photographed at various times throughout the flow cycle. With the 65% stenosis, the wall shear stress in the vicinity of the reattachment point was found to fluctuate quite strongly during the turbulent phase of the flow cycle, giving rise to instantaneous shear stresses that were at least eight times larger than those measured upstream. For the 38% stenosis, much smaller shear stresses were observed. These and other results are described in detail.

Intraabdominal hemorrhage as a result of segmental mediolytic arteritis of an omental artery: case report

This article describes the fifth reported case of segmental mediolytic arteritis and the second in a survivor. The patient had intraabdominal bleeding as a result of a ruptured omental artery. The pathologic and arteriographic findings are described. The pathology is characterized by segmental disruption of the medial smooth muscle cells and the initiation of mediolysis. Mediolysis is associated with marked segmental thinning of the vessel wall, often with only the adventitia intact. Fibrin is deposited at the adventitial and medial surfaces, and hemorrhage into the media may occur. As in this reported case, lysis of the adventitia leads to sudden, often catastrophic intraabdominal hemorrhage. Little associated adventitial inflammation occurred. Segmental mediolytic arteritis seems to involve the intra-abdominal muscular arteries in elderly patients with nonspecific abdominal symptoms. An angiogram showed patchy areas of narrowing involving ileal, gastroduodenal, and renal arteries that correlated with the pathologic findings observed in the excised omental arteries.

Development of methods to analyse transcranial Doppler ultrasound signals recorded in microgravity

During space flights, several clinical syndromes may be the result of changes in cerebral circulation. The purpose of the paper is to describe the development and initial evaluation of a system for recording, processing and displaying transcranial Doppler ultrasound (TCD) waveforms from the middle cerebral artery (MCA) in microgravity. Volunteers were repeatedly subjected to 15-20 s intervals of microgravity ('near zero gravity') during flights on the KC-135 military aircraft. Continuous TCD recordings from the MCA were stored on magnetic tape. The paper describes the system that was developed to digitise the Doppler ultrasound data and markers that corresponded to the various levels of microgravity, obtain the maximum and mean Doppler waveforms, identify the waveforms and quantify them. The results demonstrate the feasibility of making TCD recordings in a microgravity environment and illustrate excellent performance of the system and its ease of operation. Quantitative waveform analysis of the recordings from the first subject studied in the supine position showed statistically significant changes in MCA velocity waveforms during microgravity.

Physiological changes in the somatosensory forepaw cerebral cortex of adult raccoons following lesions of a single cortical digit representation

The purpose of this study was to determine whether restricted lesions within primary somatosensory (SmI) cortex cause changes in the functional organization of cortical areas bordering on the site of injury. Focal ablations of cortical tissue were made in the representational area for digit 3 within the SmI forepaw cortex of adult raccoons. Electrophysiological mapping experiments done 15-17 weeks later showed that significant alterations had occurred in the response properties of clusters of neurons within those representational zones adjoining the lesion--the zones for digit 2, digit 4, and the palmar pads. These three cortical areas were modified by the appearance of new, usually weaker secondary inputs and changes in some properties of the normal primary inputs from the forepaw. (i) Many neurons responded to stimulation of previously ineffective skin regions; the new inputs often originated from digit 3 but frequently involved other digits or the pads as well. (ii) Neuronal receptive fields (RFs), mapped at a standard suprathreshold stimulus intensity, were larger than normal. (iii) Skin type and submodality sensitivity typically were less specific than normal; more neurons had RFs that included both glabrous and hairy skin or claws and displayed mixtures of responsiveness to skin touch, hair deflection, or claw touch. (iv) The representation of RF location, skin type, and submodality sensitivity was more variable as a function of horizontal and vertical distance through the cortex. In general, the physiological changes were found to degrade the somatotopic order and response specificity of the intact cortical areas adjoining the lesion.(ABSTRACT TRUNCATED AT 250 WORDS)

Transcranial Doppler studies of flow velocity in middle cerebral artery in weightlessness

Physiological adaptation to weightlessness requires changes in cardiovascular system parameters to maintain homeostasis in the presence of cephalic fluid shifts. The cerebral circulation must respond immediately to these systemic changes or impairment of cerebral function will occur. Blood flow velocities of the middle cerebral artery were measured by transcranial Doppler (TCD) ultrasound in NASA's KC-135 aircraft from four healthy subjects in the supine position. Transcranial Doppler data with accompanying acceleration information were analyzed in three segments in each parabola. Cardiac cycles for each segment of all 20 parabolas were pooled for individual subjects. A Student's t test on the data revealed statistically significant differences in the mean and peak frequencies, systolic/diastolic ratios and Doppler power between positive 2 gz and microgravity (10(-2) gz) as well as between positive 2 gz and negative 2 gz. Velocity waveform profiles differed for the first one third of each segment, with a more resistive waveform developing during the last two thirds. Changes in systemic arterial resistance and/or raised intracranial pressure may contribute to these TCD waveform changes.

The current role of isolated profundaplasty

The opinions regarding isolated profundaplasty as documented in the literature are divergent, and it is for this reason that we reviewed our results over a 10-year period in order to define the current role for this procedure. The cumulative clinical success rate (both in patient repair and clinical improvement) was 83 +/- 4% at thirty days, 67 +/- 4.8% at one year, 57 +/- 5.9% at two years and 49 +/- 6.8% at three years. The results are best in patients with good tibial outflow (2 or 3 patent vessels), and an early postoperative improvement of ABI greater than 0.10 is predictive of long-term success. Isolated profundaplasty is a good alternative for lower limb revascularization and does not preclude the possibility for distal reconstruction.

Evidence of a possible link between poststenotic dilation and wall shear stress

The effects of an axisymmetric 65% area reduction stenosis on a pulsatile flow were investigated by use of an in vitro model that permits simultaneous visualization of the flow velocity profiles at seven sites. By use of seven lenses to focus the ultraviolet light from a nitrogen laser, seven thin blue lines were produced in the photochromic solution flowing through the tube. The displacement profiles of the dye traces were photographed, resulting in the acquisition of the velocity profiles. From these traces, the flow pattern was determined, and the wall shear stresses were measured. Turbulence was generated 3.3 to 6.5 tube diameters downstream from the edge of the stenosis, depending on the time in the pulsatile flow cycle. Maximum wall shear stress fluctuations between positive and negative values appeared to lie within 1.6 to 3.3 tube diameters downstream of the stenosis. In several illustrative clinical cases of thoracic outlet arterial compression, the poststenotic dilation was maximum at 2.0 +/- 0.3 vessel diameters downstream. Based on these observations, it is postulated that wall shear stress fluctuations may be important in the development of poststenotic dilation.

A new method for Doppler frequency analysis that promises a major improvement in performance

The Doppler grey scale waveform obtained by frequency analysis is related to the blood flow velocity in the vessel under examination. Consequently, detailed evaluation of the Doppler spectral waveform or the instantaneous Doppler spectrum is clinically useful for assessing arterial disease. The purpose of this paper is to demonstrate the potential advantages of a new frequency analysis method (autoregressive moving average) for processing and displaying continuous wave and pulsed Doppler signals by comparing the quality of the Doppler spectral waveforms produced by this new method to those obtained by standard Fast Fourier transform analysis. Continuous wave pulsed Doppler recordings were stored on a computer and reprocessed by Fast Fourier transform and autoregressive moving average methods. Varying degrees of noise were added to both types of Doppler recordings in order to simulate the problems encountered in the clinical vascular laboratory. By comparing the two methods using standard Doppler spectral waveforms and 3-dimensional spectral plots, under adverse conditions of significant noise, the autoregressive moving average technique proved to be superior to the classical Fast Fourier approach. It is concluded that the autoregressive method of frequency analysis offers the potential for achieving significant improvements in the display of the Doppler spectral waveform when compared to the classical Fast Fourier approach. Such improvements may improve the accuracy in arterial disease assessment.

Potential limitations of center-line pulsed Doppler recordings: an in vitro flow visualization study

In this study an in vitro model that permits visualization of the flow velocity profile has been used to determine if duplex pulsed Doppler recordings made with a small sample volume in the center line of the vessel can determine the severity of a stenosis in the 38% to 75% range of cross-sectional area reduction. Because most Doppler instruments measure the maximum peak frequency and the extent of spectral broadening, observations in the flow model included changes in the center-line maximum velocity and the location and intensity of flow disturbances. The results showed that center-line measurements of maximum velocity (equivalent to peak Doppler frequency) were directly related to the severity of the stenosis as long as the recordings were made from within the throat to about 1.5 to 3 tube diameters downstream, depending on the shape of the stenosis. However, flow disturbances (equivalent to spectral broadening) did not always occur in the center line of the vessel. Stenoses greater than 50% area reduction produced turbulence across the entire vessel in the region 4.5 to 7.5 diameters downstream. The turbulent period started just before peak systole and extended to just less than half the pulse cycle. In the more proximal zone a forward flow jet was present in the central part of the vessel, and reverse flow was present in the outer region. The interfacial layer between these two regions is subjected to high shear rates that resulted in the formation of waves and vortices.(ABSTRACT TRUNCATED AT 250 WORDS)

Multicenter prospective study of nonruptured abdominal aortic aneurysm. Part II. Variables predicting morbidity and mortality

A previous article (Part I) described the patient population and operative management of 666 patients who had surgery for nonruptured abdominal aortic aneurysms. This article details the perioperative complications and, by chi-square and logistic regression analysis, identifies the variables that are associated with each complication. In summarizing the results (below) the incidence of each complication is listed, along with the predictive risk factors in parentheses that have significance levels less than 0.05. Vascular morbidity data are as follows: intraoperative bleeding, 4.8%; postoperative bleeding requiring transfusion, 2.3% or repeat operation, 1.4% (large volume of blood transfusion and/or use of an autotransfusion device); intraoperative limb ischemia, 3.5%; graft thrombosis, 0.9% (femoropopliteal disease and/or distal anastomosis at the femoral level); distal thromboembolism, 3.3% (male sex, femoral popliteal disease, and/or intraoperative graft thrombosis); amputation, 1.2%; graft infection, 1 case. General morbidity data are as follows: cerebrovascular event, 0.6%; paraplegia, 1 case; cardiac event, 15.1% (age, previous episode of congestive heart failure, and/or electrocardiogram [ECG] evidence of a previous myocardial infarction); myocardial infarction, 5.2% (advancing age, angina, and/or prolonged aortic cross-clamp time); congestive heart failure, 8.9% (previous history of congestive heart failure, ECG evidence of ischemia, and/or chronic obstructive lung disease); arrhythmia requiring treatment, 10.5% (preoperative ventricular premature beats and/or respiratory failure requiring ventilation for more than 48 hours); new arrhythmia, 8.4% (angina and/or chronic obstructive lung disease); respiratory failure, 8.4% (chronic obstructive lung disease, large volume of blood transfused, and/or occurrence of postoperative bleeding, cerebrovascular accident, congestive heart failure, or myocardial infarction); renal damage with rise in creatinine or blood urea nitrogen, 5.4% and/or renal failure requiring dialysis, 0.6% (elevated preoperative creatinine, suprarenal aortic cross-clamping, and/or renal vein ligation); diarrhea without evidence of ischemia colitis, 7.1% and ischemic colitis, 0.6% (pelvic flow interrupted); prolonged ileus, 11.0% (aortoiliac occlusive disease, deterioration of renal function, prolonged ventilation, and/or preoperative history of angina); superficial wound infection, 1.5% and deep infection, 0.5% (femoral anastomosis and/or female sex); coagulopathy, 1.1% (large volume of blood transfused).(ABSTRACT TRUNCATED AT 400 WORDS)

Percutaneous transluminal angioplasty of abdominal aortic stenoses

Percutaneous transluminal angioplasty (PTA) was performed on 25 patients with localized distal abdominal aortic stenoses. All patients were smokers and all complained of bilateral lower limb claudication. Eleven patients had small distal aortas and iliac vessels. Technically successful dilatation was achieved in all patients. Long-term follow-up was available on 17 of the patients. The mean follow-up period was 38 months. Cumulative patency at 5 years was 70%. Thirteen patients remain asymptomatic 15-83 months following PTA. Late failure occurred in 4 patients, 1-38 months following PTA. No complications related to PTA were experienced. PTA of localized aortic stenoses is a safe alternative to surgery and should be the treatment of choice in this condition.

Intracortical connections of two functional subdivisions of the somatosensory forepaw cerebral cortex of the raccoon

The aim of this study was to compare the intrinsic intracortical connectivities of 2 functionally distinct subdivisions of the somatosensory (Sml) forepaw cortex of the raccoon--the somatotopic glabrous skin representation and the more heterogeneous, hairy skin and claw representation of the digits. HRP was injected into one or the other functional subdivision of a particular digit subgyrus of Sml cortex in 10 adult raccoons. The distribution of HRP-labeled neurons and axon terminals in the cortex showed that intrinsic "horizontal" connections exist within and between individual cortical digit zones; the labeling tended to have an oval-shaped configuration that was longer in the mediolateral than in the anteroposterior curvilinear plane. The 2 cortical sectors were found to have different patterns of intracortical projections. The connections of the glabrous skin region of each cortical digit zone were primarily local and confined to that same digit representation. HRP-filled neurons were concentrated near the injection site and decreased in density within the banks and fundi demarcating the injected digit subgyrus; few labeled cells were found in adjoining digit zones. Longer projections to the glabrous subdivision of a particular digit area typically originated from neurons in the heterogeneous subdivision of that same digit area. In contrast, the connections of the heterogeneous region of each digit zone were much more extensive and usually included projections from nonadjacent, as well as neighboring digit zones. The density of HRP-positive neurons declined more gradually with distance from the injection site, and considerable labeling was present in the heterogeneous sectors of adjacent digit zones. The intracortical projections of both functional subdivisions were often, but not always, reciprocal, and the cells of origin tended to be distributed in clusters. The laminar distributions of labeled neurons were similar for both sectors; HRP-filled cells were concentrated more in the supragranular layers, especially in layer III; fewer were found in the infragranular layers, mainly in layer VI and rarely in layer V. These results show that the intrinsic connections of the glabrous cortical subdivisions are fairly localized, whereas those of the heterogeneous cortical subdivisions are more diffuse and highly convergent. The differing intracortical connectional patterns of the 2 sectors are consistent with their contrasting thalamocortical projection patterns and may contribute to the unique functional properties of neurons located within each sector.(ABSTRACT TRUNCATED AT 400 WORDS)

Thalamic connections of two functional subdivisions of the somatosensory forepaw cerebral cortex of the raccoon

The purpose of this study was to compare the thalamic interconnectivities of 2 functionally distinct subdivisions of the somatosensory (Sml) forepaw cortex of the raccoon--the somatotopic subdivision representing the glabrous skin of the digits and the more heterogeneous subdivision representing the hairy skin and claws. Injections of HRP were made into one or the other functional subdivision of a specific digit subgyrus of Sml cortex in 10 adult raccoons. The distribution of HRP-labeled neurons and axon terminals in the thalamus revealed that the 2 sectors have different patterns of thalamic projections. The glabrous skin region of each cortical digit zone was interconnected with a specific crescent-shaped lamella of neurons that extended rostrocaudally through the ventral posterior lateral (VPL) nucleus and typically was separated from adjacent lamellae by small bundles of myelinated fibers. The VPL lamellae constituted relatively distinct digit subnuclei that were connected somatotopically with the glabrous subdivisions of the corresponding cortical digit areas. The projections were dense, topographic, and reciprocal; labeled neurons and axon terminals within a particular lamella overlapped considerably and tended to be arranged in clusters. In contrast, the heterogeneous region of each cortical digit zone was reciprocally connected with the somatotopically appropriate VPL digit subnucleus and with adjoining subnuclei as well. The projections were comparatively sparse, less topographic, and more widely distributed than those of the glabrous skin sectors; groups of HRP-positive neurons and terminals in VPL tended to straddle the borders of the appropriate lamella and extended into adjacent lamellae. Furthermore, small clusters of labeling were found in the dorsal, presumed kinesthetic region of VPL and in portions of the ventral posterior inferior nucleus and the posterior nucleus. These results indicate that the glabrous cortical subdivisions have precise, somatotopically organized connections with specific VPL subnuclei, whereas the heterogeneous cortical subdivisions have more diffuse and scattered connections with several subregions of VPL and other thalamic nuclei as well. These 2 thalamocortical projection patterns may account for many of the differing functional properties of neurons residing within the 2 cortical sectors. Finally, the convergent thalamic projections to the heterogeneous cortical regions could contribute, at least indirectly, to the functional reactivation that occurs within Sml cortex of the raccoon following peripheral nerve transection (Kelahan and Doetsch, 1984).

An atherosclerosis risk factor assessment program for patients with peripheral arterial occlusive disease

From a group of 251 high-risk patients less than 65 years of age, 84 with angiographic or vascular laboratory proven peripheral arterial occlusive disease were evaluated in detail. The following risk factors were identified: smoking in 91% with an average of 35 +/- 18 pack/years; treated or untreated hypertension in 40%; hyperlipidemia in 49%; obesity with a body weight greater than 120% of ideal in 18%; diabetes in 9%; family history of premature vascular disease in 70%; and hyperuricemia in 13%. Based on these results, we have introduced a practical approach for investigating and managing risk factors that can be administered by paramedical personnel, utilizing a questionnaire given to patients and standard blood tests to identify important risk factors. The results of the completed questionnaires and blood test are entered on a microcomputer. A program written using d-Base III stores the data, identifies the risk factors and grades their severity. We have designed an information booklet that highlights the individual patient's risk factors and suggests alternatives for management based on the sources of medical and community help available in our area.

Expanded PTFE prostheses as arterial substitutes in humans: late pathological findings in 73 excised grafts

Through collaboration of surgeons, pathologists and bioengineers at five centers in Canada and France, this study analyzed the late pathology and structural changes in 73 expanded PTFE arterial prostheses harvested from patients at autopsies and reoperations. The degree of tissue encapsulation increased with the duration of implantation but was reduced by the presence of infection. In several cases, the fibrous tissue penetrated the wall of the prosthesis and partitioned off the thin outer layer, thus disrupting the delicate microporous structure of the wall. The presence of aneurysms was observed in models that had no external reinforcing layer and among grafts that apparently suffered from surgical trauma. Wrinkling of grafts was noted at areas of flexion and was often associated with thickening of the external capsule and reduced luminal diameters. Endothelialization was found within only a few millimeters of the anastomoses. The luminal surfaces were generally not well healed. The PTFE structure was usually readily visible under a thin covering of loosely adhering thrombotic deposits. Bacteria were observed in 46% of the cases, even though only 29% were considered clinically infected. The incidence of lipid or cholesterol deposits was high. Avoiding iatrogenic trauma to the external wall of the prosthesis during implantation is important. Those features where design improvements are required to provide longer term structural integrity and dimensional stability in future models of expanded PTFE prostheses should be identified.

Multicenter prospective study of nonruptured abdominal aortic aneurysms. I. Population and operative management

This article describes the patient population and operative management of 666 patients with nonruptured aneurysms of the abdominal aorta. Statistical significance of variables was determined by the chi-square test and logistic regression analysis. There were no statistically significant differences (p greater than 0.05) in mortality rate for abdominal aortic aneurysm (AAA) on the basis of indication for surgery (asymptomatic, 3.9%; asymptomatic but with evidence of enlargement, 4.9%; and symptomatic, 7.2%) or the urgency of operation (elective operation, 4.5%; and urgent operation, 7.1%). Characteristics of the 72 participating surgeons did not influence the operative mortality rate. A family history of AAA was documented in 6.1% of cases and was more common if the patient was female (p = 0.03) and less than 65 years of age (p = 0.04). Patients without clinical evidence of coronary artery disease had a 0.8% mortality rate from cardiac disease compared with 6.2% if any stigmata of coronary disease were present. Prior aortocoronary bypass surgery did not reduce the incidence of postoperative cardiac events or operative mortality rate. Patients having "routine" angiography did not have a less complicated operative course, fewer thrombotic complications, or lower mortality rate than those not having it. Those patients with an inflammatory AAA (4.5%) did not have a significantly higher incidence of pain. Heparin administration (84.8%) did not reduce the complications of graft thrombosis, "trash," distal thrombosis, and/or amputation. The 6.8% of patients requiring suprarenal aortic cross-clamping had a higher incidence of postoperative renal dysfunction (p = 0.02) and intraoperative blood loss (p less than 0.001), but cardiac events were not more frequent. When the aortic cross-clamping time was prolonged (more than 70 minutes), the requirement for crystalloid fluid administration increased (p less than 0.001) and postoperative myocardial infarction was more common (p = 0.004). After ligation of the left renal vein in 7.9%, renal damage or dialysis was more frequent (p = 0.01). Patients having an intra-abdominal graft (tube, 38.5% and biiliac, 30.7%) had fewer wound infections (p = 0.02) and graft thromboses (p less than 0.001) than the patients with a femoral anastomosis. When the internal iliac artery flow was interrupted bilaterally (12%), diarrhea (p = 0.03) and ischemic colitis (p = 0.03) were more frequent complications. Reimplantation of the inferior mesenteric artery was carried out in 4.8%. After renal artery bypass in 2.1%, the mortality rate was not increased, but the incidence of transient renal dysfunction was increased (p = 0.03).(ABSTRACT TRUNCATED AT 400 WORDS)

Thoracoabdominal retroperitoneal approach for repair of abdominal aortic aneurysm associated with horseshoe kidney

This article describes a patient with an abdominal aortic aneurysm associated with horseshoe kidney that was repaired through a thoracoabdominal retroperitoneal approach. In general we believe that the retroperitoneal approach is preferable to the standard transabdominal approach since it avoids the two major difficulties associated with aneurysm repair in a patient with a horseshoe kidney. These are the renal artery anomalies which can be reanastomosed from within the aneurysm sac and the renal isthmus anterior to the aorta which is retracted with the kidney.