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Biomedical subjects

Y Douville

Publications and source records attributed to Y Douville.

36 records · Page 2Linked to original sources
PubMed1991

A pathological study of arterial prostheses surgically excised after overt clinical infection.

Infection caused regarding vascular grafts in vascular surgery still remains a major problem. To reduce this problem and the complications which follow, the surgeon must be able to apply the best surgical management and also be confident with the vascular substitute used. There are two important factors to be considered: the biomaterial must have low propensity to infection and good stability if and when infected. In an attempt to verify this problem, 93 vascular grafts surgically excised for overt infection were examined. Techniques used for examinations were gross morphology, histopathology and scanning electron microscopy (SEM) evaluation. There were 23 human umbilical vein (HUV) grafts, 51 Dacron grafts and 19 expanded polytetrafluoroethylene (ePTFE) grafts. Histopathological signs of infection were absent in 57% of the ePTFE and Dacron grafts and in 17.4% of the HUV grafts. The latter were more heavily histologically infected and in some cases the walls were destructed. Histopathological signs of infection were seen on all the prosthetic walls in 36% of all the specimens and were mainly on the external portion of the grafts for the remaining prostheses. Bacteria were seen in respectively 21.7, 15.7 and 20% of the HUV, Dacron and ePTFE grafts with the Gram stain and in 86.9, 84.3 and 94.7% with SEM. The implantation period was shorter for the bioprostheses compared to that of the synthetic grafts because of the site and the indication of implantation. The stability of the bioprostheses was lower compared to that of the synthetic grafts when infected, leading to a breakdown of the wall along the length of the graft. The infection was found on the external capsule of the grafts rather than on the luminal surface.

Arteries↗
PubMed1991

[Ruptured abdominal aortic aneurysm: long-term survival].

Despite technological improvement, surgery for ruptured aortic abdominal aneurysm (AAA) only gets about 50% of patients to survive past the operative period. This series addresses the long-term outcome of those survivors. Eighty consecutive patients operated on for ruptured AAA between January 1983 and June 1990 at l'hôpital du Saint-Sacrement by three vascular surgeons, were studied and compared to 279 patients submitted to elective aneurysm surgery during the same period. The operative mortalities were respectively of 45% (ruptured) and 6.1% (elective). Five year survivals added up to 30 and 68%. When the 5 year survivals were recalculated, including only patients who were discharged from hospital, we found no statistically significant difference (p greater than 0.05) between the ruptured (55%) and the elective groups (68%). Data from this series demonstrate that long-term survival of patients undergoing ruptured AAA surgery is good and compares with that of AAA elective surgery. Therefore, aggressive treatment of ruptured AAA remains justified.

Actuarial Analysis↗
PubMed1989

In vivo evaluation of four chemically processed biological grafts implanted as infrarenal arterial substitutes in dogs.

Four chemically processed grafts implanted as arterial substitutes in dogs were evaluated as blood conduits in terms of patency rates, healing characteristics and biostability. Omniflow, Biopolymeric, Dardik-Biograft of the second generation and BIMA grafts were implanted as infrarenal aortic substitutes for 4, 24 and 48 h (short-term), 1, 2 and 4 wk (medium-term), 3 and 6 month (long-term), each type of graft being implanted for a complete series. The explanted grafts were evaluated macroscopically and processed for light and scanning electron microscopy. One Omniflow graft was occluded at 6 months and two Dardik-Biografts were thrombosed, one at 24 h and one at 1 month. All explanted grafts in the Biopolymeric series and in the BIMA were patent at the animals' death. Histological studies revealed frequent subintimal fibrosis in the Biopolymeric and Omniflow grafts. A peripheral inflammatory reaction was present in most grafts explanted. Scanning electron microscopy showed an aggravation of flow surface irregularities, after implantation of Omniflow, Biopolymeric and Dardik-Biograft, compared to virgin prostheses. These grafts presented an internal capsulae on the graft flow surface along the anastomoses. The capsulae slightly extended towards the centre of the graft after long-term implantation, (6 month) and corresponded to the pannus. Endothelial-like cells covered this pannus. The BIMA graft performed the most satisfactorily and retained its blood compatibility best, that is, the luminal surface was smooth with only minor thrombotic deposits and a thin pannus along the anastomotic lines.

Animals↗
PubMed1989

Arterial reconstruction to the foot vessels: is it worth the trouble?

Between 1974 and 1988, 32 patients with severe rest pain and ischemic ulcerations of lower extremities underwent 34 arterial reconstructions to the foot vessels, using, in the majority of cases, the in-situ vein technique. There were 10 early graft failures, resulting in the loss of five extremities. The indication for surgery, presence of diabetes and type of bypass were not predictive of early thrombosis. Five-year primary and secondary patency rates were 52.8% and 62.6%, with a foot salvage rate of 74%. Although a number of these long bypass grafts fail early because of the severity of tibial disease, this procedure appears to be durable in a selected group of patients.

Adult↗
PubMed1985

Accuracy of carotid Doppler peak frequency analysis: results determined by receiver operating characteristic curves and likelihood ratios.

To determine the accuracy of peak Doppler frequency measurements in the diagnosis of extracranial carotid arterial disease and to apply the results to the assessment of the individual patient, 397 studies of continuous-wave Doppler frequency analysis were compared with the results of arteriography. The diagnostic accuracy of the measurement of peak frequency was determined in two ways. First, receiver operator characteristic curves were calculated for different threshold levels of peak frequency. The results showed that the measurement of the peak frequency can be related in only an approximate way to the severity of the arteriographic stenosis because of the uncertainty of the probe-to-vessel angle. Nevertheless, the overall maximum diagnostic accuracy was approximately 91% (Kappa = 0.82 +/- 0.05). Second, likelihood ratios were calculated to take into account the degree of abnormality of the peak frequency measurements. The probability of carotid disease increased as the peak frequency increased, giving likelihood ratio ranges from 0.03 to 25.71. To be able to apply the peak frequency measurements to the assessment of the individual patient in the vascular laboratory, our results were used to construct tables that show the posttest probability of carotid disease based on the clinically estimated pretest probability of disease and the measured peak frequency. It is concluded that the measurement of peak Doppler frequency is an adjunct in the diagnosis of carotid artery disease.

Aged↗
PubMed1982

Detection of occlusive disease of the carotid artery with continuous wave Doppler spectral analysis.

The accuracy of Doppler spectral analysis for diagnosing stenoses of the carotid artery was evaluated in this study. Two hundred and five patients were examined, using a 4 megahertz continuous wave Doppler velocity meter and a real-time frequency analyzer. By a comparison of the results of arteriography, peak Doppler frequencies of greater than 3.8 kilohertz were diagnostic of internal carotid artery stenoses having residual lumen diameters of 3.2 millimeters, or less, with a sensitivity rate of, 91 per cent and a specificity rate of 92 per cent. Spectral broadening, evaluated by subjective grading, yielded similar results.

Arterial Occlusive Diseases↗
PubMed1978

Survival in colorectal cancer.

The authors studied the hospital records of 258 patients with colorectal cancer diagnosed between 1965 and 1974 at l'Hôpital du Saint-Sacrement, Quebec and computed expected and relative survival rates to adjust for deaths from other causes. Life-table methods based on full intervals only were used to analyse survival. The patients (138 men and 120 women) ranged in age from 24 to 96 years (mean, 64.9 +/- 12.7 years). The 5-year relative survival rate expressed as a percentage was 48.6 +/- 4.7 for the total group and 64.1 +/- 5.6 for patients in stages A, B and C of Dukes' classification. The overall operative mortality rate of 2.7% compared favourably with that reported elsewhere. Among patients with cancer of the sigmoid colon or rectum (the most readily detectable), the diagnosis was made at stage A in one out of nine and at stage D in approximately one out of four. Despite the introduction of universal medical insurance in Quebec in 1970, there has been no significant trend towards earlier diagnosis.

Adult↗
PubMedDate not supplied

An in vitro model and its application for the study of carotid Doppler spectral broadening.

A new in vitro model has been developed for studying the changes in the ultrasound Doppler spectrum that occur in the region of a stenosis. Pulsatile flow in rigid acrylic tubes was produced by means of a modified hemodialysis pump. The Doppler spectral waveforms were measured using a continuous wave Doppler system, a probe of a known field pattern, a real-time high resolution frequency analyzer, and a video display and recording system. The flow velocity waveforms were found to be nearly identical to those seen in the human carotid. Measurements were made to determine the critical stenosis and the results are similar to those reported from in vivo studies. In a preliminary study, the extent of spectral broadening was found to be dependent on the recording site in relation to the stenosis, the severity of the stenosis, and the flow rate. Using qualitative methods it was not possible to determine either the influence of the shape of the stenosis or the phase of the cardiac cycle on spectral broadening.

Carotid Arteries↗
PubMedDate not supplied

Determination of the hemodynamic factors which influence the carotid Doppler spectral broadening.

In the diagnosis of extracranial carotid arterial disease, quantitative measurements from the continuous wave (CW) Doppler spectrum have the potential for detecting stenoses and occlusions. The measurement of maximum peak Doppler frequency at the site of stenosis has been shown to detect severe, but not minor or moderate, stenoses. Diagnosis of minor or moderate stenoses may be possible by assessing the degree of flow disturbance beyond the stenosis. Such flow disturbances cause the Doppler spectrum at peak systole to be broadened, and it has been suggested that the measurement of spectral broadening may be of diagnostic value. This paper describes the results of an in vitro study aimed at determining the hemodynamic factors that influence the severity of the Doppler spectral broadening. The spectral broadening index (SBI) at peak systole, defined as SBI = 1 - Fmean/Fmax, was used to quantify the instantaneous spectrum. In a pulsatile flow in vitro model that produced spectral waveforms virtually identical to those recorded in the human carotid, we observed a direct linear relationship between SBI and the severity of stenosis, at least for those stenoses having greater than 40% cross-sectional area (R = 0.82 to 0.93). The SBI was found to be maximum when recorded immediately beyond the stenosis and returned to normal 4-5 cm downstream from the stenosis. The SBI was higher for nonsymmetrically shaped stenoses than for symmetrical stenoses for lesions greater than 60%, but not for stenoses less than 60%. In this model, the SBI recorded from both normal or abnormal waveforms was not affected by the flow rate.(ABSTRACT TRUNCATED AT 250 WORDS)

Carotid Arteries↗
PubMedDate not supplied

Low Reynolds number turbulence modeling of blood flow in arterial stenoses.

Moderate and severe arterial stenoses can produce highly disturbed flow regions with transitional and or turbulent flow characteristics. Neither laminar flow modeling nor standard two-equation models such as the kappa-epsilon turbulence ones are suitable for this kind of blood flow. In order to analyze the transitional or turbulent flow distal to an arterial stenosis, authors of this study have used the Wilcox low-Re turbulence model. Flow simulations were carried out on stenoses with 50, 75 and 86% reductions in cross-sectional area over a range of physiologically relevant Reynolds numbers. The results obtained with this low-Re turbulence model were compared with experimental measurements and with the results obtained by the standard kappa-epsilon model in terms of velocity profile, vortex length, wall shear stress, wall static pressure, and turbulence intensity. The comparisons show that results predicted by the low-Re model are in good agreement with the experimental measurements. This model accurately predicts the critical Reynolds number at which blood flow becomes transitional or turbulent distal an arterial stenosis. Most interestingly, over the Re range of laminar flow, the vortex length calculated with the low-Re model also closely matches the vortex length predicted by laminar flow modeling. In conclusion, the study strongly suggests that the proposed model is suitable for blood flow studies in certain areas of the arterial tree where both laminar and transitional/turbulent flows coexist.

Arteries↗
PubMedDate not supplied

Can collagen impregnated polyester arterial prostheses be recommended as small diameter blood conduits?

A collagen impregnated graft and its parent preclotted prosthesis were implanted as thoraco-abdominal bypasses in dogs for periods ranging from 4 hr to 6 months and evaluated for their ease of handling, imperviousness, and healing behavior in terms of luminal surface thrombogenicity using labeled platelets and fibrinogen, prostacyclin (PGI2) secretion, histomorphometric determination of internal capsule thickness, and histopathologic and scanning electron microscopic studies. The collagen impregnated graft was impervious to blood and both grafts showed excellent handling characteristics. Fibrin uptake was negligible on both grafts; however, platelet uptake was higher on the collagen impregnated graft than on the control graft at 4 and 24 hr. The healing behavior of the collagen impregnated graft was also found to be different than that of the control graft between 1 and 6 months post implantation. The development of a host collagenous internal capsule at the anastomoses, and a confluent endothelial lining, was observed in both grafts at 1 month; in later implantation periods, the healing of the medial region was found to be more irregular in the collagen impregnated grafts, showing a lower mean PGI2 secretion than the preclotted control grafts. Histomorphometric analysis showed the internal capsule on the collagen impregnated grafts to be thicker than on the control grafts for most periods of implantation. The current study illustrates that the healing process of collagen impregnated grafts is delayed and that bovine collagen has a stimulating effect on tissue encapsulation. Current impregnated polyester arterial prostheses therefore cannot be recommended as small diameter blood conduits.

Animals↗
PubMedDate not supplied

Comparison of the in vivo behavior of polyvinylidene fluoride and polypropylene sutures used in vascular surgery.

To find a nonabsorbable suture material that is equivalent to polypropylene in ease of handling and tensile properties, and that has low thrombogenicity and tissue reactivity but improved biostability, some researchers and clinicians see merit in considering the suitability of monofilaments made from polyvinylidene fluoride. The current animal study investigated the relative biocompatibility and biostability of these two suture materials by using them to anastomose a polyester arterial prosthesis in a canine thoracoabdominal bypass model for 10 periods of implantation ranging from 4 hr to 2 years. Biocompatibility was assessed with light and scanning electron microscope examinations of the explanted sutures, and biostability of the cleaned sutures was determined by Fourier transform infrared spectroscopy and scanning electron microscope analysis. The polyvinylidene fluoride and polypropylene sutures were found to have similar handling and healing characteristics. During the first months in vivo, both types of suture experienced a temporary increase in carbonyl group absorption that coincided with the duration of the inflammatory response. After 1 and 2 years in vivo, the explanted polypropylene sutures showed visual evidence of surface stress cracking. This was not found with the explanted polyvinylidene fluoride sutures. These results suggest that polyvinylidene fluoride may be more biostable than polypropylene in the long term.

Animals↗
PubMedDate not supplied

Fresh venous allografts as arterial substitutes in dogs: the importance of donor-recipient tissue compatibility.

Fresh venous allografts were investigated in dogs matched according to donor-recipient tissue compatibility, either originating from the same litter or chosen at random (pound dogs). Five centimeter long segments of femoral vein were interposed as carotid substitutes in an autografting and allografting manner between paired dogs. During a 5-month implantation period, donor-specific antibody development was measured in the recipient serum by a flow-cytometric assay using cultured donor vascular endothelial cells. Autografts and allografts were investigated in terms of patency, histopathology, and endothelial cell function. Fifteen of 16 autografts remained patent. Allografts between littermate dogs, whether compatible or incompatible, showed no donor-specific antibody development and were all patent at retrieval. Compatible and incompatible allografts in littermates did not show any difference in prostacyclin (PGI2)/thromboxane A2 (TXA2) ratios. In pound dogs, both compatible allografts were patent and one dog developed donor-specific antivascular endothelial cell antibodies. Among incompatible dogs, antibody formation was detected at 1 month in five of six recipients and graft patency was as follows: two partial thromboses, two stenoses, and two patent grafts. The PGI2/TXA2 ratio was significantly lower in incompatible allografts than in compatible ones (p = .028). These results show the importance of donor-recipient histocompatibility matching in improving the outcome of vein allografts.

Animals↗
PubMedDate not supplied

Can the infusion of elastase in the abdominal aorta of the Yucatán miniature swine consistently produce experimental aneurysms?

The intraluminal elastase perfusion model has been proved to be potentially effective in producing abdominal aortic aneurysm in rodents, but it produced unpredictable results in larger animals. The purpose of this study was to explore the potential ability of such a model to produce experimental aneurysm consistently in the Yucatán miniature swine. Six Yucatán miniature swine received infusion with porcine elastase into an isolated segment of the infrarenal aorta. The excised arterial segments were examined macroscopically to assess the luminal surface characteristics and histologically to describe the different pathologic injuries induced by the elastase treatment on the intima, media, and adventitia of the arterial wall. Histologic examination revealed that the elastic network of the media was destroyed. In the first week after perfusion, altered smooth muscle cells were located in the intima and innermost layer of the media in juxtaposition with the occlusive thrombus. Infiltration of inflammatory cells was observed in these regions of elastic network and smooth muscle cell alterations. In the arterial segments of swine sustained for 3 weeks, a reduction of smooth muscle cells was noted in some areas. An important number of necrotic lesions was observed, and they were associated with the development of calcium deposits. Significant intimal hyperplasic reaction was identified at day 19 and again at day 21. However, no aneurysmal development was observed. This study constituted the first experiment with infusion of porcine elastase in the Yucatán miniature swine infrarenal aorta. The present experimental protocol induced important elastic network and smooth muscle cell alterations leading to severe necrotic lesions associated with calcium deposition, but it produced no aneurysmal dilatation. This model requires further testing to obtain a more complete degradation of the elastic network in both the media and adventitia and more significant collagenolysis without early thrombotic events.

Animals↗
PubMedDate not supplied

Fresh venous femoral autografts and allografts as carotid substitutes in matched dogs from the same litter.

Pathological and biochemical investigations were performed on femoral veins used as fresh autografts and allograft substitutes in the carotid arteries of dogs from the same litter and separated in two groups described as compatible and incompatible after a mixed leukocyte culture (MLC). After 5 months of implantation, all the arterial substitutes were patent. The analyses gave the following results: 1. The haematologic parameters were not affected by the grafts. 2. Light microscopy (LM) and scanning electron microscopy (SEM) indicate a thrombotic accumulation and the presence of inflammatory cells in the compatible and the incompatible allografts. The occurrence of pathological changes was more pronounced in the incompatible group. 3. Immunostaining of anti-factor VIII-related antigen reveals a better preservation of the endothelial cell wall on the autograft. 4. The 6-keto-PGF1 alpha/TXB2 ratios of the autografts and the compatible allografts were similar.

6-Ketoprostaglandin F1 alpha↗
PubMedDate not supplied

Why make monofilament sutures out of polyvinylidene fluoride?

In recent years some clinical reports have associated suture failures with polypropylene monofilaments. Therefore there is interest in developing an alternative suture material that is less thrombogenic than polyester and similar in handling characteristics but less prone to mechanical failure than polypropylene. To this end, Peters Laboratoire Pharmaceutique has developed a new monofilament suture material from polyvinylidene fluoride (PVDF), which has been subjected to a special treatment to modify its crystalline form and level of crystallinity. The purpose of this study was to evaluate its mechanical, chemical, and biologic properties and to compare its performance, in a peripheral vascular application, to that of a polypropylene control. A series of in vitro tests were performed to study the morphology, tensile properties, creep, surface chemistry, thermal characteristics, and resistance to iatrogenic trauma. In addition, an in vivo trial was undertaken in which vascular prostheses anastomosed with either PVDF or polypropylene sutures were implanted as a thoracoabdominal bypass for 6 months in the dog. Histologic and degradation analyses were performed on the explants. The results from the mechanical tests on 4-0, 5-0, and 6-0 PVDF and polypropylene sutures demonstrated that although both materials have similar breaking strengths, the PVDF has a higher extension at break, has less delayed extension when under tensile creep testing, and suffers less trauma than the polypropylene when compressed by a standard needle holder. While chemical analyses found evidence of surface oxidation on both types of sutures, thermal analysis confirmed that the level of crystallinity of the PVDF polymer is higher than that of the polypropylene control. During the pilot study in animals, PVDF sutures were found to have good handling and frictional characteristics that facilitated the tying of knots. Histologic analysis of the explants found no inflammatory cells in the tissue surrounding either the PVDF or polypropylene sutures, and scanning electron microscopic examination of the cleaned suture surfaces found no evidence of degradation during 6 months in vivo. Though preliminary in nature, these findings indicate that monofilament sutures made from PVDF provide an attractive alternative to those made from polypropylene for use in cardiovascular surgery. In addition to providing acceptable in vivo behavior and being easy to manipulate and more resistant to iatrogenic injury, PVDF materials can be sterilized by beta or gamma radiation and so can reduce dependence upon ethylene oxide and chlorofluorohydrocarbons.

Animals↗