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Biomedical subjects

M Tabbara

Publications and source records attributed to M Tabbara.

12 recordsLinked to original sources
PubMed1997

A technique for prolonged arterial infusions of fibrinolytic agents in the immediate postoperative period through a cutaneous venostomy.

Prolonged use of fibrinolytic agents post thrombectomy is limited by present techniques that require arterial puncture and indwelling arterial catheters. This limitation can be avoided by attaching a short segment of saphenous vein to the arteriotomy used for the thrombectomy and bringing this out to the skin as a "venostomy"; thus providing ready access to the vascular tree for arteriography, prolonged infusion of thrombolytic agents, or selective catheter placement. In delayed thrombectomies (Categories 2 & 3 as described by the Ad Hoc Committee on Reporting Standards, J Vasc Surg 1986;4:80-94), extending the use of these agents may represent the only hope for limb salvage.

Adult↗
PubMed1992

Holmium:YAG laser ablation of human intervertebral disc: preliminary evaluation.

Percutaneous discetomy has become a viable alternative in the treatment of herniated intervertebral disc. This study determined the effectiveness of holmium: YAG laser for ablation of human disc tissue. Human cadaveric intervertebral disc was harvested and stored in cold saline-soaked gauze for evaluation within 24 hr of removal. Using a specially designed apparatus, a 600 microns diameter fiber was advanced perpendicular through the annulus fibrosis at a controlled force of 0.098 Newtons (10 g). Samples were lased in air (n = 17) and in room temperature saline (n = 32). The laser energy was delivered at 5 Hz, 250 microseconds pulsewidth, and from 50 mJ/mm2 to 1,100 mJ/mm2 fluence. Three to six holes were lased using identical parameters in each tissue specimen and were evaluated histologically and by morphometric analysis. The maximum zone of thermal necrosis and thermal denaturation occurred at 700-1,100 mJ/mm2; 140 microns and 590 microns in air and 80 microns and 730 microns in saline, respectively. At fluences between 200 and 700 mJ/mm2, the thermal necrosis ranged from 20 to 60 microns in air and from 10 to 50 microns in saline, the zone of denaturation also being less. The holes created with the 600 microns fiber were circular in shape, with a mean diameter of 500 microns (n = 3). The etch rates (penetration/pulse) appeared to increase with increasing fluences. In saline, the etch rate ranged from 7 to 53 microns/pulse (r = 0.57, P less than or equal to 0.10), and, in air, the values ranged from 7 to 65 microns/pulse (r = 0.79, P less than or equal to 0.03).(ABSTRACT TRUNCATED AT 250 WORDS)

Acoustics↗
PubMed1991

In vivo human comparison of intravascular ultrasonography and angiography.

This study evaluates the in vivo correlation of intravascular ultrasonography and uniplanar angiography in determining the luminal dimensions of normal and moderately atherosclerotic human arteries. Five French and 8F rotating A scan intravascular ultrasound catheters were used to obtain 48 images in four superficial femoral arteries, five iliac arteries, and one aorta in eight patients undergoing vascular surgery. Cross-sectional areas measured by intravascular ultrasonography were compared to cross-sectional areas calculated by uniplanar angiography of the same location in the vessel. Maximum and minimum luminal diameters were also measured from intravascular ultrasound images. An ellipticity index was defined as the maximum/minimum diameter ratio (max/min) and ranged from 1.0 to 1.8 (mean, 1.2). Comparison of the cross-sectional areas measured from intravascular ultrasound images and those calculated from uniplanar angiography showed no significant difference at any level of ellipticity studied. However, when the values of cross-sectional areas were analyzed in groups corresponding to the diameter of the vessel, that is, aortic, iliac, and femoral, the values for the iliac arteries calculated from uniplanar angiography were significantly greater by 9.8% +/- 0.7% (n = 29, p = 0.03) when compared to those measured by intravascular ultrasonography. In addition to providing accurate luminal determinations, intravascular ultrasound images displayed transmural morphology, the location and character of the atherosclerotic lesions, and the thickness of the vessel wall. We conclude that intravascular ultrasound imaging provides accurate, novel information regarding human vessels and that this technology may play a significant role in future diagnostic and interventional therapies.

Angiography↗
PubMed1990

Holmium:YAG laser ablation of vascular tissue.

The ablation of atherosclerotic lesions without collateral thermal or shock wave damage is thought to be a key element for successful laser angioplasty. This study evaluated the effectiveness of pulsed holmium:YAG laser (2.1 microns wavelength) for this application. Fresh normal tissue (n = 139) and arteriosclerotic canine arteries (n = 21) as well as formalin-preserved normal canine (n = 31) and atherosclerotic human arteries (n = 177) were irradiated under saline via a 600 microns diameter fiber placed perpendicular to the intimal surface with 0-10 gm of force. The laser was operated in the free running mode (FRM; 250 microseconds pulsewidth, 5 Hz, 30-7,100 mJ/mm2) and in the Q-switched mode (QSM; 200 nsec pulsewidth, 6 Hz, 30-1,100 mJ/mm2). Following the experiments, the samples were prepared for histologic and morphometric analysis. Ablation thresholds in the FRM were 60 and 180 mJ/mm2 in fresh and preserved canine tissue, respectively. Ablation thresholds in the QSM for fresh and preserved canine tissues were 75 and 180 mJ/mm2, respectively. Thresholds for human atherosclerotic tissue were dependent on the amount of calcification. In the QSM and FRM, there were no samples that could not be penetrated at 1,100 mJ/mm2 and above. Histologic examination of the FRM samples revealed confined columns of tissue ablation, with approximately 55-250 microns and 70-140 microns zones of thermal effect being apparent in the fresh and formalin-preserved samples, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Angioplasty, Laser↗
PubMed1990

In vitro and in vivo evaluation of intraluminal ultrasound in normal and atherosclerotic arteries.

This study evaluated the dimensional and morphologic precision of arterial images obtained using intraluminal rotating A-scan ultrasound catheters [5.0F (30 mHz) and 8.0F (20 mHz)]. Dimensions of in vitro ultrasound images from human arteries (eight normal and nine arteriosclerotic) were compared with those from histologic sections of the vessels. In addition, in vivo ultrasound studies (23 normal and 22 arteriosclerotic) of canine femoral arteries were compared with luminal dimensions obtained from angiograms of the vessels. The correlation of in vitro ultrasound images to luminal diameters (n = 22, r = 0.96), adventitial diameters (n = 19, r = 0.83), and wall thickness (n = 19, r = 0.68) in normal human vessels was significant (p less than 0.05). In vitro measurements of images and histologic specimens from human atherosclerotic arteries also correlated significantly (p less than 0.05) with luminal diameters (n = 27, r = 0.91), adventitial diameters (n = 24, r = 0.60), and wall thickness (n = 24, r = 0.62). Morphologically, in vitro images of the wall of normal human arteries had a concentric laminated appearance and atherosclerotic vessels had patchy echodense and echolucent areas. In vivo studies showed significant correlation of diameters for both normal (n = 16, r = 0.91, p less than 0.05) and arteriosclerotic (n = 16, r = 0.57, p less than 0.05) canine arteries compared with luminal dimensions measured from uniplanar angiograms. We conclude that rotating A-scan intraluminal ultrasound accurately defines both normal and atherosclerotic arterial wall morphology and dimensions. This technology may be valuable for intravascular guidance of angioplasty devices by identifying the location and consistency of lesions.

Animals↗
PubMed1990

Intravascular ultrasound: a new potential modality for angioplasty guidance.

Current angioplasty devices are limited by significant rates of arterial perforation and dissection, due to inadequate techniques of guidance, and by restenosis, which may be partly attributed to inadequate debulking of lesions. This paper describes the authors' initial experience in-vitro and in-vivo with intravascular ultrasound as a possible method of enhancing the three-dimensional guidance of devices through atherosclerotic obstructions. Using an in-vitro model they correlated the dimensions and histologic morphology of animal and human arteries with ultrasound images of the specimens. Additional in-vivo evaluations of this technology in canine arteriosclerotic and human atherosclerotic arteries preliminarily support the hypothesis that intravascular ultrasound defines the transmural arterial morphology and may enhance the accuracy of angioplasty procedures. Simultaneous imaging with angioscopy and intravascular ultrasound is demonstrated as a potential method of accurately defining both intraluminal and transmural arterial wall characteristics.

Angioplasty, Balloon↗
PubMed1986

Neonatal appendicitis: case report and a revised review of the English literature.

A case of perforated neonatal appendicitis in a surviving premature infant is presented. An up-dated review of the English literature on this subject is included. Of 111 cases with adequate documentation, 29 neonates had the inflamed appendix located within the inguinal hernial sac and survived after operation. In contrast only 24 (29%) of the remaining 82 patients with intra-abdominal acute appendicitis survived. The operative mortality rate in this review since 1901 with and without appendiceal perforation was 61% and 41% respectively. The diagnosis of acute appendicitis since 1976 was made at laparotomy in all patients except one, whereas it was made at necropsy in 57% of the cases of abdominal appendicitis that were reported previously.

Appendectomy↗
PubMed1983

Fetal renal maturation. Studies on urinary beta 2 microglobulin the neonate.

Beta 2 microglobulin [B2m] and creatinine [Cr] concentrations were measure in the urine of 27 newborn infants. At birth, urinary [B2m] and [B2m]/[Cr] ratios were significantly lower in infants born beyond 36 weeks' gestation. Serial measurements, postnatally, showed a progressive decrease in the urine [B2m]/[Cr] ratio of infants born prematurely. These findings suggest an increase in tubular uptake of B2m with increasing gestational and postnatal age. The current findings tend to support the hypothesis that the decrease in [B2m] observed in amniotic fluid beginning at approximately 36 weeks' gestation reflects maturation of fetal proximal renal tubular function.

Amniotic Fluid↗
PubMedDate not supplied

A canine iliac artery occlusion model.

This report describes an occlusive canine iliac artery model for use in experimental angioplasty procedures. Lesions were induced by overdistending and breaking the internal elastic lamina of the artery and implanting a 2-cm long occlusive collagen plug. The collagen plug diameter was varied to fit the iliac artery and caused immediate bilateral iliac occlusions. Histology of the lesions at 9 and 14 days (n = 2) showed that the lumen was filled with a mixture of fresh thrombus and collagen pad material (more collagen than thrombus) with focal disruptions of the internal elastic lamina. At 36 days (n = 2) the lumen was obliterated with a mixture of organizing thrombus and collagen pad material (more organizing thrombus than collagen). At 60 (n = 4) and 80 (n = 8) days the collagen pad had been completely replaced with organizing thrombus consisting of collagen fibers and hemosiderin-laden macrophages with persistent focal disruptions of the internal elastic lamina. These initial data demonstrate the ability to create fibrotic arterial occlusions in as short a time as 60 days and to provide a practical model to study methods for treating localized peripheral vascular occlusive disease.

Animals↗
PubMedDate not supplied

Laser-fused biologic vascular graft anastomoses.

Tissue fusion using laser energy is a promising new technology that may improve the healing of anastomoses. This study evaluated the feasibility of using argon laser energy to fuse vascular tissue and biologic vascular prostheses (St. Jude Medical, Inc.) in a canine arteriovenous (A-V) fistula model. Five animals had 4-cm length, 3-mm internal diameter grafts (n; eq 10) placed bilaterally as side-to-side A-V interpositions from the femoral artery to femoral vein. One A-V graft was placed using argon laser energy with the vessel edges aligned by 6-0 polypropylene traction sutures at 3 to 4 mm intervals. The contralateral graft was sutured using running 6-0 polypropylene suture. Anastomoses were successfully fashioned in all animals except for episodes of delayed bleeding at two laser-fused segments (15 min and 2 hrs) and one segment in a suture control (6 days). The implants were removed to evaluate the integrity and healing of the anastomoses at 2 hrs, 8 days, and at 7, 9, and 11 weeks. In all instances, there was no evidence of anastomotic dehissance or enlargement. Histologic examination of the anastomoses revealed coapted vessel and prosthetic edges in laser-fused specimens and a limited foreign-body response to the permanent sutures in the suture controls. In the longer term specimens there was marked intimal proliferation at the venous anastomosis in all implants, with recent bilateral occlusions of the 7 and 11 week implants at the venous connection. We conclude that laser fusion of biologic vascular prostheses to autogenous vessel is possible with healing and no evidence of anastomotic dehissance.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

Eccentric iliac artery stenosis: a canine model for angioplasty.

A canine model was developed to induce eccentric iliac artery stenosis. Lesions were induced by exposing the medial aspect of the right and left common iliac arteries in four animals to direct argon laser energy (LA). A 2.5-mm diameter side-firing laser probe was used to deliver 10 W of power in 5-s intervals. Twenty-five pulses were delivered over a 5-cm length of artery with an approximate spot size of 0.8 mm2. Selected arteries (n = 2, LA + Ca) were injected in the same laser injury site with calcium chloride (10% solution). Injections were accurately accomplished using an angioscopically guided guidewire/needle device. In all cases, the internal elastic lamina was broken with focal disruptions of the media. At 9 and 14 days, the LA (n = 3) and LA + Ca vessels (n = 1) had minimal stenoses (< 5% area reduction). These vessels contained edematous media with replacement of necrotic smooth muscle by fibrous tissue. At 23 days, the LA (n = 1) and LA + Ca (n = 1) vessels contained 22% and 33% luminal reductions, respectively, with moderate neointimal proliferation and no evidence of calcification. At 56 days the LA vessels (n = 2) contained 30 and 42% luminal area stenoses with marked neointimal hyperplasia. This preliminary data suggests that controlled arterial wall injury with LA irradiation can induce eccentric fibrointimal lesions in a canine model.

Angioplasty↗