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Biomedical subjects

R Beyar

Publications and source records attributed to R Beyar.

At least 37 records · Page 2Linked to original sources
PubMed1999

Continued expansion of the nitinol self-expanding coronary stent: angiographic analysis and 1-year clinical follow-up.

BACKGROUND: This study sought to report the first-year clinical outcome with the nitinol self-expanding coil stent and to provide angiographic data on the effect of self-expansion during implantation and follow-up. Self-expanding stents do not reach their nominal diameter at implantation. The long-term effects may therefore depend, in part, on continued expansion after initial implantation. METHODS: Between January 1995 and January 1996, 86 stents were deployed in 64 patients for indication of suboptimal results. All patients were clinically followed up for 1 year, and 72% had follow-up angiography. RESULTS: The majority (55%) of the lesions were class B2 or C. Balloon angioplasty increased the minimal lumen diameter from 1.07 +/- 0.73 mm to 2.24 +/- 0.57 mm; stent deployment further increased the diameter to 2.63 +/- 0.48 mm, and within-stent balloon dilatation to 2.96 +/- 0.62 mm. Angiographic follow-up performed at 7.8 +/- 1.1 months (range 7-9 months) showed that the minimal lumen diameter was 2.15 +/- 0.80 mm (late lumen loss of 0.81 +/- 0.69 mm), and the mean stent diameter expanded to 3.58 +/- 0.48 mm (self-expanding late stent gain of 0.62 +/- 0.55 mm). The extent of this expansion was inversely related to the late lumen loss (r = 0.67, slope 0.81, P <.01). At 1 year 51 (80%) of 64 patients were event free; 3 had undergone coronary artery bypass grafting, 2 had had a myocardial infarction, and 9 had repeat angioplasty. In the subgroup of a simple lesion (<15 mm) covered by 1 stent, 18 (86%) of 21 patients were event free. CONCLUSIONS: The self-expanding nitinol stent exerts its acute effect on minimal lumen diameter through its intrinsic radial force aided by balloon expansion. The stent continues to expand until it reaches its nominal diameter over the follow-up period. The extent of this expansion is inversely related to the late lumen loss, leading to an acceptable rate of long-term clinical events in this first cohort of patients with complex disease morphology.

Alloys↗
PubMed1999

Effect of aneurysmectomy on left ventricular shape and function: case studies.

The three dimensional (3D) conformational changes in three patients with large anterior aneurysm in the left ventricle (LV) were examined before and two years after aneurysmectomy by using 3D Cine-computerized tomography (CT). Endocardial and epicardial tracings of 6-9 short axis images encompassing the entire LV were used to reconstruct the LV in 3D. Thickness and percent thickening were calculated using our 3D-volume element approach. A regional wall stress index (stress/pressure) was calculated from regional curvature and thickness. The analysis showed that following resection of the aneurysm the end-diastolic volume was reduced from 257+/-39 to 183+/-39 ml, end-systolic volume from 172+/-39 to 92+/-46 ml and, ejection fraction increased from 34+/-7 to 51+/-13%. The endocardial aneurysm area decreased from 19.7+/-15.9 to 10.1+/-6.5 cm2, whereas the normal zone area was minimally reduced from 87.4+/-17.6 to 79.8+/-10.8 cm2. The percent thickening of the normal zone increased significantly. It is documented here for the first time by detailed 3D analysis that the resection of the LV aneurysm reduces the aneurysmal area and LV size and improves the global and regional function of the remote normal zone. Therefore, the 3D approach can help to design better surgical technique for this complex operation.

Aged↗
PubMed1999

Regional differences in shape and load in normal and diseased hearts studied by three dimensional tagged magnetic resonance imaging.

OBJECTIVES: We aimed to characterize regional geometry in relation to load in two groups of patients with hypertrophic cardiomyopathy (HCM) and right ventricular pressure overload (RVPO) in relation to a group of subjects with normal left ventricular (LV) function. BACKGROUND: Both these diseases are associated with marked changes in LV shape and function, which have not been studied with detailed three dimensional tools. METHODS: Three dimensional (3D) tagged magnetic resonance imaging (MRI) was used to characterize the 3D geometry and regional stresses of the left ventricles in patients with HCM and RVPO. Curvatures, stresses, wall thickness, and endocardial motion were calculated from surface and volume elements. RESULTS: Hearts with RVPO exhibited more circumferential and meridional flattening of the septum than normal and HCM hearts. The stress indices were lowest in the HCM hearts, compared to normal and RVPO hearts, due to the larger thicknesses. There was a more significant difference between lateral wall motion and other regional wall motions in the HCM and RVPO hearts as compared to normal hearts. CONCLUSIONS: It is suggested that curvature and stress mapping by 3D tagged MRI can be used as an important clinical tool for characterizing and distinguishing between healthy and diseased hearts. The results provided here validated previous knowledge on HCM and RVPO known from planary imaging methods.

Adult↗
PubMed1999

Initial and long-term results with the CrossFlex stent--data from a national registry.

The Cordis CrossFlex trade mark stent is a balloon expandable helical coil made of stainless steel. OBJECTIVE: To assess the short- and long-term safety and efficacy of this stent by conducting a multi-center national registry. METHODS: One hundred and sixteen stents were implanted in 109 patients (mean age 59 3 10 years, 95 males). The lesions were classified as type B2 or C in 56 patients (51%). Successful deployment was achieved in 103 patients (94.5%). Failure was due to damage to the stent (two patients) or inability to reach the lesion (four patients). High-pressure deployment (>14 atm) was used in 68% of cases. RESULTS: Edge dissections occurred in nine patients after high-pressure deployment and necessitated implantation of a second stent. One patient with a large acute myocardial infarction died during hospitalization. Side branch occlusion occurred in five patients (4.6%). Subacute thrombosis occurred in two patients (1.8%) during the first four weeks. During a six-month follow-up period, 18 patients (16.5%) were rehospitalized with recurrent angina. Fifteen patients had coronary angiography and 13 (12.1%) needed additional target lesion revascularization (TLR). Twelve patients required a second PTCA for in-stent restenosis, and one needed a coronary artery bypass graft operation. CONCLUSIONS: The CrossFlex coronary stent can successfully be used in complex coronary lesions, with few short-term complications and a low TLR rate. Operators should be aware of the possibility of edge dissection during high-pressure implantation.

Journal Article↗
PubMed1999

One-year clinical follow-up with the serpentine balloon expandable stent: report of the first 100 patients.

BACKGROUND: We recently reported a high technical and 30-day clinical success rate among the first 100 patients treated with the tubular, serpentine design, stainless steel, balloon-expandable stent (beStent) in Israel. The present study examined the clinical results in these patients after the first year. METHODS: Seventy-eight men and 22 women were included in the study. Previous myocardial infarction, bypass surgery and percutaneous transluminal coronary angioplasty had occurred in 52%, 12% and 26% of the patients, respectively. Diabetes mellitus was present in 30 patients and hypertension in 34 patients. One hundred and forty-eight stents of 15, 25, and 35 mm lengths were used. The indications for stenting were suboptimal results (n = 85), bailout conditions (n = 10) or for the prevention of restenosis (n = 8), and lesion types were A (n = 10), B1 (n = 29), B2 (n = 20), and C (n = 44). All patients were clinically monitored with regular visits at 1, 3, 6, 9 and 12 months. RESULTS: Overall, the 12-month event-free survival rate was 82%. Subacute thrombosis occurred in two patients. There were two non-cardiac deaths, one O-wave myocardial infarction, six elective bypass surgeries and 12 target lesion revascularizations. Event-free survival was significantly higher for those with lesions shorter than 15 mm than for those with lesions longer than 15 mm (90% versus 67%, P = 0.003), and for women compared with men (96% versus 78%, P = 0.02). CONCLUSIONS: The initial experience with the beStent shows favorable long-term results with an overall event rate of 18% for this subset of relatively complex lesions; higher event rates were observed for longer lesions.

Angioplasty, Balloon, Coronary↗
PubMed1999

Interventional cardiology--promises and challenges.

The current explosion in coronary stent use for the treatment of coronary artery disease has helped to better define who really benefits from coronary stenting. It is clear that plain old balloon angioplasty can be at least as efficacious as stenting in certain patient groups. Patients with reference vessel diameter of < 2.5 mm, a small post-stent minimal lumen diameter, lesion length > 30 mm, diabetes mellitus and end-stage renal failure--all associated with a high incidence of diffuse in-stent restenosis--should not be stented routinely. The judicious use of stents in percutaneous revascularization will improve patient outcomes and decrease cost. The progress that has been achieved in coronary stent designs has led to many new questions, such as which patients benefit the most from stenting and whether adjunctive therapies or stent coatings will effectively prevent restenosis. Despite the advances in stent/balloon technology, antiplatelet agents, and interventional operator skill, the problems of in-stent restenosis remain. Novel therapeutic strategies for the management of severe coronary artery disease are evolving rapidly. Radiation therapy shows promise on this front. This therapy may reduce rates of restenosis by inhibiting smooth muscle proliferation and migration. However, important issues regarding the type of radiation and the matter of edge-restenosis are yet to be resolved, and the results of ongoing prospective randomized trials should provide valuable information on the efficacy of this modality. Patients with severe, non-revascularizable coronary artery disease and debilitating symptoms represent another frustrating clinical problem. PMR performed in the cardiac catheterization laboratory may improve symptoms of angina in patients with end-stage coronary artery disease. The early results are propitious. Among patients who have undergone this procedure 80-90% have improved from class IV (the most severe chest pain) to class I or II, enabling them to live relatively normal lives. Most investigators believe that PMR may be used only for those who are unsuitable candidates for percutaneous or surgical revascularization. Finally, gene therapy, by stimulating angiogenesis and improving coronary collateral development, may prove to be the most optimal treatment. Each of these strategies is currently under active investigation to confirm the results of the pilot studies, identify patient subgroups likely to respond to therapy, and determine long-term safety. Together with its challenges, the future of interventional cardiology is indeed bright.

Cardiac Surgical Procedures↗
PubMed1998

Percutaneous closure of a coronary aneurysm with a vein-coated stent.

Coronary artery aneurysm is a rare but recognized complication following percutaneous intervention. We report the formation of such an aneurysm after recanalization with Excimer laser wire of a chronic totally occluded left anterior descending coronary artery and stent implantation and its subsequent treatment using an autologous vein graft-coated stent.

Adult↗
PubMed1998

Evaluation of the compressive mechanical properties of endoluminal metal stents.

The mechanical properties of metal stents are important parameters in the consideration of stent design, matched to resist arterial recoil and vascular spasm. The purpose of this study was to develop a system for a standardized quantitative evaluation of the mechanical characteristics of various coronary stents. Several types of stents were compressed by external hydrostatic pressure. The stent diameter was assessed by placing a pair of small ultrasonic sono-crystals on the stent. From pressure-strain diagrams the ultimate strength and radial stiffness for each stent were determined. For all stents, except the MICRO-II and the Wiktor stent, the diameter decreased homogeneously until an ultimate compressive strength was exceeded, causing an abrupt collapse. Expanded to 3 mm, the mechanical behavior of the beStent, the Crown and the Palmaz-Schatz stent (PS153-series) were comparable. The spiral articulated Palmaz-Schatz stent showed twice the strength (1.26 atm) of the PS-153 (0.65 atm). The NIR stent yielded a maximum strength of 1.05 atm. The MICRO-II and the Wiktor stent did not collapse abruptly but rather showed a continuous decline of diameter with increasing external pressure. The Cardiocoil stent behaved in a fully elastic manner and showed the largest radial stiffness. Difference in mechanical properties between stents were documented using a new device specifically developed for that purpose. These mechanical stent parameters may have important clinical implications.

Alloys↗
PubMed1998

Determinants of regional myocardial function in patients with chronic significant coronary stenosis or occlusion.

BACKGROUND: Our aim was to study the effect of collateral flow, stenosis severity, antegrade flow, and location of the lesion on regional myocardial function in patients with chronic left anterior descending (LAD) coronary artery disease. METHODS AND RESULTS: Seventy-four patients who underwent coronary angiography and ventriculography were divided into three groups: group A (n = 9), patients with normal coronary angiogram and ventriculogram; group B (n = 32), patients with LAD stenosis >75%; and group C, 33 patients with LAD occlusion. The effect of collateral flow, stenosis severity, location, and antegrade flow on regional myocardial function in the LAD territory was studied. Regional function was impaired in both groups B and C. In group B, univariate analysis confirmed that antegrade flow had a significant effect on regional function (p < 0.02). With the use of multiple regression, none of the other variables had an additional independent effect. In group C, no significant correlation was found between regional function and the study variables by univariate analysis; however, multiple regression revealed a significant correlation between anterobasal function, the lesion site (p = 0.01), and collateral flow (p = 0.02). CONCLUSIONS: In patients with LAD stenosis, antegrade flow has the strongest effect on regional myocardial function, with no additional effect of visible collaterals. In patients with LAD occlusion, both angiographic collateral flow and the site of the lesion have a significant effect on the function of the anterobasal area.

Blood Flow Velocity↗
PubMed1998

Cone and plate(let) analyzer: monitoring glycoprotein IIb/IIIa antagonists and von Willebrand disease replacement therapy by testing platelet deposition under flow conditions.

Exposure of citrated whole blood samples to polystyrene plates under flow conditions with the cone and plate(let) analyzer (CPA) results in surface immobilization of plasma von Willebrand factor (vWF) followed by platelet deposition. Staining the plates allows measurement of the percentage of surface covered (SC) by the adhered particles and their average size (AS). Both SC and AS parameters depend on platelet count and hematocrit level and reach maximal values after 2 minutes; only AS is shear rate dependent. Under optimal assay conditions (2 minutes at 1800 sec(-1)) normal blood samples yielded an SC of 14.9% +/- 2.5% and an AS of 39.4 +/- 5.2 microm2. Severe von Willebrand disease (eight patients) yielded low SC (5.2% +/- 2.1%), which was restored to normal by testing with vWF precoated surfaces. Glanzmann's thrombasthenia (six patients) samples demonstrated no adhesion of platelet at all. Blocking of the glycoprotein (GP) IIb/IIIa receptor by the chimeric antibody abciximab, and of the GPIb by a recombinant vWF fragment, have yielded a dose-response inhibition demonstrating the crucial role of these receptors in platelet deposition on polystyrene plates in this system. Evaluation of a patient with severe von Willebrand disease receiving replacement vWF factor VIII therapy revealed a comparable response as tested by both the CPA and the Ricof methods. In vitro testing of the GPIIb/IIIa blocking by a nonpeptidic analogue tirofiban and abciximab revealed a good correlation between the CPA test and the routine aggregometry. Eleven patients treated by abciximab after coronary angioplasty were studied by the CPA during the first 24 hours, demonstrating a marked decrease in SC and AS, with some diversity in the responses. We conclude that the CPA test is suitable for evaluation of primary hemostasis and for monitoring of anti-platelet drugs.

Blood Circulation↗
PubMed1998

Thermographic imaging in the beating heart: a method for coronary flow estimation based on a heat transfer model.

Intraoperative thermographic imaging in open-chest conditions can provide the surgeon with important qualitative information regarding coronary flow by utilizing heat transfer analysis following injection of cold saline into the aortic root. The heat transfer model is based on the assumption that the epicardial temperature changes are mainly due to convection of heat by the blood flow, which may, therefore, be estimated by measuring the temperature variations. Hearts of eight dogs were exposed and imaged by a thermographic camera. Flow in the left arterial descending (LAD) coronary branch was measured by a transit-time flowmeter. 20 ml of cold saline were injected into the aortic root (just after the aortic valve) and the epicardial temperature images were recorded at end-diastole, for 20-30 s. Different flow rates were achieved by 1 min occlusion of the LAD, which affected a reactive hyperemic response. The dynamics of the temperature in the arterial coronary tree was obtained by averaging the temperature over an edge-detected arterial segment for each frame. The heat transfer equation was curve-fitted, and the flow-dependent heat transfer index was correlated with the experimentally determined coronary flow (r = 0.69, p < 0.001). In summary: a method for quantitative estimation of coronary blood flow by thermography and heat transfer analysis was developed and tested in animal experiments. This method can provide important information regarding coronary blood flow during open-chest surgical procedures.

Animals↗
PubMed1998

beStent--the serpentine balloon expandable stent: review of mechanical properties and clinical experience.

The objective of this study was to present the engineering and clinical aspects of a new balloon expandable coronary stent. A new tubular, serpentine design stainless steel balloon-expandable stent, the beStent, was designed based on clinical requirements for stents and has been clinically evaluated in multiple sites. The stent is featured by terminal gold markers and rotational junctions that assure no shortening upon expansion and lead to orthogonal locking, maximizing radial strength. In terms of methods and results, the stent was clinically evaluated in the framework of a pilot evaluation in a variety of lesion types. The short- and long-term results evaluated during the course of the beStent multicenter pilot evaluation and in our single center study are reported. A variety of patients were included, including patients with long complex lesions, restenosis lesions, and total occlusions. Short-term clinical success with stenting was achieved in more than 97% of the cases. Subacute thrombosis was low in 1% of the cases. Clinical restenosis rates were acceptable with an overall 85% 6 month event free survival. In conclusion, the mechanical features of the stent providing its flexibility, scaffolding properties, radial strength, and absence of shortening were tested in a clinical study, showing that it is safe and effective for treating simple as well as long and complex lesions associated with coronary disease with a relatively low rate of complications.

Adult↗
PubMed1998

Estimation of coronary blood flow by ECG gated cardiac thermography in open-chest conditions.

Thermography is suggested as a tool to estimate myocardial and coronary epicardial flow in open-chest heart surgery. To test the feasibility and compare various methods for coronary flow estimation in open-chest surgery, thermographic imaging was applied to eight open-chest dogs which were injected with cold saline into the aortic root. Blood flow in the left arterial descending (LAD) coronary vessel was measured by a transit-time flowmeter. ECG gated images were acquired for 20-30 s, while the cold saline (20 ml) was injected into the aortic root. Several flow levels were achieved during repeated hyperaemic response to transient occlusions of the LAD. A temperature response curve for each flow level was obtained by averaging over an edge-detected arterial segment for each image frame. Several indices were calculated from the temperature curve and correlated with the measured coronary flow. These include: an index based on a corrective heat transfer model (r = 0.69, p < 0.001), the slope of the descending part of the response curve (r = 0.76, p < 0.001), the peak temperature difference (r = 0.66, p < 0.001), and the area above the temperature response curve (r = 0.61, p < 0.01). As shown, coronary flow can be estimated quantitatively by intraoperative epicardial thermography, and may therefore provide important on-line information regarding blood flow during open-chest surgical procedures. Further studies are required for optimal application of this technique so as to increase its potential as a valid clinical tool.

Animals↗
PubMed1997

Acute and 30-day results of the serpentine balloon expandable stent implantation in simple and complex coronary arterial narrowings.

We report the acute and 30-day results with a new serpentine-design, tubular, stainless steel, balloon-expandable stent (beStent) in the first 100 patients. One hundred forty-eight stents were used to treat 103 narrowings in the left anterior descending (n = 46), left circumflex (n = 20), and right coronary (n = 37) arteries. There were 85 de novo and 18 restenotic lesions (lesion length: < 10 mm [31], 10 to 20 mm [43] > 20 mm [29]; lesion type: A [10] B1 [29], B2 [20], C [44]; total occlusions, 23. More than 1 stent was used in 31 patients for treatment of long lesions that could not be covered by 1 stent. The stents used were 15-mm (n = 106), 25-mm (n = 38), or 35-mm (n = 4) long. Stent implantation strategy involved predilatation, deployment, and high-pressure dilatation, using the same balloon if possible. Clinical in-hospital success was 97% (2 patients had stent thrombosis that was recanalyzed, with myocardial infarction developing in 1, and 1 patient died on day 14 from retroperitoneal bleeding treated with surgery and complicated by sepsis). One-month event-free survival was 96%, with 1 death on day 21 due to hypertensive crisis. There were no other major adverse cardiac events in this first complex cohort of patients. In conclusion, the initial experience with this stent demonstrates its safety and efficiency for treating simple and complex coronary disease, with a relatively low rate of complications. Long-term clinical follow-up awaits further investigation.

Angioplasty, Balloon, Coronary↗