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Biomedical subjects

Rafael Beyar

Publications and source records attributed to Rafael Beyar.

At least 37 records · Page 2Linked to original sources
PubMed2005

Effect of obesity on the relationship between plasma C-reactive protein and coronary artery stenosis in patients with stable angina.

INTRODUCTION: The association between plasma C-reactive protein (CRP) and the extent of coronary artery disease (CAD) in patients with stable angina remains controversial. Obesity is strongly associated with elevated CRP levels, potentially confounding the relationship between CRP and CAD severity. METHODS AND RESULTS: We studied 830 subjects without CAD and 218 patients with CAD undergoing elective coronary angiography. Geometric means of CRP were computed in a two-way analysis of covariance model in which study participants were stratified into nine groups according to CAD status (no CAD, single-vessel disease or multivessel disease) and tertiles of BMI. There was a significant interaction between CAD and categories of BMI with regard to CRP level (P=0.002). In the lower tertile of BMI, patients with CAD had markedly higher CRP concentration compared to control subjects (1.16, 1.80 and 2.82 mg/L in subjects without CAD, patients with single-vessel disease and patients with multivessel disease, respectively; P=0.003). However, the relationship between CRP and CAD became weaker for patients in the second BMI tertile (P=0.15), whereas no significant relationship was observed for patients in the third BMI tertile (P=0.75). In patients undergoing coronary angioplasty (n=195), BMI was independently related to the magnitude of the angioplasty-induced CRP elevations (P=0.002). CONCLUSION: The level of obesity is essential to the interpretation of the relationship between CRP and severity of CAD. The production of inflammatory mediators with increasing levels of obesity becomes the dominant determinant of plasma CRP levels and masks the vascular contribution due to CAD.

Angina Pectoris↗
PubMed2005

Impact of body mass index on the outcome of patients with multivessel disease randomized to either coronary artery bypass grafting or stenting in the ARTS trial: The obesity paradox II?

The effect of body mass index (BMI) on outcomes after coronary artery revascularization remains controversial. We studied 1,203 patients who had multivessel coronary artery disease and underwent stenting (n = 599) or coronary artery bypass grafting (CABG; n = 604) in the Arterial Revascularization Therapies Study. Patients were assigned to 1 of 3 groups according to BMI: <25, 25 to 30, and >30 kg/m(2). At 3-year follow-up, the incidence of death, cerebrovascular events, or myocardial infarction was similar for these BMI categories regardless of the revascularization technique used. Rates of repeat revascularization procedures were significantly higher among patients who had been randomized to stenting but were similar across BMI groups. For patients who had been randomized to undergo CABG, there was a significant decrease in repeat revascularization procedures in obese patients (p = 0.03). Among patients who underwent stenting, BMI had no effect on the 3-year combined end point of rate of major adverse cardiac or cerebrovascular events. Among patients who underwent CABG, major adverse cardiac or cerebrovascular event rates were significantly lower for patients who were obese (11%) or overweight (16%) compared with patients who had a normal BMI (24%; p = 0.008). Thus, in a large cohort of patients who had multivessel coronary artery disease and underwent surgical or percutaneous revascularization, BMI had no effect on 3-year outcome of those who underwent stenting. Conversely, among patients who underwent CABG, those who were overweight or obese had a significantly better outcome than did those who had a normal BMI with regard to survival without major adverse cardiac or cerebrovascular events, mainly due to lower rates of repeat revascularization procedures.

Angioplasty, Balloon, Coronary↗
PubMed2005

Prospective motion correction of X-ray images for coronary interventions.

A method for prospective motion correction of X-ray imaging of the heart is presented. A 3D + t coronary model is reconstructed from a biplane coronary angiogram obtained during free breathing. The deformation field is parameterized by cardiac and respiratory phase, which enables the estimation of the state of the arteries at any phase of the cardiac-respiratory cycle. The motion of the three-dimensional (3-D) coronary model is projected onto the image planes and used to compute a dewarping function for motion correcting the images. The use of a 3-D coronary model facilitates motion correction of images acquired with the X-ray system at arbitrary orientations. The performance of the algorithm was measured by tracking the motion of selected left coronary landmarks using a template matching cross-correlation. In three patients, we motion corrected the same images used to construct their 3D + t coronary model. In this best case scenario, the algorithm reduced the motion of the landmarks by 84%-85%, from mean RMS displacements of 12.8-14.6 pixels to 2.1-2.2 pixels. Prospective motion correction was tested in five patients by building the coronary model from one dataset, and correcting a second dataset. The patient's cardiac and respiratory phase are monitored and used to calculate the appropriate correction parameters. The results showed a 48%-63% reduction in the motion of the landmarks, from a mean RMS displacement of 11.5-13.6 pixels to 4.4-7.1 pixels.

Algorithms↗
PubMed2005

From organ to molecules: steps and consequences.

The classic cardiac research programs revolved around measurable properties such as pressures, work done, vascular blood flow, electrical propagation, and other such parameters that defined the global heart functions in health and decease. Consistently, the first Henry Goldberg Workshop, held in Haifa in 1984, focused on the interactions between cardiac mechanics, electrical activation, perfusion, and metabolism of the whole heart. Questions focused on the macroscale cardiac function and performance. These studies involved engineering science, simulation, and modeling tools that were essential for the understanding of the complex interactions within the cardiac system. Three-dimensional imaging, ventricular structure, fiber mechanics, circulation and cardiovascular flow, electrical propagation, and blood pumping were all major foci of research at that time. However, it was soon obvious that in order to understand organ level characteristics, one must explore the complex cellular and intracellular control mechanisms; these became the foci of our subsequent workshops. Better understanding of organ level performance required integrated studies of organ and tissue structure and function with genetic, molecular, and cellular characteristics, including cellular communication and ionic and molecular signaling. Analysis of the cardiac system thus depends on continuous probing of the heart system with modern measurement techniques and on integrating data and acquired knowledge with analytical models, constantly evolving to match reality.

Heart↗
PubMed2005

The impact of GP IIb/IIIa inhibitors during primary percutaneous coronary intervention in acute myocardial infarction patients.

The use of glycoprotein (GP) IIb/IIIa inhibitors during percutaneous coronary interventions (PCI) in the acute phase of myocardial infarction (AMI) is still a matter of debate. The aim of the present study was to compare the outcomes of patients with acute ST-segment elevation myocardial infarction who underwent primary PCI and were concomitantly treated with GP IIb/IIIa inhibitors with those who were not treated with these drugs. Between January 1996 and November 2003, a total of 418 consecutive patients underwent PCI in the setting of ST-segment elevation AMI. At the operator's discretion, 287 patients were concomitantly treated with GP IIb/IIIa inhibitors and 115 patients were not. Angiographic success and final TIMI 3 flow in the infarct-related artery was achieved more frequently in patients treated with GP IIb/IIIa inhibitors (90% vs. 77%; p=0.001). The in-hospital composite endpoint of death, reinfarction and bleeding complications was significantly better in patients treated with GP IIb/IIIa inhibitors (4% vs. 12%; p=0.005). Furthermore, the adjusted 12-month survival rate was significantly better in these patients (RR: 2.99, CI: 1.29-6.9; p=0.01). Therefore, adjunctive therapy with GP IIbIIIa inhibitors during primary PCI is associated with improved short-term outcomes and one-year survival without an increased risk of bleeding.

Abciximab↗
PubMed2004

Evaluation of routine functional testing after percutaneous coronary intervention.

Following percutaneous coronary intervention, 348 patients were randomized to either routine or selective functional testing strategies. For the primary end point of maximal exercise endurance on a treadmill at 9 months, achievement was similar in the routine and selective groups. For the secondary end points measuring functional status and quality of life, scores were also similar. There was little difference in the rates of invasive cardiac procedures for the 2 groups at 9 months.

Angioplasty, Balloon, Coronary↗
PubMed2004

Vertebral artery stenting using distal emboli protection and transcranial Doppler.

Recent studies have shown the feasibility and safety of the percutaneous approach for the treatment of vertebrobasilar disease using either balloon angioplasty alone, coronary stents, or combined angioplasty followed by stenting. The major concern in performing percutaneous procedures for the treatment of obstructive disease of the vertebrobasilar circulation involves the risk of embolic phenomena. We describe the successful treatment of a symptomatic patient with bilateral vertebrobasilar disease utilizing a distal protection filter during stenting with simultaneous use of transcranial Doppler to measure microembolization and vertebral artery blood flow during the procedure.

Blood Flow Velocity↗
PubMed2004

Neointimal vascularization and intimal thickening in response to self-expanding stents: a swine model.

BACKGROUND: Neovascularization has been suggested as a biological response to vessel injury and associated with restenosis. Self-expanding (SE) stents generate a lasting force on the arterial wall and may lead to an increased arterial response with time. OBJECTIVES: To characterize the process of neovascularization with SE stents, and to correlate it with vascular injury, inflammation and intimal proliferation. METHODS: Sixty-nine SE stents were im-planted in 37 non-atherosclerotic pigs.Detailed, multisection histological examination was performed at 15 days, 1, 3 and 6 months post-deployment. Neo-vascularization in addition to other histologic parameters where determined and scored. RESULTS: Intravascular-ultrasound-based average vessel diameter was 3.3 +/- 0.04 mm; stent size was 3.75 +/- 0.35 mm leading to an oversizing ratio of 1.14 +/- 0.15. Intimal thickness (IT), inflammatory score (IFS) and vascularization score(VAS) reached peak values at three months (IT = 344 +/- 202 1m, IFS = 0.91 +/- 0.5, and VAS = 1.56 +/- 0.8). In contrast,the injury score (INS) continued to increase at all time-points, with maximum value at six months (INS = 1.6 +/- 0.7). Both vascularization and inflammation indices increased with an increase in the injury score (p < 0.01). When vessels were divided according to vascularization score (VAS <1.5 and >1.5) there was a significant difference in IT. CONCLUSION: Neovascularization in response to SE stents is a time-dependent phenomenon and interacts with injury and inflammation. The remodeling of the vessel wall caused by the sustained force of the SE stent on the arterial wall enhances the formation of neovascularization. Neointimal formation is related to the degree of neovascularization.

Animals↗
PubMed2004

"No-reflow" phenomenon during percutaneous carotid angioplasty in a scleroderma patient.

Atherosclerosis remains the most common etiology of carotid artery stenosis, but other systemic diseases can also cause this disease. Percutaneous carotid angioplasty and stenting (CAS) with and without distal embolic protection devices is gaining acceptance as the treatment of choice. No-reflow phenomenon due to distal embolization has been previously described mainly during percutaneous intervention of degenerated saphenous vein graft. We describe a patient with systemic sclerosis who underwent CAS with distal embolic protection device with occurrence of no-reflow phenomenon during the procedure that resolved after retrieval of the filter device.

Aged↗
PubMed2004

Novel approaches to reduce restenosis.

Percutaneous coronary intervention (PCI) has become the major technique of revascularization and is replacing cardiac bypass surgery. PCI is typically performed today with a combination of balloon dilatation and stents, with some 80% of the procedures followed by stent implantation. After balloon dilatation, an acute recoil response can be responsible for some 30% immediate loss of the vessel lumen at the end of the procedure. Restenosis is the late loss (within 6-9 months) of the lumen of the artery due to vessel shrinkage (negative remodeling) and an intense proliferative response to the local injury. Stents reduce restenosis by 30% by preventing acute recoil and reducing long-term negative arterial remodeling. Yet, long-term pressure of the stent struts against the vessel wall stimulates an increased arterial proliferative response, which is the major cause for stent restenosis. Limiting the proliferative response by local radiation (brachytherapy) have reduced restenosis, at a cost of increased late thrombogenicity and delayed vessel healing. Drug-eluting stents have shown extremely promising results in limiting restenosis. Rapamycin and paclitaxel are the major drugs in eluting stents in clinical use today, having reduced restenosis to less than 10%. Local cellular and genetic therapy approaches are currently at preclinical phases. The future of percutaneous revascularization remains bright and will enhance the effectiveness of PCI as the primary revascularization therapy for coronary artery disease.

Brachytherapy↗
PubMed2004

Augmentation of dilated failing left ventricular stroke work by a physiological cardiac assist device.

A novel physiological cardiac assist device (PCAD), otherwise known as the LEVRAM assist device, which is synchronized with the heartbeat, was developed to assist the left ventricle (LV) in chronic heart failure (CHF). The PCAD utilizes a single cannula, which is inserted in less than 15 s through the apex of the beating LV by means of a specially designed device. Blood is withdrawn from the LV into the PCAD in diastole and is injected back to the LV, through the same cannula, during the systolic ejection phase, thereby augmenting stroke volume (SV) and stroke work (SW). CHF with dilated LV was induced in sheep by successive intracoronary injections of 100-microm beads. The sheep (92.2 +/- 25.9 kg, n = 5) developed stable CHF with increased LV end-diastolic diameter (69.4 +/- 3.3 mm) and end-diastolic volume (LVEDV = 239 +/- 32 mL), with severely reduced ejection fraction (23.8 +/- 7.6%), as well as mild-to-moderate mitral regurgitation. The sheep were anesthetized, and the heart was exposed by left thoracotomy. Pressure was measured in the LV and aorta (Millar). The SV was measured by flow meters and the LV volume by sonocrystals. Assist was provided every 10 regular beats, and the assisted beats were compared with the preceding unassisted beats, at the same LVEDV. The PCAD displaced 13.6 +/- 3.4 mL, less than 8% of LVEDV. Added SW was calculated from the assisted and control pressure-volume loops. The efficiency, defined as an increase in SW divided by the mechanical work of the PCAD, was 85.4 +/- 16.9%. We conclude that the PCAD, working with a small displaced blood volume in synchrony with the heartbeat, efficiently augments the SW of the dilated failing LV. The PCAD is suggested for use as a permanent implantable device in CHF.

Animals↗
PubMed2004

Percutaneous coronary interventions in diabetic patients: is complete revascularization important?

BACKGROUND: The long-term prognosis of diabetic patients with multivessel coronary artery disease (CAD) treated by surgical or percutaneous coronary revascularization is significantly worse as compared to non-diabetics. Lower rates of complete revascularization may be one factor that influences the poor long-term outcome in the diabetic population. Our study assessed the impact of complete revascularization on the long-term prognosis in diabetic patients with CAD treated by percutaneous coronary intervention (PCI). The study included 658 consecutive diabetic patients (mean age, 60.9+/-10.1 years) who underwent PCI. Multivessel disease was present in 352 patients (53.5%). Revascularization was complete in 94 (26.7%) and incomplete in 258 (73.3%) patients with multivessel disease. Reasons for incomplete revascularization included angioplasty of only the culprit lesion (43.4%); small vessel size (22.8%); moderate lesion, defined as diameter stenosis 50-69% (18.6%); chronic total occlusion of the non-intervened vessel (6.6%); and others (8.5%). Overall survival rate at 5 years was 87.4%. Patients who underwent complete revascularization had a 94.5% survival rate, compared to 83.0% for those with incomplete revascularization (p<0.001). Similarly, the rates of myocardial infarction-free survival were significantly higher in patients with complete versus incomplete revascularization (92.9% versus 79.9%, respectively). Incomplete revascularization was the most powerful independent predictor of mortality at follow-up (relative risk 95% confidence interval, 1.54-7.69; p=0.003). Our data suggest that complete myocardial revascularization may improve the long-term prognosis after PCI of diabetic patients with multivessel CAD.

Adult↗
PubMed2004

Traditional versus automated injection contrast system in diagnostic and percutaneous coronary interventional procedures: comparison of the contrast volume delivered.

UNLABELLED: Contrast injection with a manual stopcock-manifold system is the standard technique during diagnostic coronary angiography or percutaneous coronary intervention (PCI). The ACIST Injection System is a new automatic injection device that allows online hemodynamic monitoring, as well as control of injection rate and amount of contrast to be delivered. The aim of the study was to compare the amount of contrast media delivered using the two methods, i.e., the traditional (manual injection plus standard power injection for the left ventriculography using the ANGIOMAT-6000) versus the ACIST System programmed injector. A total of 453 consecutive patients underwent diagnostic cardiac catheterization and/or PCI at our institution. Patients were randomly assigned to either automated contrast injection with the ACIST device (n = 253) or to conventional contrast injection using a stopcock-manifold system and contrast injection by hand syringe (n = 200). In the diagnostic catheterization group, the mean quantity of contrast volume was significantly lower in the ACIST group compared to the control group (130 +/- 60 ml versus 257 +/- 64 ml, respectively; 97.4% more contrast media; p < 0.001). When the data were analyzed for patients who underwent diagnostic catheterization plus PCI, the mean quantity of contrast volume was 228 +/- 90 ml versus 350 +/- 94 ml, respectively (53.8% more contrast media; p < 0.001). For patients who underwent PCI alone, the mean quantity of contrast volume was 175 +/- 76 ml versus 275 +/- 100 ml, respectively (57.3% more contrast media; p = 0.009). When only the total volume of contrast media delivered to the patient was considered (not including the contrast wasted outside), the results were very similar. CONCLUSION: There was a significant reduction in the total volume of contrast media used (amount injected to the patient as well as the amount wasted) and in the net amount of contrast delivered to the patient with the ACIST power device when compared to the traditional method of manual contrast injection.

Angioplasty, Balloon, Coronary↗
PubMed2003

Stent deployment failure: reasons, implications, and short- and long-term outcomes.

Stents have revolutionized percutaneous coronary interventions (PCI), impacting on both acute and long-term results. However, despite improvements in stent design, stent deployment failure is not an unusual event. The aim of the present study was to assess the frequency and causes of stent deployment failure, as well as the outcome of these patients. Between 1997 and 2001, a total of 3,537 patients underwent stent-assisted PCI and delivery of 5,275 stents was attempted. In the majority of patients (118; 78.1%), stenting was performed as provisional; in the remaining 33 (21.8%) as a bailout procedure. A total of 175 (3.3%) stents in 151 (4.3%) patients failed. Failure to deliver the stent to the lesion site was the main cause in 139 patients (92%) and failure either to expand adequately the stent or premature disengagement of the stent from the balloon in only 12 patients (8%). Peripheral stent embolization occurred in 10 (0.3%) patients. Deployment of a different stent in place of the failed one was attempted in 122 patients and was successful in the majority (108; 88.5%). In-hospital major adverse cardiac events were observed in six patients (4%): three patients required emergency coronary artery bypass surgery, two had a myocardial infarction (MI), and one patient underwent urgent repeat coronary intervention. At a mean follow-up of 32.2 +/- 17.7 months, 22 major adverse cardiac event occurred in 17 patients (11.2%): 1 cardiac death, 3 patients had an MI, and 18 patients required target vessel revascularization. One-year event-free survival for the whole group was 91.2%. Patients with stent embolization did not have any major adverse cardiac or vascular events. Thus, the rate of stent deployment failure in our series was 3.3%, mainly due to failure to deliver the stent to the site. Another stent was successfully deployed in the majority of cases and these patients had favorable short- and long-term outcomes.

Aged↗
PubMed2003

Diagnostic coronary angiography induces a systemic inflammatory response in patients with stable angina.

BACKGROUND: Systemic markers of inflammation increase after percutaneous coronary intervention (PCI). The rise in inflammatory markers after PCI is frequently attributed to the inflammatory stimulus associated with coronary artery injury during balloon inflation and coronary stent implantation. The aim of this study was the determine whether diagnostic coronary angiography performed in patients with stable angina triggers a systemic inflammatory response. METHODS: We prospectively studied patients with chronic stable angina undergoing either coronary angiography (n = 13) or coronary angiography followed by PCI (n = 13). Peripheral blood samples were obtained before and 24 hours, 48 hours, and 4 weeks after the procedure and analyzed for C-reactive protein (CRP), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-alpha). Patients with periprocedural myocardial necrosis were excluded. RESULTS: There was a significant increase in CRP levels at 24 and 48 hours in both the coronary angiography (P <.05) and PCI (P <.01) groups. IL-6 levels peaked at 24 hours in both the coronary angiography (median, 2.5-9.5 pg/mL; P =.01) and PCI (median, 3.0-8.2 pg/mL; P <.005) groups. At 4 weeks, both CRP and IL-6 returned to baseline levels. TNF-alpha levels were unchanged with either coronary angiography or PCI. The magnitude of the rise of CRP and IL-6 levels was not significantly different between the groups. There was a fair correlation between baseline and peak postprocedural levels of CRP (r = 0.67, P =.008) and IL-6 (r = 0.48, P =.016). CONCLUSION: Uncomplicated diagnostic coronary angiography triggers a systemic inflammatory response in patients with stable angina. The contribution of coronary angiography should be considered in interpreting the significance of the systemic inflammatory response observed after PCI.

Angina Pectoris↗