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Biomedical subjects

A Machraoui

Publications and source records attributed to A Machraoui.

At least 19 recordsLinked to original sources
PubMed2005

Normal angiogram in acute coronary syndrome-preangiographic risk stratification, angiographic findings and follow-up.

BACKGROUND: Coronary angiographies performed during acute coronary syndrome show different coronary morphologies-vessel occlusions, thrombi and various types of stenoses. In a few cases of acute coronary syndrome, angiography reveals normal coronary arteries. It is the purpose of this study to analyze this specific subset of patients who presented with an acute coronary syndrome but had a normal coronary angiogram with respect to the preangiographic diagnostics, risk stratification and clinical follow-up. METHODS AND RESULTS: A total of 897 coronary angiographies were performed as an emergency procedure in our institution. The majority of patients (n = 821) presented with coronary artery disease and the majority was treated by mechanical revascularization (86.3%). In 76 patients (8.5%), no coronary artery stenosis was documented. However, according to the preangiographic risk stratification, coronary artery disease was expected in these patients. Observations documented angiographically included coronary spasms (6.6%) and muscle bridges (5.3%). During a mean follow-up of 11.2 +/- 6.4 months, one patient developed an acute myocardial infarction requiring coronary intervention. All other patients were free of any cardiac event. CONCLUSIONS: In summary, we have to consider that coronary angiography may not always detect the cause of myocardial ischemia in every patient. There is a small group of patients with normal coronary angiograms during acute coronary syndrome. Additional diagnostic procedures like intravascular ultrasound (IVUS) or the assessment of intracoronary physiological parameters may increase the diagnostic value of angiography.

Acute Disease↗
PubMed2002

Coronary artery stenting in diabetes mellitus--unfavourable clinical outcome due to increased rate of myocardial ischemia and percutaneous interventions.

Diabetes mellitus is one of the major risk factors for cardiovascular diseases. The aim of this study was to analyze if diabetic patients, compared to nondiabetic patients, have a worse angiographic and clinical success rate and a reduced clinical and angiographic outcome at three-months follow-up after coronary artery stenting according to postprocedural complications, recurrent angina, myocardial ischemia, restenosis and revascularization. A total of 307 unselected patients with coronary artery disease and myocardial ischemia who underwent intracoronary stenting were included in this study. Diabetes was present in 49 patients. Morphological criteria, angiographic results and clinical in-hospital outcome did not differ significantly between both groups. At follow-up diabetics presented significantly more often recurrent angina and myocardial ischemia. The rate of restenosis and target lesion revascularization was not different. Among diabetics, the rate of percutaneous coronary interventions because of different lesions was significantly increased. Diabetes does not reduce the angiographic result initially and at follow-up after coronary artery stenting. Diabetes mellitus limits the clinical outcome because of recurrent angina, myocardial ischemia and the need of coronary interventions.

Aged↗
PubMed2002

[Cardiomyopathies].

Cardiomyopathies are characterized by ventricular enlargement, thickness or stiffness. According to the WHO classification, diseases of unknown origin (cardiomyopathies) are distinguished from heart muscle diseases with known origin or having a relationship with other organ systems (specific heart muscle diseases). Cardiomyopathies are characterized by a worsening of cardiac work resulting from failure of the pump function and ventricular compliance or from severe arrhythmias. Consequences in prognosis and work capacity depend on the degree of heart failure and arrhythmias.

Cardiomyopathies↗
PubMed2001

Efficacy and safety of ticlopidine monotherapy versus ticlopidine and aspirin after coronary artery stenting: follow-up results of a randomized study.

A combined antiplatelet treatment with ticlopidine and aspirin has been accepted as standard pharmacological regimen after coronary artery stenting. No data of a randomized trial are available on ticlopidine monotherapy. This prospective, randomized monocenter trial investigates the role of ticlopidine monotherapy versus combined antiplatelet therapy with ticlopidine and aspirin in unselected patients undergoing coronary artery stenting. After successful placement of 378 coronary artery stents, two hundred and forty-three consecutive patients were randomly assigned to receive antiplatelet therapy with 2 x 250 mg ticlopidine (121 patients) or a combination of 2 x 250 mg ticlopidine plus 100 mg aspirin (122 patients) daily. The primary endpoint included the absence of death, cardiac events and vascular access-site complications during the in-hospital phase. Angiographic and clinical assessment was repeated at the 3-month follow-up exam. Two hundred and thirty-seven patients (97.5%) were free from cardiac and non-cardiac events. Stent thromboses were seen in 2 patients of the combined treatment group, while none were observed in the monotherapy group. No statistically significant differences were found between the 2 groups regarding the primary endpoint. Angiography performed in 210 patients (86.4%) at follow-up revealed a restenosis rate of 29.4% in the combined treatment group and 27.8% in the monotherapy group. Monotherapy with ticlopidine is as safe and effective as a combined regimen of ticlopidine plus aspirin after coronary artery stenting in an unselected patient population. These results need to be confirmed in a larger multicenter trial.

Aged↗
PubMed2000

Coronary morphologic findings after stent implantation.

Clinical studies demonstrated a reduction of acute complications by high-pressure stenting. This study was performed to correlate the histomorphologic changes of the vessel wall after coronary stenting with stent expansion pressure. We studied the effects of intravital and postmortem stenting on coronary morphology in human hearts. Artifact-free analysis and morphometry of the artery segments' cross section was performed after plastic resin embedding and cutting and grinding sectioning. By comparing intra- and postmortem findings we demonstrated that postmortem stent implantation can serve as an adequate model to study the mechanical effects of coronary stenting. A consistent histologic feature was eccentric stent expansion. Larger calcified areas of the vessel wall were not deformed by implanted stents. The highest degree of vessel injury and deformation was apparent in anatomically "nondiseased" or only slightly fibrotic parts of the arterial wall. Dissections were predominantly located directly adjacent to calcified plaques and appeared as "half-moon"-like tears reaching into the arterial media. A statistically significant stent lumen gain was found when the implantation pressure was increased up to 15 atm. Stent symmetry was not influenced by the applied implantation pressure but depended mostly on local coronary morphology. Thus, increasing implantation pressures during coronary stenting seemed to improve the stenting result up to 15 atm. When applying histomorphologic criteria, the higher pressures (>15 atm) did not cause further optimization of stent expansion. Morphometric analysis of stents implanted postmortemly and intravitally revealed comparable results. Postmortem stenting seems to be an appropriate model for studying stent expansion and stenting results in human coronary arteries.

Aged↗
PubMed2000

Hyperfibrinogenemia increases the risk of cardiac events after coronary artery stenting.

Primary success rates, and the angiographic and clinical outcome after percutaneous coronary intervention, are influenced by many different factors. Clinical features and morphologic characteristics of the target lesion are important. Also, interventionally caused endothelial trauma may trigger atherogenetic and procoagulatory factors leading to intraluminal thrombosis. The study population consisted of 228 consecutive, unselected patients with symptomatic coronary artery disease or exercise-induced myocardial ischemia and coronary artery stenoses eligible for percutaneous intervention. We analyzed different clinical, morphological, and laboratory (total cholesterol, high-density lipoprotein-cholesterol, low-density lipoprotein-cholesterol, triglycerides, fibrinogen) features in those patients with adverse cardiac events (stent thrombosis, myocardial infarction, urgent target vessel revascularization, death) after primary successful coronary artery stenting, compared with a control group without adverse events. In the group with adverse cardiac events we found a significantly higher level of fibrinogen compared with the control group. Other laboratory data and clinical characteristics were not significantly different between the two groups. The study shows a possible association between hyperfibrinogenemia and adverse cardiac events after intracoronary stenting. In clinical practice, the potential role of elevated levels of fibrinogen in an unfavorable outcome after percutaneous coronary interventions should be considered when planning coronary artery stenting.

Aged↗
PubMed2000

[Scanning electron microscopic analysis of vessel wall reactions after coronary stenting].

High restenosis rates are still a major factor limiting the use of minimal invasive coronary stenting. Tissue reactions to the implanted alloplastic endoprostheses are still barely understood. 18 coronary artery segments 32 hours up to 340 days after stent implantation of 16 patients were post-mortem investigated. The pathomorphological findings of the vessel wall after stent insertion were studied by scanning electron microscopy (SEM). Stent integration can be divided with intraindividual differences in three phases: In the acute phase (<6 weeks) the border between vascular lumen and arterial wall is constituted by a thin, multi-layered thrombus. During the time course of integration, increasing amounts of Smooth Muscle Cells (SMC) and extracellular matrix can be detected. No endothelial cells can be found in the implantation zone. In the intermediate phase (6 weeks to 12 weeks) the neointima consists of extracellular matrix and increasing numbers of SMC. The borderline between lumen and neointima is generated by SMC and extracellular matrix. Increasing amounts of endothelial cells are found on the luminal surface of the stent neointima. Complete reendothelization is first noted in the chronic phase three months after stenting. Matrix structures are increasing whereas the amount of SMC decreases. In all phases of stent incorporation, the alloplastic stent material is covered by a thin (few nanometer) proteinaceous layer.

Aged↗
PubMed2000

Segmentation of 3D intravascular ultrasonic images based on a random field model.

Segmentation of intravascular ultrasound images provides important information about the degree of vessel obstruction as well as about the shape and size of plaques. To address the problems of inter- and intra-observer variances associated with conventional manual tracing, a fully automated segmentation was developed. The algorithm is based on the optimisation of a maximum a posteriori estimator, implementing the Rayleigh distribution of speckle and a priori information about the contours. Within 3D image sets, additional information by the blood flow resulting in a decorrelation of the pixels within the luminal boundary is used to initialise the segmentation. To accelerate the estimation, dynamic programming was used. The segmentation algorithm was realised as a Windows 95 application on a Pentium II/233 MHz and delivered reliable and reproducible results independent of the catheter position and the total image brightness (except overflow). In contrast, contours drawn by two physicians for an evaluation of 29 clinical cases showed large intra- and inter-observer variances. In vivo images were acquired with a 20 MHz transducer array (EndoSonics InVision). Comparison with the contours drawn by the physicians and histology demonstrates the potential of the segmentation algorithm.

Algorithms↗
PubMed2000

Acute and chronic tissue response to coronary stent implantation: pathologic findings in human specimen.

OBJECTIVES: The aim of our study was to analyze the cellular components of neointimal tissue regeneration after coronary stenting. BACKGROUND: High restenosis rates are a major limiting factor of coronary stenting. To reduce the occurrence of restenoses, more insights into the mechanisms leading to proliferation and expression of extracellular matrix are necessary. METHODS: Twenty-one autopsy cases with coronary stents implanted 25 h to 340 days before death were studied. The stented vessel segments were analyzed postmortem by light microscopy and immunohistochemical staining. RESULTS: In the initial phase stents are covered by a thin multilayered thrombus. Alpha-actin-positive smooth muscle cells (SMCs) are found as the main cellular component of the neointimal tissue. Later (>6 weeks) extracellular matrix increases and fewer SMCs can be found. In every phase the SMC layers are loosely infiltrated by inflammatory cells (T lymphocytes). In the early postinterventional phase all endothelial cells are destroyed. The borderline between the vessel lumen and the vascular wall is constituted by a thin, membranous thrombus. Six weeks after stenting, SMCs form the vessel surface. Complete reendothelialization is first found 12 weeks after stenting. CONCLUSIONS: Stent integration is a multifactorally triggered process with proliferating SMCs generating regenerative tissue. In the early phase predominantly thrombotic material can be observed at the site of stenting, followed by the invasion of SMCs, T lymphocytes and macrophages. The incidence of delayed reendothelializations and the occurrence of deep dissections may be associated with excessive SMC hyperplasia.

Actins↗
PubMed1999

[Problems of clinical evaluation of hemodynamics at rest and during exercise in chronic heart disease. Value of cardiac catheterization and problems of clinical classification].

BACKGROUND: NYHA classification is mostly used for graduation of clinical limitation due to cardiac failure. Right heart catheterization is not generally used to evaluate hemodynamics and to define the effects of drugs in patients with chronic cardiac failure. Clinical data and results from echocardiography, stress tests or nuclear cardiology seem to be sufficient. Our aim was to demonstrate subjectivity of a classification system (NYHA) comparing the graduation done by physicians and by patients and to represent the difficulty to prognosticate hemodynamic data of patients with heart failure. PATIENTS AND METHODS: Limitation of 53 patients with heart diseases was classified by physicians and patients using NYHA classification. Pulmonary capillary wedge pressure (PCWP), stroke volume (SV) and cardiac output were predicted by physicians; they were allowed to utilize all examination data they could get. Predicted hemodynamic data were compared with the results of measurement at rest and during exercise. RESULTS: Patients classified themselves significantly worse than physicians did: 2.68 +/- 0.64 vs. 2.23 +/- 0.74 (p = 0.0012). Similarity in NYHA classification was found in 29/53 cases. Correlation of predicted and measured hemodynamic data was low: PCWP (at rest) r = 0.346; PCWP (during exercise) r = 0.232; SV (at rest) r = 0.476; SV (during exercise) r = 0.445; HMV (at rest) r = 0.412; HMV (during exercise) r = 0.538. CONCLUSION: Clinical classification systems like NYHA are subjective, classification by physicians differs significantly from classification by patients. Prediction of hemodynamics is not possible despite all examination data had been available. Right heart catheterization is necessary to define hemodynamics at rest and during exercise.

Cardiac Catheterization↗
PubMed1999

Value of Lesion Morphology and of Residual Stenosis in Predicting Late Clinical Outcomes and Restenosis Rate Post-PTCA in Single-Vessel Disease.

The study assessed an impact of stenosis morphology before coronary angioplasty (PTCA) and of residual diameter stenosis after the procedure on major adverse cardiac events and restenosis rate at 1 year after intervention in single-vessel disease. Visual analysis of stenoses, using the ABC lesion score system and on-line quantitative evaluation (ACA, DCI, Philips), was performed in 70 patients undergoing PTCA. Recurrence of angina at rest and/or positive treadmill exercise test (TET) >/=6 weeks after PTCA and/or major cardiac events were considered as evidence of restenosis. At 1 year follow-up 56 patients (80%) were event free, without angina at rest and without positive TET, with residual diameter (RD) after PTCA a mean of 2.00 +/- 0.48 mm. In the restenosis group (n = 14) RD was a mean of 1.58 +/- 0.43 mm (p < 0.01): there were three patients with angina at rest, five with Positive TET, and six with cardiac events. In this group, one-half of the stenoses was in class C of the lesion. Residual diameter stenosis, measured objectively after balloon angioplasty, and evaluation of lesion morphology before PTCA can predict late clinical outcomes after the procedure in single-vessel disease.

Journal Article↗
PubMed1999

[The current situation in training and education of assistant staff in interventional cardiology].

The number of heart catheter laboratories in Germany has been increasing for years. While there are general training regulations for cardiologists, nothing comparable exists for the assistant staff in interventional cardiology. Qualification is settled within the department. Aim of this study was the determination of the demand in general training and qualification courses. All heart catheter laboratories in North Rhine-Westphalia were questioned. Assistants (227) and medical directors (43) from 48 laboratories (54.0% returns) answered. Of the assistants 59.1% were qualified nurses, 28.2% consulting room assistants, and 10.1% medical technicians. Most of them were female (85.0%); the average age was 34.3 years. Of the assistants 73.1% were not trained in their current hospital or practice. Before their occupation in cardiac catheterization, 51.8% worked in nursing and 17.6% in ECG, sonography, etc. None of the 227 assistants was still in training at the time of questioning although 68.3% of the hospitals and practices accept trainees. Nine out of ten laboratories offer inhouse qualification, mainly in radiation protection (82.1%) and medical fields (66.7%), and 85.3% of the assistants have already attended these. Of the medical directors 90.0% and 99.2% of the assistants consider general training and qualification courses to be necessary. When asked for important fields for training programs, the assistant staff mentions "medicine" (77.6%), "examination assistance" (67.0%), and "EDP" (60.4%), while the medical directors place importance on "quality management" (89.2%) and "radiation protection" (86.5%). The job market for assistants the interventional cardiology is still good: 14.3% of the laboratories plan to take on new employees, 61.9% want to keep their number of assistants. The share of part-time work is low (16.8%). The momentary qualification and training of assistant staff in interventional cardiology does not match the demand. General programs for trainees with universally applicable teaching objectives and examination regulations are necessary.

Adult↗
PubMed1999

Comparison of the efficacy and safety of aspirin alone with coumadin plus aspirin after provisional coronary stenting: final and follow-up results of a randomized study.

BACKGROUND: The antithrombotic benefit of the conventional treatment with coumadin after coronary stenting is limited by bleeding complications. However, the superiority of an antiplatelet therapy with aspirin alone compared with coumadin plus aspirin has not been proven by randomized studies. The efficacy and safety of treatment with aspirin alone in comparison to coumadin plus aspirin were evaluated in this randomized study. METHODS: Out of 164 patients aged 59.7 +/- 9.2 years, 79 patients were randomly assigned to receive 100 mg aspirin daily (group A) and 85 patients randomly assigned to coumadin plus aspirin (group CA) after provisional coronary stenting with a high-pressure technique. The primary end point was defined as the absence of death, subacute closure of the target vessel, myocardial infarction, urgent coronary bypass surgery, repeated coronary angioplasty, and peripheral vascular complications requiring transfusion or surgery. High-pressure inflation technique was used, but ultrasound guidance was not. RESULTS: During hospitalization (median 8 days), 135 patients (82. 3%) were free of events (A, 84.8%; CA, 80.8%; P =.42). Eleven (6.7%) subacute closures occurred (A, 10.1%; CA, 3.5%; P =.09); 2 of them were lethal in the aspirin group. Emergency bypass surgery was performed in 1 patient in each group. Peripheral vascular complications were observed in 13 patients (7.9%) (A, 1.3%; CA, 14. 1%; P <.01). At 3-month follow-up, 15 (9.1%) elective revascularization procedures (A, 7.6%; CA, 10.6%; P =.51) were performed. CONCLUSION: Aspirin alone at the low dose of 100 mg administered or the combination of coumadin and aspirin after high-pressure coronary stenting does not prevent adverse clinical events when ultrasound guidance is not used.

Angioplasty, Balloon, Coronary↗
PubMed1997

[Intravascular ultrasound findings in calcifying arteriosclerosis: in vitro validation using "soft" roentgen images].

AIM: The aim of this study was to validate the detection of calcified arteriosclerotic plaques with intravascular ultrasound (IVUS). METHOD: 181 arteries were examined by 20/30 MHz IVUS. The ultrasound cross-sections were compared to the corresponding radiologic (30 kV) and histologic cross-sections. RESULTS: Calcified lesions were imaged as bright echos with shadowing. In 13 cases of 161 calcified lesions were too small to detect by IVUS. In 5 ultrasonic sections the diagnosis "calcified lesion" could not be verified neither by radiology nor by histology. The sensitivity was 91.6%, the specificity was 94.7% and the accuracy was 93.0%. CONCLUSIONS: Because of the acoustic properties of calcium, calcified lesions can be detected accurately by IVUS. IVUS can generate new insights into the effect of plaque composition on the response to catheter therapies.

Aged↗
PubMed1997

[Structural analysis of 16 different coronary stent systems].

Parallel with the increasing number of coronary stent implantation procedures, new or more elaborate coronary stents were introduced into clinical use almost every month in 1996. We have studied the architecture, surface-morphology, and shape-conversion of 16 different coronary stent systems. The objective of our study was to detect possible specific design and surface features which might influence the healing process in stent restenosis and stent thrombosis. Using electron microscopy we found ultrasmooth surfaces on 5 stents. All other coronary stents revealed individually varying and partly sharp-edged surface irregularities. Video-based morphometry showed covering between 8.3% and 26.4%. Stent shortening after in-vitro expansion ranged from 0% up to 10.5% of the initial stent length. In some stent systems balloon dilation lead to over-expansion of the stent margin. This over-expansion amounted up to 20% of the balloon diameter and the stents revealed a rather biconcave than homogeneous expansion pattern. This phenomenon was also found after postmortal stent implantation in 20 autopsied hearts.

Angioplasty, Balloon, Coronary↗
PubMed1997

High Pressure Coronary Stenting: Efficacy and Safety of Aspirin Versus Coumadin Plus Aspirin Ñ Preliminary Results of a Randomized Study.

The efficacy and safety of treatment after coronary stenting was examined with aspirin alone, 100 mg daily, as compared to coumadin plus aspirin. Data from the first 101 patients, 73 men and 28 women, aged 59.2 +/- 9.3 years, of a prospective randomized study are presented in this preliminary report. Forty-eight patients suffered from one-vessel disease, 32 had two- and 21 three-vessel disease. Indications for stenting were stable angina in 65 patients, unstable angina in 16, threatening myocardial infarction in 4 and restenosis in 16 patients. The stents were implanted by high pressure balloon inflation (14.5 +/- 2.2 atm), 55 of them were Palmaz-Schatz, 31 Micro, 10 Gianturco-Roubin, 2 Wiktor and 3 combined stents. Intravascular ultrasonographic guidance was not performed. The primary end point was defined as the absence of the following events: death, subacute coronary artery closure, acute myocardial infarction, emergency coronary bypass surgery, repeated PTCA, major bleeding or arterio-venous aneurysms needing transfusion or surgery. Eighty out of 101 patients (79.2%), 41 out of 47 (87.2%) in the aspirin group and 39 out of 54 (72.2%) in the coumadin plus aspirin group (p = 0.06) were free of events during hospitalization (9.5 +/- 5.7 days, median: 8 days). Forty-five out of 47 patients (95.7%) in the aspirin and 51 out of 54 (94.4%) in the coumadin plus aspirin group (p = 0.8) were without subacute closure. One death occurred in the aspirin group due to stent abscess two weeks after an angiographically successful stent recanalization. All 7 arterio-venous aneurysms with surgical interventions occurred in the coumadin group (p = 0.01). No emergency bypass surgery had to be performed. If these preliminary results will be confirmed by the final analysis, the combination of coumadin with aspirin does not show more efficacy or safety as compared with aspirin alone in the treatment after high-pressure coronary stenting during the hospital stay.

Journal Article↗
PubMed1997

Effect of coronary stenosis diameter on variability of on-line quantitative and qualitative arteriography.

This study assessed the impact of stenosis diameter on the variability of on-line second generation quantitative coronary arteriography (QCA) and on visual coronary analysis (VCA). Lesions (140) were evaluated by two methods: quantitative, using an Automated Coronary Analysis package, and visual, by three independent observers, from whom the estimates were averaged. Lesions were divided into groups according to the magnitude of computerized measured diameter of stenosis. The study demonstrated that variability of QCA and VCA depends upon the severity of the stenosis. The greater the diameter of the coronary lesion, the greater the variability of both quantitative and qualitative assessment and the greater the variability between the two methods.

Adult↗