PubMed Health⌕ Search

Biomedical subjects

G Louridas

Publications and source records attributed to G Louridas.

At least 19 recordsLinked to original sources
PubMed2006

Revisiting the frequency of peripheral arterial disease in patients with coronary artery disease: is there a difference between diabetic and non-diabetic patients?

BACKGROUND: The aim of this study was to investigate whether frequency of concomitant peripheral arterial disease (PAD) is associated with angiographic severity of coronary artery disease (CAD), as well as to ascertain if diabetic patients differ from those without diabetes in the association between these two manifestations of atherosclerosis. PATIENTS AND METHODS: This study included 302 patients (229 men, mean age 62.2 +/- 11.5 years) with documented CAD, divided into groups I-III, according to the angiographic severity of coronary atherosclerosis. Group I comprised 140 patients (104 men) with severe CAD, group II comprised 63 patients (48 men) with moderate CAD and group III comprised 99 patients (77 men) with mild CAD. Each of the groups I-III was further divided into the subgroups of diabetic and non-diabetic patients. Included were also 88 patients (42 men, mean age 61.7 +/- 9.5 years) without CAD and a control group of 60 healthy volunteers (30 men), aged 18-40 years. PAD was diagnosed by means of a Doppler apparatus. RESULTS: Frequency of PAD was associated with angiographic severity of CAD (p = 0.0001). This association was shown both in diabetic (p = 0.012) and in non-diabetic patients (p = 0.0041). Significantly (p < or = 0.01) higher frequency of PAD among diabetic patients was found in each of the groups I-III. CONCLUSIONS: Among patients with CAD, frequency of concomitant PAD is associated with angiographic severity of coronary atherosclerosis. This association is demonstrated both in diabetic and in non-diabetic patients. Finally, PAD is significantly more frequent in diabetic patients, irrespective of the angiographic severity of CAD.

Adolescent↗
PubMed2005

Detection of myocardial viability by dobutamine stress echocardiography: incremental value of diastolic wall thickness measurement.

OBJECTIVE: To assess the diagnostic accuracy of baseline diastolic wall thickness (DWT) alone and as an adjunct to dobutamine stress echocardiography (DSE) for prediction of myocardial viability in patients with ischaemic left ventricular (LV) dysfunction, with the recovery of resting function after revascularisation as the yardstick. PATIENTS: 24 patients with ischaemic LV dysfunction (ejection fraction < 40%) scheduled for surgical revascularisation. SETTING: Regional cardiothoracic centre. METHODS: All patients underwent DSE before and resting echocardiography six months after revascularisation. DWT was measured in each of the 16 LV segments. A receiver operating characteristic (ROC) and a multi-ROC curve were generated to assess the ability of DWT alone and in combination with DSE to predict myocardial viability. RESULTS: DWT > 0.6 cm provided a sensitivity of 80%, a specificity of 51%, and a negative predictive value of 80% for the prediction of viability in akinetic segments. DSE had an excellent specificity (92%) but a modest sensitivity (60%) in akinetic segments. A combination of improvement at DSE or DWT > 0.8 cm improved sensitivity (90% v 60%, p < 0.001) and negative predictive value (92% v 78%, p = 0.03) in akinetic segments compared with DSE alone. This was achieved with some loss in specificity (75% v 92%, p = 0.01) and positive predictive value (71% v 82%, p = 0.79). CONCLUSIONS: DWT measurement may improve the sensitivity of DSE for the detection of myocardial viability. Akinetic segments with DWT > 0.8 cm have a good chance of recovery despite the absence of contractile reserve during DSE. Further testing may be required before excluding myocardial viability in these cases.

Area Under Curve↗
PubMed2003

Wigner-Ville analysis and classification of electrocardiograms during thrombolysis.

Non-stationary analysis of electrocardiograms (ECGs) using Wigner-Ville distribution is presented. Analysis was performed on subjects with acute myocardial infarction who had undergone thrombolysis, in Holter recordings of lead V1. The distinction between successfully and non-successfully thrombolysed patients was evaluated, based on time-frequency features of the Wigner-Ville transformed ECGs at the sixth hour after lysis. Characteristic parameters were extracted from time-frequency areas, and linear discriminant analysis was performed on these parameters, leading to a prediction index to distinguish the two classes. Thirteen features were found statistically significant by t-test and were used for the classification with linear modelling. Out of these features, four corresponded to frequencies lower than 25 Hz and higher than 50 Hz for, roughly, the QRS complex, five features corresponded to all the frequency bands of, roughly, the ST area, and the last four features corresponded to the T-wave. The feature-vector used in linear modelling was iteratively generated, and the iterative prediction found all 18 features significant. The iterative method resulted in better classification than that of the standard statistical procedure (3.8% error against 18.1% with the classic method). The evolution of the prediction index with time for the first 12 h was different for the successfully and non-successfully thrombolysed groups. Specifically, in the successful thrombolysis group, oscillations and variation with time were more obvious, indicating a possible difference in the dynamics of the cardiac system.

Electrocardiography, Ambulatory↗
PubMed2002

Home care delivery through the mobile telecommunications platform: the Citizen Health System (CHS) perspective.

Health delivery practices are shifting towards home care. The reasons are the better possibilities for managing chronic care, controlling health delivery costs, increasing quality of life and quality of health services and the distinct possibility of predicting and thus avoiding serious complications. For the above goals to become routine, new telemedicine and information technology (IT) solutions need to be implemented and integrated in the health delivery scene, and these solutions need to be assessed through evidence-based medicine in order to provide solid proof for their usefulness. Thus, the concept of contact or call centers has emerged as a new and viable reality in the field of IT for health and telemedicine. In this paper we describe a generic contact center that was designed in the context of an EU funded IST for health project with acronym Citizen Health System (CHS). Since the generic contact center is composed by a number of modules, we shall concentrate in the modules dealing with the communication between the patient and the contact center using mobile telecommunications solutions, which can act as link between the internet and the classical computer telephony communication means. We further elaborate on the development tools of such solutions, the interface problems we face, and on the means to convey information from and to the patient in an efficient and medically acceptable way. This application proves the usefulness of wireless technology in providing health care services all around the clock and everywhere the citizen is located, it proves the necessity for restructuring the medical knowledge for education delivery to the patient, and it shows the virtue of interactivity by means of using the limited, yet useful browsing capabilities of the wireless application protocol (WAP) technology.

Cell Phone↗
PubMed2002

Dobutamine stress echocardiography for the detection of myocardial viability in patients with left ventricular dysfunction taking beta blockers: accuracy and optimal dose.

OBJECTIVE: To assess the accuracy of dobutamine stress echocardiography (DSE) and the optimal dose of dobutamine to detect myocardial viability in patients with ischaemic left ventricular (LV) dysfunction who are taking beta blockers, using the recovery of function six months artery revascularisation as the benchmark. PATIENTS: 17 patients with ischaemic LV dysfunction (ejection fraction < 40%) and chronic treatment with beta blockers scheduled to undergo surgical revascularisation. SETTING: Regional cardiothoracic centre. METHODS: All patients underwent DSE one week before and resting echocardiography six months after revascularisation. A wall motion score was assigned to each segment for each dobutamine infusion stage, using the standard 16 segment model of the left ventricle. The accuracy of DSE to predict recovery of resting segmental function was calculated for low dose (5 and 10 microg/kg/min) and for a full protocol of dobutamine infusion (5 to 40 microg/kg/min). RESULTS: Of the 272 segments studied, 158 (58%) were dysfunctional at rest, of which 79 (50%) improved at DSE and 74 (47%) recovered resting function after revascularisation. Analysis of results with a low dose showed a significantly lower sensitivity and negative predictive value than with a full protocol (47% v 81%, p < 0.001 and 65% v 82%, p < 0.05, respectively). The accuracy in the full protocol analysis was comparable with that reported in patients no longer taking beta blockers but was significantly lower than that in the low dose analysis (78% v 66%, p < 0.001). CONCLUSIONS: Findings suggest that beta blocker withdrawal is not necessary before DSE when viability is the clinical information in question. However, a completed protocol with continuous image recording is required to detect the full extent of viability.

Adrenergic beta-Antagonists↗
PubMed2002

The ArtAssist Device in chronic lower limb ischemia. A pilot study.

BACKGROUND: Patients with chronic critical limb ischemia following a failed bypass graft or with non-reconstructable distal disease diagnosed angiographically, have a very poor prognosis. This is a prospective pilot study to assess the influence of the ArtAssist Device on pedal blood flow and amputation rate. METHODS: Thirty-three legs in 25 patients were evaluated. Ten legs presented with rest pain, and 23 legs with tissue loss. Nine legs had previously undergone bypass surgery. RESULTS: At a mean follow-up of 3 months, 14 (42%) legs were amputated, and 19 (58%) were saved. Eleven of the amputated legs were in patients with chronic renal failure, a known risk factor. The amputation rate, excluding this group, was 13.6% (3/22). Toe pressures measured initially and after 3 months on the pump showed a significant improvement (p=0.03). Forty percent of patients presenting with rest pain improved, while 26% of foot ulcers healed on the pump. Mortality rate was 12%. CONCLUSIONS: The results from this prospective study are encouraging but need to be validated in a larger prospective randomized study.

Aged↗
PubMed2002

Communication infrastructure in a contact center for home care monitoring of chronic disease patients.

The Citizen Health System (CHS) is a European Commission (EC) funded project in the field of IST for Health. Its main goal is to develop a generic contact center which in its pilot stage can be used in the monitoring, treatment and management of chronically ill patients at home in Greece, Spain and Germany. Such contact centers, which can use any type of communication technology, and can provide timely and preventive prompting to the patients are envisaged in the future to evolve into well-being contact centers providing services to all citizens. In this paper, we present the structure of such a generic contact center and in particular the telecommunication infrastructure, the communication protocols and procedures, and finally the educational modules that are integrated into this contact center. We discuss the procedures followed for two target groups of patients where two randomized control clinical trials are under way, namely diabetic patients with obesity problems, and congestive heart failure patients. We present examples of the communication means between the contact center medical personnel and these patients, and elaborate on the educational issues involved.

Chronic Disease↗
PubMed2001

Suitability of venous and arterial conduits used for coronary artery bypass grafting in conjunction with coronary disease risk factors.

UNLABELLED: BACKGROUND/STUDY OBJECTIVES: We studied patients undergoing coronary artery bypass grafting. Risk factors for coronary disease were studied in conjunction with the histopathologic findings of the grafts prior to implantation. Our aim was to correlate the histologic condition of the grafts and evaluate the morphological changes in conjunction with existing risk factors. DESIGN/PATIENTS: In 10 candidates for surgical revascularization (nine males, mean age 60.8 years), the risk factor profile was studied (smoking, dyslipidaemia, hypertension, diabetes, family history) and the Body Mass Index was calculated. Of a total of 14 grafts, 10 were saphenous vein grafts and four left internal thoracic artery grafts. Histologic samples were studied under optical and electron microscopy. We studied the intima morphology and thickness, the width of the intercellular spaces, the texture of the subendothelial layer, the endothelial status, and the condition of the basal lamina. Histopathological changes were correlated with risk factors. RESULTS: Histopathological changes were observed in the wall structure of all grafts. The most important changes were found in the venous grafts, notably: intima thickening, existence of foam cells in the intima, widening of the intercellular spaces, subendothelial oedema, degeneration and detachment of endothelial cells, and wide multilayered basal lamina. The co-existence of two or more risk factors seems to exarcerbate morphological changes. CONCLUSION: Morphological changes are present principally in the walls of venous but also arterial conduits, even prior to implantation. These changes may be attributable to preparation techniques and preservation conditions of the grafts, but they could additionally be induced by coexisting risk factors. It is conceivable that these alterations could perhaps precipitate and accelerate atherosclerotic changes, inducing lumen narrowing or even occlusion of the graft postoperatively.

Adult↗
PubMed2001

The clinical significance of reverse redistribution in Tl201 cardiac SPET.

UNLABELLED: In an attempt to evaluate the clinical significance of reverse redistribution in Tl201 cardiac SPET, Tl201 SPET examinations included in the data base of our department have been retrospectively reviewed. PATIENTS: Six hundred ninety eight patients demonstrated the pattern of reverse redistribution. For 237 of these patients' cardiac catheterization data were also available. One hundred and six patients of these had a history of myocardial infarction while the rest of them were referred for angina symptoms. RESULTS: Catheterization showed that the infarction area was perfused by a stenosed but patent vessel in 79 of the 106 patients with a history of myocardial infarction (74.5%). Collateral circulation was evident in 21 of these 106 patients (19.8%). Only six patients (5.6%) showed a totally occluded vessel with no obvious evidence of collateral circulation. Of the 131 patients, with no myocardial infarction history, 14 (10.7%) had normal coronary vessels. The rest of the patients (89.3%) demonstrated stenotic vessels perfusing the same area where reverse redistribution was observed. Sixty-three of these patients have been reexamined after 9-36 months. On 15 of these patients (23.8%) the second scintigram showed ischemia in the same segments where reverse redistribution was initially detected. Another 17 of the above patients had a former scintigraphic examination that showed ischemia on the segments that currently demonstrated reverse redistribution. CONCLUSION: The results of the present retrospective study indicate that, in patients with known coronary disease, the pattern of reverse redistribution frequently indicates the ischemic area.

Adult↗
PubMed2000

Antiplatelet is superior to anticoagulant treatment after coronary stenting: fewer coronary and other events within 30 days after stenting.

Stent prosthesis is a high efficacious method with low complication rates. However, the ideal adjunctive therapy following stent implantation remains controversial. The authors compared the effectiveness and complication rates of aspirin-ticlopidine antiplatelet therapy vs. anticoagulant therapy with acenocoumarol within 30 days following stent prosthesis. They prospectively studied 404 patients following stent prosthesis while randomly receiving anticoagulant (Group A: 201 patients) vs. antiplatelet treatment (Group B: 203 patients). Groups A and B were similar in demographic data (age, gender), stent location, clinical presentation, indication of stenting, and type of implanted stent. Chi-square test, t test, and Wilcoxon test for two samples were used for statistical analysis of the results. Stent implantation was attempted in 434 cases. This was successful in 70/85 (82%) of the bailout, 122/135 (90%) of the suboptimal, and 212/214 (99%) of the elective cases. In 201 patients anticoagulant treatment with acenocoumarol was administered for 4 weeks (group A), while 203 received antiplatelet treatment with ticlopidine (group B). The need for reintervention was less and total cardiac events were fewer in group B than in group A: three (1.5%) and nine (4.4%) vs 18 (9%) and 29 (14.4%), p<0.0008 and p<0.006 respectively. Hemorrhagic complications and total noncardiac events were fewer in group B than in group A: six (3%) and six (3%) vs. 18 (9%) and 19 (9.5%), p<0.01 and p<0.007 respectively. The length of hospital stay was shorter in group B than in A, p<0.0001. In conclusion, in this study of intracoronary stenting the authors had a high success rate in 434 attempted cases. Antiplatelet therapy was accompanied by fewer cardiac and noncardiac 1 month events when compared with anticoagulant therapy, supporting its role as the adjunctive treatment of choice post-stenting for the time being.

Acenocoumarol↗
PubMed1999

Coronary-subclavian steal syndrome: treatment with percutaneous transluminal angioplasty and stent placement.

The aim of this study was to assess the efficacy of percutaneous transluminal angioplasty (PTA) and stenting in the management of the coronary-subclavian steal syndrome (CSSS). A 56-year-old man presented with CSSS due to occlusion of the left subclavian artery. He was treated with PTA and placement of two stents in the left subclavian artery. Systolic blood pressure became equal in both arms and dizziness disappeared. There were no complications. Percutaneous transluminal angioplasty and stenting can effectively and safely manage CSSS.

Angioplasty, Balloon↗
PubMed1999

Model-based morphological segmentation and labeling of coronary angiograms.

A method for extraction and labeling of the coronary arterial tree (CAT) using minimal user supervision in single-view angiograms is proposed. The CAT structural description (skeleton and borders) is produced, along with quantitative information for the artery dimensions and assignment of coded labels, based on a given coronary artery model represented by a graph. The stages of the method are: 1) CAT tracking and detection; 2) artery skeleton and border estimation; 3) feature graph creation; and iv) artery labeling by graph matching. The approximate CAT centerline and borders are extracted by recursive tracking based on circular template analysis. The accurate skeleton and borders of each CAT segment are computed, based on morphological homotopy modification and watershed transform. The approximate centerline and borders are used for constructing the artery segment enclosing area (ASEA), where the defined skeleton and border curves are considered as markers. Using the marked ASEA, an artery gradient image is constructed where all the ASEA pixels (except the skeleton ones) are assigned the gradient magnitude of the original image. The artery gradient image markers are imposed as its unique regional minima by the homotopy modification method, the watershed transform is used for extracting the artery segment borders, and the feature graph is updated. Finally, given the created feature graph and the known model graph, a graph matching algorithm assigns the appropriate labels to the extracted CAT using weighted maximal cliques on the association graph corresponding to the two given graphs. Experimental results using clinical digitized coronary angiograms are presented.

Algorithms↗
PubMed1999

Intermittent P wave sensing in a patient with DDD pacemaker.

We present the case of a patient with a DDD pacemaker and intermittent P wave sensing due to T wave oversensing by the ventricular lead. The T wave sensing caused initiation of an extended atrial refractory period and the P waves, falling within this period, were not sensed. The problem was solved by decreasing the ventricular sensitivity.

Aged↗
PubMed1998

Coronary vessel perforation during balloon angioplasty: a case report.

Coronary perforation can be managed with prolonged balloon inflations, covered stents, or embolization of the vessel. We report on a case of a balloon-induced perforation of the distal left anterior descending artery, that was sealed by injecting preclotted autologous blood through the balloon catheter lumen at the site of the perforation. The patency of the distal vessel was maintained.

Aged↗
PubMed1997

Coronary artery skeleton detection based on topographic features.

A new approach to the problem of detecting the skeletons of coronary arteries in coronary angiograms is proposed. The digitized grayscale coronary angiograms are regarded as noisy sampling of the underlying continuous surface. After the application of Gaussian filtering to reduce noise, the topographic features of the smoothed image are detected based on first and second order image derivatives. Then, the candidate arteries skeleton points are detected based on the observation that arteries are smooth elongated objects having approximately a Gaussian smoothed semi-elliptical profile. Experimental results on real digitized coronary angiograms are presented.

Algorithms↗
PubMed1994

Stenting the distal anastomotic site of the left internal mammary artery graft: a case report.

The major problem associated with the long-term patency of the internal mammary artery graft is the early occurrence of stenosis usually at its distal anastomotic site; its management by balloon angioplasty has been associated with a high success rate. We report the case of an unsuccessful balloon angioplasty of an anastomotic stenosis of a left internal mammary artery graft that was successfully managed by stenting with one-half of a Palmaz-Schatz stent.

Angina, Unstable↗