Coronary stents have revolutionized the treatment of coronary artery disease. Improvement in clin... more Coronary stents have revolutionized the treatment of coronary artery disease. Improvement in clinical outcomes requires detailed evaluation of the performance of stent biomechanics and the effectiveness as well as safety of biomaterials aiming at optimization of endovascular devices. Stents need to harmonize the hemodynamic environment and promote beneficial vessel healing processes with decreased thrombogenicity. Stent design variables and expansion properties are critical for vessel scaffolding. Drug-elution from stents, can help inhibit in-stent restenosis, but adds further complexity as drug release kinetics and coating formulations can dominate tissue responses. Biodegradable and bioabsorbable stents go one step further providing complete absorption over time governed by corrosion and erosion mechanisms. The advances in computing power and computational methods have enabled the application of numerical simulations and the in silico evaluation of the performance of stent devices...
Advanced Topics in Scattering Theory and Biomedical Engineering - 9th International Workshop on Mathematical Methods in Scattering Theory and Biomedical Engineering, 2010
Cardiovascular disease (CVD) is the leading cause of death in predialysis chronic kidney disease ... more Cardiovascular disease (CVD) is the leading cause of death in predialysis chronic kidney disease (CKD) and dialysis patients as well as in renal transplant recipients (RTRs). Left ventricular hypertrophy (LVH) starts early during the course of CKD and is a strong predictor of CVD in this population. Regression of LVH after a successful renal transplantation remains a debatable issue among investigators, whereas there is little data comparing echocardiographic measurements between patients with predialysis CKD and RTRs. The aim of this study was to compare echocardiographic measurements of LV structure and function between predialysis CKD patients and RTRs of similar renal function level. We conducted a case control study with individual (1:2) matching from the Renal Transplant and the predialysis CKD Outpatient Clinic. For each of the 36 RTRs, two matched for gender, age and estimated glomerular filtration rate (eGFR) predialysis CKD outpatients (72 patients) were included. All pati...
The management of abdominal aortic aneurysm with endovascular repair (EVAR) requires extended exp... more The management of abdominal aortic aneurysm with endovascular repair (EVAR) requires extended exposure to ionizing radiation, before, during and after the intervention. The aim of this study was to quantify the radiological risks to patients and operating team, and to develop strategies to assess and reduce them. EVAR was carried out in 97 patients using either a low-power mobile or a high-power stationary fluoroscopic unit. Empirically determined relationships between the indicated dose area product (DAP) and peak skin dose, obtained by direct in vivo dosimetry in a subgroup of patients, were used to predict the peak skin dose. Individual worker monitoring was used to assess personnel radiological burden. The probability for radiation induced biological effects due to the repair itself and the preoperative and life-long surveillance, as carried out, was about 2.4 10-3. The peak skin dose of repairs was linearly correlated with the DAP and did not exceed 1.2 Gy. The collective effec...
Cardiovascular drugs and therapy / sponsored by the International Society of Cardiovascular Pharmacotherapy, 1998
We investigated the effects of coronary rotational atherectomy (PTCRA) on plasma levels of endoth... more We investigated the effects of coronary rotational atherectomy (PTCRA) on plasma levels of endothelin-1 (ET-1), atrial natriuretic peptide (ANP), and cyclic adenosine monophosphate (cAMP). We studied 14 patients undergoing PTCRA and compared them with 14 patients undergoing plain balloon angioplasty. Blood samples were taken from the femoral vein at baseline, after the end of the atherectomy, after the first balloon inflation, after the end of the procedure, and 4 hours later. ET-1 increased in the angioplasty group from 6.3 +/- 3.2 pmol/L at baseline to 8.5 +/- 3.9 pmol/L at the end of the procedure (F = 3.83, P = .02), whereas it did not change in the PTCRA group. ANP increased in the PTCRA group from 78.1 +/- 15.7 pmol/L at baseline to 89.7 +/- 24.0 pmol/L at the end of the procedure (F = 6.75, P = .0001), whereas it did not change in the angioplasty group. cAMP decreased in the PTCRA group, whereas it did not change in the angioplasty group. In conclusion, ET-1 increases less, A...
Macrophages that uptake modified lipoproteins are activated and may initially behave as endotoxin... more Macrophages that uptake modified lipoproteins are activated and may initially behave as endotoxin-stimulated macrophages. This study was undertaken in order to determine whether signal transduction pathways controlling endotoxin-mediated activation may also influence the lipoprotein-mediated activation of macrophages. Rat peritoneal macrophages were incubated for 16 hours with acetylated low-density lipoprotein and certain agents that modify the phosphoinositide/calcium- and cyclic AMP-mediated pathways, such as 2-[4-morpholinyl]-8-phenyl-1[4H]-benzopyran-4-one (LY-294002), autocamtide 2-related inhibitory peptide (AIP), N-(2-[p-bromocinnamylamino]-ethyl)-5-isoquinolinesulfonamide hydrochloride (H-89) and actinomycin D. The production of nitric oxide and the intracellular and extracellular activities of acid phosphatase were assayed. Macrophages incubated with acetylated low-density lipoprotein showed an increased production of nitric oxide and intracellular acid phosphatase activit...
The purpose of this article is to report the initial experience with endovascular repair of thora... more The purpose of this article is to report the initial experience with endovascular repair of thoracic aortic disease in a single tertiary vascular unit in northwestern Greece. Between 2003 and 2005, 16 patients were treated with endovascular techniques for various pathologies of the descending thoracic aorta. Twelve patients were treated electively and four emergently. Operative and follow-up data for a mean time of 18.4 months were retrospectively collected and analyzed. Primary technical success was obtained in 14 (87.5%) cases. No early or late deaths occurred, and there was no major operation-related complication. No paraplegia was observed in our patients. Stent graft-related complications occurred in 18.75% (one type 2 and two type 3 endoleaks), but they all had a favorable outcome. No further problems have been reported in any of our patients. Endovascular stent graft repair for diseases of the thoracic aorta seems to be a promising alternative to open surgery, especially for ...
Hellenic journal of cardiology : HJC = Hellēnikē kardiologikē epitheōrēsē
During reperfusion of ischemic myocardium, oxygen-derived free radicals are produced and can caus... more During reperfusion of ischemic myocardium, oxygen-derived free radicals are produced and can cause deleterious effects, known as reperfusion injury. We aimed to determine if a combination of the antioxidant ascorbic acid and an iron-chelating agent desferrioxamine, which reduces the production of the hydroxyl radical via ferrum-catalyzed reactions, can exert a protective action against reperfusion injury. Twenty-two young male farm pigs were anesthetized and subjected to 45 mins of ischemia and 3 and a half hours of reperfusion, in the left circumflex coronary artery territory, via the inflation and deflation of an angioplasty balloon. Animals were randomly assigned to receive either an intravenous infusion of 100 mg/ kg ascorbic acid and 60 mg/kg desferrioxamine (treatment group, TG) or an equal amount of normal saline (control group, CG). The I/R ratio, the ratio of the infarcted (necrotic) zone (I) to the myocardial area at risk (R) after 3 and a half hours of reperfusion, was ca...
Despite the exposure of the entire vasculature to the atherogenic effects of systemic risk factor... more Despite the exposure of the entire vasculature to the atherogenic effects of systemic risk factors, atherosclerotic plaques preferentially develop at sites with disturbed flow. This study aimed at exploring in vivo the relationship between local endothelial shear stress (ESS) and coronary plaque characteristics in humans using computational fluid dynamics and frequency-domain optical coherence tomography. Three-dimensional coronary artery reconstruction was performed in 21 patients (24 arteries) presenting with acute coronary syndrome using frequency-domain optical coherence tomography and coronary angiography. Each coronary artery was divided into sequential 3-mm segments and analyzed for the assessment of local ESS and plaque characteristics. A total of 146 nonculprit segments were evaluated. Compared with segments with higher ESS [≥1 Pascal (Pa)], those with low ESS (<1 Pa) showed higher prevalence of lipid-rich plaques (37.5% versus 20.0%; P=0.019) and thin-cap fibroatheroma ...
Coronary stents have revolutionized the treatment of coronary artery disease. Improvement in clin... more Coronary stents have revolutionized the treatment of coronary artery disease. Improvement in clinical outcomes requires detailed evaluation of the performance of stent biomechanics and the effectiveness as well as safety of biomaterials aiming at optimization of endovascular devices. Stents need to harmonize the hemodynamic environment and promote beneficial vessel healing processes with decreased thrombogenicity. Stent design variables and expansion properties are critical for vessel scaffolding. Drug-elution from stents, can help inhibit in-stent restenosis, but adds further complexity as drug release kinetics and coating formulations can dominate tissue responses. Biodegradable and bioabsorbable stents go one step further providing complete absorption over time governed by corrosion and erosion mechanisms. The advances in computing power and computational methods have enabled the application of numerical simulations and the in silico evaluation of the performance of stent devices...
Advanced Topics in Scattering Theory and Biomedical Engineering - 9th International Workshop on Mathematical Methods in Scattering Theory and Biomedical Engineering, 2010
Cardiovascular disease (CVD) is the leading cause of death in predialysis chronic kidney disease ... more Cardiovascular disease (CVD) is the leading cause of death in predialysis chronic kidney disease (CKD) and dialysis patients as well as in renal transplant recipients (RTRs). Left ventricular hypertrophy (LVH) starts early during the course of CKD and is a strong predictor of CVD in this population. Regression of LVH after a successful renal transplantation remains a debatable issue among investigators, whereas there is little data comparing echocardiographic measurements between patients with predialysis CKD and RTRs. The aim of this study was to compare echocardiographic measurements of LV structure and function between predialysis CKD patients and RTRs of similar renal function level. We conducted a case control study with individual (1:2) matching from the Renal Transplant and the predialysis CKD Outpatient Clinic. For each of the 36 RTRs, two matched for gender, age and estimated glomerular filtration rate (eGFR) predialysis CKD outpatients (72 patients) were included. All pati...
The management of abdominal aortic aneurysm with endovascular repair (EVAR) requires extended exp... more The management of abdominal aortic aneurysm with endovascular repair (EVAR) requires extended exposure to ionizing radiation, before, during and after the intervention. The aim of this study was to quantify the radiological risks to patients and operating team, and to develop strategies to assess and reduce them. EVAR was carried out in 97 patients using either a low-power mobile or a high-power stationary fluoroscopic unit. Empirically determined relationships between the indicated dose area product (DAP) and peak skin dose, obtained by direct in vivo dosimetry in a subgroup of patients, were used to predict the peak skin dose. Individual worker monitoring was used to assess personnel radiological burden. The probability for radiation induced biological effects due to the repair itself and the preoperative and life-long surveillance, as carried out, was about 2.4 10-3. The peak skin dose of repairs was linearly correlated with the DAP and did not exceed 1.2 Gy. The collective effec...
Cardiovascular drugs and therapy / sponsored by the International Society of Cardiovascular Pharmacotherapy, 1998
We investigated the effects of coronary rotational atherectomy (PTCRA) on plasma levels of endoth... more We investigated the effects of coronary rotational atherectomy (PTCRA) on plasma levels of endothelin-1 (ET-1), atrial natriuretic peptide (ANP), and cyclic adenosine monophosphate (cAMP). We studied 14 patients undergoing PTCRA and compared them with 14 patients undergoing plain balloon angioplasty. Blood samples were taken from the femoral vein at baseline, after the end of the atherectomy, after the first balloon inflation, after the end of the procedure, and 4 hours later. ET-1 increased in the angioplasty group from 6.3 +/- 3.2 pmol/L at baseline to 8.5 +/- 3.9 pmol/L at the end of the procedure (F = 3.83, P = .02), whereas it did not change in the PTCRA group. ANP increased in the PTCRA group from 78.1 +/- 15.7 pmol/L at baseline to 89.7 +/- 24.0 pmol/L at the end of the procedure (F = 6.75, P = .0001), whereas it did not change in the angioplasty group. cAMP decreased in the PTCRA group, whereas it did not change in the angioplasty group. In conclusion, ET-1 increases less, A...
Macrophages that uptake modified lipoproteins are activated and may initially behave as endotoxin... more Macrophages that uptake modified lipoproteins are activated and may initially behave as endotoxin-stimulated macrophages. This study was undertaken in order to determine whether signal transduction pathways controlling endotoxin-mediated activation may also influence the lipoprotein-mediated activation of macrophages. Rat peritoneal macrophages were incubated for 16 hours with acetylated low-density lipoprotein and certain agents that modify the phosphoinositide/calcium- and cyclic AMP-mediated pathways, such as 2-[4-morpholinyl]-8-phenyl-1[4H]-benzopyran-4-one (LY-294002), autocamtide 2-related inhibitory peptide (AIP), N-(2-[p-bromocinnamylamino]-ethyl)-5-isoquinolinesulfonamide hydrochloride (H-89) and actinomycin D. The production of nitric oxide and the intracellular and extracellular activities of acid phosphatase were assayed. Macrophages incubated with acetylated low-density lipoprotein showed an increased production of nitric oxide and intracellular acid phosphatase activit...
The purpose of this article is to report the initial experience with endovascular repair of thora... more The purpose of this article is to report the initial experience with endovascular repair of thoracic aortic disease in a single tertiary vascular unit in northwestern Greece. Between 2003 and 2005, 16 patients were treated with endovascular techniques for various pathologies of the descending thoracic aorta. Twelve patients were treated electively and four emergently. Operative and follow-up data for a mean time of 18.4 months were retrospectively collected and analyzed. Primary technical success was obtained in 14 (87.5%) cases. No early or late deaths occurred, and there was no major operation-related complication. No paraplegia was observed in our patients. Stent graft-related complications occurred in 18.75% (one type 2 and two type 3 endoleaks), but they all had a favorable outcome. No further problems have been reported in any of our patients. Endovascular stent graft repair for diseases of the thoracic aorta seems to be a promising alternative to open surgery, especially for ...
Hellenic journal of cardiology : HJC = Hellēnikē kardiologikē epitheōrēsē
During reperfusion of ischemic myocardium, oxygen-derived free radicals are produced and can caus... more During reperfusion of ischemic myocardium, oxygen-derived free radicals are produced and can cause deleterious effects, known as reperfusion injury. We aimed to determine if a combination of the antioxidant ascorbic acid and an iron-chelating agent desferrioxamine, which reduces the production of the hydroxyl radical via ferrum-catalyzed reactions, can exert a protective action against reperfusion injury. Twenty-two young male farm pigs were anesthetized and subjected to 45 mins of ischemia and 3 and a half hours of reperfusion, in the left circumflex coronary artery territory, via the inflation and deflation of an angioplasty balloon. Animals were randomly assigned to receive either an intravenous infusion of 100 mg/ kg ascorbic acid and 60 mg/kg desferrioxamine (treatment group, TG) or an equal amount of normal saline (control group, CG). The I/R ratio, the ratio of the infarcted (necrotic) zone (I) to the myocardial area at risk (R) after 3 and a half hours of reperfusion, was ca...
Despite the exposure of the entire vasculature to the atherogenic effects of systemic risk factor... more Despite the exposure of the entire vasculature to the atherogenic effects of systemic risk factors, atherosclerotic plaques preferentially develop at sites with disturbed flow. This study aimed at exploring in vivo the relationship between local endothelial shear stress (ESS) and coronary plaque characteristics in humans using computational fluid dynamics and frequency-domain optical coherence tomography. Three-dimensional coronary artery reconstruction was performed in 21 patients (24 arteries) presenting with acute coronary syndrome using frequency-domain optical coherence tomography and coronary angiography. Each coronary artery was divided into sequential 3-mm segments and analyzed for the assessment of local ESS and plaque characteristics. A total of 146 nonculprit segments were evaluated. Compared with segments with higher ESS [≥1 Pascal (Pa)], those with low ESS (<1 Pa) showed higher prevalence of lipid-rich plaques (37.5% versus 20.0%; P=0.019) and thin-cap fibroatheroma ...
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Papers by Lampros Michalis