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Biomedical subjects

K Toutouzas

Publications and source records attributed to K Toutouzas.

At least 37 records · Page 2Linked to original sources
PubMed1998

Unfavorable effects of passive smoking on aortic function in men.

BACKGROUND: The aorta acts as both a conduit and an elastic buffering chamber that modulates left ventricular function and coronary blood flow. Previous studies have shown that active smoking has unfavorable effects on aortic elasticity. OBJECTIVE: To study the association between passive smoking and the elastic properties of the human aorta. DESIGN: Comparison of nonsmokers during passive smoking studies and smokers during active smoking or sham smoking studies. SETTING: Academic medical center. PARTICIPANTS: 16 male nonsmokers were assigned to passive smoking studies, and 32 current, long-term, male smokers were randomly assigned to either active smoking (16 patients) or sham smoking (16 patients) studies. INTERVENTION: All participants underwent diagnostic catheterization. In the passive smoking group, environmental tobacco smoke was vented into an exposure chamber for 5 minutes (mean carbon monoxide level, 30 parts per million). Each participant in the active smoking group smoked one filtered cigarette (1.0 mg of nicotine) under standardized conditions within 5 minutes; each participant in the sham smoking group performed a similar pattern of inhalation with one unlit cigarette. MEASUREMENTS: Aortic elastic properties were studied by measuring the aortic pressure-diameter relation before and for 20 minutes after passive, active, or sham smoking. Instantaneous diameter of the thoracic aorta was measured with a high-fidelity ultrasonic dimension catheter. Instantaneous aortic pressure and diameter were measured at the same site. RESULTS: Both passive and active smoking were associated with changes in the aortic pressure-diameter relation (change in mean distensibility in the passive smoking group, from 2.02 to 1.59 x 10(-6) cm2 x dyne(-1) [for comparisons of time course between passive and sham smoking groups, P < 0.001]; change in mean distensibility in the active smoking group, from 2.08 to 1.51 x 10(-6) cm2 x dyne(-1) [for comparisons of time course between active and sham smoking groups, P < 0.001]). These changes represent decreases of 21% and 27%, respectively. No changes in aortic elasticity were seen in the sham smoking group. CONCLUSIONS: Both passive and active smoking are associated with an acute deterioration in the elastic properties of the aorta. This association between exposure to tobacco smoke and aortic elasticity indicates that aortic function deteriorates during passive or active smoking.

Adult↗
PubMed1998

Total reconstruction of a diseased saphenous vein graft by means of conventional and autologous tissue-coated stents.

This is the first report of a total reconstruction of a diseased saphenous vein graft, with thrombus-containing lesion and multiple stenoses, by the implantation of arterial graft- and venous graft-coated stents, and of conventional stents. The procedure was successful without any complications, and follow-up angiography after 6 months revealed patency of the vessel.

Angioplasty, Balloon↗
PubMed1998

Aortic stiffness in young patients with heterozygous familial hypercholesterolemia.

BACKGROUND: Dyslipidemia is a primary risk factor for the development of atherosclerosis. Aortic distensibility is an important determinant of left ventricular function and coronary blood flow whose possible alterations in patients with dyslipidemia have not been fully investigated. METHODS: To assess the effect of dyslipidemia on the elastic properties of the aorta, we studied 60 patients (mean age 37+/-11 years) with heterozygous familial hypercholesterolemia and no manifest arterial disease and compared them with 20 of their normolipidemic siblings (mean age 34+/-10 years). Two indexes of the aortic elastic properties were measured: aortic distensibility was calculated by use of the formula: 2 x (AoS-AoD)/PP x AoD, and aortic stiffness index was calculated by use of the formula: In (SBP/DBP)/(AoS-AoD)/AoD, where AoS and AoD are aortic root end-systolic and end-diastolic diameters, respectively, SBP and DBP are systolic and diastolic arterial pressure, respectively, and PP is pulse pressure. Internal aortic root diameters were measured at 3 cm above the aortic valve by use of two-dimensional guided M-mode transthoracic echocardiography, and arterial pressure was measured simultaneously at the brachial artery by sphygmomanometry. RESULTS: The mean aortic systolic and diastolic diameter index did not differ significantly between the two groups. In contrast, aortic distensibility was found to be significantly reduced in subjects with isolated familial hypercholesterolemia compared with that in the control group (2.15+/-1.72 cm2.dynes(-1).10(-6) vs 3.18+/-1.58 cm2.dynes(-1).10(-6), p < 0.02). In addition, the mean aortic stiffness index was double in patients with familial hypercholesterolemia compared with that in normolipidemic subjects. CONCLUSIONS: Severe dyslipidemia does not overtly influence aortic dimensions but leads to impairment of aortic elastic properties before the occurrence of clinical manifestations of atherosclerotic disease.

Adult↗
PubMed1998

Effects of ventricular pacing-induced tachycardia on aortic mechanics in man.

OBJECTIVE: Effects of pacing-induced tachycardia on left ventricular function have been studied extensively. However, little attention has been focused on aortic elastic properties during heart rate increments. The aim was to determine the effects of right ventricular pacing on the aortic elastic properties. METHODS: We studied 14 normal subjects (baseline blood pressure, 129/84 +/- 10/6 mmHg; aortic diameter, 23.5/21.3 +/- 2.4/1.9 mm) at rest, during rapid right ventricular pacing (at five stepwise heart rate increases of 20 bpm every 2 min) and after 5 min recovery. Shifts as well as changes in the slope and the stiffness constant of the pressure diameter (p-d) relation, derived from simultaneous tip-micromanometer aortic pressure recordings and high-fidelity ultrasonic intravascular aortic diameter recordings, were used as indices of aortic stiffness. Wave reflection was also studied. RESULTS: Aortic pulse pressure and strain significantly decreased after pacing-induced tachycardia (p < 0.0001 and < 0.05, respectively). During pacing, the slope of the linear p-d relation as well as the stiffness constant were decreased, followed by increases at recovery (p < 0.0001). The augmentation index and the aortoventricular coupling ratio were significantly decreased (p < 0.0001). CONCLUSIONS: Pacing-induced increases in pulse frequency may result in improved aortic distensibility and aortoventricular coupling.

Aorta↗
PubMed1998

Assessment of left atrial pressure-area relation in humans by means of retrograde left atrial catheterization and echocardiographic automatic boundary detection: effects of dobutamine.

OBJECTIVES: This study sought to validate and apply a new method for obtaining the left atrial (LA) pressure-area relation. BACKGROUND: In physiologic investigations, the pressure-area relation is the most accurate and representative index of LA hemodynamic status. METHODS: We applied real-time two-dimensional echocardiographic imaging with automatic boundary detection to estimate LA area changes. To obtain LA pressure, a catheter-tipped micromanometer was introduced retrogradely into the left atrium using a steerable cardiac catheter developed at our institution. Twenty-five patients (11 normal subjects, 7 patients with an enlarged left atrium due to heart failure, 7 patients with atrial fibrillation) were studied before and after dobutamine administration. From the LA pressure-area relation, the area of the A loop (the first counterclockwise loop) and the V loop (the second clockwise loop), the pressure-minimal area relation and the LA passive elastic chamber stiffness constant were measured. RESULTS: Normalized pressure-minimal area relation was highly linear and sensitive to changes in inotropic state (normal subjects: from 0.96 to 1.27 mm Hg/cm2, p < 0.01; patients with heart failure: from 0.59 to 0.68 mm Hg/cm2, p = NS; patients with atrial fibrillation: from 0.80 to 1.06 mm Hg/cm2, p < 0.05). The LA stroke work index was accurately calculated, and a very good correlation was found with LA preload. LA stroke work index was lower in patients with heart failure (3.9 +/- 0.8 cm2 x mm Hg, p < 0.001), whereas the LA stiffness constant was increased in patients with heart failure (0.801 +/- 0.097 cm(-2), p < 0.01) and atrial fibrillation (0.796 +/- 0.091 cm(-2), p < 0.01) compared with normal subjects (stroke work index 7.3 +/- 1.9 cm2 x mm Hg, stiffness constant 0.623 +/- 0.107 cm(-2), respectively). In addition, increased inotropic state after dobutamine administration resulted in improved LA pump function (stroke work index) in normal subjects (from 10.2 +/- 0.9 to 13.8 +/- 1.9 cm2 x mm Hg, p < 0.001) and patients with heart failure (from 4.3 +/- 0.4 to 7.6 +/- 0.4 cm2 x mm Hg, p < 0.001), as well as in decreased stiffness constant in all groups of patients (normal subjects: from 0.712 +/- 0.141 to 0.473 +/- 0.089 cm(-2); patients with heart failure: from 0.896 +/- 0.181 to 0.494 +/- 0.093 cm(-2); patients with atrial fibrillation: from 0.779 +/- 0.145 to 0.467 +/- 0.086 cm(-2), p < 0.001). CONCLUSIONS: The method described here is both safe and reproducible for obtaining the LA pressure-area relation. LA function is impaired in patients with heart failure and in those with atrial fibrillation and may be acutely improved with inotropic agents in both normal and diseased atria.

Adrenergic beta-Agonists↗
PubMed1998

Effects of balloon mitral valvuloplasty on left atrial function in mitral stenosis as assessed by pressure-area relation.

OBJECTIVES: This study sought to investigate the changes induced on the pressure-area relation of the left atrium in patients with mitral stenosis after percutaneous balloon mitral valvuloplasty. BACKGROUND: Left atrial (LA) function is influenced by changes in LA afterload. The latter is increased in mitral stenosis as a result of increased resistance to blood flow imposed by the stenotic mitral valve. METHODS: We studied the effects of acute alterations of LA afterload induced by retrograde nontransseptal balloon mitral valvuloplasty (RNBMV) on LA function in patients with mitral stenosis. LA pressure-area relations were obtained in 15 patients with mitral stenosis (8 with sinus rhythm, 7 with atrial fibrillation) before and after valvuloplasty, as well as in 15 normal subjects. LA pressure was recorded by a catheter-tipped micromanometer introduced retrogradely into the left atrium while LA area was recorded simultaneously using acoustic quantification. The areas of the A and V loops of the pressure-area relation as well as the LA chamber stiffness constant were calculated. RESULTS: Balloon valvuloplasty resulted in a significant increase in mitral valve area (p < 0.001) and a substantial reduction of the mean transmitral pressure gradient (p < 0.001) and mean LA pressure (p < 0.001). The area of the A loop in patients with sinus rhythm and the area of the V loop in those with atrial fibrillation increased significantly after completion of the procedure (p < 0.001). Furthermore, LA stiffness decreased in both groups. CONCLUSIONS: After RNBMV, there is a significant increase in LA pump function in patients with sinus rhythm, a significant increase in LA reservoir function in patients with atrial fibrillation and a significant reduction in LA stiffness in all patients. Marked alterations of the configuration of the LA pressure-area relation occur immediately after successful RNBMV in patients with mitral stenosis.

Adult↗
PubMed1997

Aortic function in arterial hypertension determined by pressure-diameter relation: effects of diltiazem.

BACKGROUND: Aortic elastic properties, important determinants of left ventricular function and coronary blood flow, are compromised in hypertension. The aim of this study was to determine aortic function in hypertensive patients and in normal subjects before and after administration of diltiazem, a calcium antagonist widely used in the treatment of essential hypertension. METHODS AND RESULTS: The aortic pressure-diameter relation was obtained before and after diltiazem administration in 15 hypertensives and 15 control normotensives. Instantaneous diameter of the thoracic aorta was acquired with a high-fidelity intravascular catheter developed in our institution and previously validated. Instantaneous aortic pressure was measured simultaneously and at the same aortic level with a catheter-tip micromanometer. Energy loss due to the viscosity of aortic wall was measured from the area of the loop. Aortic distensibility was calculated using the formula 2 x (pulsatile change in aortic diameter)/([diastolic aortic diameter] x [aortic pulse pressure]). At baseline, aortic distensibility was lower and energy loss was greater in hypertensives than in normotensives (distensibility: 1.4+/-0.3 versus 3.5+/-0.7 cm2 x dyne(-1) x 10(-6), respectively, P<.001; energy loss: 14.1+/-3.3 versus 8.2+/-2.2 mm x mm Hg, respectively, P<.001). After diltiazem administration, aortic distensibility was increased, whereas energy loss was decreased in both hypertensives (peak response: distensibility, 2.0+/-0.4 cm2 x dyne(-1) x 10(-6), P<.001; energy loss, 9.3+/-1.6 mm x mm Hg, P<.001) and normotensives (peak response: distensibility, 5.2+/-0.5 cm2 x dyne(-1) x 10(-6), P<.001; energy loss, 5.0+/-1.2 mm x mm Hg, P<.001). CONCLUSIONS: Aortic elastic properties are compromised and energy loss due to aortic wall viscosity is increased in hypertensives compared with normotensives. Function of the aorta is improved in both hypertensive and normotensive subjects after the administration of diltiazem.

Adult↗
PubMed1997

Unfavorable effect of smoking on the elastic properties of the human aorta.

BACKGROUND: Smoking is a major risk factor for cardiovascular morbidity and mortality. Because previous studies have shown that smoking affects vasomotor response, we hypothesized that smoking may also acutely alter aortic elastic properties. METHODS AND RESULTS: We studied 40 male current and long-term smokers who underwent diagnostic cardiac catheterization for chest-pain evaluation. Twenty subjects (age, 48 +/- 2 years, mean +/- SEM) were randomly assigned to smoking and 20 (age, 47 +/- 2 years) to sham smoking studies. Aortic elastic properties were studied with the determination of the aortic pressure-diameter relation before smoking, every minute for the first 5 minutes after the initiation of smoking or sham smoking, and every 5 minutes for the following 15 minutes. Instantaneous diameter of the thoracic aorta was measured with a special ultrasonic dimension catheter developed in our laboratory and previously validated. Instantaneous aortic pressure was measured at the same site as was diameter with a Millar micromanometer. Smoking was associated with significant changes in the aortic pressure-diameter relation that denote deterioration of the elastic properties and were maintained during the whole study period: the slope of the pressure-diameter loop became steeper (baseline, 35.43 +/- 1.38; minute 1, 45.26 +/- 1.65; peak at minute 10, 46.36 +/- 1.69 mm Hg/mm; P < .001) and aortic distensibility decreased (baseline, 2.08 +/- 0.12; minute 1, 1.60 +/- 0.08; nadir at minute 5, 1.54 +/- 0.07 x 10(-6) cm2.dyne-1; P < .001). In contrast, no changes in aortic elasticity indexes were observed with sham smoking. CONCLUSIONS: Smoking is associated with an acute deterioration of aortic elastic properties. This effect of smoking may contribute to the unfavorable consequences of smoking on the cardiovascular system.

Aorta, Thoracic↗
PubMed1997

Autologous vein graft-coated stents for the treatment of thrombus-containing coronary artery lesions.

Recent studies have shown that stents may have a potential role in the treatment of thrombus-containing lesions. We report on the application of an autologous vein graft-coated stent (AVGCS) as the primary therapeutic modality for acute myocardial infarction in 10 patients. AVGCS delivery and deployment were successful and uneventful. Mean minimal lumen diameter and TIMI trial flow grade increased significantly (from 0.04 +/- 0.09 mm pre-AVGCS to 3.02 +/- 0.32 mm post-AVGCS, and from 10 patients with flow grade 0-1 pre-AVGCS to 10 patients with flow grade 3 post-AVGCS, respectively). Ten-day angiogram revealed maintenance of the immediate results. Nine patients had a negative exercise stress test 2 mo post-AVGCS, and at a mean follow-up of 30 +/- 7 weeks, all 9 were symptom-free. One patient, 3 wk after implantation and while being hospitalized for hypovolemic shock, developed recurrent infarction. These favorable preliminary outcomes suggest that AVGCS may play a useful role in the treatment of thrombus-containing lesions.

Angioplasty, Balloon↗
PubMed1997

Arterial autologous graft-stent for treatment of coronary artery disease: a new technique.

The radial artery has been used as a free bypass graft with excellent results. An autologous vein graft-coated stent, a novel type of stent developed at our institution, has been applied successfully under both experimental and clinical conditions. To extend the spectrum of biological linings for coated stents, we used an arterial graft. We describe the first application of the radial artery as an autologous coating for a conventional stent to be used in treatment of coronary artery disease.

Aged↗
PubMed1997

Impaired compensatory coronary artery enlargement in atherosclerosis contributes to the development of coronary artery stenosis in diabetic patients. An in vivo intravascular ultrasound study.

AIMS: Coronary arteries affected by atherosclerosis undergo focal compensatory enlargement, which can be detected by intracoronary ultrasound but not by angiography. Diabetic patients when compared with non-diabetics have a more accelerated progression of coronary artery disease and a more diffuse narrowing of the coronary arteries. Intracoronary ultrasound can clarify if this is due to less compensatory coronary artery enlargement as a response to atherosclerosis. METHODS AND RESULTS: Ten non-diabetic and 15 diabetic patients with coronary artery disease, with angiographically determined one- or two-vessel disease, underwent intracoronary ultrasound examination of the non-stenotic coronary artery. Forty-five sites with luminal stenosis, detected by intracoronary ultrasound, were analysed (15 in non-diabetics, 30 in diabetics). Vessel and lumen area, atherosclerotic plaque area and plaque composition were evaluated. Vessel area was also measured proximal and distal to the healthy segment. In the diabetic patients, there was less vessel area increase from the proximal healthy segment into the atherosclerotic segment than in the non-diabetic patients (99% separate-variance confidence intervals for differences between diabetics' and non-diabetics' means = 0.29 mm2, 2.71 mm2). The proximal plaque free vessel area, the atherosclerotic plaque area and plaque composition were similar between the two groups. CONCLUSION: Diabetics with atherosclerosis have less compensatory coronary artery enlargement than non-diabetics. This may explain the diffuse and accelerated course of coronary artery disease in these patients.

Constriction, Pathologic↗
PubMed1996

A new adjustable temporary stent catheter for management of acute dissection during balloon angioplasty.

Acute coronary dissection remains a limitation of percutaneous transluminal coronary angioplasty. For the management of acute coronary dissection, a new adjustable temporary stent catheter that can be positioned to the lesion, deployed, and retrieved at a later stage was developed. This catheter has at its distal end a spiral stent that can be reduced and expanded in a controlled fashion by external manipulations. The adjustable temporary stent catheter was applied in three clinical cases with acute coronary dissection during balloon angioplasty. In all cases, the adjustable temporary stent catheter restored blood flow when it was expanded to the lesion for 60 min and this restoration was maintained after device removal. It is envisioned that this temporary stent device may prove a useful means for the treatment of acute coronary dissection during percutaneous transluminal coronary angioplasty.

Angina Pectoris↗
PubMed1996

Autologous vein graft-coated stent for treatment of coronary artery disease.

Acute or subacute thrombosis and late restenosis remain the main limitations of permanent stenting. In an effort to address these limitations, an autologous vein graft-coated stent (AVGCS) was developed at our institution. This stent consists of a conventional stent (Palmaz or Palmaz-Schatz, Johnson and Johnson), which is covered by an autologous vein graft. After successful experimental implantation, we report here the immediate results of the percutaneous implantation of AVGCS in 7 patients with coronary artery disease (6 de novo lesions and 1 bailout case). The results of this preliminary study indicate that the preparation of the AVGCS is easy and feasible. The implantation of the AVGCS was uncomplicated, and the immediate angiographic results were excellent. This new type of coated stent may be useful in addressing current limitations of balloon angioplasty.

Aortic Dissection↗
PubMed1996

Stents wrapped in autologous vein: an experimental study.

OBJECTIVES: A new type of coated stent, consisting of a conventional stent covered by an autologous vein graft, was developed at our institution. BACKGROUND: Coated stents are under investigation to address stenting limitations. However, experimental implantation of coated stents covered by autologous tissue has not been reported. METHODS: An autologous vein graft was removed and carefully prepared. Subsequently, a Palmaz stent was covered by the vein graft both internally and externally. Twenty-seven stents were implanted in the normal iliac arteries of 27 pigs weighing 18 to 33 kg. In 15 of the pigs, 15 noncoated Palmaz stents were implanted in the contralateral artery; these animals served as the control group. The animals were followed up angiographically for a period ranging from 7 days to 6 months. At the time of death, the stented segments were removed, and histomorphometric analysis was performed. RESULTS: Autologous vein graft-coated stent preparation and implantation was feasible and uncomplicated. In both stents, angiographic follow-up revealed the absence of thrombosis, except for two cases of subacute thrombosis in the control group. The thickness of the intimal layer was greater in the coated stents and seems to be due to the existence of the internal vein layer ([mean +/- SD] 0.57 +/- 0.12 vs. 0.27 +/- 0.13 mm, p = 0.001). The arterial media of the coated stent segments was thinner than that in the control group (0.14 +/- 0.03 vs. 0.18 +/- 0.01 mm, p = 0.02). CONCLUSIONS: The autologous vein graft-coated stent seems to be nonthrombogenic, and only minimal hyperplasia was observed in the pigs. Further studies are needed to explore the efficacy of this technique in humans.

Animals↗
PubMed1995

Pressure-diameter relation of the human aorta. A new method of determination by the application of a special ultrasonic dimension catheter.

BACKGROUND: Pressure-diameter relation of the aorta provides important information about the elastic properties of the vessel. However, owing to methodological limitations, data regarding this relation are limited in conscious humans. In the present study, we assessed a new method for the direct estimation of the elastic properties of the aorta in conscious humans by simultaneous acquisition of instantaneous aortic pressure and diameter. METHODS AND RESULTS: With this method, instantaneous diameter of the thoracic aorta was acquired by a newly designed intravascular catheter developed in our institution that incorporates an ultrasonic displacement meter at its distal end. Instantaneous aortic pressure was acquired simultaneously at the same aortic level with a catheter-tip micromanometer. Aortic pressure-diameter loops were derived from computer analysis of data. After in vitro and animal testing, elastic properties of the aorta were investigated in coronary artery disease (CAD) patients (n = 15) and compared with those of control subjects (n = 10). Aortic distensibility was less in the CAD group than in the control group (1.73 +/- 0.33 versus 3.95 +/- 1.09 x 10(-6) x cm2 x dyne-1, P < .001). Compared with control subjects, the mean value of the slope of the pressure-diameter loops was significantly greater in the CAD group (38.89 +/- 8.75 versus 19.62 +/- 5.46 mm Hg.mm-1, P < .001), whereas the mean value of the intercept was lower in this latter group of patients (-785.60 +/- 177.55 versus -313.43 +/- 126.41 mm Hg, P < .001). An excellent correlation was found between the slope of pressure-diameter loop and age in the group of control subjects (r = .827). Ninety-three percent of the patients with CAD had values above the upper 95% confidence limits of the control subjects (P < .001). In a third group of patients (n = 16) in whom assessment of pulse wave velocity was also included in the study of the elastic properties of the aorta, pulse wave velocity had a strong inverse correlation with aortic distensibility (r = -.95) and a strong positive correlation with the slope of the pressure-diameter loop (r = .97). CONCLUSIONS: This new method of determination of pressure-diameter of the aorta enables an accurate and reliable evaluation of the elastic properties of the aorta in conscious humans and may be useful for a profound study of human aorta mechanics.

Animals↗