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Biomedical subjects

A Amico

Publications and source records attributed to A Amico.

At least 19 recordsLinked to original sources
PubMed2001

Response of biochemical markers of bone turnover to estrogen treatment in post-menopausal women: evidence against an early anabolic effect on bone formation.

Bone loss following menopause can be prevented or reduced by estrogen replacement therapy (ERT). The primary action of estrogen on bone is generally considered to be antiresorptive, but some evidence would also suggest a stimulatory effect on bone formation. The aim of this study was to assess the effect of ERT on biochemical markers of bone resorption (urinary pyridinoline and deoxypyridinoline), and of bone formation (bone-specific alkaline phosphatase--B-ALP, and the C-terminal propeptide of type I collagen--CICP) in a group of 25 postmenopausal women with no evidence of osteoporosis. Since the suggested anabolic effect of estrogen seems to take place in the early period of ERT, we measured the response of markers immediately before and after the start of treatment (30, 60, 120 and 180 days). The markers of bone resorption started to decrease at 30 days and remained low thereafter. We also observed a similar decrease in serum levels of B-ALP and CICP, reflecting a reduction of bone formation rate. Our data would indicate that ERT at the given dose does not have early anabolic effects on bone, in addition to its recognized suppressive effect on bone resorption.

Alkaline Phosphatase↗
PubMed1999

Immobilization-dependent bone collagen breakdown appears to increase with time: evidence for a lack of new bone equilibrium in response to reduced load during prolonged bed rest.

The purpose of this study was to evaluate the effect of prolonged immobilization on bone, in order to investigate how skeletal turnover adapts to bed rest. We examined indices of bone formation and bone resorption in the serum and urine of fifty-four patients (26 males and 28 females) immobilized after an episode of paralytic stroke. The length of immobilization ranged from 30 to 180 days. A significant, time-dependent increase in markers of resorption - urinary pyridinoline (Pyr) and deoxypyridinoline (D-Pyr), serum Type I collagen cross-linked C-telopeptide (ICTP) - was observed in immobilized patients, as compared to free-living healthy subjects. The positive correlation between resorption markers increase and the length of immobilization suggests that the rate of bone resorption did not decrease with time. On the other hand, the levels of markers of bone formation - bone-specific alkaline phosphatase (B-ALP), and the carboxyl-terminal propeptide of Type I procollagen (PICP) - remained within the normal range in all patients, regardless the length of immobilization. Our results would indicate an uncoupling between bone formation and bone resorption during bed rest, and suggest that the bone collagen break-down was not a self-limiting process in immobilized patients, and that a new equilibrium or "steady state" in response to the reduced load was not reached in the skeleton.

Aged↗
PubMed1996

Myocardial contrast echocardiography in acute myocardial infarction. Pathophysiological background and clinical applications.

Myocardial contrast echocardiography is a technique used in experimental and clinical settings in order to visualize the pattern of intramyocardial perfusion. In the acute phase of myocardial infarction, regional absence of flow during myocardial contrast echocardiography delineates the area at risk of necrosis, while the definitive non-perfused area expresses infarct size. Reopening the infarct-related artery, which may be achieved spontaneously by thrombolysis or percutaneous transluminal coronary angioplasty, is not a reliable indicator of intramyocardial reperfusion. If myocardial ischaemia due to coronary occlusion has been sufficiently prolonged and severe, not only myocyte viability, but also microvascular integrity is lost. Myocardial contrast echocardiography, using intracoronary injection of sonicated contrast medium, gives information about microvascular integrity and the effective presence of intramyocardial reflow. Anatomical integrity of microvasculature does not necessarily imply preserved function, and thus the microvessel vasodilating reserve may also be impaired. Myocardial contrast echocardiography has the potential to assess alterations in microvascular function, showing, in the myocardial area with reduced coronary reserve, a relatively reduced increase in echocontrast signal intensity when an intravenous vasodilator agent is administered.

Animals↗
PubMed1993

[Oxidative stress in patients undergoing general anesthesia].

The alterations in the normal biological oxide-reductive balance can be due both to an increase of the plasmatic concentration of the free radicals and to the less of the protective mechanism. These conditions lead to damage to cellular structure by the mechanism of lipoperoxidation, particularly in the liver, in the kidney and in the central nervous system. In this study we have studied the lipoperoxidative effects of the use of anesthetic drugs.

Anesthesia, General↗
PubMed1991

Echo-Doppler evaluation of the effects of heart rate increments on left atrial pump function in normal human subjects.

It is commonly believed that the atrial contribution to left ventricular filling increases during heart rate increments. However, the relative contribution of the pump function (atrial systole) and of the passive role (diastasis and reservoir) of the atrium to end-diastolic left ventricular filling is not well known. In order to investigate this problem, we performed a two-dimensional echo-Doppler study during right atrial pacing. Transmitral flow velocity curves were obtained by means of pulsed Doppler. Pacing was performed (1) at the lowest heart rate at which it was possible to obtain a stable capture of the atria, (2) at the heart rate at which the early and late Doppler filling waves almost completely overlapped. In both stages pacing was interrupted for a few seconds to obtain some post-pacing beats. Doppler tracing recorded at rest, during pacing and in the immediate post-pacing beats were analysed to obtain well-known parameters of atrial contribution; atrial peak flow velocity, early to atrial peak flow velocity ratio, and time-velocity integral of the atrial wave. Furthermore, in order to distinguish end-diastolic passive flow from the active contribution of atrial systole to filling, we superimposed the envelope of the last Doppler curve obtained during atrial pacing over the envelope of the first post-pacing curve. In this way the area of the atrial wave of the paced beat was divided by the mid-diastolic part of the post-pacing one into two areas, the integrals of which correspond to the active and passive atrial contribution respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Prediction of cardiac events after uncomplicated myocardial infarction by cross-sectional echocardiography during transesophageal atrial pacing.

Atrial pacing can safely be utilized shortly after myocardial infarction. To evaluate the prognostic value of wall motion abnormalities induced by such pacing 83 consecutive patients with recent uncomplicated myocardial infarction underwent transthoracic cross-sectional echocardiography during transesophageal atrial pacing and upright bicycle exercise stress test. Patients were followed-up for 14 +/- 5 months. During the atrial pacing and the echocardiography, patients were defined at high risk if abnormalities of wall motion were detected in left ventricular regions remote from the infarcted area. Then, during the exercise stress test, high risk patients were those with ST segment depression greater than or equal to 1 mm. On the other hand, patients were considered to be at low risk if they had no abnormalities of wall motion during atrial pacing in remote regions or, in the case of the stress test, if they did not develop ST depression greater than or equal to 1 mm. Of the 83 patients, 21 had major cardiac events during the period of follow-up. Cardiac events occurred in 15/23 (65%) and 5/60 (8%, P less than 0.001) patients assigned to the groups adjudged to be at high and low risk, respectively, on the basis of echocardiographic results. Exercise testing was less reliable in identifying patients at risk of future cardiac events. Major events occurred in only 6 of the 19 patients with a positive stress test (32%, P less than 0.05 vs positive stress echocardiography) and in 14 of the 64 patients with a negative exercise stress test (22%, P = NS vs positive exercise stress test, P less than 0.05 vs negative atrial pacing echocardiography).

Cardiac Pacing, Artificial↗
PubMed1990

Errors in measurements of stroke volume for invasive and echo-Doppler evaluations of valvular regurgitant fractions. Clinical evaluation and computer simulation.

The aim of this study was to compare cardiac catheterization (CATH) with 2D echo-Doppler (ED) in clinically evaluating the stroke volumes (SV) needed to calculate aortic and mitral regurgitant fractions (aortic and mitral SV for the ED method, thermodilution and angiographic SV for the CATH). As there is no 'gold standard' for this kind of measurement, only subjects without valvular regurgitation were considered. In these subjects, though the two SV measurements needed to calculate the regurgitant volume should have been identical, there was, in fact a difference due to the systematic and random errors of the methods. We calculated the mean value and the standard deviation of this difference in a series of patients without valvular regurgitation in order to obtain an estimate of both systematic and random errors. In 20 patients studied by ED a difference of 11.9 +/- 16.7 ml was found. In 36 patients studied by cardiac catheterization the difference was 19.6 +/- 20.1 ml. A significant systematic error was found for both ED and the invasive method; The transmitral SV tended to be larger than the aortic and the angiographic SV larger than that obtained by thermodilution. To try to determine the extent to which the random errors could be attributed to the reproducibility of the measurements, we carried out computer simulations. The SVs of 50 000 hypothetical patients were randomly generated and then attributed a random error calculated on the basis of the variability of the CATH (thermodilution 4%, angiography 10%) and the ED measurements (aortic annulus 6%, mitral annulus 18%, mitral time velocity integral 10%, aortic time velocity integral 8%).(ABSTRACT TRUNCATED AT 250 WORDS)

Angiography↗
PubMed1988

Effects of acute intrathoracic pressure changes on left ventricular geometry and filling.

Acute changes in intrathoracic pressure (ITP) affect left ventricular (LV) function. It has been suggested that this functional impairment could be the result of an alteration in LV filling caused by a reduction in LV compliance induced by the rearrangement of biventricular geometry that occurs under these conditions. Therefore, to evaluate the effects of an acute increase or decrease in ITP on LV geometry and filling, we used two-dimensional and Doppler echocardiography to study 25 normal volunteers both during the Müller maneuver (acute decrease in ITP induced by a forced inspiration against a closed airway) and during continuous positive airway pressure breathing. During both maneuvers LV geometry was altered as demonstrated by the significant increase in the normalized curvature radius of the interventricular septum and the unchanged curvature radius of the LV free wall. LV filling was altered during both maneuvers as demonstrated by significant decreases in early peak flow velocity, early-to-late peak flow velocity ratio, and early deceleration rate. Thus, during maneuvers that acutely decrease or increase ITP, alterations in LV geometry occur. These acute distortions of LV geometry may be one of the mechanisms responsible for alterations in LV filling.

Adult↗
PubMed1988

Doppler echocardiographic evaluation of the effect of atrial pacing-induced ischemia on left ventricular filling in patients with coronary artery disease.

Very little is known about the effects of acute myocardial ischemia on left ventricular filling. Previous studies of these effects have been of limited value because they were performed with 1) imaging techniques that, like cineventriculography or radionuclide ventriculography, do not allow beat to beat monitoring of left ventricular filling throughout the entire ischemic attack; and 2) exercise, which, even if effective in inducing myocardial ischemia in patients with coronary artery disease, also considerably shortens cycle length, thus leading to additional nonischemic filling alterations. To overcome these limitations, left ventricular filling was studied by means of Doppler echocardiographic evaluation of transmitral flow velocities before and immediately after rapid atrial pacing in 17 patients. Eight patients had coronary artery disease but did not develop ischemia (ST depression greater than or equal to 1.5 mm) during atrial pacing (Group 1) whereas nine had coronary artery disease and developed ischemia during atrial pacing (Group 2). No differences were observed from rest to postpacing in any of the filling variables considered in Group 1 patients. In contrast, a significant rearrangement of left ventricular filling occurred during ischemia in Group 2 patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

Prediction of the extent of coronary artery disease with the evaluation of left ventricular wall motion abnormalities during atrial pacing. A cross-sectional echocardiographic study.

UNLABELLED: In patients with coronary artery disease, left ventricular performance during stress is affected by the degree of coronary stenosis. In order to verify whether there exists a relationship between the extent of wall motion abnormalities detectable during atrial pacing and the degree of coronary obstruction, 76 patients, without previous myocardial infarction, were studied. Each patient underwent cross-sectional echocardiography during transesophageal atrial pacing and exercise electrocardiography before coronary angiography. Of the 76 patients, 46 had significant coronary artery disease (stenosis greater than or equal to 75% of at least one major coronary vessel), while 30 had normal coronaries or a stenosis of less than 75%. Eighteen patients had single-, 14 had two- and 14 had three-vessel disease. For each patient a coronary score was obtained: the score used took into consideration the site, number and severity of the stenosis. This score was then correlated with the wall motion score, obtained from the analysis of 9 segments of the left ventricle. A weak correlation was obtained between wall motion score at rest and coronary score (r = -0.42), while the correlation between coronary score and the difference between wall motion score at rest and during transesophageal atrial pacing was slightly better (r = 0.53); this correlation further improved if wall motion score during pacing was considered (r = -0.63). If the patients with discordant diagnostic tests (echocardiography during transesophageal atrial pacing and exercise electrocardiography) were excluded, the correlation coefficient between coronary score and wall motion score during pacing increased even more (r = -0.77). IN CONCLUSION: (1) analysis of wall motion of the left ventricle during atrial pacing is useful for the non-invasive evaluation of the severity of coronary disease; (2) cross-sectional echocardiography during atrial pacing, apart from being a useful diagnostic tool, is also a help in judging the degree of severity of coronary artery disease.

Adult↗
PubMed1987

Color Doppler evaluation of aortic dissection.

Color Doppler studies were performed in 16 adult patients with proven DeBakey type I and III aortic dissection. Simultaneous opacification of both aortic lumina with oppositely directed flow was noted by color Doppler in at least one aortic segment in 14 of 16 patients (12 type I, two type III). In two patients (one type I, one type III), flow was seen in one lumen only, with clot demonstrated in the other lumen in one of them. Of 12 patients in whom communication between two aortic dissection channels was shown by angiography/surgery, color Doppler correctly identified them in nine patients (four ascending aorta, two aortic arch, and three descending aorta), either by direct visualization of flow moving from one lumen into the other (six patients) or indirectly by analyzing differences in timing of opacification of the two lumina and flow direction (three patients). Also, color Doppler correctly diagnosed aortic regurgitation as severe (aortic regurgitation jet occupying more than 75% of left ventricular outflow) in three patients and moderate in four patients. Color Doppler provides comprehensive evaluation of flow dynamics in aortic dissection.

Adult↗