PubMed Health⌕ Search

Biomedical subjects

M A García-Fernández

Publications and source records attributed to M A García-Fernández.

At least 19 recordsLinked to original sources
PubMed2006

Cardiac motion analysis from ultrasound sequences using nonrigid registration: validation against Doppler tissue velocity.

Early detection of cardiac motion abnormalities is one of the main goals of quantitative cardiac image processing. This article presents a new method to compute the 2-D myocardial motion parameters from gray-scale 2-D echocardiographic sequences, making special emphasis on the validation of the proposed technique in comparison with Doppler tissue imaging. Myocardial motion is computed using a frame-to-frame nonrigid registration technique on the whole sequence. The key feature of our method is the use of an analytical representation of the myocardial displacement based on a semilocal parametric model of the deformation using Bsplines. Myocardial motion analysis is performed to obtain displacement, velocity and strain parameters. Robustness and speed are achieved by introducing a multiresolution optimization strategy. To validate the method, velocity measurements in three different regions-of-interest in the septum have been compared with those obtained with Doppler tissue velocity in healthy and pathologic subjects. Regression and Bland-Altman analysis show very good agreement between the two different approaches, with the great advantage that the new method overcomes the angle-dependency limitations of the Doppler techniques, providing both longitudinal and radial measurements.

Echocardiography↗
PubMed2006

Support vector analysis of color-Doppler images: a new approach for estimating indices of left ventricular function.

Reliable noninvasive estimators of global left ventricular (LV) chamber function remain unavailable. We have previously demonstrated a potential relationship between color-Doppler M-mode (CDMM) images and two basic indices of LV function: peak-systolic elastance (Emax) and the time-constant of LV relaxation (tau). Thus, we hypothesized that these two indices could be estimated noninvasively by adequate postprocessing of CDMM recordings. A semiparametric regression (SR) version of support vector machine (SVM) is here proposed for building a blind model, capable of analyzing CDMM images automatically, as well as complementary clinical information. Simultaneous invasive and Doppler tracings were obtained in nine mini-pigs in a high-fidelity experimental setup. The model was developed using a test and validation leave-one-out design. Reasonably acceptable prediction accuracy was obtained for both Emax (intraclass correlation coefficient Ric, = 0.81) and tau (Ric, = 0.61). For the first time, a quantitative, noninvasive estimation of cardiovascular indices is addressed by processing Doppler-echocardiography recordings using a learning-from-samples method.

Algorithms↗
PubMed2005

Effects of angiotensin converting enzyme inhibitors in hypertensive patients with aortic valve stenosis: a drug withdrawal study.

OBJECTIVE: To determine the effects of angiotensin converting enzyme (ACE) inhibitors in hypertensive patients with aortic valve stenosis (AS). DESIGN: Observational, drug withdrawal, single blinded study, with randomisation of the order of tests. SETTING: Hypertension and asymptomatic AS. PATIENTS AND INTERVENTIONS: 20 patients (aged 73 (9) years, valve area 0.7 (0.3) cm2, left ventricular ejection fraction > or = 45%) were enrolled. Each patient underwent two sets of tests (with and without taking the drug), each of which included clinical evaluation, Doppler echocardiogram, and symptom limited exercise echocardiography. MAIN OUTCOME MEASURES: Functional and haemodynamic variables while taking and not taking ACE inhibitors. RESULTS: Drug intervention induced no change in patients' subjective functional class. While taking ACE inhibitors, patients had a lower systolic blood pressure (140 (18) mm Hg with ACE inhibitors v 159 (12) mm Hg without ACE inhibitors, p = 0.02), a higher mean pressure gradient (34 (15) mm Hg v 28 (18) mm Hg, p = 0.037), and a higher left ventricular stroke work loss (19 (6)% v 14 (10)%, p = 0.009). Other baseline functional and haemodynamic parameters were unmodified. Five patients had an abnormal blood pressure response during one of the exercise tests (two patients while taking the drug and three patients while not taking the drug). When taking ACE inhibitors, patients had a higher stroke volume at peak stress (59 (11) ml v 54 (25) ml, p = 0.046). All other stress variables remained constant. CONCLUSIONS: In AS, the afterload relief caused by ACE inhibitors is blunted by a parallel increase in the pressure gradient. However, ACE inhibitors favourably affect stress haemodynamic function in most hypertensive patients with AS and should not be discontinued.

Aged↗
PubMed2004

Two years' activity of the Veterinary Toxicology Attention Service of Lugo, Spain.

The Veterinary Toxicology Attention Service was created at the beginning of 2001 as the first on-line toxicology service for veterinarians and animal owners in Spain. In the present study, data about the general functioning of the Service and the toxicological analysis and consultations performed are summarized. Canine-related cases constituted the main call group and veterinary practitioners represented half of the consultations. Coordination between all veterinary toxicology services in Spain and the rest of the European Union should improve this service.

Animals↗
PubMed2003

Portable spectral Doppler echocardiographic device: overcoming limitations.

BACKGROUND: There is evidence that new portable echocardiographic devices are useful in evaluating heart anatomy and function, but a lack of Doppler modes has up to now been an important limitation in obtaining haemodynamic data. OBJECTIVES: To report the Doppler capabilities of a new hand held echocardiographic device. DESIGN: Blinded comparison of two types of echocardiography machine. SETTING: Tertiary care centre. PATIENTS: 98 consecutive patients were randomly imaged with the hand held device, with a standard platform as reference. OUTCOME MEASURES: Pulsed wave transmitral Doppler inflow tract velocities, deceleration time, and continuous wave Doppler measurements of aortic ejection and tricuspid regurgitation peak velocities were recorded. RESULTS: There was excellent agreement between the hand held device and standard echocardiography for the evaluation of diastolic E and A waves, E/A ratio, and deceleration time with pulsed wave Doppler (intraclass correlation coefficients of 0.97, 0.93, 0.90, and 0.78, respectively). In addition, good agreement was found between continuous wave Doppler measurements of aortic ejection and tricuspid regurgitation velocities (intraclass correlation coefficients of 0.96 and 0.80). However, there was a significant difference between patients with tricuspid regurgitation measured with the hand held device (25.5%) and by standard echocardiography (65.3%), resulting in misdiagnosis of eight patients with pronounced pulmonary hypertension. CONCLUSIONS: New hand held devices with Doppler capabilities overcome previous limitations in evaluating haemodynamic variables. With colour Doppler they are now suitable for the complete evaluation of valvar disease and diastolic function. However, important limitations remain in the evaluation of pulmonary pressures.

Aortic Valve Stenosis↗
PubMed2001

Spatio-temporal mapping of intracardiac pressure gradients. A solution to Euler's equation from digital postprocessing of color Doppler M-mode echocardiograms.

Doppler assessment of intracardiac pressure gradients using the simplified Bernoulli equation is inaccurate in the absence of a restricted orifice. The purpose of this study is to develop a new general method to map instantaneous pressure gradients inside the heart using Doppler echocardiography. Color Doppler M-mode recordings are digitally postprocessed with a software algorithm that decodes flow velocity and fits a bivariate spatio-temporal tensor-product smoothing spline. Temporal and spatial accelerations are then calculated by analytical derivation of the fitted velocity data, allowing solution of both inertial and convective terms of Euler's equation. A database of 39 transmitral inflow and transaortic outflow color Doppler M-mode recordings from 20 patients with a number of cardiac conditions was analysed, along with matched pulsed-wave spectral recordings. A close agreement was observed between the spectral and postprocessed color Doppler velocity values (error = 0.8 +/- 11.7 cm/s), validating the data decoding and fitting process. Spatio-temporal pressure-gradient maps were obtained from all studies, allowing visualisation of instantaneous pressure gradients from the atrium to the apex during left ventricular filling, and from the apex to the outflow tract during ejection. Instantaneous pressure differences between localised intracardiac sample points closely matched previously published catheterization findings, both in magnitude and waveform shape. Our method shows that intracardiac instantaneous pressure gradients can be analysed noninvasively using color Doppler M-mode echocardiography combined with image postprocessing methods.

Adult↗
PubMed2001

Use of contrast echocardiography in the diagnosis of subacute myocardial rupture after myocardial infarction.

Myocardial rupture is an uncommon and catastrophic complication after acute myocardial infarction. It can present in an acute form or in a subacute form, with slower hemorrhage and thrombus formation at the site of rupture. These patients can survive several hours or days before the diagnosis is confirmed and the myocardial ruptured repaired. Two-dimensional Doppler echocardiography is very useful in the diagnosis of this complication, but the number of false-positive diagnoses is high, even in the presence of a large amount of pericardial effusion. In these patients, administration of a contrast agent can be useful to demonstrate active bleeding into the pericardium. We report a case of subacute myocardial rupture for which contrast echocardiography was useful in demonstrating the presence of persistent hemorrhage into the pericardium. To reduce the number of false-positive diagnoses, contrast echocardiography should be considered in patients with possible subacute myocardial rupture.

Aged↗
PubMed2001

[Meaning of clinical and electrical positivity in the myocardial perfusion scintigraphy during the administration of dipyridamole].

BACKGROUND AND OBJECTIVES: Administration of dipyridamole produces angina and ST depression in 20%-30% and 6%-34% of patients, respectively. This study aimed to evaluate the clinical implications of the presentation of angina and/or ST depression during the administration of dipyridamole in the study of coronary heart disease by myocardial perfusion SPECT (MPS). METHODS: The study population is constituted by 593 consecutive patients without left branch block or ventricular pacemaker rhythm who were referred to our service to undergo MPS with dipyridamole. A SPECT was performed after the administration of 99mTc-tetrosfosmine and drug stimulation with dipyridamole (0.142 mg/kg/min for 4 minutes). A coronariography was performed in 338 patients (57%). The frequency of clinical and electrical positivity and their relationship with the MPS and the coronariography were studied. RESULTS: The rate of angina and ST depression was 32% (n = 190) and 10% (n = 58), respectively. Myocardial perfusion defects were observed in 465 patients (78%), and signs of scintigraphic ischemia in 311 (52%). The patients with ST depression presented a higher frequency of perfusion defects (93% vs 76%, p = 0.0012) and scintigraphic ischemia (89% vs 49%, p < 0.0001). In addition, perfusion defects in more than one territory were observed in these patients in a higher percentage (53% vs 34%, p = 0.0036). Among the patients who underwent cardiac catheterization, those who had a ST depression had a greater extension of coronary heart disease (1.8 +/- 1.2 vs 1.3 +/- 1.0 diseased vessels, respectively. p = 0.0100) and a higher frequency of multivessel disease (61% vs 43%, p = 0.0380). Those patients who had clinical positivity showed a scintigraphic ischemia more frequently (66% vs 47%, p < 0.0001), however no statistically significant differences were observed between the presence of patients with perfusion defects or in the extension of these defects as well as in the number of diseased vessels in the coronariographic study. CONCLUSIONS: During the administration of dipyridamole, the ST depression is associated with more frequent scintigraphic ischemia, larger extension of perfusion defects and more diseased vessels. The appearance of angina is associated with scintigraphic ischemia, but it is not necessarily associated with the extension of perfusion defects or greater number of diseased vessels.

Angina Pectoris↗
PubMed2001

Doppler tissue imaging.

This paper try to give a general overview of the main areas of DTI clinical application, its main technical limitations, new directions still under investigation and some potential future developments of this emerging imaging technique. In this review article we pretend to discuss the main aspects of the new DTI method, its present "state of the art" and future perspectives of scientific and technical development.

Diastole↗
PubMed2001

Dynamic three dimensional evaluation of intracardiac flow.

Three-dimensional color Doppler is a new technique that provides three dimensional images of intracardiac flow jets. Despite the different measurement methods available, noninvasive quantification of valve regulation is still controversial in some cases. It is also sometimes difficult to appreciate the spatial extension of the jet. Visualisation of regurgitant flows in three dimensions shows its complex shape, origin, direction and spatial distribution, and correlates accurately with regurgitant volume and regurgitant fraction by different methods (angiography, two-dimensional Doppler). Unnoticed its in the two-dimensional image have been detected with the three-dimensional image and additional qualitative information to the two dimensional image has been provided by this new technique in a high percentage of patients.

Aortic Valve Insufficiency↗
PubMed2001

Quantification of myocardial perfusion using contrast echocardiography: methodological basis of image postprocessing.

Intravenous contrast agents have provided the opportunity to clinically assess myocardial perfusion using ultrasound. In perfusion echocardiography, obtaining maximal diagnostic information requires the use of digital image postprocessing techniques, since subjective visual interpretation can be frequently inaccurate. Prior research using other intravascular tracers such as radioactive microspheres provides the theoretical basis for perfusion analysis that can be readily implemented to contrast echocardiography. Aspects of digital videodensitometric quantification, fitting to gamma-variable mathematical wash-in/wash-out functions and parameter analysis have been well validated for other tracers and have demonstrated excellent applicability in contrast echo. Currently available scanner technologies provide with a number of image-acquisition modalities, from standard continuous to intermittent-triggered images that require specific postprocessing algorithms. The present paper reviews the basis of temporal and spatial contrast postprocessing. The issues of image registration, background subtraction, videointensity measurement and mathematical function fitting are also discussed. This theoretical background should be helpful to understand the general aspects of currently available and future systems of perfusion densitometric systems.

Coronary Circulation↗
PubMed2000

Predictors of left atrial spontaneous echo contrast and thrombi in patients with mitral stenosis and atrial fibrillation.

The purpose of this study was to investigate the independent factors associated with the presence of left atrial (LA) spontaneous echo contrast (SEC) and thromboembolic events in patients with mitral stenosis (MS) in chronic atrial fibrillation (AF). Factors independently associated with LASEC, thrombi, and embolic events have been mainly investigated in patients with nonvalvular AF or inhomogeneous populations with rheumatic heart disease. Transesophageal and transthoracic echo studies were performed in 129 patients with MS in chronic AF. Previous embolic events were documented in 45 patients, 20 of them within 6 months, and 65 patients were receiving long-term anticoagulation. The intensity of LASEC and mitral regurgitation, the presence of thrombi and active LA appendage flow (peak velocities > or = 20 cm/s), and LA volume as well as other conventional echo-Doppler determinations were investigated in every patient. The prevalences of significant LASEC (degrees 3+ and 4+), thrombus, active LA appendage flow, and significant mitral regurgitation (>2+) were: 52% (67 patients), 29.5% (38 patients), 32% (41 patients), and 36% (47 patients), respectively. Multivariate analysis showed that decreasing mitral regurgitation severity, absence of active LA appendage flow, and mitral valve area were the independent correlates of LASEC (odds ratio [OR] 3.7, 5.4, and 0.17, respectively; all p <0.02). Active LA appendage flow and anticoagulant therapy were associated negatively, whereas the severity of LASEC was associated positively with the finding of LA thrombus (OR 9.6, 3.9, and 1.6, respectively; all p <0.05). The intensity of LASEC and previous anticoagulant therapy (OR 1.74 and 4.5, respectively; p <0.005) were the independent covariates of thrombi and/or recent embolic events. In conclusion, the severity of mitral regurgitation and lack of active LA appendage flow were, respectively, the strongest independent correlates of significant LASEC and thrombus in patients with MS in chronic AF. LASEC remains the cardiac factor most strongly associated with thrombus and/or recent embolic events in these patients.

Atrial Appendage↗
PubMed2000

Frequency of left ventricular free-wall rupture in patients with acute myocardial infarction treated with primary angioplasty.

A total of 590 patients with myocardial infarction treated with primary angioplasty were studied, to assess the incidence and related factors of free-wall rupture in patients with acute myocardial infarction when treated with primary angioplasty. The incidence of free-wall rupture was 2.2% (13 patients); this incidence was higher in patients >65 years old, women, nonsmokers, as well as in those with anterior location and an initial TIMI grade 0 flow, but it was similar in patients with a successful or unsuccessful angiographic result.

Angioplasty, Balloon, Coronary↗
PubMed2000

Flow dynamics of stenotic aortic valves assessed by signal processing of Doppler spectrograms.

Clinical assessment of aortic stenosis (AS) is sometimes challenging, because all hemodynamic indexes of severity are modified by flow rate. However, the mechanisms underlying flow dependence remain controversial. Analysis of instantaneous flow dynamics has provided crucial information in a number of cardiovascular disorders and may add new insight into this phenomenon. This study was designed to analyze in vivo the effects of flow interventions on instantaneous valvular dynamics of stenotic valves. For this purpose, a custom algorithm for signal processing of Doppler spectrograms was developed and validated against a control population. Digital Doppler recordings at the aortic valve and left ventricular outflow tract were obtained in 15 patients with AS, at baseline and during low-dose dobutamine infusion; 10 normal subjects were studied as controls. Spectrograms were processed by signal averaging, time alignment, modal-velocity enhancement, envelope tracing, and numerical interpolation. Instantaneous relative aortic valve area (rAVA) was obtained by the continuity equation and plotted against normalized ejection time. Curves were classified as either type A (rapid, early-systolic opening) or type B (slow, end-systolic opening). Curves from controls closely matched prior knowledge of normal valve dynamics, but curves from patients were clearly different: all controls except 2 (80%) had type A, whereas all patients except 3 (80%) had a type B pattern (p = 0.03). Dobutamine infusion in patients increased and slightly anticipated peak rAVA by accelerating valve opening. Despite similar values of area and pressure difference, type B dynamics were associated with lower blood pressure (p = 0.01) and worse long-term outcome (>3 years) than type A flow dynamics (p = 0.02). Signal processing of Doppler spectrograms allows a comprehensive assessment of aortic flow dynamics. Differences in timing of valve aperture and in maximal leaflet excursion account for flow-mediated changes in valve area, suggesting complementary effects of inertia and elasticity on the kinetics of stenotic aortic valves. Flow-dynamic analysis provides novel clinical information regarding physiology of AS unavailable to conventional indexes.

Aged↗
PubMed2000

[Results of myocardial scintigraphy with 99mTc-tetrofosmin and dipyridamole administration in patients diagnosed of microvascular angina].

The objective of the study was to evaluate the results of the myocardial scintigraphy with 99mTc-tetrofosmin (Tc-Tf) and pharmacological stimulation with dipyridamole in patients diagnosed of microvascular angina. The study population is made up of 50 patients discharged with the diagnosis of microvascular angina who had undergone Tc-Tf-dipyridamole. Clinical and electrical positivity appeared in 40% and 12% of the patients, respectively. Myocardial perfusion defects were found in 35 patients (70%), and were reversible in 21 (60%), fixed in 11 (21%), and combined in 3 (9%). Abnormalities were inferior, anteroseptal and lateral in 21, 18, and 2 patients, respectively. Patients with a positive exercise treadmill test, compared with those with a negative one, had more frequent perfusion abnormalities (91% vs 50%, p = 0.0327) and myocardial ischemia (64% vs 20%, p = 0.392). Women, in comparison with men, had angina (56% vs 22%, p = 0.013), and anteroseptal perfusion abnormalities (26% vs 4%, p = 0.028) more frequently. On the contrary, men had inferior perfusion abnormalities more frequently (57% vs 30%, p = 0.057). Thus, Tc-Tf-dipyridamole shows perfusion abnormalities in 70% of patients with microvascular angina (91% in patients with a positive exercise treadmill test). Scintigraphic pattern may be partially conditioned by gender in these patients.

Coronary Circulation↗