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Biomedical subjects

S Lafitte

Publications and source records attributed to S Lafitte.

At least 19 recordsLinked to original sources
PubMed2006

[Identification of candidates for multisite pacing: results and presumed mechanisms of action after five years experience].

Biventricular resynchronisation is an additional therapeutic option in the management of refractory heart failure, with a functional and haemodynamic benefit as well as an improved morbidity and mortality. However, the rate of non-responsive patients has prompted a re-think about the presumed mechanisms of action for this procedure. This study aims to identify candidates more successfully. Based on five years experience in this centre, our work confirmed a medium and long term clinical benefit with multisite pacing. Nevertheless, there was evidence of a relative discordance between the functional benefit and the haemodynamic impact in terms of ejection fraction achieved with resynchronisation. While QRS narrowing appears to be a predictive factor for a successful procedure, the ECG alone is not sufficient to select 'unsynchronised' candidates. Statistical analysis reveals that before implantation the independent predictive factors to identify non-responsive patients include the presence of a complication of myocardial infarction and a low grade mitral leak. The limits of the ECG suggest a more mechanical than electrical approach to understanding the mechanisms of action for resynchronisation. Its effectiveness in cases of right bundle branch block confirm the hypothesis of left intra-ventricular conduction defects, not apparent on the surface ECG but accessible through new imaging techniques. Based on the hypothesis of delayed movement of the ventricular walls, the principle of resynchronisation aims to restore homogenous contraction. Echocardiography allows observation of electromechanical delay and opens new perspectives in the future for selecting patients for pacing. Ar

Cardiac Pacing, Artificial↗
PubMed2006

[Thrombosis of valvular prostheses: the role of medical treatment].

Thromboses of valvular prostheses represent a rare but serious complication for mechanical valves, and are sometimes fatal. Obstructive thromboses present an immediate threat to life, while the more common, more insidious, non-obstructive thromboses are essentially manifested by thrombo-embolic events. These thromboses often occur at times of insufficient anticoagulation, especially during the first post-operative year and during treatment breaks for non-cardiac surgery, an increasingly common situation. The therapeutic management of an 'obstructive' thrombosis is above all surgical. However, fibrinolysis represents an effective alternative, although it does present a not insignificant risk of systemic embolism (in the order of 10 to 15%). The main indications for fibrinolysis are thromboses of right heart valves, and for left heart prostheses, patients in a very unstable haemodynamic state, remoteness from a cardiac surgery centre, any surgical contraindications, and cases where a large thrombus has been excluded by trans-oesophageal ultrasound. In cases of contraindications to both surgery and fibrinolysis, treatment with heparin might be proposed, but without any great hopes of completely unblocking the prosthesis. Treatment of a 'non-obstructive' thrombosis is primarily medical: optimising anticoagulation with intravenous heparin, or even the addition of aspirin. When the thrombus is large and mobile, surgery should be envisaged if medical treatment fails.

Algorithms↗
PubMed2005

[Asynchronism and right ventricular pacing].

UNLABELLED: In patients with congenital heart block (CHB), dual-chamber pacing restores physiological heart rate and atrio-ventricular synchronization. However, patients with narrow QRS junctional escape rhythm may be deleteriously affected by long-term, permanent, apical ventricular pacing. We assessed the impact of apical ventricular pacing on echocardiographic ventricular dyssynchrony and hemodynamic parameters. METHODS: Fourteen CHB adults (23 +/- years, 58% male), with a DDD transvenous pacemaker and a junctional escape rhythm (QRS<120 ms) before implantation, were studied. Echocardiography coupled with tissue Doppler imaging (TDI) and Strain rate was performed in spontaneous rhythm (VVI mode 30/mn) and during atrio-synchronized ventricular pacing. RESULTS: The heart rate (43 +/- 09 vs 68 +/- 07: p<0.01), cardiac output (2.9 +/- 0.7 vs 3.7 +/- 0.6 L/min) and left ventricular filling time (325 +/- 38 vs 412 +/- 51 ms; p<0.01) were significantly less in the escape spontaneous rhythm compared with atrio-ventricular synchronized apical pacing. However, interventricular dyssynchrony (28 +/- 12 vs 59 +/- 25 ms, p<0.05), intra-left ventricular dyssynchrony (36 +/- 11 vs 57 +/- 29 ms; p<0.05), extent of left ventricular myocardium displaying delayed longitudinal contraction (26 +/- 10 vs 39 +/- 17%: p<0.05) were significantly less in the escape rhythm compared with paced rhythm. CONCLUSION: Once implanted with a DDD pacemaker, CHB patients present with increased cardiac output secondary to the restoration of physiological heart rate and improved diastolic function. However, the apical site is not optimal, as it creates detrimental ventricular dyssynchrony in patients with previous nearly physiological ventricular activation. Alternative pacing sites should be investigated.

Adult↗
PubMed2005

[Echocardiography and biventricular resynchronisation].

Biventricular resynchronisation has been recently shown to be an effective therapeutic option in patients with refractory dilated cardiomyopathy. Based on the finding of ventricular asynchrony, the aim of the method is to restore uniform contraction of the ventricular walls. However, the initial electrocardiographic criteria for selection of patients were only associated with a 70% rate of response. Consequently, it became necessary to refocus this method in patients with true ventricular asynchrony. Echocardiography is one of the non-invasive techniques which provides morphological and functional analysis of the myocardium with a high degree of accessibility. The multiplication of tools for echocardiographic quantification has been very valuable from a theoretical point of view for assessing ventricular asynchrony. In practice, techniques such as Doppler tissue imaging are being validated, but already offer the possibility of a multi-directional approach to this pathology. The diagnosis of asynchrony is based on a range of echocardiographic findings which not only improve the selection of patients but also optimise the programming of multisite stimulation.

Cardiac Pacing, Artificial↗
PubMed2005

[Diagnosis difficulty in occult constrictive pericarditis].

We report the case of a 42 years woman known to have a cardiac heart failure attributed to restrictive cardiomyopathy for want of any other plausible diagnosis. Evolution and repeted investigations finally permitted to rectify the diagnosis by revealing a constrictive pericarditis, remained occult 9 years during. The differentiation of restrictive cardiomyopathy and constrictive pericarditis has been a perennial problem in clinical cardiology. Diagnosis of constrictive pericarditis is based on associated signs sometimes too poor to go straight to thoracotomy. We discuss the mean to approach more precisely this uncommon pattern named occult constrictive pericarditis.

Adult↗
PubMed2005

[Myocardial perfusion and contrast echocardiography. Application to acute coronary syndrome].

After mastering epicardial revascularisation, the therapeutic management of acute coronary syndrome has progressively turned towards the preservation of the capillary microcirculation. In this respect, contrast echocardiography provides all the answers to the main questions which arise, and is available within a timeframe and place compatible with the management of such patients. The techniques for microbubble detection, quantification tools, and contrast agents are well optimised for routine use both for initial diagnosis as well as monitoring the therapeutic effectiveness. It is only the administrative authorisation which is currently lacking treatment.

Angina, Unstable↗
PubMed2004

["Optigo" hand-held echocardiography in post-surgery of coronary artery bypass graft].

INTRODUCTION: After all the advances in electronic miniaturization, first hand-held echocardiographs have finally appeared in echocardiographic laboratories. However, questions still remain about their usefulness in our everyday practice and also about their good diagnosis accuracy. Since some of them do not offer modes such as pulsed or continuous wave Doppler, nor M-mode, they cannot compete with conventional devices. However, they do offer advantages such as their long autonomy, the good quality of their image as well as the one obtained with colour-Doppler mode, in addition obviously to the fact that they can be carried around very easily. OBJECTIVES: To better define their possible uses, we assessed capabilities of one of them, the Optigo (Philips Ultrasound) to analyse patients who had undergone coronary artery bypass surgery. METHOD: Fifty patients have been included in this study few days after the surgery. Each of the patients had two echocardiographic examinations, one with a conventional device and one with the Optigo. Two separated and blinded observers for a subsequent and side-by-side criteria comparison performed the two echocardiograms. RESULTS: Hand-held echocardiography had a good diagnosis accuracy varying from 85% to 95% depending on the analysed criteria. It was more specifically good in the analysis of global or regional left heart function and of the right cavities as well as detecting the existence of pericardial effusion. CONCLUSION: Hand-held echocardiographic device demonstrated high accuracy in assessing patients with recent coronary bypass surgery especially regarding cardiac function and pericardial effusion diagnosis.

Coronary Artery Bypass↗
PubMed2003

Interventricular and intra-left ventricular electromechanical delays in right ventricular paced patients with heart failure: implications for upgrading to biventricular stimulation.

OBJECTIVE: To correlate, in patients with right ventricular pacing (RVP), the QRS width with electromechanical variables assessed by pulsed Doppler tissue imaging echocardiography. Secondly, to find reliable parameters for selecting RVP patients who would respond to biventricular pacing (BVP). METHODS: 26 randomly selected control patients with RVP (mean (SD) ejection fraction 74 (3)%) (group A) were matched on sex and age criteria with 16 RVP patients with drug resistant heart failure (mean (SD) ejection fraction 27 (5)%) (group B). All patients were pacemaker dependent and all underwent pulsed Doppler tissue imaging echocardiography. This technique provided the intra-left ventricular (LV) electromechanical delay and the interventricular electromechanical delay. The Gaussian curve properties of data from group A patients provided the normal range of ECG and echographic parameters. DESIGN: Prospective study. SETTING: University hospital (tertiary referral centre). RESULTS: Data from the control group showed that an interventricular electromechanical delay or an intra-LV electromechanical delay > 50 ms would identify patients with a significantly abnormal ventricular mechanical asynchrony (p < 0.05). In the same manner, a QRS width > 190 ms was considered significantly larger in group B patients (p < 0.05) than in controls. In Group B patients, there was no correlation between the QRS width and the interventricular electromechanical delay (r = -0.23, NS) or the intra-LV electromechanical delay (r = 0.19, NS). Seven group B patients (44%) were misclassified by ECG criteria for ventricular mechanical asynchrony identification: four patients (25%) had a QRS width similar to that of controls but with a significantly prolonged intra-LV electromechanical delay and interventricular electromechanical delay; and three patients (19%) had a QRS width significantly larger than that in controls but without significant ventricular mechanical asynchrony. CONCLUSIONS: The QRS width is not a reliable tool to identify RVP patients with ventricular mechanical asynchrony. In RVP patients, an interventricular electromechanical delay or intra-LV electromechanical delay > 50 ms reflects a significant ventricular mechanical asynchrony and should be required to select patients for upgrading to BVP.

Aged↗
PubMed2003

[Cardiac manifestations of amyloidosis by deposits of transthyretin and apolipoprotein A1. Report of 3 families].

Amyloidosis is characterised by extracellular deposits of a heterogenous protein. Compared with secondary forms, hereditary amyloidosis due to genetic mutations is rare. The authors report the cardiac manifestations in a French family of 5 sisters and 1 brother, three of whom presented with amyloidosis with deposits of transthyretin and apolipoprotein A1 due to a new genetic mutation.

Adult↗
PubMed2003

[Contrast echocardiography: from experimental validation to practice].

After a long wait, contrast echocardiography is at last becoming a reality. The experimental validation step has been passed with success and the first clinical results bring confirmation. The second generation contrast agents which are arriving on the market, and the spread of enhancement techniques such as Real-Time mode allow perfect visualisation of microbubbles within the left ventricular cavity, but equally at the level of the myocardial crown, thus targeting two direct applications in echocardiography: the first, indisputably, concerns the improvement in the detection of the endocardium in all the situations where it is insufficient, and in particular during stress echography; the second, more ambitious, confronts the study of myocardial perfusion, with a yet to be defined place in clinical practice.

Contrast Media↗
PubMed2003

[Contrast echocardiography: from experimental validation into practice].

Contrast echocardiography is at last becoming a reality. The experimental validation step has been completed with success and the first clinical results bring confirmation. The second generation contrast agents which are becoming available on the market, and the spread of enhancement techniques as Real-time mode allow perfect visualization of microbubbles within the left ventricular cavity, but equally at the level of the myocardial crown, thus targeting two direct applications in echocardiography: the first, indisputably, concerns improvement in the detection of the endocardium in all situations where it is insufficient, and in particular during stress echocardiography; second, more ambitious, is with regards to the study of myocardial perfusion with a potential role in clinical practice that remains to be determined.

Contrast Media↗
PubMed2002

[Microbubbles-ultrasound interactions].

Echographic contrast agents have a dynamic behaviour in the ultrasound field which is the base of their detection as well as that of myocardial perfusion quantification.

Contrast Media↗
PubMed2002

[Study of variations in preload on the new echocardiography parameters of diastolic function in health subjects].

The standard Doppler indices of transmitral filling are changed by variations in preload, relaxation and left ventricular compliance. Recent work in the literature suggests that the new parameters of diastolic function [mitral flux propagation speed in colour TM. (Vp) and tissue Doppler mitral ring velocities (Ea)] are independent of loading conditions. The objective of this work was to study the effect of modifications in the preload on Vp and Ea in normal subjects. Therefore, we have studied various Doppler echocardiographic measurements performed at rest, during a Trendelenberg manoeuvre at 60 degrees, and after sublingual administration of trinitrate in 25 healthy young (2 +/- 8 years) male volunteers. The end diastolic volume increased from 126 +/- 25 ml in the resting state to 145 +/- 24 ml during the Trendelenberg (p = 0.009) then decreased after trinitrate to 121 +/- 28 ml. The peak of the E wave increased from 88 +/- 12 cm/s in the resting state to 90 +/- 15 cm/s during the Trendelenberg and decreased to 70 +/- 11 cm/s after trinitrate (p < 0.0001). The peak Ea annular velocities of the septal and lateral walls were 22 +/- 4 cm/s and 15 +/- 1.6 cm/s in the resting state, without variation during the Trendelenberg (22 +/- 5 cm/s and 15 +/- 2 cm/s) but with a significant reduction after trinitrate to 19 +/- 5 cm/s and 13 +/- 2 cm/s (p = 0.02 and p = 0.002). In contrast, no significant variation was noted in Vp (60 +/- 14 cm/s in the resting state, 62 +/- 12 cm/s during the Trendelenberg and 59 +/- 14 cm/s after trinitrate). We conclude that Vp is not significantly affected by preload whereas Ea is not independent of the loading conditions.

Adult↗
PubMed2002

[Fibrinolysis and thrombosis of mechanical valvular prosthesis: risk stratification by transesophageal echocardiography].

The place of fibrinolysis in the treatment of mechanical valvular prostheses is still much discussed. The aim of this work is to define the role of transoesophageal echocardiography in risk stratification. This monocentric study draws on 49 cases of thrombolysis preceded by transoesophageal echocardiography (average age 62.1 years, 37 mitral, 11 aortic, 1 tricuspid, 1 mitro-tricuspid). There were 41 obstructive thromboses (OT) and 8 non-obstructive thromboses (NOT). Clinical events and the effectiveness of fibrinolysis were studied as a function of the obstructive or non-obstructive character of the thrombosis and the size of the thrombus < 10 mm (n = 33) or > or = 10 mm (n = 16). Complete success was observed in 34 patients (69.4%). Follow up revealed 2 early cerebral haemorrhages (4.1%) of which one was in the NOT group, and six systemic emboli (12.2%) of which one was in the NOT group. There was a relationship between the size of the thrombus and embolus at the limit of significance in favour of an increased risk of embolus for a voluminous thrombus. Furthermore, the mobility of the thrombi went in hand with an increased rate of systemic emboli (p < 0.01). The rate of failure of fibrinolysis and/or complications correlated with the size of thrombus (complete success in 88% of the < 10 mm thrombus group, versus 35% in the > or = 10 mm; p < 0.01). This work underlines the significance of trans-oesophageal echocardiography in the therapeutic choice for valvular prosthesis thrombosis and suggests that the existence of a voluminous thrombus especially if mobile is a contra-indication for fibrinolysis.

Adult↗
PubMed2001

Comparison of real-time and intermittent triggered myocardial contrast echocardiography for quantification of coronary stenosis severity and transmural perfusion gradient.

BACKGROUND: Both intermittent triggered and real-time myocardial contrast echocardiography (MCE) have been proposed to detect impaired myocardial perfusion. We compared the ability of these 2 methods to quantify altered myocardial blood flow (MBF) and transmural distribution of MBF produced by graded coronary stenoses. METHODS AND RESULTS: In 8 open-chest dogs, we created 4 graded left anterior descending coronary artery (LAD) stenoses: 3 levels of reduced adenosine hyperemia (non-flow-limiting at rest) and 1 grade of flow-limiting at rest. Real-time MCE was performed with SonoVue infusion using low-energy power pulse inversion (ATL) imaging, whereas ECG-gated intermittent triggered imaging used high energy at pulsing intervals from 1:1 to 1:10. LAD signal intensity (SI) was plotted versus time by real-time MCE and versus pulsing intervals by triggered MCE and was fitted to a 1-exponential function to obtain plateau SI (A) and the rate of SI rise (b). Visual detection of decreased opacification was equivalent by triggered and real-time MCE. Fluorescent microsphere-derived MBF ratio in LAD/left circumflex artery beds demonstrated close correlation with both real-time imaging (b, r=0.79; Axb, r=0.81) and triggered imaging (b, r=0.78; Axb, r=0.80). The endocardial/epicardial ratio of MBF in the LAD bed demonstrated closer correlation with the endocardial/epicardial ratios of b (r=0.71) and Axb (r=0.67) obtained by real-time than triggered imaging (b, r=0.42; Axb, r=0.52). CONCLUSIONS: Real-time and triggered MCE are equivalent in their ability to identify coronary stenosis and quantify altered MBF.

Animals↗
PubMed2001

Comparative value of dobutamine and adenosine stress in the detection of coronary stenosis with myocardial contrast echocardiography.

BACKGROUND: Controversy continues as to whether adenosine or dobutamine is the superior pharmacological stress agent for myocardial contrast echocardiography (MCE). METHODS AND RESULTS: We compared real-time MCE refilling curves and wall thickening during adenosine and dobutamine stress in 14 open-chest dogs with left anterior descending and left circumflex coronary artery stenoses that reduced hyperemia by 40% to 60% and 70% to 90% (mild and severe non-flow-limiting stenosis, NFLS) and resting flow by 10% to 30% and 35% to 50% (mild and severe flow-limiting stenosis, FLS). MCE was performed with low-energy imaging during Optison infusion. After high-energy bubble destruction, time-intensity data from risk beds were fitted for an exponential function as y=A(1-e(-)(bt)), from which the rate of intensity increase (b) and maximal plateau intensity (A) were derived. Although severe NFLS and greater stenoses decreased b with both dobutamine and adenosine, with mild NFLS it was reduced in 58% of animals with dobutamine versus 8% with adenosine. The absolute decrease in b, however, was greater for adenosine than dobutamine with FLS. The A parameter was decreased with both adenosine and dobutamine only with the most severe FLS. Wall thickening was decreased with dobutamine in 33% of animals with severe NFLS and in all animals with any FLS; with adenosine, in all with severe FLS. CONCLUSIONS: Both dobutamine and adenosine significantly reduce MCE refilling rates in the setting of severe stenosis and in the absence of contractile abnormalities. Dobutamine decreases refilling rate and wall thickening at a less reduced flow grade than adenosine, but adenosine produces a greater magnitude of change than dobutamine.

Adenosine↗
PubMed2001

Quantitative assessment of myocardial perfusion during graded coronary stenosis by real-time myocardial contrast echo refilling curves.

OBJECTIVES: The present study examined the ability of real-time myocardial contrast echocardiography (MCE) to delineate abnormalities produced by graded coronary stenoses and to correlate signal intensity (SI) parameters derived from destruction/refilling curves with regional myocardial blood flow (MBF) and contractile function. BACKGROUND: Recent technological advances have enabled myocardial opacification by MCE to be achieved during real-time imaging. METHODS: In eight open-chest dogs, we created LAD occlusion and graded stenoses that were either flow-limiting at rest (FLS) or reduced adenosine hyperemia (non-flow-limiting at rest = NFLS). Myocardial contrast echo used Optison infusion and low-energy real-time power pulse inversion imaging. High-energy FLASH frames destroyed bubbles every 15 cardiac cycles. Myocardial SI-versus-time plots were fitted to a one-exponential function to obtain the rate of SI rise (b) and peak SI in the last frame. RESULTS: Dyssynergy was not observed during any NFLS, but perfusion abnormalities were. Visual detection of decreased opacification was possible with severe NFLS and FLS. b demonstrated a significant reduction with severe NFLS and near significant with moderate NFLS; peak SI did not. All exponential parameters were significantly decreased with FL stenosis and occlusion. The MBF ratio in LAD/LCx beds (fluorescent microspheres) correlated with b (r = 0.79) and the product of the peak SI and b (r = 0.80). CONCLUSIONS: In an open-chest dog model, parameters derived from microbubble refilling of the imaging field by real-time MCE correlate well with myocardial blood flow and can identify coronary stenosis.

Albumins↗