Animal Models of Mitral Regurgitation Induced by Mitral Valve Chordae Tendineae Rupture.

in Journal of Heart Valve Disease (The) (2012), 21

Background – Mitral regurgitation (MR) is a common valvular disease throughout the world. Various diagnostic techniques have been developed to assess the causes and severity of MR, and the therapeutic ... [more ▼]

Background – Mitral regurgitation (MR) is a common valvular disease throughout the world. Various diagnostic techniques have been developed to assess the causes and severity of MR, and the therapeutic approaches to this disease have been widely documented. However, treatments for chronic MR remain controversial, and various animal models of chronic MR (including chordae tendineae rupture, rapid pacing and ischemia) have been developed to study the pathophysiology and therapeutic approaches to this disease. The objective of this paper is to review the animal MR models that have been developed using a mitral valve chordae tendineae rupture technique. Animal models – Dogs and sheep have been the animals most commonly used in MR models induced by mitral valve chordae tendineae rupture, mainly due to considerations of cardiac size. Chordae tendineae cutting is performed using closed or open chest techniques. In the closed chest model, long flexible grasping forceps are positioned percutaneously in order to tear the mitral valve chordae. In the open chest model, cardiopulmonary bypass is performed and either selected chordae are cut under direct visualization, or a non specified number of chordae are cut using a metal device inserted through the left ventricular apex. Whatever the model used, MR has been found to become chronic 3 to 6 months after the induction of MR by chordae rupture. The reported mortality and complication rates of these models are high. Conclusion – In the long term, experimental evolution of chronic MR is similar to the evolution occurring naturally in patients suffering from chronic MR. These models could thus be useful in understanding the disease better and in testing new therapeutic modalities. This review summarizes the physiological effects of each of these techniques and compares the advantages and disadvantages of each procedure. [less ▲]

Structural model of the mitral valve included in a cardiovascular closed loop model

Poster (2011, December)

A minimal cardiovascular system (CVS) model including mitral valve dynamics has been previously validated in silico. However parameters of this model are difficult to link with structural and anatomical ... [more ▼]

A minimal cardiovascular system (CVS) model including mitral valve dynamics has been previously validated in silico. However parameters of this model are difficult to link with structural and anatomical components of the valve. This research describes the integration of a structural model of the mitral valve in an existing closed-loop cardiovascular system (CVS) model [less ▲]

Left ventricular dyssynchrony: a dynamic condition.

in Heart Failure Reviews (2011)

Left ventricular dyssynchrony (LVD) is common in heart failure patients with LV systolic dysfunction. Contrary to what it could be expected, LVD is not a stable phenomenon. Various conditions (inducible ... [more ▼]

Left ventricular dyssynchrony (LVD) is common in heart failure patients with LV systolic dysfunction. Contrary to what it could be expected, LVD is not a stable phenomenon. Various conditions (inducible ischemia, exercise, drug administration) may significantly alter the presence and the magnitude of LVD, which could per se modulate response to treatment for heart failure. LVD can be evaluated using validated Doppler-echocardiographic techniques as tissue Doppler imaging. Exercise and dobutamine stress echocardiography can be used tests to unmask LVD. Changes in LV synchronicity during stress test occur independently of inducible ischemia and irrespective of QRS width. The degree of LVD varies substantially from patient to patient. The dynamic increase in LVD represents a strong contributor: (1) to exercise-induced changes in mitral regurgitation, (2) to limitation of stroke volume adaptation during exercise, and (3) to exertional dyspnea. Whether dynamic LVD might independently affect the outcome has not yet been demonstrated. In the setting of CRT, the assessment of dynamic LVD might help patient selection, predict the magnitude of response, and optimize pacing delivery during exercise. Further longitudinal studies are required to confirm the value of assessing dynamic LVD. [less ▲]

Two-Dimensional, M-Mode and Pulsed Wave Doppler Echocardiographic Reference Values in Healthy Adult Saanen Goats

Poster (2011, March 18)

Echocardiography has become a routine non invasive cardiac diagnostic tool in most species. Accurate measurement of cardiac dimensions requires reference values, which are poorly documented in goats ... [more ▼]

Echocardiography has become a routine non invasive cardiac diagnostic tool in most species. Accurate measurement of cardiac dimensions requires reference values, which are poorly documented in goats. Goats are animals easy to handle with a body and heart size comparable to humans’. This makes goats an attractive candidate for the development of animal models for human cardiology research. The aim of this study was to test the repeatability and to establish the reference values of bi-dimensional (2D-), time-motion (M-) mode and pulsed wave (PW) Doppler echocardiographic variables in adult goats. Six healthy female adult Saanen goats were investigated three times by the same observer at one day interval using a standardized 2D-, M-mode and PW Doppler echocardiographic protocol. Calculation of the coefficient of variation for each variable measured within day and depending on the day allowed to evaluate their degree of variability. A single echocardiographic examination was performed in 6 other goats by the same observer, and the obtained values were added to these obtained on the third day of the 6 first goats. Then the observed mean, the standard deviation and the range of these measurements were calculated to establish the reference values of echocardiographic parameters in unsedated adult healthy female Saanen goats. Statistical analysis revealed a good inter-day repeatability of the 2D- and M-mode echocardiographic cardiac measurements, but PW Doppler parameters presented moderate to high variability, as documented in other species. Echocardiographic reference values obtained in healthy adult Saanen goats were similar to those reported in healthy adult sheep and in healthy adult humans. [less ▲]

minimal cardiovascular system model including physiological mitral valve opening

in 9th Belgian National Day on Biomedical Engineering, Bruxelles, 26th november (2010, November 26)

A minimal cardiovascular system (CVS) model has been previously validated in silico, and in several animal model studies. It accounts for valve dynamics by means of a Heaviside function to simulate the ... [more ▼]

A minimal cardiovascular system (CVS) model has been previously validated in silico, and in several animal model studies. It accounts for valve dynamics by means of a Heaviside function to simulate the “open on pressure, close on flow” law. However, this model does not describe the progressive valve opening and therefore, it is not suitable for studying valve dysfunctions. [less ▲]

Mathematical model of the mitral valve and the cardiovascular system, application for studying, monitoring and in the diagnosis of valvular pathologies

in UKACC international Conference on Control 2010 : Coventry, 7-10 september 2010 (2010, September 07)

A cardiovascular and circulatory system (CVS) model has been validated in silico, and in several animal model studies. It accounts for valve dynamics using Heaviside functions to simulate a physiological ... [more ▼]

A cardiovascular and circulatory system (CVS) model has been validated in silico, and in several animal model studies. It accounts for valve dynamics using Heaviside functions to simulate a physiological accurate “open on pressure, close on flow” law. Thus, it does not consider the real time scale of the valve aperture dynamics and thus doesn’t fully capture valve dysfunction particularly where the dysfunction involves partial closure. This research describes a new closed-loop CVS model including a model describing the progressive aperture of the mitral valve and valid over the full cardiac cycle. This new model is solved for a healthy and diseased mitral valve. [less ▲]

Risk stratification in asymptomatic moderate to severe aortic stenosis: the importance of the valvular, arterial and ventricular interplay.

in Heart (2010), 96(17), 1364-71

OBJECTIVE: We sought to evaluate prognostic markers of clinical outcome in asymptomatic patients with moderate to severe aortic stenosis (AS). DESIGN: Prospective follow-up of asymptomatic patients with ... [more ▼]

OBJECTIVE: We sought to evaluate prognostic markers of clinical outcome in asymptomatic patients with moderate to severe aortic stenosis (AS). DESIGN: Prospective follow-up of asymptomatic patients with moderate to severe AS. The patients underwent clinical and Doppler echocardiographic evaluation. SETTING: Department of Cardiology. PATIENTS: 163 patients with moderate to severe AS (aortic valve area < or =0.6 cm(2)/m(2)). MAIN OUTCOME MEASURES: Risk stratification. Predefined endpoints for assessing the outcome were the occurrence during follow-up of symptoms, aortic valve replacement or death. RESULTS: During follow-up (mean, 20 (19) months), 11 patients developed symptoms but were not operated on, 57 required aortic valve replacement and six patients died. In multivariable Cox regression analysis, four parameters that were associated with the outcome were identified: peak aortic jet velocity, left ventricular systolic (LV) longitudinal deformation, valvulo-arterial impedance and indexed left atrial area. Using receiver-operator characteristic curve analysis, a peak aortic jet velocity > or =4.4 m/s, a LV longitudinal myocardial deformation < or =15.9%, a valvular-arterial impedance > or =4.9 mm Hg/ml per m(2) and an indexed left atrial area > or =12.2 cm(2)/m(2) were identified as the best cut-off values to be associated with events. CONCLUSIONS: In asymptomatic patients with moderate to severe AS, measurements that integrate the ventricular, vascular and valvular components of the disease improve risk stratification. [less ▲]

Stress echocardiography for selecting potential responders to cardiac resynchronisation therapy.

in Heart (2010), 96(14), 1142-6

In the current ESC/ACC/AHA guidelines, the selection of patients for cardiac resynchronisation therapy (CRT) is based upon the QRS duration, which reflects interventricular dyssynchrony. However, about 30 ... [more ▼]

In the current ESC/ACC/AHA guidelines, the selection of patients for cardiac resynchronisation therapy (CRT) is based upon the QRS duration, which reflects interventricular dyssynchrony. However, about 30% of patients do not respond to CRT. It has previously been demonstrated that the presence of left ventricular mechanical dyssynchrony is predictive of response to CRT after implantation. Most criteria assessing such dyssynchrony were derived from data obtained with resting Doppler echocardiography. The recently published PROSPECT (Predictors of Response to CRT) trial failed to identify echocardiographic measures of dyssynchrony that could routinely be recommended for patient selection before CRT implantation. Therefore, solutions may come from other echocardiographic modalities, such as dobutamine stress echocardiography and exercise echocardiography. The purpose of this review is to evaluate the usefulness of stress echocardiography to predict response to CRT. This review will show how exercise-induced changes in dyssynchrony and severity of mitral regurgitation and the role of preserved contractile reserve may help to better identify potential responders. [less ▲]

Inertie clinique et observance thérapeutique dans les valvulopathies chroniques du coeur gauche.

in Revue Médicale de Liège (2010), 65(5-6), 290-8

Valvular heart diseases are of increasing importance among the general adult population. When compared with other heart diseases, there are few trials in the field of valvular heart disease and randomized ... [more ▼]

Valvular heart diseases are of increasing importance among the general adult population. When compared with other heart diseases, there are few trials in the field of valvular heart disease and randomized clinical trials are particularly scarce. Two sets of guidelines exist: one in the USA and the other in Europe. However, they are not always consistent due to the lack of randomized data and it appears that, frequently, there is a gap between the existing guidelines and their effective application. [less ▲]

Contractile reserve assessed using dobutamine echocardiography predicts left ventricular reverse remodeling after cardiac resynchronization therapy: prospective validation in patients with left ventricular dyssynchrony.

in Echocardiography (2010), 27(6), 668-76

Background: The presence of viable myocardium may predict response to cardiac resynchronization therapy (CRT). The aim of this study is to evaluate in patients with left ventricular (LV) dyssynchrony ... [more ▼]

Background: The presence of viable myocardium may predict response to cardiac resynchronization therapy (CRT). The aim of this study is to evaluate in patients with left ventricular (LV) dyssynchrony whether response to CRT is related to myocardial viability in the region of the pacing lead. Methods: Forty-nine consecutive patients with advanced heart failure, LV ejection fraction < 35%, QRS duration > 120 ms and intraventricular asynchronism ≥ 50 ms were included. Dobutamine stress echocardiography was performed within the week before CRT implantation. Resting echocardiography was performed 6 months after CRT implantation. Viability in the region of LV pacing lead was defined as the presence of viability in two contiguous segments. Response to CRT was defined by evidence of reverse LV remodeling (≥15% reduction in LV end-systolic volume). Results: Thirty-one patients (63%) were identified as responders at follow-up. The average of viable segments was 5.9 ± 2 in responders and 3.2 ± 3 in nonresponders (P = 0.0003). Viability in the region of the pacing lead had a sensitivity of 94%, a specificity of 67%, a positive predictive value of 83%, and a negative predictive value of 86% for the prediction of response to CRT. Conclusions: In patients with LV dyssynchrony, reverse remodeling after CRT requires viability in the region of the pacing lead. This simple method using echocardiography dobutamine for the evaluation of local viability (i.e., viability in two contiguous segments) may be useful to the clinician in choosing the best LV lead positioning. [less ▲]