Prof Tony Lahoutte MD, PhD
Evaluation of LV function in patients with VHD, really the gold standard?
There is no doubt that the evaluation of left ventricular function using echocardiography is a corner stone for managing patients with valvular heart disease. Evaluation of left ventricular function and geometry is recognised as mandatory in all guidelines for critical decision making in symptomatic and asymptomatic patients. Moreover, left ventricular function and geometry assessment provides very important early and late outcome information before any surgical interventions and may serve for the follow-up of these patients.
To date old techniques, like M-mode and B-mode (2DE), older than 30 years, are still used in most of these guidelines. However, these modalities have relatively low accuracy and are poorly reproducible due to their limitations: oblique measurement overestimation (a 10% error in diameter gives a 30 % error in volume), bundle branch block, regional dysfunction, translation of the left ventricle, geometric assumptions,…
Three-dimensional echocardiography (3DE) offers the unique opportunity to overcome most of these limitations. It has been shown that it is feasible and easy to perform. Semi-automated algorithms for boundary detection have facilitated the analysis of global left ventricular function and geometry, also improving its reproducibility. The accuracy and the reproducibility of 3DE compared to a reference method like cardiac magnetic resonance (CMR) is by far superior to 2DE. The repeatability over time is also superior with 3DE compared to 2DE, which is particularly important for the follow-up of patients.
Many modalities of 3DE are available at the moment: simultaneous bi-plane or tri-plane imaging and full volume acquisition and analysis. All modalities allow avoiding foreshortening. Full volume direct volume analysis also reduces geometric assumptions. The issue of lower spatial resolution compared to 2DE is closely related to boundaries detection and quality of the images. It has been demonstrated that adding contrast may further improve the accuracy of left ventricular function and geometry evaluation with 3DE compared to CMR as reference.
Geometry is also left ventricular shape and size. It is clear from now that left ventricular mass plays a critical role in the evaluation of patients with valvular heart disease. In this setting, 3DE has demonstrated added value compared to 2DE using CMR as reference.
It has recently been shown that 3DE requires less skill for left ventricular function and geometry assessment. This underlines the less observer dependency and reinforces the robustness of the technique.
Finally, evaluation of left ventricular function should not be limited to ejection fraction and size. In several conditions, left ventricular function may be overestimated just looking at these parameters. New echo modalities such as deformation imaging, torsion, twist, untwist have permitted to unmask latent dysfunction in patients with valvular disease and apparently preserved left ventricular ejection fraction. The implementation of these techniques on top of 3DE may be helpful to better stratify the patients with valvular heart disease. Moreover, the addition of one additional dimension will probably improve the application of some of these techniques compared to 2DE. Pending several technical improvements, 3DE is certainly the gold standard for left ventricular function evaluation in patients with valvular heart disease.
Teaching Course on clinical application of 3D echocardiography
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