Which anomaly are you hoping to find?
When cardiac muscle is diseased, abnormal function appears gradually. At the most advanced stage of the disease, we see a net decrease in contraction that can be quantified by a number of signs, such as the ejection fraction or the shortening fraction. Thanks to advances in ultrasound, certain techniques developed allow to measure more subtle parameters and to identify anomalies at an earlier stage, whereas the markers usually employed are still normal. Can you elaborate on these new markers?
These are ultrasound parameters called ‘strain rate imaging’. They are derived from tissue Doppler measurements or recently by 2D Strain, a very promising new technique, available to the Institute. We investigate specifically in the wall of cardiac muscle, not the movement that the eye is able to identify, but muscle deformation. The ultrasound machine evaluates this parameter by studying the subtle movement of points situated in the muscle relative to each other. In fact, a diseased muscle can still have normal movement, but an altered deformation. In addition, the movement depends on many parameters such as hydration and stressful conditions, whereas the deformation is independent of all these conditions. It is therefore more interesting to assess. In practical terms, what happens during the examination?
The examination lasts slightly longer than a standard cardiac ultrasound examination. Most of the work is subsequently carried out from the recordings. In practice, cycles are measured i.e. we record cardiac cycles (between the diastole and systole, between the time when the muscle contracts and when it relaxes). Then we transfer the data to a computer through which one draws the outlines of the muscle walls. The computer then automatically makes very accurate measures from certain points on the muscle wall and renders the results in the form of curves, diagrams, and drawings. Data acquisition during the examination must be flawless to ensure that measures are reliable. We have already, Dr Henri Marc Bécane and me, collected nearly 300 recordings and are analyzing the data to compare them to control examinations. Have you already obtained any interesting data?
Absolutely! Our team already has promising results despite the fact that we have worked so far with a machine less sophisticated than the one we are using now. We acquired this machine through the AFM, consequently thanks to the Telethon donations. Thus, in a population of patients with Becker muscular dystrophy and carrier mothers of Duchenne muscular dystrophy, our team has shown that people with contraction parameters that have been considered normal with a conventional ultrasound already had anomalies of these subtle markers.
Moreover, studies carried out by other teams in Duchenne muscular dystrophy children again showed that in some children, at an age where we thought that the heart was normal, could present with abnormalities of these deformation parameters whereas the examination appeared normal. What will be the next steps?
We must first gather as many patient records as possible so that our data are statistically reliable and compare these data to those obtained from patients without health problems, who will serve as a reference. Subsequently, we will need to know what becomes of the patients with abnormalities of these very subtle markers: do they develop or not into more important abnormalities or even heart failure? As patients are followed for consultation here, we can monitor their progress.
Finally, if we show that indeed these markers allow the identification of patients at risk of cardiac abnormality, the third step will be to conduct clinical trials in which patients will be treated with drugs at an earlier stage, taking into account just these markers to determine if their prognosis can be improved. Ultimately, the idea is to improve the prevention of future cardiac complication episodes in people in whom we have detected abnormal muscle deformation. Meune C, Wahbi K, Assous N, Weber S, Kahan A, Allanore Y.
Myocardial dysfunction in rheumatoid arthritis: a controlled tissue-Doppler echocardiography study.
J Rheumatol. 2007 Oct;34(10):2005-9. Epub 2007 Sep 1. Meune C, Avouac J, Wahbi K, Cabanes L, Wipff J, Mouthon L, Guillevin L, Kahan A, Allanore Y.
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November 2008Interview by Anne Berthomier, translation by Racquel N. Cooper