Cardiomyopathy is seen in all forms of MPS. Valvular and myocardial disease are both seen. Enzyme replacement therapy appears to have little, if any, effect on the valve disease. However, the myocardium does seem to respond, though not completely.
Echocardiography has been the standard method of evaluating cardiac involvement for many years. More recently, MRI has been shown to be more sensitive. However, there are practical limitations to MRI. In young children general anaesthesia may be required. At the very least, this is inconvenient, and it carries increased risk in MPS patients.
A relatively new tool is speckle tracking echocardiography (STE). It provides information which is not available with any of the currently used echocardiographic parameters. For a detailed discussion of STE please see this article.
Researchers in Naples have studied myocardial function in a small group of children with MPS using STE. Abnormalities were detected in various aspects of ventricular function. Importantly, some of these were seen even in the absence of any abnormalities in the standard echocardiogram.
This suggests that STE may detect myocardial dysfunction at an early stage, even before it is seen on standard echocardiography.
The only other LSD In which STE has been systematically studied is Fabry disease. This is the first such study to have been performed in MPS patients, and some limitations should be noted. Only a small number (15) were studied. There are limitations to STE at the moment and it has not yet been standardised, so that STE performed on different machines may yield different results. Finally, the clinical relevance of early myocardial involvement in MPS is unclear. For example, it does not in itself constitute an indication for ERT. In this respect it differs from Fabry disease. However, its sensitivity suggests that it may well detected responses to treatment earlier than standard echocardiography. Such studies, in large cohorts, need to be done.
So one needs to be cautious. Nevertheless, given its clear superiority to standard echocardiography, and the lack of requirement for a general anaesthetic, STE may well become a standard investigative tool in the not too distant future in MPS.