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OBJECTIVE:
Mucopolysaccharidoses (MPS) are a group of rare metabolic disorders caused by the malfunctioning or absence of lysosomal enzymes. MPS II (Morbus Hunter) is caused by the lack of iduronate sulfatase and in order to that Dermatan and Heparan sulfate accumulates and stores in the valvular apparatus and myocardium. In literature there is a lack of information regarding the impact of lysosomal storage disease on cardiac contraction and in special the contractile apparatus, examined in the skinned cardiac fiber model.
METHODS:
We examined 3 different trabeculae from a 35 years old man with MPS II and significant stenosis of mitral (Δ mean 15 mmHg) and aortic valve (Δ mean 39 mmHg), undergoing replacement of mitral and aortic valve. Human tissue was obtained from the right atrium before implementation of ECC, prepared and skinned in single muscle stripes. The concentration of calcium (pCa) was increased stepwise, the pCa-force-relationship was recorded and compared to adult human fibers undergoing replacement of aortic valve (AVR, Group I, N=3) and aortocoronary bypass operation (CABG, Group II, N=3).
RESULTS:
I.) The fibers of the MPS patient developed at the highest calcium concentration (pCa 4.5) a mean force of 0,862 mN ± 0,48 mN, at pCa 5.5 the fibers achieved 0,461 ± 0,32 mN until 0,019 mN at pCa 6.5. II.) Compared to adult fibers from patients undergoing AVR we observe a significant lower force development at pCa 4.5 (P= 0,009), pCa 5.0 (P=0,019) and pCa 5.5 (P=0,02). III.) In comparison to fibers undergoing CABG we also see statistically significant differences at three steps of calcium concentration (pCa 4.5, P=0,04; pCa 5.0, P=0,02, pCa 5.5, P=0,02 ).
CONCLUSIONS:
The data show extreme alterations of contractile performance in an MPS-patient as compared to the normal population. As myocardial tissue analysis of MPS patients is extremely rare, it seems justified, to publish results on an individual basis. It seems extremely important to consider the differences, when specific perioperative therapeutical strategies are developed for children and grown ups with MPS.