The fibrous matrix of ventricular myocardium in hypoplastic left heart syndrome: a quantitative and qualitative analysis

Background Controversy exists as to whether the right ventricle will be able to cope as the sole pumping chamber following a univentricular repair of hypoplastic left heart syndrome. The significance of the collagenous matrix on ventricular function has been studied extensively yet there is little information available on its quantity and quality in hypoplastic left heart syndrome. Methods We selected 23 specimens with hypoplastic left heart syndrome for anatomical study. Using a combination of morphometric analysis and scanning electron microscopy we analyzed the quantity and quality of the collagenous matrix. We compared the results with 16 age-matched controls. Results Hearts with hypoplastic left heart syndrome have significantly less collagen matrix than normal. The right ventricle has more collagen than the left and there is significant transmural variation. There was no difference in the ratio of the two main collagen subtypes or in the quality of the matrix. Conclusions We believe this difference in fibrous matrix to be an inherent abnormality intrinsic to the malformation affecting not only the hypoplastic left but also the “normal” right ventricle. This in turn may have significant implications for the expected long-term outcome of reconstructive surgery.