Myoarchitecture and connective tissue in hearts with tricuspid atresia

Objective-To compare the atrial and ventricular myoarchitecture in the norm al heart and the heart with tricuspid atresia, and to investigate changes i n the three dimensional arrangement of collagen fibrils. Methods-Blunt dissection and cell maceration with scanning electron micros- copy were used to study the architecture of the atrial and ventricular musc ulature and the arrangement of collagen fibrils in three specimens with tri cuspid atresia and six normal human hearts. Results-There were significant modifications in the myoarchitecture of the right atrium and the left ventricle, both being noticeably hypertrophied. T he middle layer of the ventricle in the abnormal hearts was thicker than in the normal hearts. The orientation of the superficial layer in the left ve ntricle in hearts with tricuspid atresia was irregular compared with the no rmal hearts. Scanning electron microscopy showed coarser endomysial sheaths and denser perimysial septa in hearts with tricuspid atresia than in norma l hearts. Conclusions-The overall architecture of the muscle fibres and its connectiv e tissue matrix in hearts with tricuspid atresia differed from normal, prob ably reflecting modelling of the myocardium that is inherent to the malform ation. This is in concordance with clinical observations showing deteriorat ion in pump function of the dominant left ventricle from very early in life .