Increased Type I Collagen Synthesis in Victims of Sudden Cardiac Death Due to Idiopathic Myocardial Fibrosis

Aims. Idiopathic myocardial fibrosis (IMF) was observed to be the most prevalent autopsy finding in the victims of sudden cardiac death (SCD) under the age of 40 years in the FinGesture cohort. To elucidate further the mechanisms of IMF, we examined the collagen composition from the myocardial samples taken from the victims of IMF-associated SCD.Methods. Eighteen cases with IMF as a cause of death, confirmed by autopsy, were selected for the analysis. Controls (n = 27) included were cases in whom no cardiac or non-cardiac disease could be found as a cause of unexpected death at autopsy. In addition to conventional histological examination, immunohistochemical staining of procollagens I and III (PINP and PIINP), mature collagen III (IIINTP), and the cross-linked collagen I degradation product (ICTP) were performed.Results. Increased accumulation of PINP was observed in the fibrotic tissue of the IMF cases in comparison with control samples. In contrast, type III collagen was not as frequently expressed in the fibrotic areas.Conclusion. Myocardial accumulation of PINP in the victims of IMF-associated SCD indicates increased type I collagen synthesis. Future studies on the role of circulating type I collagen biomarkers are needed to study further the implications of the described association.