Heart fibroelastosis. Close-up of a gross clinical specimen of a sectioned heart showing fibroelastosis, the replacement of heart muscle with bands of fibrous tissue. This condition is usually congenital (present at birth) and is usually fatal in the first few months of life. The presence of the fibrous tissue disrupts the normal pumping of the heart. This leads to breathlessness, wheezing, difficulties with feeding and failure of the infant to thrive. If the disease is diagnosed early, anti-arrhythmic drugs (that stabilise the heartbeat) may prolong life, but unless a donor heart is found, few patients live longer than a year.