A highly detailed analysis of chimpanzee hearts has for the first time revealed that the primates have a unique bone in their heart that may play a role in the occurrence of heart disease, abnormal rhythms, and even “sudden death”. The discovery could help manage health and conservation measures of endangered populations.

Known as the “os cordis”, the bone measures just a few millimeters in size and has been found in a handful of other animals, particularly bovines like cattle and buffalo. Writing in Scientific Reports, researchers at the University of Nottingham School of Veterinary Medicine and Science note that the bone was found in chimps with a type of heart disease called idiopathic myocardial fibrosis, one of the most significant causes of death in captive great apes.  

"The discovery of a new bone in a new species is a rare event, especially in chimps which have such similar anatomy to people. It raises the question as to whether some people could have an os cordis too," said lead author Dr Catrin Rutland from the University in a statement.

Wild chimps are considered endangered by the International Union for the Conservation of Nature (IUCN). Cardiovascular disease is common and has been reported to affect more than three-quarters of adult chimpanzees that died in captivity between 1990 and 2003. To understand how their hearts work in an attempt to manage their health, researchers imaged 16 hearts from chimpanzees (Pan troglodytes) that were either healthy or affected by heart disease using an advanced imaging method called micro-computed tomography. This higher-magnification technology allowed the team to compare the structure and morphology of each heart while also considering the age, cause of death, sex, and presence of any significant comorbidities.

Every heart diagnosed with heart disease also showed bone or cartilage formation as well as increased collagen levels in tissues adjacent to the bone or cartilage. By comparison, unaffected hearts did not have a bone or “cartilago cordis” associated with it. It is not yet clear what the function of os cordis is, but researchers say that it may provide insight into how bone growth starts. Some theories propose that its development helps to support essential heart valves, yet others suggest that the bone may develop as a result of heart disease, heart arrhythmia, and sudden death.

"Looking for ways to help chimps with heart disease is essential. Understanding what is happening to their hearts helps us manage their health,” said study co-author Sophie Moittié.

Despite the limited number of samples, the researchers note that there is a “significant association” between the presence of cartilage and bone and heart-related issues. Understanding the links could help to inform future health and conservation measures of both wild and captive chimps.