Researchers have for the first time found a way to measure the increased risk of heart damage associated with metal-on-metal hip implants.
The team at Strathclyde University have also shown how cobalt from the older type of hip replacements may be linked to reduced contraction of the heart by interfering with calcium levels.
Medicines regulators have been monitoring the impact of metal-on-metal hips since 2012 due to ‘soft tissue’ reactions related to tiny metal ions – specifically cobalt and chromium – breaking off and leaking into the blood.
Patients who have had them should receive regular monitoring with MRI as well as measurement of blood metal levels, the Medicines and Healthcare products Regulatory Agency said in 2017.
While there has also been general concern about cardiotoxicity associated with such implants, there has been a lack of detail on the mechanism.
The researchers analysed the effects of cobalt on two types of heart cells and on cardiovascular function in both a laboratory model and humans.
They were specifically examining a potential relationship between cobalt exposure and changes in the levels and activity of CaMKII.
Presenting their work at the Northern Cardiovascular Research Group, Dr Susan Currie, associate professor in cardiovascular physiology at the University of Strathclyde said that even at low levels, cobalt was found to reduce heart contractions.
All the patients they looked at had normal ECG but when they used global longitudinal strain – a highly sensitive type of ultrasound – they found some patients had abnormal contractile function.
She added: ‘There is now very strong evidence of a link between hip replacements where metals such as cobalt and chromium are used in the artificial joint bearings, and the possibility of developing heart complications.’
Further tests in vitro in heart cell lines found that the cobalt appears to interfere with calcium levels.
‘While not all hip replacements contain cobalt, for those that do, cobalt levels can rise over time in the bloodstream of patients and the metal can accumulate in various organs of the body, including the heart.
‘Left untreated, this can damage the heart and, in some cases, lead to heart failure, but doctors cannot tell whether, or when, hip replacement patients will develop heart complications.’
She added: ‘Despite the knowledge that cobalt in some hip replacements has the potential to cause heart complications, our research is the first time a robust way of measuring risk has been found.
‘This is also the first time that a link between cobalt-induced changes in calcium levels in heart muscle cells and reduced contraction of the heart has been identified.
‘Cementing this knowledge will allow further study to focus on new treatments to reduce or prevent the toxic effects of cobalt in patients with hip replacements.’
Last month, researchers reported findings that talking therapies to treat depression could reduce a related increased risk in developing cardiovascular disease.
