Thesis
Investigating the effects of metal-on-metal hip implants and circulating cobalt ions on cardiovascular function
- Creator
- Rights statement
- Awarding institution
- University of Strathclyde
- Date of award
- 2023
- Thesis identifier
- T16626
- Person Identifier (Local)
- 201985705
- Qualification Level
- Qualification Name
- Department, School or Faculty
- Abstract
- Metal-on-metal (MoM) hip arthroplasties are known to release metal ions including cobalt into the blood stream. Elevated blood cobalt at levels over 250µg/l have been shown to be a risk factor for developing cardiovascular complications including cardiomyopathy, a need for cardiac transplantation and, in some cases, death. Published case reports document cardiomyopathy in patients with elevated blood cobalt levels below 250µg/l and as low as 13µg/l. Clinical studies have found conflicting evidence of cobalt-induced cardiomyopathy in patients with MoM hips. Global longitudinal strain (GLS) is an echocardiography measurement known to be more sensitive than ejection fraction at diagnosing early cardiomyopathies. The extent of cardiovascular injury, as measured by GLS, in patients with elevated blood cobalt levels has not previously been examined and is the focus of the current study. Sixteen patients with documented blood cobalt ion levels above 13µg/l were identified from a regional arthroplasty database. They were age and sex matched with eight patients awaiting hip arthroplasty with no history of cobalt implants. All patients underwent electrocardiogram and echocardiogram assessment for signs of cardiomyopathy including left ventricular (LV) dysfunction and cardiac remodelling. Global longitudinal strain (GLS), E/e’ ratio (an index for evaluating LV filling pressure), ejection fraction, LV wall thickness, LV end diastolic dimension, LV end systolic dimension and fractional shortening were all assessed. The patients with MoM hip arthroplasties had a mean time from initial arthroplasty of 15 years and had a mean blood cobalt level of 29µg/l compared to 0.01µg/l in the control group. Echocardiographic analysis showed no difference in either LV end systolic dimension (2.8cm v 3.0cm, (MoM v control) p=0.592) or LV end diastolic dimension (4.7cm v 5.0cm, (MoM v control) p=0.259). Neither was there any difference between ejection fraction (61.5% v 63.7%, (MoM v control) p= 0.564) or fractional shortening (38.9% v 40.1%, (MoM v control) p=0.813). Ventricular wall thickness (1.2cm v 1.0cm, p=0.059) and E/e’ ratio (8.0 v 7.8, p=0.771) were also comparable across MoM and control groups and there was no difference in rates of left ventricular or atrial hypertrophy. GLS was significantly reduced in patients with MoM hip arthroplasties compared to those without (-15.2% v -18%, (MoM v control) p= 0.013). This study has demonstrated reduced cardiac function in the presence of normal ejection fraction as assessed by GLS in patients with elevated cobalt above 13µg/l. As GLS is a more sensitive measure of systolic function than ejection fraction, routine echocardiogram assessment including GLS should be performed in all patients with MoM hip arthroplasties and elevated blood cobalt above 13µg/l. Further work is recommended to assess if these cardiac changes are present in patients with elevated blood cobalt levels below 13µg/l.
- Advisor / supervisor
- Currie, Susan
- Resource Type
- DOI
- Date Created
- 2022
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PDF of thesis T16626 | 2023-06-20 | Public | Download |