A study led by researchers at the Oxford Centre for Clinical Magnetic Resonance Research (OCMR) has found that patients with heart failure with preserved normal heart functioning have excessive fat deposition in their hearts, and that these fat deposits reduce how effectively their hearts function, and therefore exercise capacity. The study, published in the Journal of Cardiovascular Magnetic Resonance, suggests that drugs targeting fat in the heart might be one way to improve the treatment of this kind of heart failure.
Some patients have heart failure with preserved ejection fraction (HFpEF), which means that despite the volume of blood ejected by the left heart ventricle being normal, there is less blood than normal filling the the left ventricle because of reduced heart relaxation. HFpEF is a common condition in many older people, and as the population gets older, treating patients with this kind of heart failure is becoming a major demand on cardiac health care services.
Metabolic changes
Heart failure is characterised by metabolic changes that encourage the deposition of fat in heart (pictured is a photomicrograph showing fat deposition in a patient biopsy), and a previous study with a small number of HFpEF patients found increased fat deposition in their hearts.
But it is unclear if this fat has any link to the main symptom of HFpEF, which are breathlessness and not being able to do much exercise.
So a team of OCMR researchers led by Drs Masliza Mahmod and Oliver Rider used advanced magnetic resonance imaging (MRI) methods to measure heart muscle fat content and heart function in 27 patients with HFpEF, and compared these results with those from 14 healthy people. The research team also tracked the participants heart and lung function while they exercised on a stationary exercise bike, to find out how much oxygen they were using (an objective measure of exercise capacity) while they exercised as hard they could.
This ‘peak oxygen’ measure is a good measure of exercise capacity, and the OCMR research team found that compared to similar age and gender healthy people, not only did the HFpEF patients have more fat in their heart muscle, their cardiac function and peak oxygen measures were also worse. They also found that the greater the fat deposition, the worse the cardiac function, with peak oxygen values lowering too.
Associate Professor Oliver Rider, the senior author on the study, said, “Our study provides evidence that cardiac fat levels are elevated in patients with exercise limitation, and are related to the relaxation speed of the heart.
Whether this is something that can be targeted to help improve exercise capacity is an interesting prospect, but remains unknown.” - Dr Oliver Rider
Dr Masliza Mahmod, Head of Clinical Trials at OCMR and the first author on the study said, “By measuring fat content in the heart muscle of HFpEF patients, we have found a promising treatment target, which has the potential to improve exercise capacity, and eventually the health outcomes in patients with HFpEF”.