Very small reductions in kidney function linked with heart disease

Study proves for the first time that having Chronic Kidney Disease can directly damage the heart.

Very small reductions in kidney function are directly linked to subtle heart and blood vessel damage, according to new research from scientists in Birmingham funded by the British Heart Foundation (BHF). This shows for the first time that the heart damage seen in people with Chronic Kidney Disease (CKD) is a direct result of their reduced kidney function.

The study, published in the journal Hypertension, looked at healthy people who had chosen to donate a kidney to see if it resulted in any adverse changes in their heart and blood vessels after donation.

The researchers found that, even in very healthy people, a small reduction in kidney function is associated with an enlarged left-side of the heart, which makes the heart stiffer and impairs its ability to contract. This shows the clear link between reductions in kidney function and cardiovascular disease.

Dr William Moody, a BHF Research Fellow at Queen Elizabeth Hospital and the University of Birmingham, who worked on the study said: "It should be noted that the effects on the kidney donors were very small and no studies of people who have donated a kidney have shown a cardiovascular risk that is higher than that of the general population."

The results could, however, have significant consequences for people suffering with CKD. In England in 2008/09 there were over 1.5 million people registered with CKD, though it is expected that the actual number is much larger than this¹. People with CKD have impaired cardiac function to the extent that this is often the cause of premature death, although the mechanism is not clear. By demonstrating that in otherwise healthy people there is small but measurable heart and blood vessel damage following kidney donation, the researchers have shown that in patients with CKD, poor kidney function has a direct adverse effect on heart function.

For one year the researchers tracked 68 kidney donors and 56 similar adults who had not donated a kidney. The adverse changes following donation included an enlarged left-side of the heart (increased left ventricular mass), increased stiffness of the aorta, the main artery providing blood to the body, and reduced heart function. However, these effects were extremely small and at an individual level the extra risk associated with the changes is very small.

Past large studies of patients with kidney disease have shown that a worse kidney function increases likelihood of an increased left ventricular mass, which is a strong predictor of risk for cardiovascular death.

A major research effort is now needed to understand what the risk is and find measures to reduce it in patients with CKD, to prevent premature death.

This research was also funded by NIHR/Wellcome Clinical Research Facility and Queen Elizabeth Hospital Birmingham Charity.

Dr William Moody, a BHF Research Fellow at the University of Birmingham and the author of the paper said: "Early stage kidney disease is a public health problem because it is common and carries an increased risk of heart and circulatory disease. A major research effort is needed to understand this risk and to find measures to prevent this damage.

"For now, people with blood tests showing slightly reduced kidney function should certainly consider discussing heart disease risk with their doctors and consider how best to reduce this."

Professor Jeremy Pearson, Associate Medical Director at the British Heart Foundation said: "By studying healthy kidney donors, this Birmingham team supported by BHF funding have been able to show convincingly for the first time that loss of kidney function has direct adverse effects on the heart, unrelated to changes in blood pressure.

"While the adverse effects in the kidney donors are small, the study suggests strongly that identification of the mechanisms involved could provide new avenues to reduce the progressive impairment of heart function seen in patients with chronic kidney disease. However it is important to note that these findings should not put anyone off donating a kidney, as those individuals are highly selected as healthy subjects and effects of kidney donation will still not even get them to an 'average' risk level".