A group of researchers from Harvard Medical School—in collaboration with several British universities and medical centers—investigated the association between kidney function post-kidney transplant and cardiovascular performance. Their research, published in JAMA Cardiology, found that patients who received a kidney transplant showed improved cardiovascular functional reserve one year post-transplant.*

Background information

Cardiovascular functional reserve, or cardiac reserve, refers to the difference between the rate at which the heart pumps blood and its maximum capacity for pumping blood at any given time. For a healthy individual, cardiac reserve may be up to five times superior to a resting value. 

In the case of a stress reaction, cardiac reserve can deliver excessive blood and energy resources, subsequently increasing one’s heart rate. 

Data about cardiac reserve is an essential health indicator to show in what condition the heart and coronary arteries are in. Changes in cardiac reserve may point to coronary artery disease, chronic heart failure, and other cardiovascular diseases.

Research and investigation details

Researchers conducted a collaborative investigation; their study aimed to reveal any potential effects of kidney transplants on cardiovascular functional reserve. Of the 253 study participants, three different patient groups were examined:

• 81 patients with stage 5 chronic kidney disease (CKD) who had undergone a kidney transplant; 
• 85 patients with stage 5 CKD who had not yet had a transplant and were on a waiting list; and 
• 87 patients with hypertension only.

For the first two groups, the investigation began pre-transplant and continued post-transplant. The data from the first two patient groups was then compared against the data of the third patient group.

Results and conclusions

The results showed that kidney transplantation improved cardiovascular functional reserve one year post-operation. Concurrently, wait-listed patients with CKD experienced a decline in cardiovascular functional reserve. 

Improved cardiovascular reserve after a kidney transplant may be due to some beneficial structural and functional alterations to the cardiovascular system. However, the improvement was not associated with a change in left ventricular muscle mass. Alteration of the left ventricular mass (hypertrophy) is a thickening of the heart muscle of the left ventricle of the heart, which occurs as a pathological reaction to cardiovascular disease or high blood pressure. 

A secondary reason for improved cardiovascular functional reserve may be uremia reversal after kidney transplantation. Uremia refers to raised, or abnormally high, levels of nitrogenous waste compounds, like urea, in the blood, which occurs when the kidneys are no longer filtering properly. Urea is one of the primary components of urine, which a healthy kidney should excrete. In patients with kidney disease, the excretion of urea is reduced. Uremia typically occurs when a patient is the final stage, or stage 5, of CKD.

Additional reading material and insight can be found in DocWire News’ article, “Kidney Transplant Improves Cardiovascular Reserve, But Not For Reasons You Might Think”.

*Lim, K., Ting, S., Hamborg, T., McGregor, G., et al. (2020, Apr. 1). “Cardiovascular Functional Reserve Before and After Kidney Transplant.” JAMA Cardiology.