Heart diseases are the leading cause of death in end-stage renal disease. It seems most often related to atherosclerosis and other risk factors found in renal failure like high blood pressure.
Fluid and potassium overload
Your kidneys play an important role in regulating fluid balance in the body. If your kidneys stop working, fluid builds up quickly in the lungs, heart, brain and in other body tissue. This increases the workload of the heart and could lead to heart failure. The excess fluid also causes a rise in blood pressure, which is as detrimental for the kidneys as for other parts of your body. Failed kidneys also cannot control potassium effectively and high levels of this mineral affect the heart and are life threatening.
Chronic renal failure is characterized by anaemia, where you have insufficient red blood cells. This is due to the loss of kidney cells that produce an important hormone, erythropoietin. This hormone stimulates bone marrow to make your oxygen-carrying red blood cells. Having anaemia can put strain on the heart and its demand for oxygen by increasing the heart rate and output.
Dialysis and the fistula
If you need dialysis, a fistula is created to provide access to your blood. It is done by connecting an artery and a vein, most often on your arm. The fistula, fluid excess, anaemia and hypertension contribute to certain hemodynamic factors that put strain on your cardiovascular system. Insufficient dialysis can also lead to pericarditis, an inflammation of the heart’s outer layers. During dialysis excess fluid are removed and chemicals are balanced. This process is complicated and electrolyte disturbances can lead to irregular heart rhythm. Blood pressure rises if insufficient fluid was removed.
Your kidneys are your body’s waste collectors and when they fail, wastes build up in your blood. When dietary protein is broken down a product called urea is formed. High levels of urea, called uremia, literally means “urine in the blood”. This condition is toxic to the body and could lead to a dangerous inflammation of the outer layers of the heart, the pericardium. It is treated with dialysis.
Atherosclerosis and heart attack
Heart diseases are the leading cause of death in end-stage renal disease. It seems to be related to atherosclerosis and other risk factors found in renal failure like high blood pressure. Although people without kidney problems also show a high incidence of heart disease, those with kidney failure have various factors that increase their risk. Co-existing diseases like diabetes, often the cause of kidney failure, are per se a major risk factor for heart disease. High blood fats lead to atherosclerosis, which occludes the coronary arteries and lead to angina and heart attack.
Hypertension – high blood pressure
Hypertension is an important underlying cause of kidney failure. Conversely, kidney failure can lead to hypertension. Excess fluid and salt build up rapidly in the body if the kidneys are unable to regulate it, and contributes to high blood pressure. With loss of kidney cells an overproduction of renin, that elevates blood pressure, can follow. Control of hypertension in patients with renal failure is crucial because it accelerates the renal injury from other causes, like diabetes. Hypertension also damages the inner lining of blood vessels and thereby promotes the formation of fatty deposits (atherosclerosis) inside the blood vessels. Certain drugs for high blood pressure help to limit the progression of renal failure.
Written by Dr K. Coetzee, reviewed by Dr R. Moosa, head of the Renal Unit, Tygerberg Academic Hospital.