What’s the link between heart and kidney? How do they impact each other?

Heart failure is a risk factor for kidney disease. When the heart is not able to pump blood to the body efficiently, it becomes congested with blood, causing pressure to build up in the main vein connected to the kidneys. Meanwhile, kidney disease speeds up plaque deposits in heart arteries, says Dr Sunil Wani, Consultant Cardiology, Kokilaben Dhirubhai Ambani Hospital, Mumbai

Both the heart and kidney can have individual problems and impact the other organ. (Source: Pixabay)

Written by: Dr Sunil Wani

5 min readNew DelhiJun 27, 2023 09:40 PM IST First published on: Jun 27, 2023 at 12:56 PM IST

The heart is at the centre of the human circulatory system and is connected to all vital organs in the body. But it is interconnected to the kidney in such a manner that they both require each other and consequently impact each other. The heart’s job is to supply oxygenated blood to all parts of the body. On its part, the kidney filters the blood, extracting waste and expelling it in the form of urine. It helps regulate the water and salt levels to control blood pressure.

In fact, the two are so interrelated that the kidney can become dysfunctional within a narrow window of three to six minutes after the heart stops due to heart failure. That’s why heart failure is now considered a significant risk factor for kidney disease. When the heart is not able to pump blood to the body efficiently, it becomes congested with blood, causing pressure to build up in the main vein connected to the kidneys. So there is clogging of blood in the kidneys, too. The problem multiplies because there is a reduced supply of oxygenated blood.

When the kidneys become impaired, the body’s hormone system reacts and activates an emergency mode, thereby increasing blood supply to the kidneys. The heart then has to pump against the higher pressure that’s already built up in the arteries and is under extreme stress. That’s how intricately both are linked.

HEART AND KIDNEY PROBLEMS THAT AFFECT BOTH ORGANS

Both the heart and kidney can have individual problems and impact the other organ. But sometimes both can have problems because of extraneous factors. A heart attack, heart failure or cardiomyopathy may decrease the blood supply, putting pressure on the kidney. But the moment the heart recovers, the kidney recovers too. Usually, the kidney gets impacted when the heart function is low, about 15 to 20 per cent, the heart muscle is fatigued and there is decreased blood supply to it. Problems in the heart valves also cause problems in the kidney.

Sometimes kidney diseases, like Chronic Kidney Disease (CKD), overwork the heart as it needs to pump harder to get the blood to help the diseased kidneys. This elevates blood pressure (BP) and can cause heart disease. CKD can also accelerate atherosclerosis or plaque deposition in the heart arteries, especially if there is an existing burden from the early stages. This is because of the high levels of creatinine building up in the kidney, when it cannot throw it out through urine. This has a direct correlation with the extent of atherosclerosis. That’s why when you develop blood pressure and hypertension rather early, doctors test you for creatinine. This is done to ascertain the exact cause of your blood pressure as drugs given to lower it, when you have kidney dysfunction, can impair kidney functioning further. CKD is also closely linked with peripheral vascular disease, cerebral vascular disease and decreased blood circulation to the lower limbs.

Kidney disease with diabetes is the worst trigger for both cardio and brain strokes. Sometimes, CKD can cause uremia, a condition in which urea accumulates in the blood because the kidney cannot filter it away. It can cause a condition called the uremic heart, where the toxin buildup reduces the contractility of the heart and leads to breathlessness and congestion in the lung. These are all classified under the umbrella term of the cardio renal syndrome.

HOW TO PREVENT COMPLICATIONS?

However, preventing or managing one condition can help you prevent and manage the others and lower risk of complications. The risk factors are again similar to any other trigger for heart disease and require lifestyle corrections, taking care of high blood sugar, high blood pressure, factoring in family history, obesity, smoking, diet and physical inactivity. High blood sugar damages the kidneys over time. Approximately one in three adults with diabetes has CKD.

WHAT ARE TESTS AND TREATMENT?

A simple blood test can check if the level of creatinine is within safe limits. Some patients may also need an ultrasound or CT scan to examine their kidneys’ structure and function. For the heart, there are echo, MRI and angiography. Besides, if needed, there are options for heart and kidney biopsy or a PET scan. BP monitoring is a must.

Combined heart and kidney disease is usually treated with several drugs. Controlling high blood pressure is important, so you may be prescribed diuretics to reduce blood pressure and remove excess fluid as they make the kidneys excrete more water and salt. Other drugs include ace inhibitors, beta blockers and aldosterone blockers, which are prescribed for heart failure and neutralise an over-active hormone system. However, they can have a negative effect on the kidneys, so it takes careful monitoring by the doctor and frequent blood tests to get the balance right. In fact, a cardio-nephrology team should be consulted for managing the cardio-renal syndrome.