Heart failure and kidney disease: how are they linked?

The organs that keep your body functioning do not work in isolation – they are connected by your circulatory system.

This is a network of blood vessels like arteries and veins, which supply blood to your organs to help them work properly.  

Because of this, if you develop a problem in one organ, it can have a knock-on effect on another organ.

This is especially true of your heart and kidneys.

When you have problems in one that causes problems in the other, it can lead to a condition called cardiorenal syndrome. 

What is cardiorenal syndrome?

Cardiorenal syndrome can happen quickly (acute) or over time (chronic), and can be life-limiting without treatment, because the damage to your heart and kidneys might become permanent. 

You are at higher risk of cardiorenal syndrome if you have heart failure or chronic kidney disease (CKD).

There are several risk factors that these conditions share:

• high blood pressure (hypertension)
• atherosclerosis (a build-up of fatty material in the artery walls supplying the heart and/or kidneys)
• obesity
• diabetes.

This means that when someone develops heart failure, they may already have some damage to their kidneys.

How do the heart and kidneys work together?

Your heart and kidneys work in partnership to keep your body functioning correctly.

Around 20 to 25 per cent of the blood pumped out by each beat of your heart goes to your kidneys.

Your heart’s job is to:

• Pump a constant supply of blood rich in oxygen and nutrients around your body via the blood vessels, to help your organs, like the kidneys, and muscles work.
• Pump blood containing unwanted carbon dioxide into your lungs so they can breathe it out.

Your kidneys’ job is to:

• Filter your blood of waste products and send these to your bladder to pass out of your body as urine.
• Regulate your body’s water, mineral and salt levels, to control blood volume and blood pressure.
• Release a number of different hormones, including: renin (which increases your blood pressure by instructing your small blood vessels to narrow); and erythropoietin (which stimulates the production of red blood cells to carry oxygen around your body and prevent anaemia).

How does heart failure damage the kidneys?

Problems can arise between your heart and kidneys when you have heart failure, which is when your heart cannot pump blood around the body as well as it should.

This is because heart failure causes fluid to build up in blood vessels, including the main vein carrying blood from your kidneys to your heart.

Your kidneys can also become damaged because they’re not getting enough oxygen-rich blood from the heart to keep them working properly.

They respond to the lack of oxygen by secreting more renin to increase your blood pressure and get an increased blood supply. This puts more strain on your heart and your blood vessels.

It’s a vicious cycle as the 2 organs work against each other – heart failure damages the kidneys and the injured kidneys aggravate the heart failure. 

If this goes untreated, it can lead to chronic kidney disease and even kidney failure.

How does kidney disease damage the heart?

Kidney Research UK says people with chronic kidney disease are 20 times more likely to die from cardiovascular disease than kidney failure, such is the impact it has on the heart and blood vessels. 

British Heart Foundation (BHF) funded research from 2024 also shows that people with kidney failure are 8 times more likely to have a heart attack and up to 4 times more likely to have a stroke than the general population.

This is because when your kidneys become damaged and develop chronic kidney disease, they are unable to do their many jobs properly, like removing extra fluid and salt.

This causes high blood pressure, which in turn strains your heart and circulatory system.

You may also:

• Suffer from a lack of red blood cells and develop a condition called anaemia, which means the blood cannot carry enough oxygen.
• Retain fluid in your tissues, leading to swelling.

Another complication could be having too much potassium in your blood, which is known as hyperkalaemia, because your kidneys cannot regulate it very well.

Some medicines used to treat chronic kidney disease can also raise potassium levels. 

Having above normal levels of potassium can cause heart an abnormal heart rhythm (arrhythmia).

What are the symptoms and signs of cardiorenal syndrome?

If you have heart failure you may not spot the signs of kidney disease or kidney failure initially. 

This is because they have some overlapping symptoms, including:

• tiredness
• swollen ankles and feet or hands
• shortness of breath
• urinating less
• low blood pressure (hypotension).

Due to the close link between the organs, your doctor should routinely check your kidneys if you have heart failure, and check your heart if you have chronic kidney disease. 

If this is not happening, you can request that they carry out tests to detect cardiorenal syndrome.

If you have heart failure, monitoring of your kidneys would include a blood test to check if you have raised levels of creatinine, a waste product usually secreted by your kidneys, suggesting they are not working properly. 

You might also be offered an ultrasound or a CT scan to help examine your kidneys’ structure and function.

If you have chronic kidney disease, you may get blood tests that look at your cholesterol levels and specific tests to see if your heart is functioning well or under strain. 

You may also be offered an ECG (electrocardiogram), echocardiogram or X-ray of your heart and lungs.

How is cardiorenal syndrome treated?

There's a huge amount doctors can do to treat people and extend life expectancy.

The main aim is often to reduce fluid overload (congestion) while keeping an adequate blood supply to blood organs.

This should result in lowering high blood pressure too.

Cardiorenal syndrome is usually managed with the help of several medicines. 

Medicines

You will likely be prescribed water tablets (diuretics) that help to reduce fluid build-up in your tissues by making your kidneys excrete more water and salt.

You may also be started on medicines to control your blood pressure. 

These include:

• ACE inhibitors (angiotensin converting enzyme inhibitors): ramipril, enalapril, lisinopril, perindopril.
• Beta blockers: bisoprolol, carvedilol, nebivolol.
• ARBs (angiotensin receptor blockers): candesartan, losartan and valsartan. 

These help people with heart failure as they counteract the over-activation of the hormone system and can have benefits for their kidneys too, reducing the decline in kidney function over time.

Your doctor will monitor you while you are taking these medicines to make sure they are working well.

They will be looking out for any signs of acute kidney injury (AKI), which is when your kidneys suffer a sudden decline in function.

If this happens your doctor may want to stop these medicines.

However, this is not always necessary, or helpful, because of their positive, life-prolonging benefits for your heart.

Make sure your kidney doctor speaks to your heart team first or puts a plan in place to restart them later.

Do not feel scared about asking questions if you are unsure about changes to your medicines.

You may be prescribed SGLT2 inhibitors too: dapagliflozin, canagliflozin, empagliflozin, ertugliflozin.

These medicines help the kidneys to remove excess sugar from the blood but can also ease heart failure symptoms and slow the progress of kidney disease.

Diet and supplements

If you have chronic kidney disease, your doctor may recommend a low potassium diet to reduce the levels in your blood and lessen your risk of heart problems. But you should only try this if it’s advised by your healthcare team.

Your doctor may also give you iron supplements via intravenous infusion to treat low blood levels of iron (iron deficiency) or anaemia, which are both common side effects of heart failure and chronic kidney disease.

The BHF-funded IRONMAN study found this treatment improved symptoms and outcomes for those with heart failure who also had iron deficiency. 

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