Heart Failure – The Overlooked Diabetes Complication, Part 1: What and Why?

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By Ben Pallant

Learn what heart failure is, what it has to do with diabetes, and how to identify and talk about this complication that’s often less discussed.

Healthcare professionals often discuss diabetes complications such as vision loss (retinopathy), chronic kidney disease (nephropathy), and cardiovascular disease (referred to as atherosclerotic cardiovascular disease by healthcare professionals). However, there is a less talked about heart complication, heart failure. Heart failure refers to a condition where the heart’s ability to pump blood is less than normal, often meaning not enough blood is effectively circulating to the rest of the body.

This is part one of a two-part series on heart failure and diabetes.

What is heart failure?

First, it’s important to differentiate heart failure from other conditions such as cardiovascular disease, a heart attack, or cardiac arrest. There is also the broad term “heart disease,” which can encompass any heart issue. Because the names can get confusing, here are some brief explanations:

  • Cardiovascular disease, or atherosclerotic cardiovascular disease, is related to the process called atherosclerosis, which occurs when a substance called plaque builds up in your arteries making it difficult for blood to flow normally. The plaque buildup can be caused by high blood pressure, high cholesterol or triglycerides, smoking, or a number of other reasons. When it builds up in the arteries that supply blood to heart muscles or the brain, a heart attack or stroke can occur. Read our article on diabetes and heart disease here.

  • In a heart attack, the blood flow (and the oxygen supply, since blood carries oxygen throughout the body) to the heart muscle is blocked, causing damage to the heart muscle.

  • Heart failure happens when the heart isn’t able to pump enough blood to the rest of the body.

  • Cardiac arrest is the sudden loss of heart function. Usually due to an issue with the heart’s electrical system that disrupts a regular heartbeat, cardiac arrest causes the heart to stop pumping blood to the rest of the body.

There are a number of reasons why heart failure can occur, including coronary artery disease, high blood pressure, previous heart attacks, or other conditions and structural issues that damage the heart muscle (like cardiomyopathy or heart valve problems). Your chances of developing heart failure also increase as you get older. The heart’s inability to pump enough blood usually happens in one of two ways:

  1. When the heart muscle becomes stiff, the chambers in the heart cannot relax. This decreases the fill capacity of your heart chambers. Nevertheless, the heart is still able to release more than 50% of the blood in the heart chamber to the rest of the body. This type of heart failure is called “heart failure with preserved ejection fraction,” or HFpEF.

  2. When the heart muscle becomes weaker, not enough blood goes out to the body with each heartbeat. Thus, the percentage of blood that is released to the body is less than 50% of the amount in the heart chamber. This type of heart failure is called “heart failure with reduced ejection fraction,” or HFrEF.

Diabetes and prediabetes have been associated with both types of heart failure. Heart failure overall is a widespread health challenge – over 6 million Americans live with heart failure, and it leads to about 1 million hospitalizations per year in the US.

Heart failure is usually a chronic condition that progresses over time. At first, people may not experience any physical symptoms at all because the body has ways of trying to compensate – the heart may become bigger, it could develop more muscle mass, or it could try to pump faster. Over time though, heart failure worsens leading to shortness of breath, fatigue, inability to exercise, and more. Eventually the heart’s decreased ability to pump blood causes fluid to build up in other parts of the body, including the legs and lungs, which makes ordinary things like breathing and walking difficult. This is called congestive heart failure (CHF).

To learn more about heart failure, check out the American Heart Association’s heart failure resources.

What does heart failure have to do with diabetes?

Heart failure is unfortunately one of the most common and deadly complications of diabetes, especially for people with type 2 diabetes. They are two to four times more likely to develop heart failure than people without diabetes, and having diabetes increases a person's risk for repeat hospitalizations for heart failure. This is partly because many of the key risk factors for heart failure are common in people with type 2 diabetes, such as a body mass index (BMI) over 25 (click here for a BMI calculator), high blood pressure, coronary artery disease, or a history of a heart attack. Other risk factors for heart failure include heart valve problems, sleep apnea, lung disease, and smoking.

But the shared risk factors alone don’t explain everything – diabetes itself is an independent risk factor for heart failure. According to several research studies, each percentage point increase in A1C is associated with an increased risk (8-36%) of heart failure. Researchers suspect that over time, high blood sugar levels either damage the cells of the heart muscles or force the heart to work harder due to damage to smaller blood vessels throughout the body and in the heart – this may be why high glucose levels are associated with heart failure.

Signs, symptoms, and screening

The Mayo Clinic and the American Heart Association have identified a number of possible symptoms of heart failure. These include:

  • Shortness of breath during activity or when you lie down

  • Tiredness and weakness

  • Swelling in your legs, ankles and feet, and very rapid weight gain (due to fluid retention)

  • Rapid or irregular heartbeat

  • Persistent coughing or wheezing (or coughing that produces pink, foamy mucus)

  • Chest pain if the heart failure is caused by a heart attack

  • Lack of appetite or nausea

  • Confusion or impaired thinking

It is especially important to seek immediate medical attention if you experience chest pain, severe fatigue or weakness, rapid or irregular heartbeats with shortness of breath or fainting, or sudden, severe shortness of breath especially if it is associated with coughing up pink, foamy mucus. For CHF especially, seeking timely medical attention is essential.

Talking to your healthcare team is key to making sure you are staying healthy, and it can help identify an early diagnosis. If you are experiencing any of the above symptoms, ask your healthcare professional if you can be tested for heart failure. Even if you aren’t exhibiting symptoms, start a conversation about what you can do to stay healthy and prevent future complications.

How do healthcare professionals test for heart failure?

Heart failure is most commonly assessed using medical imaging techniques that allow healthcare professionals to “see” the heart and assess its function. The most common test associated with heart failure is echocardiography (often called an “echo”) which is a non-invasive, painless ultrasound image of the heart. The echocardiogram can show how thick the heart muscle is and how much blood is pumped out of the left ventricle (one of the heart’s four chambers) with each beat. This information can be used to determine whether heart failure involves preserved or reduced ejection fraction.

Other imaging tests include an x-ray, an MRI, and a myocardial perfusion scan. An x-ray can see if the heart is enlarged or if there is fluid in the lungs, two signs of CHF. If your healthcare professional is concerned that there may be damage to the heart muscle or blockages of major blood vessels to the heart muscle, they may recommend an MRI. A myocardial perfusion scan uses a tiny amount of a radioactive substance that allows the heart to be imaged. It can show how well the heart muscle is pumping and areas with poor blood flow. This scan is often done with an exercise stress test (explained below).

In addition to these different imaging techniques, healthcare professionals use exercise stress tests (which measure how a person responds to increasingly difficult exercise) as a measure of heart function, blood tests to check for heart failure-associated strain on the kidney and liver, or an electrocardiogram (EKG or ECG) test to look at the heart’s electrical activity for signs of a heart attack and to see if the heart rhythm is abnormal.

Before any of these heart tests are ordered, your healthcare team will usually conduct a physical exam to determine what your symptoms are and what tests are needed. It’s important to be honest – your healthcare team needs to know about your lifestyle, including whether you smoke cigarettes, eat a lot of high-fat foods, and are physically active. Be prepared to answer other questions too:

  • When did symptoms begin?

  • How severe are the symptoms?

  • Does anything make the symptoms better or worse?

  • Do you have a family history of heart disease, diabetes, or high blood pressure?

  • Are you taking any medications, including over-the counter-drugs, vitamins, supplements, or prescriptions?

To learn more about heart failure, including prevention, medication options, and management tips, read “Heart Failure – The Overlooked Diabetes Complication, Part 2: Prevention and Management,” which our team will be updating this summer. You can also check out the Know Diabetes By Heart resources on heart failure.

This article was originally published on June 15, 2018. It was updated in May 2021 by Matthew Garza as part of a series to help people with diabetes learn how to support heart health, made possible in part by the American Heart Association and American Diabetes Association’s Know Diabetes by Heart initiative.