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

By Ben Pallant

Learn what heart failure is, what it has to do with diabetes, and how to identify and talk about this often-forgotten complication

Healthcare providers often discuss diabetes complications such as vision loss (retinopathy) and kidney disease (nephropathy), but a less-talked-about complication is heart failure. Heart failure, which is different from a heart attack, is when the heart isn’t able to pump enough blood to the rest of the body. This article will break down the details of heart failure, including the leading hypothesis of why diabetes increases heart failure risk, signs of heart failure, and how healthcare providers can test for it.

This is part one of a two-part series on heart failure and diabetes. To read part two, which is about heart failure prevention and management, click here.

What is Heart Failure?

First, it’s important to note that heart failure is different from a heart attack and from cardiac arrest. Because the names get confusing, here are some brief explanations:

  • In a heart attack, the blood flow, and therefore the oxygen supply, to the heart muscle is blocked, causing damage to the heart muscle.
  • In cardiac arrest, the heart completely stops beating in any coordinated way.
  • Heart failure is when the heart isn’t able to pump enough blood to the rest of the body.

There are a number of different causes for why heart failure can occur (a non-fatal heart attack can actually be one of those causes), but, basically, the heart’s inability to pump enough blood happens in one of two ways:

  1. When the heart muscle becomes stiff, the chambers fail to relax, decreasing the fill capacity; however, the percentage of blood going out to the body is still above 50% of the amount in the heart chamber. This type 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 beat (less than 50% of amount in heart chamber). This type is called “heart failure with reduced ejection fraction” or HFrEF.

Diabetes and prediabetes have been associated with both of these varieties of heart failure, and it’s clear that heart failure overall is a widespread health challenge - close to 6 million Americans live with heart failure, and it leads to nearly 1 million hospitalizations per year in the US.

Heart failure is usually a chronic condition that progresses over time rather than happening “all at once.” At first, people may not experience any physical symptoms at all. Over time though, heart failure can lead to shortness of breath, fatigue, lack of ability to exercise, and more. Eventually the heart’s decreased ability to pump blood causes fluid to build up in tissues including legs and lungs, making ordinary things like breathing and walking around difficult – this is called “congestive heart failure,” or CHF.

What does heart failure have to do with diabetes?

People with type 2 diabetes are 2.5 times as likely to develop congestive heart failure than people without diabetes. 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 over 25 (BMI, 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 including from smoking.)

But the shared risk factors alone don’t explain everything – diabetes itself is an independent risk factor for CHF. According to one large study, each percentage point increase in A1C is associated with approximately a 30% increase of CHF risk. (For comparison, another major study found that each percentage point increase in A1C is associated with a similar 35% percent increase in diabetes complications like vision loss, kidney damage, and nerve damage.) Though it is not known for certain why diabetes is an independent factor risk for heart failure, researchers suspect that over time, high blood sugar either damages the cells of the heart muscles or forces the heart to work harder due to damage to smaller blood vessels throughout the body and in the heart.

In major diabetes heart health trials, heart failure was just as common a reason for hospitalization as the more commonly considered heart complications, like heart attacks, strokes, or coronary bypass surgeries. Why then, does heart failure tend to get overlooked? No one can say for sure, but one possible explanation is that heart attacks and strokes are more sudden and defined “events,” rather than a slower progressive process like heart failure.

Signs, Symptoms, and Screening

The Mayo Clinic identifies a number of possible symptoms of heart failure. Some of the most notable include:

  • Shortness of breath during exertion or when you lie down

  • Fatigue and weakness

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

  • Rapid or irregular heartbeat

  • Coughing up pink, foamy mucus

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

They note that it is especially important to seek immediate medical attention if you experience chest pain, severe fatigue or weakness, rapid or irregular heartbeats associated with shortness of breath or fainting, or sudden, severe shortness of breath especially if it is associated with coughing up pink, foamy mucus.

How do healthcare providers test for HF?

Heart failure is most commonly assessed using medical imaging techniques that allow health professionals to “see” the heart and assess its function. The most common test associated with heart failure is an “echocardiogram,” which is an ultrasound of the heart. The echocardiogram can show how much blood is pumped out of the left ventricle, one of the heart’s four chambers, with each beat. This can be used to tell whether heart failure involves preserved or reduced ejection fraction. An x-ray can also see if the heart is enlarged or if there is fluid in the lungs, which would be a sign of congestive heart failure. Lastly, if a key concern is damage to the heart muscle or blockages of major blood vessels, your healthcare provider may recommend an MRI.

In addition to these different imaging techniques, healthcare providers can use exercise stress tests (which measures 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, and an EKG test, which measures the heart’s electrical activity and can be used to look for evidence of a past heart attack or for thickening of the heart muscle.

If going into the health clinic to be tested for heart failure, be prepared to answer questions like:

  • When did symptoms begin?

  • How severe are the symptoms?

  • Does anything improve or worsen the symptoms?

  • Is there a family history of heart disease, diabetes, or high blood pressure?

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