The symptoms of a heart attack can appear suddenly and often with strong warnings, but experts say that spotting heart failure is more subtle. Dr. Kevin Campbell, a leading cardiologist with Cano Health, tells Newsmax that more than 5 million Americans are living with congestive heart failure (CHF).

“CHF more often occurs when there is a weakened heart muscle due to a previous heart attack,” he says. “However, there are other causes such as alcohol, drug use, or infections that can result in a weakened heart. Some patients have a genetic disposition to CHF and others may have normal heart function.

Campbell, the author of Women and Cardiovascular Disease, says that CHF describes a cluster of symptoms including shortness of breath at rest or during exertion.

“This may be due to the fact fluid beings to ‘backup’ in the lungs due to poor heart pump function,” he explains. “When this happens, we become short of breath.”

In addition, other symptoms include having trouble lying flat, waking up gasping for air, and swelling of the belly, ankles, or legs due to excess fluid.

“It is important to evaluate these symptoms promptly,” says Campbell. “You must see your doctor and determine if these symptoms represent a heart problem or not, as they may be signs of other conditions.”

According to Eat This, Not That!, fatigue is common symptom of heart failure, because your major organs and brain are not getting enough blood. While we all feel tired from time to time, the Mayo Clinic describes fatigue as “unrelenting exhaustion” that is not alleviated by rest.

Low blood pressure can also signal CHF, so make sure to have your blood pressure checked regularly, say experts. Impaired kidney function is another sign that your heart is failing, says Dr. Weining David Xu, a specialist in heart failure at Medstar Health in Baltimore. Here again, regular checkups can help diagnosis these symptoms.

Sudden upper back pain without a history of injury could indicate a problem with your heart, according to Eat This, Not That! Your doctor may prescribe a stress test to see if your heart is pumping correctly. If you are having trouble breathing while walking uphill, that’s another sign that could be evaluated by a stress test to see if the difficulty is due to heart failure.

Rapid weight gain that does not seem to be associated with excess calories can mean that your body is retaining excess fluid due to CHF. Dr. Campbell says that you must be diligent about monitoring your heart symptoms and make an appointment with your doctor if you experience any unusual indications that could be signal heart failure. He says this advice is especially important for women, who tend to ignore their heart health, erroneously thinking that heart disease is a male-dominated illness.

“As a cardiologist, I have devoted much of my career to being an advocate for women’s heart health,” says Campbell. “We have made great strides towards more equitable care in the last decade, but women with heart disease remain under-treated and under-served.

“While more women than men die every year from heart disease, many still think heart disease is only a disease of men. We must do more to educate patients, families, physicians and women that they are at risk and must better understand these risks and hot to modify them.”