When James Hicks, 75, was diagnosed with heart failure, it felt like the beginning of the end.

Mr. Hicks, a former railroad worker from Rogers, Ark., had quietly dealt with various health problems, from carpal tunnel syndrome in both arms to dual knee replacements. But now his heart was giving out, and the doctors chalked it up to the wear and tear of old age. “There’s just not exactly a surgery to fix this,” he said.

Soon enough, Mr. Hicks couldn’t walk from his grandson’s high school basketball game to the car, without stopping several times to catch his breath. His feet and ankles would swell if he didn’t elevate them. He could feel his heart racing uncontrollably, unable to find a steady rhythm. Mr. Hicks’ doctors tried a half-dozen different medications, but nothing really helped.

It wasn’t until 2023, some 10 years after the original diagnosis, that a local cardiologist raised the possibility of cardiac amyloidosis, a little-known form of heart failure.

Over the past 50 years, heart failure has become one of the fastest-growing cardiac killers. It was long considered a disease of aging, caused by gradual yet unavoidable changes to the heart. But doctors are now discovering that about 15 percent of cases are caused by a rogue protein called amyloid, perhaps best known for its role in Alzheimer’s. While one type tangles neurons in the brain, others infiltrate the heart, making the muscle stiff and less able to pump blood.

Until recently, cardiac amyloidosis was a death sentence, but the advent of new medications, including two approved by the Food and Drug Administration in the past year, have made this disease increasingly manageable. “We shouldn’t just be fatalistic — ‘you’re tired, you’re short of breath, you’re just old,’” said Dr. Michelle Kittleson, a cardiologist at Cedars-Sinai Medical Center. “There is a lot of hope for people with heart failure.”

Diagnoses on the Rise

For decades, cardiac amyloidosis was cast aside as a rare disease. Early signs include carpal tunnel syndrome, a narrowing of the spine and a rupture of the biceps tendon, as amyloid plaques accumulate across the body. But with little awareness of the condition, it was difficult for doctors to connect the dots.