Daniel Moore was about 30 the first time it happened. At the end of a long, hot, stressful day, he chugged an ice-cold glass of milk.

When you have transthyretin amyloid cardiomyopathy (ATTR-CM), proteins called amyloids build up in your heart, stiffening the muscle and interfering with its ability to pump blood throughout the body.

One initial treatment is a cardioversion, which involves using a defibrillator to deliver an electric shock to the heart to restore rhythm. It’s often successful, but sometimes only temporarily.