When I was diagnosed with breast cancer at MD Anderson in January 2019, my biggest concern wasn’t actually my breasts. It was my heart. Because 23 years earlier, I’d been diagnosed with cardiomyopathy, a weakening of the heart muscle that can make general anesthesia riskier.

I found out I had that condition in 1996, when my heart failed just five days after my son was born. In my case, it was caused by the strain of pregnancy....