As a kid, I enrolled in a study whose results were never published—meaning I'll live the rest of my life with a heart implant, but may never know how well it actually works.
Emma Yasinski in The Atlantic:
I’d been diagnosed in the first year of my life with an atrial-septal defect, a hole in the heart that sends blood flowing the wrong way, forcing the right side of the heart to work harder than it should. In some cases the hole closes on its own during early childhood, but mine hadn’t shown any change, and now my heart was beginning to grow unevenly. Without surgery, I would face an adulthood characterized by fatigue, shortness of breath, and possibly heart failure. To prevent these things, a surgeon at the Children’s Hospital of Philadelphia would have to slice open my chest, crack my sternum, and stitch the hole in my heart together.
But there was another option, the doctor explained: He’d heard of a clinical trial that was recruiting pediatric patients with my condition. If I were placed in the experimental group, a cardiologist would insert a catheter into my upper thigh and direct it toward the hole in my heart. The catheter would deliver a tiny, metal mesh umbrella, which would cover the hole in my heart until my cells grew over it, making the umbrella a permanent part of my body. I would be in the hospital for just a weekend, with no broken ribs, no cardio-bypass machine, and no huge scar on my chest.
More here.