reporter: for years, leonardo battled a genetic condition called danon disease that weakens muscles, including the heart. >> i was very, very ill. i got so sick to the point that they told me i had to stay in reporter: this new heart, transplanted into leonardo's body last month at tufts medical center, saved his life. >> oh, man, i have energy. i have warmness in my body. reporter: he was also the 38th person this year to receive a heart transplant at tufts, breaking a 25-year-old record for new england hospitals. and placing the tufts program in the top 10 nationally for heart transplants. >> we usually do about 20 heart this year, we're on a pace to triple the amount of heart transplants we've done in the past. reporter: dr. david denofrio is the medical director of the advanced heart failure program at tufts. >> every day, we are waiting and hoping for a heart for these patients. reporter: this year, about 30% of the transplanted hearts at tufts have come from a surprising source -- people who died from a drug overdose. the opioid crisis resulting in more available hearts. >> it'