The day her brother died she rushed to his bedside, Ms. Rivera, 56, said recently in an interview at her home in the Pelham Bay section of the Bronx. She stayed for hours, then went to his apartment around 3 a.m. and slept fitfully in his recliner. Her sister and her parents arrived from East Stroudsburg, Pa., the next morning, and then they all went to the hospital to say their goodbyes.

At 53, Mr. Rivera, the “baby boy” of the family, had seemed unstoppable, Ms. Rivera said. He worked two full-time jobs until the end. Each morning at 7, he would arrive at Bronx Criminal Court, where he worked for almost two decades. He finished there at 5 p.m. and would drive straight to his second job with Delta Air Lines at La Guardia Airport, where he worked through the evening, returning home at 1 a.m. He would sleep four hours, then start again.

Ms. Rivera said her brother’s work ethic came from a desire to provide for his son, Andrew. Although Mr. Rivera never finished college, she said, he was determined to give his son more opportunities, including putting him through college.

“He gave his son everything,” Ms. Rivera recalled. “He had such a big heart.”

But Mr. Rivera had not told his family that he had an enlarged heart. And his on-the-go lifestyle, like eating fast food between shifts, complicated the problem.