American tennis ace Taylor Fritz suffered a heart scare during his first-round defeat to Australia’s James Duckworth at the Toronto Masters 1000 event on Monday.

Fritz endured a scary moment at 4-4 in the first set when he grabbed his chest, before doctors checked his blood pressure on the court.

The world No 40 soldiered on before losing 7-6 (7/2), 6-3 to Duckworth, who is ranked 85th.

After the match, the 23-year-old Fritz took to social to explain what happened.

“Hey guys…I’m okay. Probably one of the weirdest things I’ve ever experienced,” he wrote on Twitter.

“[My] heart was going absolutely crazy for no reason, I only continued cause it was so odd I thought it maybe would go away and I really hate quitting, even if it was probably the smart thing to do.”

Fritz also opened up on several death threats and abusive messages he received from bookmakers after his straight-sets defeat.

“And to all the gamblers giving me the typical death threats for not pulling out, I’m really not concerned about your degenerate gambling addictions while I’m playing a match,” he added.

Picture: Twitter/Getty Images