Sagan's Olympic bid hit by fresh heart problems
The seven-time Tour de France green jersey winner has retired from road racing and instead at 34 is hoping for an Olympic swansong on his preferred mountain bike event.
But in late February Sagan's heartbeat went above 200 bpm during a tachycardia episode suffered during a mountain bike race at Valencia, leading to a first intervention at an Ancona hospital.
The Slovak rider was soon back in the saddle but suffered a second incident preparing for a race at Marseille this weekend, he explained on social media.
"While I was training on the rocky roads of Marseille, my heart experienced a few jolts. Nothing alarming, but it seems like my heart needs a pit stop," he said.
"I'm going to have surgery next week," he said, promising to be back in competition swiftly.
As well as his world titles between 2015-2017, Sagan won a dozen stages on the Tour de France.
He also won cycling's one-day holy grail, the Tour of Flanders, and the so called Hell of the North cobbled classic Paris-Roubaix amongst his 121 professional career victories.
He planned to bring down the curtain on a 14-year career after the Games and a season on the mountain bike circuit.