The Hague - Dutchman Robert Gesink will undergo a heart operation after suffering pain during last week's Tour of the Basque Country, the Belkin rider has revealed on Tuesday.
The 27-year-old has pulled out of Sunday's Amstel Gold race and will also likely miss July's Tour de France.
"At the Tour of the Basque Country last week, I felt pain again. Short but around the heart," said Gesink at a press conference in Schipol near Amsterdam.
"It's not the first time it's happened and it's worrying."
Gesink revealed he had been to see a radiologist who had decided he needs an operation to correct the problem.
It's not the first time he has suffered from such a condition and Gesink said he was also afflicted by hyperventilation, which could have precipitated the heart problem.
"Every time I suffered from hyperventilation, my heart raced," he added.
"It makes me worried when that happens and it affects my performances as I'm afraid something bad will happen."
Earlier on Tuesday the Algemeen Dagblad newspaper had reported that Gesink would miss the Amstel race, the first of three Ardennes Classics.
They had claimed he suffers from stress in major races which had triggered the problems with his heart beat.
Gesink retired during the fifth stage of last week's Tour of the Basque country, while in March he also failed to complete the Tirreno-Adriatico.
He previously had to pull out of the 2011 Dutch championships and the Giro d'Italia last year.
An all-rounder, Gesink has enjoyed some success in stage races, winning the Tour of Oman in 2011 and the Tour of California a year later.
He also finished fifth in the Tour de France in 2010 and three times claimed top seven spots at the Tour of Spain.
He's also performed well in the Ardennes Classics in the past, finishing fourth at La Fleche Wallonne in 2008 and third at the Amstel Gold race a year later.
In 2008 he finished 10th in both the road race and time-trial at the Beijing Olympics.