French President Nicolas Sarkozy has spent the night in hospital having heart tests after he was taken ill while out jogging on Sunday.
The 54-year-old collapsed in the park of the Chateau of Versailles. His doctor was called and Sarkozy was flown to the Val de Grace military hospital in Paris.
The presidential diary has been cleared for today and a decision will be taken later about events due to take place in the week.
“All the factors which typically lead to this kind of problem came into play at the same time: a busy schedule, a huge workload, the heat and physical exercise,” said a cardiac specialist.
Sarkozy, who likes to be known for his dynamic attitude to work, has had a busy time of it recently.
He presided over the Bastille Day parade in Paris on July 14 and welcomed UN Secretary General Ban ki-Moon to the Elysee Palace.
Presidential health problems have traditionally been kept almost secret from the French public. Jacques Chirac was treated for what is thought to have been a minor stroke in 2005.
President Francois Mitterrand, meanwhile, was diagnosed with cancer shortly after being elected in 1981 but did not reveal the information until 1992.