Prime Minister Tony Blair is to undergo a heart procedure in hospital on Friday to correct a continuing "flutter".
Mr Blair says his children keep him youthful
He was treated in October last year for supraventricular tachycardia (SVT), but the problem has returned.
Although he describes the condition as "not particularly alarming", the news could be seen as at odds with Mr Blair's image as an action man prime minister.
When he is not criss-crossing the world on red-eye flights attempting to solve diplomatic crises, he can be found pounding the treadmill or playing tennis in a bid to keep fit.
Mr Blair, who turned 50 last year, says his stress-busting exercise regime ensures he feels "great, physically".
In fact, weighing just under 13 stone, the prime minister reckons he does more exercise today than he has done since he was at school.
"I pay more attention to looking after myself - I watch my diet a bit. But really I find it's exercise that's fantastically helpful for coping with stress," he told Saga magazine last year.
Mr Blair often exercises early in the morning and works out several times a week using the gym running machine.
While the youthful good looks he brought to office in 1997 have been worn by age and the pressures of seven years in the top job, he has kept good health.
At last year's Labour party conference, he even tried out a rowing machine during a visit to the cardiac unit at the Royal Bournemouth Hospital.
The father-of-four - including young son Leo - first suffered a heart problem in October 2003. The irregular heartbeat was treated but has since returned.
Mr Blair took time out during last year's party conference for some exercise
Mr Blair has said in the past that he has no difficulty in switching off from the job, citing his family, tennis, swimming, football with the kids and playing his guitar as his pastimes.
The prime minister's elderly father, also called Leo, was only 39 when he suffered a stroke, and took three years to recover his speech.
While he returned to work and became an industrial tribunal chair, he was forced to leave behind his political ambitions.
He was left frail by a second stroke two years ago.
Tony Blair has spoken of how his own character was shaped by his father's setbacks.
His mother, Hazel, died in 1975 following a five year fight against thyroid cancer.
Asked once by Saga magazine if genetic factors had made him concerned about his own health, Mr Blair admitted: "Yes, I suppose so."