Pope Benedict XVI had a secret operation three months ago to replace the batteries in his pacemaker but this did not influence his decision to resign, the Vatican has confirmed.
"It was a routine operation. He already had a pacemaker. This had nothing to do with the decision of the Holy Father," Vatican spokesman Federico Lombardi said at a press briefing.
While the pope's heart troubles were widely known, the fact he had an operation so recently was only reported by Italian daily Il Sole 24 Ore on Tuesday.
The report fuelled speculation that the pope was resigning because of illness, even though he himself said he was resigning because his advancing age prevented him from carrying out his duties.
The newspaper report cited people close to the pope saying the operation had encouraged him to "question himself with simplicity and decisiveness over his capacity to guide the Ship of Saint Peter".
The 85-year-old pope has suffered a number of health-related incidents in recent years, although the Vatican has emphasised that he is not suffering from any major illness except for old age.
In 2009, the elderly pope broke his wrist while on holiday in the Alps when he slipped in the bath.
As Cardinal Joseph Ratzinger, he suffered a stroke which weakened his heart and briefly affected his eyesight and in a separate incident suffered a head wound for which he required stitches.
He also has arthritis in his hip, knees, and ankles, which affects his walking.