Juventus midfielder Sami Khedira could be out of action for over a month while he undergoes treatment after being diagnosed with an irregular heartbeat, according to reports in Italy on Wednesday.

The World Cup winner has been ruled out of Wednesday’s Champions League tie at Atletico Madrid because of atrial arrhythmia. The condition causes an irregular and fast heart rate and can result in dizziness, shortness of breath and tiredness.

Khedira had suddenly felt his heart beat faster in training on Tuesday and immediately went for treatment. “Sami Khedira is out of the squad, he stayed in Turin to undergo further tests,” said coach Massimiliano Allegri. “He’s an important player for us with good international experience.”

The 31-year-old could be sidelines for between 30 to 40 days, according to sports dailies Gazzetta and Corriere Dello Sport. Arsenal defender Stephan Lichsteiner suffered from the same condition when playing for Juventus at the end of 2015 and was out for a month before returning to action.

Khedira has been struggling with various health problems this season, and has played just nine league games and 15 matches in total. He suffered a thigh injury in September which ruled him out for five weeks and then hurt his ankle on his return in November.