The reigning European and Italian national champion had finished second in yesterday’s stage in Sant Feliu de Guíxols, which was won by Australia’s Michael Matthews.

Colbrelli was reported as being stable in hospital yesterday by his team.

Bahrain Victorious issued an update today, confirming Colbrelli had been suffering from an unstable cardiac arrhythmia.

"Following the end of Stage 1 of Volta a Catalunya, our medical team can confirm that Sonny Colbrelli suffered from an unstable cardiac arrhythmia that required defibrillation," a statement read.

"The cause is still to be determined, and the Italian rider will undergo further tests tomorrow at the Hospital Universitari de Girona.

"The team would like to thank Borja Saenz de Cos - Emergency Nurse at Sistema d’Emergencies Mediques (Catalan Emergency Service) - for his prompt assistance at the finish yesterday and for supporting our medical staff in the management of the incident.

"Sonny Colbrelli’s clinical situation is good, and we wish him a prompt recovery."

Colbrelli had been forced to withdraw during Paris-Nice earlier this month with suspected bronchitis.

He also missed Milan-San Remo on Saturday (March 19).

Bahrain Victorious took part in the second stage of the race, with German rider Phil Bauhaus missing out on a stage victory.

He had been part of the leading group of riders, after crosswinds led to a split in the peloton with 20 kilometres remaining of the 202.3km stage from L’Escala to Perpignan in France.

Australia’s Kaden Groves sprinted to victory in a time of 4 hours, 44min, 28sec, giving Team BikeExchange-Jayco back-to-back stage wins.

Bauhaus finished on the same time in second, with France’s Hugo Hofstetter completing the top three.

Norway’s Jonas Iversby Hvideberg now leads the race after earning bonus seconds during the stage.

He has a one second advantage over Matthews in the general classification.

Pre-race favourite Simon Yates, fellow Briton Hugh Carthy and the Netherlands' Tom Dumoulin finished 33 seconds behind the lead group.

Yates had been caught up in a late crash, while Carthy and Dumoulin lost time due to missing splits in the crosswinds.

The International Cycling Union (UCI) World Tour race will continue tomorrow with a 161km stage beginning in Perpignan and taking the riders back into Spain with a finish at La Molina.