Fruean, who had his second open-heart surgery last year, complained of an irregular heartbeat (arrhythmia) that affected his breathing in the Chiefs' 36-20 victory over the Stormers last Friday.
Fruean, 25, joined the Chiefs this season after he was released last year by the Canterbury Crusaders.
He has been on the fringe of All Blacks selection over the last two or three seasons but never made the final step despite impressive form at Super Rugby and provincial level.
The Chiefs, who are unbeaten after three games this season and lead the New Zealand conference, will also travel to face Australia's Western Force and South Africa's Bulls and Cheetahs without winger James Lowe and centre Charlie Ngatai.
All Blacks flanker Sam Cane, who sustained a knee injury in a pre-season clash with the Auckland Blues, has returned to join the 27-man travelling squad.
- Sports & Recreation
- irregular heartbeat
- Canterbury Crusaders
- Super Rugby