Jansen (chest) returned to Los Angeles for further testing Thursday due to an irregular heartbeat and will not be available for this weekend's series at Colorado, Andy McCullough of the Los Angeles Times reports.
Jansen was listed as unavailable for Thursday's game with what was originally described as an illness but is in reality a much larger concern. The 30-year-old also missed some time as recently as 2012 with an irregular heartbeat, and he underwent ablation surgery on his heart to address the issue that October. Scott Alexander notched the save Thursday and should continue to see ninth-inning opportunities while Jansen is unavailable.