She had to be rushed to a hospital for an overnight stay after suffering a cardiac arrhythmia during an experiment.

FORBES: EPA Charged With Lethal Experiments On Hundreds Of Unsuspecting Subjects

"Sorry Sydney for a short set tonight but Vince had to be rushed to the hospital for internal pain, " bassist Sixx tweeted.

CNN: Kidney stones force rocker Vince Neil from stage

"Sorry Sydney for a short set tonight but Vince had to be rushed to the hospital for internal pain, " bassist Nikki Sixx tweeted.

CNN: Kidney stones force rocker Vince Neil from stage