Hartnell told the training staff of odd twitching in his right arm between periods, and when he was examined, an abnormal heart rate was discovered. As a precaution, Hartnell was held out of the third period of that game, skipped Sunday's practice and will not play in Monday's preseason game against the Rangers.
"I feel fine," he told NHL.com. "Last game in Detroit, my heart rate wouldn't settle down as it usually does. Arms were shaking a little bit. Just more precautionary, stay off the ice for a couple days.
"Have a big test tomorrow, a stress test, and hopefully everything will be fine."
Hartnell, 29, said he's never had a problem like this in his life, so he understands the need to be extra cautious.
"When it comes to your heart or vital organs, you've got to be cautious about it. (GM Paul) Holmgren and Peter (Laviolette, coach) obviously have been great in that respect. Tomorrow is a big day."