What is the Maximum Heart Rate of a Kardia EKG? Updated December 20, 2017 04:53 The maximum heart rate calculated from a Kardia EKG is 300 bpm. Related articles Can Kardia Mobile or Kardia Band detect Arrhythmias other than AFIb? What does it mean if my EKG is Unclassified? Can Kardia Mobile record my QT interval? What is the Paper Speed of the Kardia EKGs recorded with Kardia devices? I keep getting recordings that look noisy and with an “Unreadable” results. What does that mean and how can I prevent it?