The best replacement for heart rate is pulse.

The best alternatives to heart rate are rated as following:
★★★★★  pulse
★★★★  blood pressure
★★★  age
★★★  pulse rate
★★  calories burned
★  exercise
★  rhythm
★  calories
★  rpe
★  stroke volume
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Your alternative for heart rate is not listed? Suggest!
Speaking about heart rate, one probably shouldn't forget about afib.

Other search terms related to heart rate and their ratings are:
★★★★★ afib
★★★★ low blood pressure
★★★ high blood pressure
★ blood pressure
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increasing blood pressure
You have in mind a companion for heart rate and it is not yet here? Propose!



Google Trends

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heart rate
pulse
blood pressure