A 70-year-old woman had an ECG at her annual checkup. Using her lead II recording below calculate her hea rate
High-Yield Explanation
The hea rate can be calculated by 60 divided by the R-R interval, which is 0.86 second. This results in a hea rate of 70 beats/min. (1500/No of small squares between R-R interval - but R-R interval should be regular)