HEART SPEACIALIST IN BANGALORE
By definition, sinus tachycardia is a heart rate ≥ 100/minute and sinus bradycardia is a heart
rate ≤ 50/minute.3
To calculate the heart rate from the ECG, the R-R interval in mm can be divided into 1500.
For example, an R-R interval of 20 mm gives a rate of 75/minute and an R-R interval of 15 mm
gives a rate of 100. Similarly, large 5 mm squares can be divided into 300; thus three squares give
a rate of 100/minute. In regular rhythms, any two congruous points of the P-QRS-T sequence
can be used to estimate the rate. An ECG ruler has a scale that enables rapid rate measurement
and calculation of other intervals. With practice, the rate can be estimated at a glance.