Calculating Heart Rate Three Ways
Flashcards covering the 300 rule, 6-second method, and 1500 method for determining EKG rate.
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Questions Covered in This Set
10 cards to master
Standard EKG paper speed
25 mm/sec
Duration of one small box / one large box
Small box = 0.04 sec; large box = 0.20 sec (5 small boxes)
How many large boxes equal 6 seconds?
30 large boxes (5 large boxes = 1 second)
Recite the 300 rule sequence
300 – 150 – 100 – 75 – 60 – 50 – 43 – 37, counted per large box between R waves
When can the 300 rule be used?
Only for regular rhythms, where every R-R interval is essentially identical
Quick anchors from the 300 rule
Fewer than 3 large boxes = tachycardia; more than 5 large boxes = bradycardia
Steps of the 6-second method
Find a 6-second window (30 large boxes), count the QRS complexes inside it, multiply by 10
Why is the 6-second method essential in atrial fibrillation?
Irregular R-R intervals make single-interval methods wildly inaccurate; averaging over 6 seconds gives a true average ventricular rate
Formula for the 1500 method
Rate = 1500 ÷ number of small boxes between two consecutive R waves
Atrial rate vs. ventricular rate
Ventricular rate is measured R-to-R; atrial rate is measured P-to-P using the same three methods — identical in normal sinus rhythm
