An ECG strip is shown. Calculate the heart rate.

NORCET 10 Prelims-2026

Medical Surgical Nursing

Medium

Appeared in: NORCET 10 Prelims-2026

Explanation

The most accurate method for calculating heart rate from a regular ECG rhythm is the '1500 method'.
This involves counting the number of small 1-mm squares between two consecutive R-waves (the R-R interval).
In the provided ECG, there are approximately 36 small squares within one R-R interval.
The heart rate is calculated by dividing 1500 by the number of small squares: 1500 / 36 = 41.67.
Rounding to the nearest whole number gives a heart rate of 42 beats per minute (bpm).

Option B: A heart rate of 45 bpm would correspond to an R-R interval of approximately 33 small squares (1500 / 45 ≈ 33.3), which is fewer than the 36 squares observed on the ECG strip.
Option C: A heart rate of 50 bpm would correspond to an R-R interval of exactly 30 small squares (1500 / 50 = 30), which is significantly shorter than the interval shown.
Option D: A heart rate of 38 bpm would correspond to an R-R interval of approximately 39-40 small squares (1500 / 38 ≈ 39.5), which is longer than the 36 squares observed.

Visual 1: Diagram - An annotated ECG strip highlighting one R-R interval, with the small squares counted and labeled to demonstrate the 1500 method calculation.
Visual 2: Flowchart - A decision tree showing how to choose the correct heart rate calculation method: Start -> Check Rhythm -> Regular -> Use 1500 or 300 Method; Irregular -> Use 6-Second Strip Method.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain ECG Interpretation and Heart Rate Calculation as background academic context rather than a clinical decision trigger.
Accurate heart rate calculation is a fundamental nursing skill for identifying arrhythmias like bradycardia (<60 bpm) or tachycardia (>100 bpm).
A rate of 42 bpm is sinus bradycardia. The nurse must assess the patient for symptoms like dizziness, fatigue, syncope, or chest pain and check for potential causes like medications (beta-blockers) or underlying heart conditions.
What if? - If the rhythm were irregular, the 1500 method would be inaccurate. The nurse would need to use the 6-second strip method: count the number of QRS complexes in a 6-second strip (30 large squares) and multiply by 10 to get the average heart rate.

How to Approach the Question

Step 1: Analyze the provided ECG strip to determine if the rhythm is regular or irregular by checking if the R-R intervals are consistent.
Step 2: Since the rhythm is regular, select an appropriate calculation method. The '1500 method' (dividing 1500 by the number of small squares in the R-R interval) is the most precise.
Step 3: Carefully count the number of small 1-mm squares between the peaks of two consecutive R-waves.
Step 4: Perform the division: 1500 divided by the number of small squares counted.
Step 5: Compare the calculated result to the given options and select the closest value.

Concept Tested & Keywords

Concept Tested: ECG Interpretation and Heart Rate Calculation
Stem keywords: ECG strip, heart rate, calculate
Lead-in keywords: Calculate
Clinical cues: The ECG shows a regular rhythm, which is a key factor in choosing the calculation method.

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