NSG210 Week 06 Practice: ECG Strip Interpretation
A four-strip practice worksheet for rate and rhythm interpretation, paired with the dysrhythmia content in nsg210-week-06-summary. Source material: raw/nsg210_wk04_PracticeECGStrips.pdf (the strips) and raw/nsg210_wk04_practiceECGnotes.md (worked answers); the “wk04” prefix reflects when the files were added to raw/, not the academic week, as noted in nsg210-week-06-summary.
Rate method used throughout: count large boxes between R waves and use the sequence 300-150-100-75-60-50 (approximate method), or divide 1,500 by the number of small boxes in one R-R interval (exact method), or count QRS complexes on a 6-second strip and multiply by 10 (best for irregular rhythms). See nsg210-week-06-summary for the full rate/rhythm determination method.
Strip A - Regular Sinus Rhythm, 72 bpm
Lead MCL1.
- Approximate method: 4 large boxes + 2 small boxes, between 75 and (2-3 less) is about 72 bpm.
- Exact method: 1,500 / 21 small boxes = 71.4 bpm.
- 6-second strip: just over 7 complexes, consistent with the low-70s rate.
Note: the QRS is wide. A wide QRS in MCL1 is worth a second look - MCL1 is chosen specifically to help distinguish ventricular ectopy or bundle branch block from normal conduction, so a widened complex here is a flag to check for bundle branch block or another intraventricular conduction delay even though the rate and rhythm are otherwise a normal sinus pattern.
Strip B - Regular Sinus Bradycardia, 56 bpm
Lead II.
- Approximate method: 5 large boxes + 2 small boxes, between 60 and (4 to 5 less) is about 56 bpm.
- Exact method: 1,500 / 27 small boxes = 55.5 bpm.
- 6-second strip: just over 5 complexes, consistent with a rate under 60.
Note: PR interval is approximately 0.16 seconds, within the normal 0.12-0.20 second range - so this is sinus bradycardia with normal AV conduction, not an AV block.
Strip C - Regular Sinus Rhythm, 88 bpm
Lead II.
- Approximate method: 3 large boxes + 2 small boxes gives roughly 93 bpm (noted with a question mark - the approximate method is less precise here).
- Exact method: 1,500 / 17 small boxes = 88.2 bpm.
- 6-second strip: about 9 complexes, consistent with the high-80s rate from the exact method.
Note: the QRS is tall, raising a question of left ventricular hypertrophy. Rate and rhythm are otherwise normal sinus; QRS amplitude isn’t something the small/large box rate method addresses, so this is flagged as a follow-up question rather than a confirmed finding.
Strip D - Regular Sinus Tachycardia, 150 bpm
Lead II.
- Slightly irregular: the first beat is faster than the rest.
- Approximate method: about 2 large boxes per R-R interval, consistent with 150 bpm.
- 6-second strip: more than 15 complexes, consistent with a rate above 150.
Note: the T wave is encroaching on the next P wave. At this rate that’s worth watching - if the T and P waves start to merge it becomes hard to distinguish sinus tachycardia from SVT, so this strip is flagged as a possible SVT concern rather than a clear-cut sinus tachycardia.