Mobile tip: Turn your phone sideways (landscape) to see the full life-size 6-second strip on one screen.
Rhythm strip · Lead II · life size (25 mm/s · 10 mm/mV)
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0.04 s · 0.1 mV
0.20 s · 0.5 mV
View: 100% life size · 1 large box ≈ 5 mm
← 6.0 seconds →
Salient Features
Systematic Approach
Work top to bottom: rate, regularity, P waves, PR, QRS, then name the rhythm and the next action.
Rate Helper
6-second count
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QRS × 10
Large-box rule
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300 ÷ # large boxes between R waves
Strip rate
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Engine estimate
Count large boxes between R waves
Memorize this sequence (1 large box = 0.20 s). Rate ≈ 300 ÷ number of large boxes:
Select a regular rhythm to highlight the closest step.
Very slow rates (about <20 bpm) with sparse, wide, bizarre ventricular complexes are often taught as agonal rhythm (terminal / pre-asystolic pattern) — not just “slow IVR.” Morphology and clinical context matter, not rate alone.
Tip: 6-second count (QRS × 10) works for irregular rhythms. Large-box / 300-rule is best when the rhythm is regular.