How to read any ECG · Part 1 of 6

Orientation: the paper & the rate

Vent. rate 62 bpm PR interval 200 ms QRS dur 88 ms QT/QTc 416/423 ms P-QRS-T axes 87 63 69 SYNTHETIC 12-LEAD ECG for training only — not for diagnosis I aVR V1 V4 II aVL V2 V5 III aVF V3 V6 II · rhythm strip (10 s) 25 mm/s · 10 mm/mV · 0.05–150 Hz · ~50/60 Hz · 10 s
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The ECG grid

An ECG is printed on grid paper. Left to right is time; up and down is voltage (the size of the heart's electrical signal). The smallest squares are 1 mm across, and every fifth line is bold, making a "big box" of 5 small squares. You read everything on an ECG, the rate, the durations and the heights, by counting these boxes, so first you need to know what one box is worth. That depends on two settings, speed and gain (next).