TOPICS: QRS axis, left axis deviation, right axis deviation, extreme axis deviation, isoelectric limb lead, positive deflection, negative deflection, rate, 60-100 bpm, tachycardia, bradycardia, heart rate, rhythm, SA node, P waves, QRS complex, PR interval, segments and intervals, graph paper, 25 mm/s, PR interval < 200 ms, ORS < 120 ms, QT interval < ½ RR interval, ST segment
