ECG-ALGORITHM
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RATE
1. ASSESS RATE: 300/(large squares) interval in mm. Bradycardia if HR < 60/min; tachycardia if HR > 100/min.
RYTHM
2. ASSESS RYTHM: RR intervals (1 small square variation is normal) & check that a P precedes a QRS complex.
INTERVALS
3. EXAMINE PR INTERVAL: normal 120-200ms, prolonged if heart block present.
4. EXAMINE QRS INTERVAL: normal < 100ms. Prolonged in BBB, WPW, ventricular pacemaker, tricyclics.
5. EXAMINE QT INTERVAL: 340-470 ms. Prolonged in tricyclic overdose, hypo-Ca/Mg/K, starvation, hypothermia, quinidine, sotalol, amiodarone use.
WAVEFORMS
6. INTERPRET WAVEFORM.
7. ASSESS ST-SEGMENT: elevated in ACS, pericarditis, Prinzmetal angina and others.
OTHERS
8. ASSESS AXIS: Normal is -30 to +100. +I +aVF: normal; -I +aVF: RAD; +I -aVF: LAD; -I -aVF: RAD/LAD. LAD is a marker for CAD, RAD is normal for children, young adults; RVH in older adults.
9. ASSESS HYPERTROPHY:
10. ASSESS BRANCH BLOCK: LBBB (QRS 120-180 ms), RBBB (QRS > 120 ms)
