Approach
- Rate: 300/RR squares (regular) or 6-sec rule
- Rhythm: regular, irregular, P-QRS relationship
- Axis: lead I + II positive = normal
- PR: 120–200 ms
- QRS: <120 ms
- QTc: <440 ms (M), <460 ms (F)
- ST: elevation/depression
- T waves: inversion, peaked, flattening
Common patterns
- STEMI: ST elevation in contiguous leads
- NSTEMI: ST depression / T inversion
- PE: S1Q3T3, RBBB, sinus tachy
- HyperK: peaked T → wide QRS → sine
- Hypothermia: J waves
- Pericarditis: saddle ST elevation, PR depression
