6. What if rate is <50/min or rhythm is irregular ? Count the number of R waves in a 6 second strip and multiply by 10. For example, if there are 7 R waves in a 6 second strip, the heart rate is 70 (7x10=70).
11. Intervals PR interval: <200 msec (one big box) QRS complex:<100 msec (2½ small boxes) ST segment: evaluate for elevation or depression below baseline QT segment: roughly less than half of R-R interval At high or low heart rates, calculate corrected QT interval QTc  =  QT interval  ÷  square root of the RR interval (in sec) The normal value for the QTc is <440 msec (2½ big boxes)
16. One or more of the precordial leads (V1-V6) and leads I and aVL suggest anterior wall ischemia or infarction Leads V4 to V6 suggest apical or lateral ischemia or infarction
31. New LBBB: Treat as ST Elevation MI i.e. rush to cath lab for PCI LBBB Diagnosis: Slurring of S wave in V5 and V6 and QRS duration > 100 msec (i.e more than 2½ small squares)