What is the difference between the standard and augmented limb leads? augmented= 2 leads together to form a ground. If the sa node remains the sole pacemaker but the rate drops below 60 beats/min- sinus. Automaticity foci: atria: inherent rate change 60-80/ min. Draw the precordial leads draw a standard 12- lead. Clinical usefulness of ekg: past or evolving infarction 2)life threatening arrthymias 3) reassurance for stating exercising (not easy) use accessory muscles= alter reading. Problem with an av node complete block is that ventricles will constrict at own rate and contracting will be much slower. Which limb lead most isoelectric qrs deflection= v3 normally (up and then down deflection same mm) Systematic hypertension= deflections v5 and v6 become more positive and v1 becomes more negative. Rv hypertrophy: electric axis shifts to v3 and v4 because there is more rv mass.