2. Volume Conductor Principles and ECG Rules of Interpretation the last cells in the ventricle to depolarize are the first to repolarize. ATRIUM VENTRICLE
3. American College of Cardiology (ACC)/American Heart Association (AHA) guidelines that: “Recording the resting 12-lead ECG continues to be the most commonly used laboratory procedure for the diagnosis of heart disease.” In addition, “The procedure is safe, simple, and reproducible; the ECG record lends itself to serial studies; and the relative cost is minimal.
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5. Transient current that contributes to phase 4 pacemaker currents in SA and AV nodal cells T - type ( I Ca - T ) Slow inward, long - lasting current; phase 2 non - pacemaker cardiac action potentials and phases 4 and 0 of SA and AV nodal cells; important in vascular smooth muscle contraction L - type ( I Ca - L ) Calcium Channels Open in response to Ca ++ influx in vascular smooth muscle Calcium - activated ( I K, Ca or BK Ca ) Activated by acetylcholine; Gi - protein coupled Acetylcholine - activated ( I K, ACh ) K ATP channels; inhibited by ATP; therefore, open when ATP decreases during hypoxia; in vascular smooth muscle, adenosine removes the ATP inhibition and opens these channels, producing vasodilation ATP - sensitive ( I K, ATP ) Phase 3 repolarization of cardiac action potentials Delayed rectifier ( I Kr ) Contributes to phase 1 of non - pacemaker cardiac action potentials Transient outward ( I to ) Maintains phase 4 negative potential in cardiac cells Inward rectifier ( I ir or I K1 ) Potassium Channels " Funny " pacemaker current ( I f ) in cardiac nodal tissue Slow Na + Phase 0 depolarization of non - pacemaker cardiac action potentials Fast Na + Sodium Channels CHARACTERISTICS CHANNEL
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