EKG Flashcards
What does the EKG record?
rate, rhythm, and conduction of the ELECTRICAL activity of the heart (measured as a difference in voltage on the surface)
The EKG only records electrical activity from which parts of the heart?
atrial and ventricular muscle; cannot measure activity from His-Purkinje system, SA node, or AV node
What do upward and downward waveforms on the EKG correspond to?
a wavefront (vector) moving toward or away from a recording electrode– NOT depolarization or repolarization
Where is the normal mean frontal plane vector oriented and why?
down and to the left because left ventricle is largest chamber and generates the most electrical current
Why does the ST segment normally lie on an isoelectric line?
because during the ST interval, the entire ventricular myocardium is depolarized (any deviance from isoelectric line may indicate ischemic damage to the myocardium)
