Flashcards in Normal ECGs DSA Deck (63)
What causes the heart to beat?
rhythmic discharge of electrical stimuli
What is an EKG?
records the electrical activity of the heart, provides a record of cardiac electrical activity, & info about heart function/structure
What does the EKG record?
electrical activity of contraction of heart muscle (myocardium)
How does the depolarization move throughout the heart?
cell to cell conduction of depolarization is carried by fast-moving Na+ ions
Where can you detect the heart's electrical activity?
from the skin surface using electrodes
What does an upward wave indicate on an EKG?
depolarization wave moving toward positive electrode
What is the SA node?
in upper posterior wall of RA & is the heart's dominant pacemaker
What is automaticity?
ability of SA node to generate pacemaking stimuli
What does the P wave represent?
contraction of BOTH atria
What happens to depolarization when it reaches the AV node?
depolarization slows down to allow time for blood in atria to enter the ventricles (b/c carried by slow moving Ca2+ ions)
What happens when depolarization reaches the ventricular conduction system?
depolarization rapidly shoots through the His bundle & the L/R bundles branches
What are Purkinje fibers?
rapidly conducting cells that use fast moving Na+ ions for conduction of depolarization to ventricular myocytes
What is the QRS complex on the EKG?
depolarization of the entire ventricular myocardium
How does ventricular depolarization spread?
from terminal filaments of Purkinje fibers beneath endocardium that proceeds outward to epicardium of ventricles
What does the ST segment represent?
What does an abnormal ST segment indicate?
sign of serious pathology (if elevated or depressed beyond normal baseline level)
What is the T wave?
rapid phase of ventricular repolarization (K+ leaving the myocytes)
What does ventricular systole include?
begins w/ QRS & persists until end of T wave
What is a long QT interval syndrome?
pts vulnerable to dangerous rapid ventricular rhythms
What ions are used in cell to cell conduction in myocardium?
by Na+ ions
What ions are used in AV node conduction?
slow movement of Ca2+ ions
Where would you place electrodes?
on R & L arms, L leg
What are the lateral leads?
Leads I & AVL b/c each has a positive electrode positioned laterally on the L arm
What are the inferior leads?
leads II, III & AVF b/c each of these leads has a positive electrode positioned inferiorly on the L foot
What is at the center of leads V1 to V6?
What are leads V3 & V4 over?
oriented over the interventricular septum (V3 near RV & V4 near LV)
What are bipolar limb leads?
pair of electrodes on each limb that has 1 positive & 1 negative
What direction is lead I in?
horizontal (L arm is + & R arm is -)
What is + & - in lead III?
L arm is negative & L leg is positivve