EKG 2 Flashcards
Intermodal and interatrial tracts
. Specialized pathways of cells which more rapidly conduct the impulse from SA node to AV node and both atria
Bachmann’s bundle
. Major tract from RA to LA
AV node
. Specialized region in the RA
. APs similar to SA node
. Region of very slow conduction
Bundle of His
. Large bundle of specialized fibers arising from AV node
. Penetrates into the ventricles and divides into L and R bundle branches
Purkinje fibers
. Mesh of specialized fibers w/ very fast conduction
. Rapidly spread impulse throughout much of R/L ventricles
. Primarily on inner portion of ventricular wall subendocardium)
. Makes ventricles depolarize from endocardium to epicardium
P wave
. Depolarization of both atria
QRS complex
. Depolarization of both ventricles
. Q wave: initial downward deflection of complex prior to any upward deflection, corresponds to depolarization of ventricular septum
. R wave: upward deflection of complex, corresponds to ventricular depolarization
. S wave: downward deflection after R wave, corresponds to ventricular depolarization too
QS wave
. Single large deflection in place of QRS complex
T wave
Repolarization of ventricles
U wave
. Only seen occasionally (hypokalemia)
. Due to late repolarization of some region in ventricles
Interval in EKG
. Periods of time that includes waves
Segments
. Periods of time btw waves
Segment in EKG recording
. Periods of time btw waves
. Normally isoelectric
P-R interval
. Measured from beginning of P wave to beginning of QRS complex
. Represents time for atrial depolarization and delay through AV node
. Normal value 0.12-0.2 sec
QRS interval
. Measured from beginning of Q wave (or R if no Q) to end of S wave
. Represents time for depolarization of ventricles
QT interval
. From beginning of QRS complex to end of T wave
. Time for ventricular depolarization and repolarization
. Approx time for ventricular AP
. Dependent on heart rate
QTc interval
. Normalized QT interval
. Normalizes QT interval to heart rate
. QT interval/ sq rt of R-R interval
P-P interval
. Time btw consecutive atrial depolarizations
. Measured from beginning of one P to beginning of next P
. Can be used to determine atrial rate
R-R interval
. Time btw consecutive ventricular depolarizations
. Measured from beginning of 1 QRS to beginning of next one
. Can be used to determine ventricular rate
P-R segment
. Isoelectric period btw end of P wave and beginning of QRS complex
. Period btw atrial and ventricular depolarization
. Used as baseline to evaluate S-T segment displacement
S-T segment
. Time btw end of QRS complex and beginning of T wave
. Corresponds to period btw completion of ventricular depolarization and beginning of ventricular repolarization
. Normally isoelectric
. Does not mean ventricles are at rest
. Corresponds to plateau of ventricular AP
Most common abnormal interval/segment
. Prolonged P-R interval
. Indicative of slower than normal conduction through AV node