Lecture 25 10/18/23 Flashcards
What is the chronotropic effect of sympathetic activation?
increased sinus rate
What is the chronotropic effect of parasympathetic activation?
decreased sinus rate
What is the dromotropic effect of sympathetic activation?
increased rate of conduction through AV node/bundle
What is the dromotropic effect of parasympathetic activation?
decreased rate of conduction through AV node/bundle
What is the role of an EKG?
to measure electrical potential difference
How does a positive deflection occur on an EKG?
a wave of depolarization towards the positive electrode causes a positive deflection
How does the normal heart depolarize?
-right to left
-cranial to caudal
-dorsal to ventral
What does the P wave represent?
atrial depolarization
What does the QRS complex represent?
ventricular depolarization
What does the T wave represent?
ventricular repolarization
How can a T wave appear?
-positive
-negative
-biphasic
What does a QRS complex always indicate?
ventricular activation
How can electrical cardiac activity be described by a vector?
based on magnitude and direction
What are the diagnostic utilizations of EKG?
-description of rate/rhythm (main use)
-chamber enlargement/heart failure
-ischemia/inadequate blood supply
What does important diagnostic information relate to?
-rate
-consistency of RR intervals/heart cycle length
-relationship between atrial and ventricular activity
-determination of QRS origin
How is a heart rate calculated from an EKG?
-at 50mm/sec, 30 boxes = 3 sec
-HR = number of complexes in 3 sec x 20
What is RR interval?
the cycle length/heart period
How does heart rate relate to RR interval?
HR = 60/RR in seconds
What are the characteristics of supraventricular QRS origin?
-normal origin
-activation through both bundle branches
-narrow QRS
-occurs proximal to bifurcation of His/at nodes
What are the characteristics of ventricular QRS origin?
-abnormal origin
-takes longer than normal due to bundle branches not being involved
-wide QRS
-occurs distal to bifurcation of His/in ventricular walls
How can heart rate be calculated from RR?
60/(number of boxes/10)
