Defectives Flashcards
a defective SA node can lead to
ectopic focus
hyperexcitable heart
a defective AV node can lead to
total or partial heart block
an abnormal pacemaker may appear and take over the pacing of heart rate, or the AV node may become the pacemaker.
ectopic focus
The pace set by the AV node is referred to as
junctional rhythm
explain junctional rhythm
40 to 60 beats per minute, slower than sinus
rhythm but still adequate to maintain circulation.
ectopic pacemakers appear even when the SA node is operating normally. T or F
T
A small region of the heart becomes
_____, sometimes as a result of too
much caffeine (several cups of coffee) or nicotine
(excessive smoking), and generates impulses
more quickly than the ___ node.
hyperexcitable
SA
a hyperexcitable heart can lead to
premature contraction or extrasystole before
the SA node initiates the next contraction
The only route for impulse transmission from atria
to ventricles is through the
AV node
Any damage to the AV node interferes with the
ability of the ventricles to receive pacing impulses,
causing
heart block
In total heart block _________ and
the ventricles beat at their _______, which is
too ___ to maintain adequate circulation.
no impulses get through
intrinsic rate
slow
In ________, only some of the atrial
impulses reach the ventricles.
partial heart block
____________ are implanted
to recouple the atria to the ventricles as necessary.
These programmable devices speed up in
response to increased physical activity just as a
normal heart would.
artificial pacemakers
an enlarged R wave hints of
enlarged ventricle
an S-T segment that is elevated or
depressed indicates
cardiac ischemia
a prolonged Q-T interval reveals a
repolarization abnormality that
increases the risk of ventricular
arrhythmias
The SA node is nonfunctional. As a result:
• P waves are absent.
• The AV node paces the heart at 40-60 beats per minute.
junctional rhythm
The AV node fails to conduct some SA node impulses.
• As a result, there are more P waves than QRS waves.
• In this tracing, there are usually two P waves for each QRS wave.
2nd degree heart block
Electrical activity is disorganized. Action potentials occur randomly
throughout the ventricles.
• Results in chaotic, grossly abnormal ECG deflections.
• Seen in acute heart attack and after an electrical shock.
ventricular fibrillation
