Chapter 6: Rhythm, Part II: Blocks Flashcards
Blocks ______ or _______ the conduction of ______________ stimuli.
retard, prevent, depolarization
p. 173
Blocks can develop in…
…the SA Node, AV Node, the His Bundle, the Bundle Branches, or in either of the two subdivisions of the Left Bundle Branch (called a Hemiblock).
(p. 173)
With Sinus Block, an unhealthy SA Node stops its pacing activity for at least ___ ________ _____, so the block is usually _________.
However, remember that the pause may induce an ______ ____ from an automaticity focus.
one complete cycle
transient
escape beat
(p. 174)
Some experts claim that the SA Node does generate a stimulus, but that it is blocked from _______ the __ ____. This is referred to as Sinus “____” Block.
leaving, SA Node
“Exit”
(p. 174)
Sick Sinus Syndrome is a wastebasket of arrhythmias caused by SA Node dysfunction associated with ____________ supraventricular automaticity foci, which are also _____________ and can’t employ their normal escape mechanism to assume ______ ______________.
unresponsive
dysfunctional
pacing responsibility
(p. 175)
____ _____ ________ most often occurs in elderly patients who have heart disease.
Sick Sinus Syndrome (SSS)
p. 175
SSS is usually characterized by marked _____ ___________, but without the normal escape mechanisms of atrial and junctional foci. It may also present as recurrent episodes of _____ _____ or _____ ______ associated with faulty or ______ escape mechanisms of all supraventricular foci.
sinus bradycardia
Sinus Block or Sinus Arrest
absent
(p. 175)
Because of extensive parasympathetic innervation to the SA Node and all supraventricular foci, excessive parasympathetic activity depresses the pacing rate of the SA Node, as well as the atrial and junctional foci. Therefore, young, healthy conditioned athletes, who often have _______________ _____________ at rest, appear to exhibit convincing signs of SSS (a.k.a. “______” SSS).
parasympathetic hyperactivity
pseudo-
(p. 175)
Patients with SSS may develop intermittent episodes of ___ (sometimes even atrial _______ or atrial ____________) mingled with the sinus bradycardia. This is called ___________-___________ ________.
SVT, flutter, fibrillation
Bradycardia-Tachycardia Syndrome
(p. 175)
The AV Blocks either ______ and/or _________ conduction from the atria to the ventricles.
retard, eliminate
p. 176
Minor AV blocks simply ________ the brief pause btw atrial and ventricular ______________.
But, MOST AV blocks __________ block some or all supraventricular impulses from reaching the __________.
lengthen, depolarization
completely, ventricles
(p. 176)
A first degree block retards __ ____ conduction, prolonging the __ ________ more than one large square (___ ___) on EKG.
AV Node, PR interval, 0.2 sec
p. 177
The PR interval is measured from the _________ of the _ ____ to the beginning of the ___ _______.
Keep in mind that technically, a “segment” is a _______ of ________, while as “interval” contains __ _____ ___ ____.
beginning, P wave, QRS complex
portion of baseline, at least one wave
p. 177
A 1st degree block is present when the PR interval is ____________ prolonged the ____ amount in every cycle, and the P-QRS-T sequence is normal in every cycle also.
consistently, same
p. 178
2nd degree AV blocks allow ____ atrial depolarizations to conduct to the ventricles, while some are _______, leaving lone P waves without an associated ___.
some, blocked
QRS
(p. 179)
2nd degree blocks of the __ ____ are “Wenckebach”, formerly called “___ ______ ____ _”.
2nd degree blocks of ________ _____ bundles (His bundle or bundle branches) are ______, formerly called “___ ______ ____ _”.
AV Node, 2nd degree type I
Purkinje fiber, Mobitz, 2nd degree type II
(p. 179)
In a Wenckebach 2nd degree AV block, the PR interval gradually _________ in successive cycles, but the last P wave of the series fails to _______ to the __________.
Lengthens
Conduct to the ventricles
(p. 180)
The typical Wenckebach pattern (“footprint”) consists of anywhere from ___ to _____ or more cycles.
Two to eight
p. 180
Wenckebach is sometimes caused by _______________ excess or drugs that mimic such effects.
Parasympathetic
p. 180