clinical tx of arrhythmia Flashcards
Initiation of the cardiac cycle normally begins with
initiation of the impulse at the sinoatrial (SA) node.
A resulting wave of depolarization passes through the right and left atria, which produces the P wave on the surface ECG and stimulates atrial contraction.
Following activation of the atria, the impulse proceeds to the:
atrioventricular (AV) node, which is the only normal conduction pathway between the atria and the ventricles.
The AV node functions to
slows impulse conduction which allows time for contraction of the atria and the pumping of blood from the atria to the ventricles prior to ventricular contraction.
______ accounts for most of the duration of the PR interval.
Conduction time through the AV node
bundle of His is a
small portion of the last part of the PR interval
what produces a P wave on the surface ECG
A resulting wave of depolarization passes through the right and left atria, which produces the P wave on the surface ECG and stimulates atrial contraction.
The QRS complex on the ECG represents the
depolarization of the ventricular muscle mass.
The T wave on the ECG represents the
repolarization and relaxation of the ventricles.
Atrial repolarization and relaxation occurs during the QRS complex.
QRS complex.
types of arrhythmias
- bradyarrhythmia (too slow)
2. tachyarrhythmia (too fast)
Bradyarrhythmias: Where in the conduction system can problems develop?
- Sinus node
- AV node
- below the AV node
Bradyarrhythmia: sinus node dysnfuction
- sinus bradycardia
- sinus arrest/pause
- tachy-brady syndrome
- chronotropic incompetence
chronotropic incompetence
is
the inability to mount age-appropriate HR with exercise
Sinus Bradycardia is
Persistent slow rate from the SA node.
Sinus Bradycardia rate
less than 60 bpm (~55)
sinus bradycardia PR interval is
180 ms (.18 sec)
Sinus arrest is
- failure of sinus node discharge resulting in absence of atrial depolarization and period of ventricular asystole
- no relationship between the pause and the basic cycle length
sinus arrest rate:
75 bpm
sinus arrest PR interval
180 ms
sinus arrest, how long is an arrest
2.8 second arrest
Sinus Node Dysfunction – Bradycardia-Tachycardia (Brady-Tachy) Syndrome
- intermittent episodes of slow and fast rates from the SA node or atria
- occurs when the SA node has alternating periods of firing too slowly and too fast
- often manifests in period of atrial tachycardia, flutter or fibrialltion
- cessation of tachycardia is often followed by long pauses from the SA node
Sinus Node Dysfunction – Bradycardia-Tachycardia (Brady-Tachy) Syndrome:
rate during bradycardia:
43 bpm
Sinus Node Dysfunction – Bradycardia-Tachycardia (Brady-Tachy) Syndrome: rate during tachycardia?
130 bpm
Bradyarrhythmias: AV node
- first degree AV block
2. Mobitz I 2nd degree AV block (Wenkebach)
first degree AV block is
- AV conduction is delayed and the PR interval is prolonged (>200 ms or .2 sec)
- delay in the AV conduction but each atrial signal is conducted to the ventricles in a 1:1 ratio
1st degree AV block rate:
79 bpm
1st degree AV block PR interval
340 ms
2nd degree AV Block: Mobitz I (wenckebach)
- progressive prolongation of the PR interval until a ventricular beat is dropped
- characterized by intermittent failure of atrial depolarizations to reach the ventricle
- 2 patterns of 2nd degree AV block
4.
2nd degree AV Block: Mobitz I (wenckebach): Ventricular rate is
irregular
2nd degree AV Block: Mobitz I (wenckebach): atrial rate is
90bpm
2nd degree AV Block: Mobitz I (wenckebach): PR interval is
progressively longer until a P wave fails to conduct
Wenckebach or Mobitz Type I block is marked by
progressive prolongation of the PR interval in cycles preceding a dropped beat.
The_____ is most commonly the site of Mobitz I block.
AV node
The QRS duration is usually normal.
