Cardiology #4 Conduction Disorders Flashcards
In an EKG, what are the following parts related to?
-P wave
-PR segment
-QRS complex
-T wave
P wave: atrium contraction
PR segment: AV node
QRS complex: Ventricular contraction
T wave: Ventricular repolarization
How do you calculate the rate of an EKG strip?
Count the large boxes in an R - R segment
300 / 1, 2, 3, 4, 5
=300, 150, 100, 75, 60
Explain the process of conduction and relate it to the parts of an EKG
-Sinus node sends impulse through RA to AV node (atrial contraction). PR segment (nothing happens) when it goes through AV node. Then, rapid condition through Bundle of His –> contraction of ventricle (QRS complex)
Normal sinus rhythm has a rate of ________
60-100 bpm
Sinus bradycardia, which is decreased HR with a rate of __________, has causes such as what?
HR < 60 bpm from sinus node
Causes: young athletes, BB, CCB, SA node ischemia, hypothyroid
Treatment for sinus bradycardia
-Symptomatic: Atropine (1st line)
–Epinephrine or Transcutaneous pacing
-Asymptomatic
–No treatment needed
Sinus tachycardia is HR > 100 bpm from the sinus node. What are some causes? What is the treatment?
-Exercise, stress, kids/infants, fever, pain, hypoxia, shock, cocaine
Treat underlying cause (1st line), BB if needed
What is sinus arrhythmia?
No treatment is needed in most cases.
Norma variation of sinus rhythm. Beat to beat variation with respiration. Increase in rhythm with inspiration, decrease in rhythm with expiration.
Sick sinus syndrome is dysfunction of the sinus node leading to what rhythm?
Combination of sinus arrest with alternating periods of tachycardia and bradycardia.
What is the MCC of sick sinus syndrome?
Sinus node fibrosis
Others: old age
Treatment for sick sinus syndrome
-Atropine (first line)
-Long term: Permanent pacemaker (definitive), AICD if alternating
What happens in a junctional rhythm?
What is seen on an EKG with this type of rhythm?
AV node becomes the dominant pacemaker
Inverted P waves or not seen at all. Narrow QRS
What segment of an EKG strip is the most useful in determining an AV Block?
PRI interval
What does the ECG with a First Degree AV block look like?
Treatment?
Prolonged PR interval, but all P waves are followed by a QRS complex
-Asymptomatic: observation
-Atropine (1st line)
-Pacemaker (definitive)
What is the pathophysiology of a 2nd degree AV block? What is the first type of second degree AV Block, what is seen on an ECG, and what is the treatment?
Not all atrial impulses are conducted to the ventricles, leading to P waves without QRS complexes
-Mobitz 1: Wenkebach
-ECG: P waves are constant, Progressive PRI lengthening –> dropped QRS
Atropine, Epi, Pacemaker
What is the other type of 2nd degree AV block, what is seen on an ECG, and what is the treatment?
Mobitz II
P waves constant, constant/prolonged PRI –> dropped QRS
Atropine or temporary pacing, pacemaker definitive
Both 2nd degree AV blocks occur where in the heart?
Bundle of His
Mobitz I causes
Mobitz II causes
1 (Wenkebach): inferior wall MI, BB/CCB/Digoxin, Myocarditis
2: Rarely in patients without structured heart disease (myocarditis, endocarditis, myocardial fibrosis)
A third degree AV block is due to AV dissociation. No atrial impulses are reaching the ventricles. Causes of this are similar to 2nd degree AV block because it can progress to a 3rd degree. Name them.
Inferior Wall MI
AV nodal blocking agents (BB, CCB, Digoxin)
Lyme, Endocarditis, Myocarditis
Hypothyroidism, Hyperkalemia
What does the ECG for a 3rd degree AV block look like?
Regular R-R and P-P intervals, but not related to each other
-P’s and Q’s don’t agree, then you have a third degree
Treatment for a 3rd degree AV block
-Transcutaneous pacing followed by permanent pacemaker (definitive)