EKGS

Question 1

AV-nodal block

Answer 1

Mobitz I
Arterial supply: Poserior descending artery (usually from right circumflex)
PR intervals increasing in length until dropped beat (if 2º).
QRS: normal
Escape: junctional narrow QRS, rate 50-60
Causes: inferior infarct, digitalis, beta blockers, increased vagal tone, decreased sympathetic tone
Therapy: atropine

Question 2

His-purkinje block

Answer 2

Mobitz II
arterial supply: Anterior descending artery
PR intervals constant
QRS: often prolonged
Escape: idioventricular, 30-40
Causes: anterior infarct, chronic fibrosis
Treatment: pacemaker

Question 3

Wolff-Parkinson-White Syndrome

Answer 3

Re-entry rhythm
associated with supra-ventricular tachycardia.
During tachycardia, QRS normal, but during NSR QRS includes delta wave.
Delta wave = depolarization traveling through bypass tract - “Bundle of Kent”
NSR –> APB –> Supraventricular tachycardia
Can see inverted P wave in II (circuit traveling in retrograde fashion through atria)

Question 4

AV-nodal reentrant tachycardia

Answer 4

1. Begins and ends abruptly (usually beginning with APC)
2. Regular, with rate = 150-280
3. P waves are usually buried in the QRS complex
4. QRS morphology is usually normal
5. Most common variety of paroxysmal SVT
6. Typically occurs in otherwise healthy persons without structural heart disease
7. Usually well tolerated.
8. Termination with carotid massage, drugs (A-V nodal blockers)
9. Prevention with drugs (A-V nodal blockers)

Question 5

Automatic “ectopic” atrial tachycardia

Answer 5

repetitive firing of APB
multiple non-conducted P waves
not resolved with carotid sinus massage

Question 6

Atrial fibrillation:

Answer 6

1. Irregular, undulating baseline
   (“fibrillation waves,” propagating into A-V node @ up to 400/min.)
   Irregular ventricular response, @ 75-150/min.
   The ventricular rate is a function of A-V nodal refractoriness. The degree of AV block can be increased by A-V nodal blockers, thereby slowing the ventricular rate.
   Carotid sinus massage increases the degree of block, and may make diagnosis apparent by revealing the fibrillation waves.
   Atrial flutter and atrial fibrillation may occasionally alternate in the same patient.
   “1. Most common supraventricular arrhythmia
2. May be “idiopathic” in otherwise normal hearts, but more commonly is associated with cardiac abnormalities, such as atrial enlargement (e.g., hypertension with LVH, aortic or mitral valve disease, heart failure), lung disease, hyperthyroidism, or acute alcohol ingestion
3. Can produce embolic stroke (Stagnant blood in fibrillating atrium leads to clot formation)
4. Most important medical treatment is anticoagulation to prevent stroke
5. Medical therapy: A-V nodal blockers for rate control
   primary antiarrhythmic drugs to maintain NSR
6. Electrical cardioversion: most common treatment to convert arrhythmia to NSR
7. Ablation: Radiofrequency ablation of reentrant pathway for A Flutter, for tissue surrounding pulmonary veins for Atrial Fibrillation