Arrhythmias

Question 1

List four causes of wide-complex, regular tachycardias.

Answer 1

• VT, VT, VT!!! (NB: If >60 and previous heart disease - 98% of these arrhythmias are VT)
• SVT w/ aberrancy
• HyperK
• Na channel blocker toxicity

Question 2

Outline the approach to tachyarrhytmias.

Answer 2

1. Stable or unstable
2. Wide or narrow
3. Regular or irregular
4. Atrial activity? Presence of p-waves

Question 3

List ten ECG findings that suggest VT rather than SVT w/ aberrancy.

Answer 3

• Extreme (NW) axis
• Fusion beats (sinus beat and ventricular beat occur simultaneously -> hybrid complex)
• Capture beats (AV transmission of a “normal” beat with “normal” QRS morphology
• Very broad complexes (>160ms)
• +ve or -ve concordance throughout the chest leads
• RsR’ complexes with dominant R-wave (ie R>R’) - this is the opposite of the case in RBBB
• Josephson’s sign - notching near the nadir of the S-wave
• Brugada’s sign - nadir of S-wave occurs > 100ms from beginning of the QRS complex
• AV dissociation
• Absence of typical LBBB or RBBB morphology

Question 4

List five drugs that can be used for cardioversion of a stable tachyarrhythmia.

How does each work?

Answer 4

1. Amiodarone - Na, K+ and Ca channel blocker + beta blocking properties -> Class I-IV anti-arrhythmic. (Predominantly Na+ and K+)
2. Metoprolol - beta-blocker
3. Procainamide - Class Ia Na+ channel blocker
4. Diltiazem - Class IV Ca++ channel blocker (non-dihydropyridine Ca++ channel blocker)
5. Magnesium - myocyte stabiliser

Question 5

List characteristics of the ECG to differentiate SVT from AF from AFlutter.

Answer 5

1. SVT is VERY regular vs AF irregular
2. SVT rate >120,
3. AFlutter is usually at 150 or 100bpm (atrial rate 300)
4. In AFlutter, look for p-wave at midpoint btw each pair of QRS

Question 6

LIst two possible choices (with pros and cons) for two pharmaceutical agents to revert SVT.

Answer 6

1. Adenosine 6mg -> 12mg -> 18mg rapid IV push
   
   1. Effective (87%)
   2. Fast
   3. Feels horrible
   4. May not work if caffeine in system
2. Diltiazem 15mg over 10mins
   
   1. Better tolerated
   2. Lasts longer to keep patient out of SVT
   3. At least as effective as adenosine (98%)
   4. Can drop BP

Question 7

List two possible pharmaceutical agents to treat stable VT.

Answer 7

• Amiodarone 150mg IV over 10mins - repeat to max 2.2g
• Procainamide (better but not available in Aust)

Question 8

List the differential for narrow-complex, regular tachycardias.

How can they be differentiated on the ECG?

Answer 8

1. Sinus tachycardia
2. SVT
3. AFlutter w/ 2:1 block

• Rate of 150bpm (+/-20) is highly suspicious for Aflutter (ie atrial rate of 300 with 2:1 block)
• P-wave mid-way btw QRS’s -> Aflutter (Bix Rule)
• SVT may have retrograde p-waves

Question 9

List the common causes of Torsades.

What is the difference btw Torsades and non-torsades polymorphic VT.

Answer 9

• Electrolytes - HypoMg, HypoK, HypoCa
• Med’ns - Na channel blockers
• Elevated ICP

Torsades is a polymorphic VT that ALSO has evidence of prolonged QT interval.

Question 10

What is the differential for narrow-complex, irregular tachycardia.

How can they be differentiated on the ECG?

Answer 10

1. AF - no p-waves
2. AFlutter w/ variable block -> regular p-waves @ 300bpm
3. MAT - p-waves for each QRS w/ varying p-wave morphology

Question 11

What two

Answer 11

1. Sinus tach
2. MAT