Tachy arrythmias summary

Question 1

Causes and Pathophysiology of Tachy Arrhythmias

Answer 1

Increased Automaticity: something else is dominant pacemaker
-injury (leaky), electrolyte imbalance, ischemia, drugs, high sympathetic, 
Re-entry:
-tissue with uni-directional block (doesn’t depolarize initially) AND slowed retrograde conduction (backwards)
Triggered/After-depolarization:
Early: higher influx of Na/Ca in later part of Phase 2, re-fire and can trigger surrounding newly repolarized cells.
-low K or Mg, genetics (K or Na channel), K channel blocking drugs
Late: Na/Ca influx in Phase 4, depolarize a bit, can re-fire heart
-catecholamines/sympathetic, drugs (digoxin, etc.)

Question 2

Describe clinical syndromes of Tachy Arrhythmias

Answer 2

Definition: >3 fast beats in a row
Premature beats:
-Atrial (APB): more automaticity
-Ventricular (VPB): more automaticity or drugs. Ok if ø structural disease
Narrow complex tachy = Supra-ventricular (SVT)
-7 main types (normal to least):
1.sinus
2. ectopic atrial
3. AV Node Re-entry Tachy (2-part AV - one fast/slow, other fast/slow - cycle)
4. AV reciprocating Tachy; bypass tract. WPW syndrome)
5. Multi-focal Atrial Tachy (>3 different P waves; severe liver disease or low Mg)
6. Atrial flutter (re-entry, AV node allows ratio through)
7. fibrillation
Wide complex = usually VT (rare SVT w. block)
-usually scar mediated = re-entry
-Torsades-de-points = after-depolarizations, due to long QT

Question 3

Symptoms of Tachy Arrhythmias

Answer 3

Tachycardia…

Question 4

Signs and Physical findings of Tachy Arrhythmias

Answer 4

Tachycardia…

Question 5

Key lab tests and findings of Tachy Arrhythmias

Answer 5

EKG all the way

• APB: premature P wave, or ectopic P wave
• VPB: wide bizarre QRS (naming ex. every 2 beats = bigeminy)
• AVNRT: retrograde/hidden P waves
• AVRT: retrograde P waves
• MAT: >3 different P waves
• A flutter: Saw tooth in b/w QRS, in set ratio
• A fib.: no organized P waves
• VT: dissociated P waves marching, concordance (chest leads all up or all down), axis (-90º to 180º)
• Torsades-de-pointes = sine wave

Question 6

Tx of Tachy Arrhythmias

Answer 6

SVT: AV nodal blocking / ablations - rate slowing drugs (ß block, ø Ca ch, digoxin)
VT: arrhythmia drugs if heart ok, defibrillator +/- drugs if not ok
TdP: fix K/Mg deficit, drugs/pacemaker to quicken heart,
V fib: defibrillation

Question 7

Electric shock details of Tachy Arrhythmias

Answer 7

Depolarize all cells same time, then hope sinus returns
Still has pulse: synchronized cardioversion
No pulse: defibrillation