Pharmacotherapeutics IV - Arrhythmias
Terms
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Class 1a agents
1)Conduction velocity
2)refractory period
3)automaticity -
1) decrease
2) increase
3) decrease -
Class 1b
1)conduction velocity
2)refractory period
3)automaticity -
1)0/decrease
2)decrease
3)decrease -
Class 1c
1)conduction velocity
2)refractory period
3)automaticity -
1)decrease
2)0
3)decrease -
Class II
1)conduction velocity
2)refractory period
3)automaticity -
1)decrease
2)increase
3)decrease -
Class III
1)conduction velocity
2)refractory period
3)automaticity -
1)0
2)increase
3)0 -
Class IV
1)conduction velocity
2)refractory period
3)automaticity -
1)decrease
2)increase
3)decrease -
Supraventricular arrhythmia
SINUS BRADYCARDIA
Causes -
1)excesive vagal stimulation from vomiting or straining during a bowel movement
2)drugs such as beta-antagonists, calcium antagonists, and digoxin
3)sinus node abnormalities due to an inferior wall AMI or open heart surgery -
SINUS BRADYCARDIA
Treatment (symptomatic) -
1)Atropine
2)TCP
3)dopamine
4)epinephrine
5)isoproterenol -
SINUS BRADYCARDIA
Cautions -
1) do NOT give doses smaller than 0.5mg of atropine to adults due to paradoxial bradycardia
2)excessive tachycardia may worsen ischemia or the extent of myocardial infarct in AMI patients -
Supraventricular arrhythmia
SINUS TACHYCARDIA
Causes -
1)decrease vagal tone
2)increased sympathetic tone
3)AMI
4)fever
5)stress
6)hypotension
7)CHF
8)drugs -
SINUS TACHYCARDIA
Treatment (symptomatic) - Propanolol, Verapamil, Diltiazem, Digoxin
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SINUS TACHYCARDIA
Treatment (symtomatic patient with CHF) - Digoxin
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SUPRAVENTRICULAR TACHYCARDIA
a)PAT
Cause
b)PSVT
Cause -
a)AMI, chronic lung dx, drug intoxication
b)healthy individuals or WPW -
SUPRAVENTRICULAR TACHYCARDIA
goal of treatment - interupt the AV nodal re-entry loop by slowing condution through this node
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PSVT
Treatment (severe hemodynamic compromise) - Synchronized cardioversion
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PSVT
Treatment (hemodynamically stable) -
1)vagal maneuvers
2)Adenosine
3)Verapamil/Diltiazem
4)Propanolol/digoxin - Adenosine drug interactions
-
Dipyridamole - prolongs effect (start with 1/2 dose)
Theophylline - decreases efficacy - Adenosine adverse effects
- Transient flushing and SOB
- Adenosine precautions
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1)asthmatics
2)wide QRS complex tachycardias
3)2 OR 3rd degree AV blockade - Delay in AV conduction manifested by a prolonged PR interval
- First degree AV block
- First degree AV block causes
-
1)increase vagal tone
2)drugs
3)hypoxia - First degree AV block tx
- none
- Progressive prolongation of AV nodal conduction and PR interval until an atrial impulse is completely blocked by the AVN and a QRS complex is dropped
- Second degree AV block
- Second degree AV block causes
-
1)inferior AMI
2)increased vagal tone
3)drugs - Second degree AV block treatment
-
Usually transient and does not require tx
Atropine if sx'matic of hypoperfusion that may occur if ventricular rate is excessively slow - None of the atrial stimuli are transmitted through the AVN, no P waves conducted to the ventricles
- Third degree AV block (complete heart block)
- Third degree AV block causes
-
1)anterior AMI
2)cardiomyopathy
3)sarcoidosis - Third degree AV block treatment
- 1)temporary pharmacological pacing with isoproterenol may be of benefit until (2) a permanent pacemaker can be inserted
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PREMATURE VENTRICULAR CONTRACTIONS (PVCs)
Causes -
1)common post AMI
2)CHF
3)hypoxia
4)digoxin toxicity
5)sympathomimetic drugs -
PVCs
Treatment - Amiodarone or Lidocaine for multifocal, paired PVCs, R-on-T, but NOT unifocal PVCs
- Lidocaine toxicities
- Paresthesias, respiratory arrest, seizures, muscle fasciculations, diz and drows
- Agents for chronic PVC suppression
- Class 1a's and propanolol
- Life-threatening arrhythmia defined as 3 or more consecutive PVCs
- Ventricular tachycardia
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Ventricular tachycardia
Causes - Post AMI
- Ventricular tachycardia treatment in the unstable patient (SBP <80-90
- Cardioversion
- Ventricular tachycardia (monomorphic) treatment in the stable patient (SBP>80-90) with a poor EF
- Amiodarone IVP or Lidocaine IVP THEN use synchronized cardioversion
- Ventricular tachycardia (monomorphic) treatment in the stable patient (SBP>80-90) with a normal EF
- Procainamide or Sotalol
- A life-threatening arrhythmia, totally disorganized depolarization of the ventricles-caused by many ventricualr ectopic focii, there is no pulse or blood pressure.
- Ventricular fibrillation
- VF causes
- After AMI, chest trauma, drug toxicity, or electrolyte abnormalities
- VF treatment
- 3 shocks -> epinephrine or vasopressin -> 1 shock -> lidocaine or amiodarone -> 1 shock -> Mg -> 1 shock -> procainamide
- Defined as no ventricular activity and appears as a flat line on ECG
- Asystole
- Asystole treatment
- Transcutaneous pacing -> epinephrine -> atropine -> decide whether to cease resuscitative efforts