Cardio Exam 4 - Part 2

How do class 1b antiarrhythymics affect repol

• shorten by increasing rate of repolarization
• slow phase 0 depol and prolonged repol -> decrease reentry
• increase threshold potential and decrease phase 4 slope -> decreasing firing rate and automaticity
• decrease automaticity of SA nodal cells
• block open L-type Ca channels to slow conduction in SA and AV nodes

What are class 1b antiarrhythmics effective in treating

• supraventricular arrhythmias
• ventricular arrhythmias
• supraventricular and ventricular arrhythmias

What are examples of class 1b antiarrhythmics

• Lidocaine
• Mexiletine
• Phenytoin
• Dofetilide
• Propafenone

Lidocaine has a smaller therapeutic window than many other antiarrhythmics

• true
• FALSE (larger)

Due to its large therapeutic window, what is Lidocaine effective for

• ischemic myocardium
• prolonged QT situations
• decreasing maximum conduction rate
• slow rate of dissociation from Na channels

Why is phenytoin not commonly used as an antiarrhythmic

• it is an antiepileptic drug with antiarrhythmic activity
• it is an antihistamine with antiarrhythmic properties
• it is an antidepressant with antiarrhythmic activity

What indication is phenytoin effective for in children

• a-fib
• v-tach
• a-flutter
• TdP<br />

Which subclass of class I antiarrhythmics has a significant effect in blocking fast Na channels

• 1a
• 1b
• 1c

How do class 1c antiarrhythmics affect repol

• increase
• decrease
• no effect

What are class 1c antiarrhythmics typically used for

• life-threatening supraventricular tachycardia
• ventricular tachyarrhythmias
• supraventricular tachyarrhythmias
• atrial fibrillation