Cardiac Dysfunction CHF Angina

Question 1

Class I A: Na channel blockers
broad spectrum antiarrhythmics
mech of action
ECG effect
drug

Answer 1

block Na channel in ventricular muscle
inc AP duration (mature, normal timing)
inc refractory period
dec automaticity

inc QRS complex duration
inc QT interval

(QDP)

• qui-ni-dine
• diso-pyramide
• pro-cain-amide

Question 2

Class I B: Na channel blockers
mech of action
ECG effect
drug

Answer 2

block Na channel in ventricular muscle
inc AP duration (mature, normal timing
dec automaticity

• no effect on refractory period
• inc QT internal
• lido-caine
• mexi-letine

Question 3

Class II: β-blockers
mech of action
ECG effect
drug

Answer 3

antagonism of symp input to heart
dec SA node and AV node
dec contractility
dec ventricular ectopic automaticity

inc PR duration (and PP)

Question 4

Class III: K channel blockers
mech of action
ECG effect
drug

Answer 4

block K channels
dec AP repolarization
inc AP duration
inc refractory period

inc QT duration

• amio-darone
• drone-darone

Question 5

Class IV: Ca channel blockers
(Ca channel antagonist)
mech of action
ECG effect
drug

Answer 5

blocks Ca channels
dec SA node
dec myocardyal contractility
dec conduction rate

inc PR interval
no effect on ref period

• vera-pamil
• dil-tiazem