B4-017 CBCL: Dysrhythmias Flashcards
normal sinus rhythm
normal conduction velocity: PR interval
.2s
5 small boxes
normal conduction velocity: QRS
.12s
3 small boxes
normal conduction velocity: QT interval
.44s
- time between start of SA node and AV firing
- occurs due to “pause” effect of AV node
PR interval
time to depolarize all of the ventricular myocardium
QRS
time to repolarize all of ventricular myocardium
QT interval
first degree AV block
2nd degree AV block
Mobitz I
2nd degree AV block
Mobitz 2
- progressive lengthening of PR until a beat is dropped
- variable RR with a pattern
- regularly irregular
- usually asymptomatic
2nd degree AV block
Mobitz I
- dropped beats that are not preceded by a change in PR interval
- indicates structural issue: ischemia, fibrosis, sclerosis
- requires pacemakers
2nd degree AV block
Mobitz II
- P waves and QRS complexes are rhythmically dissociated
- atria and ventricles beat independently of each other
- atrial rate> ventricular rate
- usually requires pacemaker
complete/ 3rd degree heart block
complete/3rd degree heart block
junctional rhythm
sinus bradycardia
asystole
check lead placement
sinus tachycardia
atrial flutter
atrial fibrillation
supraventricular tachycardia
monomorphic ventricular tachycardia
polymorphic ventricular tachycardia
ventricular fibrillation
torsades de pointes
irregularly irregular with no distinct p wave
atrial fibrillation
rapid succession of identical, consecutive artial depolarization waves causing a “sawtooth” appearance
atrial flutter
- regular rhythm and rate
- > 100 bpm
- QRS > 120ms
- commonly due to cardiomyopathy/ishchemia after infarction
- high risk of sudden cardiac death
ventricular tachycardia
treatment of torsades de pointes
magnesium
- polymorphic v tach
- shifting sinusoidal waveforms
- may progress to v fib
- long QT interval predisposes risk
torsades de pointes
what causes drug induced long QT?
anti-Arrythmics
anti-Biotics
anti-Chychotics
anti-Depressants
anti-Emetics
anti-Fungals
Navir (protease inhibitors)
Opiods
ABCEDEF + NO
- disorganized rhythm with no identifiable waves
- fatal without immediate defibrillation
ventricular fibrillation
- prolonged PR interval
- benign and asymptomatic
first degree heart block
classes of drugs used for rate control
- B-blocker
- Ca+ channel blockers
- digoxin
classes of drugs used for rhythm control
- Na+ channel blockers
- K+ channel blockers
class 1 of antiarrhythmic drugs are
Na+ channel blockers
class 2 antiarrhythmic drugs are
B blockers
class 3 antiarrhythmic drugs are
K+ channel blockers
class 4 antiarrhythmic drugs are
Ca+ channel blockers
Drugs in class IA
- Procainaminde
- Quinidine
- Disopyramide
The queen proclaims Diso’s pyramid
Drugs in class 1B
- Lidocaine
- Mexiletine
drugs in class 1C
- Flecainide
- Propafenone
- Moricizine
drugs in class 2
- propranolol
- metoprolol
- esmolol
drugs in class 3
- amiodarone
- dronedarone
- sotalol
- ibutilide
- dofetilide
drugs in class 4
- verapamil
- diltiazem
other antiarrhythmic drugs
- adenosine
- digoxin
- magnesium
what class of drugs decrease the slope for phase 4 depolarization in SA node
Class 1
what class of drugs decrease the heart rate but elevating the threshold for excitation
class 1
- moderate Na+ channel block
- dissociate with intermediate kinetics
- prolong APD
class 1A
- mild Na+ channel block
- fast dissociation
- shorten APD
class 1B
- strong Na+ channel block
- slow dissociation
- minimal effect on APD
class 1C
has ganglion blocking activity which reduces peripheral vascular resistance and can cause hypotension
especially IV
procainamide
long term therapy can cause a reversible lupus type syndrome
* rash
* arthralgia
* arthritis
* pericarditis
procainamide
does procainamide elevate digoxin levels?
no
least useful class 1A drug due to short half life and adverse effects
procainamide
drug of second or third choice for sustained ventricular arrhythmias associated with myocardial infarction
procainamide
similar to procainamide, with modest antimuscarinic effect
quinidine
- blocks a-adrenergic receptors to cause vasodilation
- marked hypotension and reflex tachycardia
quinidine
adverse effects
- increase plasma digoxin
- thrombocytopenia
- adverse GI effects
quinidine
rarely used because of cardiac and extracardiac adverse effects and better bioavailbility of other drugs
quinidine
similar effects to quindine and procainamide, but more antimuscarinic effects
disopyramide
adverse effects:
- urinary retention
- dry mouth, blurred vision, constipation
- worsening of glaucoma
atropine-like activity
disopyramide
- not used very often because of antimuscarinic effects
- only approved in USA to treat ventricular arrhythmias
disopyramide
must be given IV due to high first-pass hepatic metabolism
lidocaine
- treats unstable v tach
- relatively uneffective for atrial flutter or fibrillation
lidocaine
low incidence of toxicity and high degree of effectiveness
lidocaine
lidocaine analog, but resistant to first-pass metabolism
mexiletine
- useful for ventricular arrythmias
- can be used off label for diabetic neuropathy
mexiletine
adverse effects
predominantly neurologic:
* tremor
* blurred vision
* lethargy
* nausea
mexiletine
increase mortality from cardiac arrest or arrhythmic sudden death in patients with recent MI
Class 1C antiarrhythmics
- no QT prolongation
- no antimuscarinic effects
- used to treat supraventricular arrhythmias
- effictive in suppressing PVCs
flecainide
- blocks Na+ channels, weak B blocker
- has metallic taste
- may exacerbate arrythmias and cause constipation
propafenone
- antiarrhythmic phenothatzine derivative
- used for ventricular arrhythmias
- withdrawn from US market
moricizine
- frequently used for rate control
- treat supraventricular and ventricular arrythmias causes by SNS
- prevent ventricular fibrillation
2
propranolol (nonselective)
atenolol (b1 selective)
- short acting drug
- IV
- used for acute tachycardias occurring during surgery
esmolol (b1 selective)
harmful effect of Class 2: b-blockers
negative inotrope
- dimish SNS activation of the heart and vessels
- dimish cardiac workload
- clear mortality benefit in CHF
Class 2: b- blockers
- oral or IV
- treats atrial fibrillation
amiodarone
- prolongs AP duration by blocking K+ channels
- decreases rate of firing in pacemaker cells by blocking Na+ channels
- blocks a- and b- adrenergic receptors and Ca+ channels
- bradycardia
amiodarone
causes peripheral vasodilation after IV administration
amiodarone
can cause pulmonary fibrosis
amiodarone
can cause gray-blue skin discoloration
amiodarone
can cause corneal microdeposits and blindess
amiodarone
can cause hypo or hyper thyroidism
amiodarone
- long half life
- measurable even after a year
amiodarone
- metabolized by CYP3A4
- can elevate digoxin or warfarin
amiodarone
structural analog of amiodarone, no iodine
dronedarone
can cause severe liver toxicity to the point of requiring transplant
dronedarone
“black box” FDA warning regarding an increased risk of death, stroke, and heart failure in patients with decompensated heart failure or permanent a fin
dronedarone
- non selective b-blocker that prolongs ADP
- treatment of life-threatening ventricular arrhythmias in pediatrics
sotalol
dofetilide is administed
orally
ibutilide is administered
IV
- block rapid component of delayed rectifier K+ current to slow cardiac repolarization
- good to restore normal sinus rhythm in a fib or flutter
2
dofetilide or ibutilide
- orally active
- block L type Ca+ channels
- rate control for a fib
2
verapamil, diltiazem
opens inward rectifier K+ channels –> hypopolarization
adenosine
- inhibits L type calcium channels
- mainly effects AV node, not SA node
- very short half life
- treats paroxysmal supraventricular tachycardia
adenosine
adverse effects
- flushing
- SOB
- chest burning
- headache
- hypotension
- nausea
- paresthesia
adenosine
- potent and selective NaKATPase inhibitor
- positive inotrope
digoxin
- stimulates vagus nerve to decrease heart rate without affecting blood pressure
- used in a fib
digoxin
- very narrow therapeutic window
- many drug-drug interactions
digoxin
drugs that enhance digoxin toxicity
- quinidine
- amiodarone
- captopril
- verapamil
- dilitiazem
- cyclosporine
- GI: nausea, vomiting, diarrhea, abdominal discomfort
- Cardiac: can lead to almost all arryhthmias
digoxin toxicity
administed parenterally
magnesium
used to prevent/treat torsades de pointes
and digoxin induced arrhythmias
magnesium
- effective mainly in the treatment of ventricular arrhythmias
- stable v tach
magnesium