Cardiac Rhythm Disturbances Flashcards
Instability as related to cardiac rhythm d turbances means that the dysrhythmia is
(1) impairing perfusion and threatening vital organ function
( 2) has the potential to deteriorate into cardiac arrest
most common bradycardia
- sinus bradycardia
- junctional rhythm
less commonly, idioventricular rhythm
Atrial fibrillation or flutter with slow ventricular response are uncommon; these rhythms are usually seen in patients
experiencing significant conduction system disease,
ssick sinus syndrome
suffering from excessive AV node blocking medications.
If the patient is unstable, the vast majority of AV blocks
third-degree heart block
followed much less frequently by second-degree AV block
If the patient is stable, most frequently seen
- second-degree type I AV block
third-degree AV block is less common
second-degree type II AV block is quite rare.
Atropine MOA
enhances the automaticity of the sinoatrial (SA) node and p tiates conduction through the AV node by direct vagolytic activity.
β-Adrenergic agents MOA
chronotropic and inotropic cardiac activity,
as well as enhancing electrical conduction within the AV node and infranodal system,
thus their potential to produce ischemia and ectopy
Glucagon
inotropic and chronotropic cardiac activity independent of the β-adrenergic receptors.
Glucagon is primarily used for bradycardias due to cardiotoxicity from β-blocker or calcium channel–blocker overdose.
most appropriate pacing method for the acutely symptomatic patient
Transcutaneous pacing
Atropine
0.5- to 1.0-milligram IV push; may repeat every 3–5 min until desired heart rate is achieved or to total dose of 3 milligrams
Most effective for bradydysrhythmias due to sinus and higher AV nodal disease
Dopamine
IV infusion at rate 2–20 micrograms/kg/min; titrate to desired heart rate
May precipitate myocardial ischemia and ectopy
Epinephrine
IV infusion at rate 2–10 micrograms/min; titrate to desired heart rate
May precipitate myocardial ischemia and ectopy
Glucagon
3–10 milligrams IV infused over 1–2 min, followed by an IV continuous infusion of 1–5 milligrams/h
Used for cardiotoxicity associated with β-blocker and calcium channel–blocker overdose
Limited human data are available supporting its use Nausea and vomiting are often limiting side effects Tachyphylaxis may develop during infusion
Adenosine
6-milligram rapid IV push;
if after 1–2 min the dysrhythmia persists,
repeat rapid IV push with 12 milligrams;
may repeat once more if dysrhythmia persists
Effective in terminating narrow QRS complex reentrant tachydysrhythmias involving the AV node
Verapamil
5–10 milligrams IV bolus over 2–3 min;
if after 15 min the dysrhythmia persists,
may repeat with dose of 10 milligrams
Effective in terminating narrow QRS complex reentrant tachydysrhythmias involving the AV node and reducing ventricular rate in atrial fibrillation or flutter
Diltiazem
15–20 milligrams IV bolus over 2 min,
followed by IV infusion at 5–10 milligrams/h;
a repeat bolus of 20–30 milligrams may be given after 15 min if inadequate response to initial bolus
Effective in terminating narrow QRS complex reentrant tachydysrhythmias involving the AV node and reducing ventricular rate in atrial fibrillation or flutter
Esmolol
500 micrograms/kg IV bolus over 1 min, followed by IV infusion starting at 50 micrograms/kg/min; titrate infusion to desired heart rate
Effective in terminating narrow QRS complex reentrant tachydysrhythmias involving the AV node and reducing ventricular rate in atrial fibrillation or flutter
Metoprolol
2.5–5 milligrams IV every 2–5 min; maximum total dose 15 milligrams IV over 10–15 min
Effective in terminating narrow QRS complex reentrant tachydysrhythmias involving the AV node and reducing ventricular rate in atrial fibrillation or flutter
Metoprolol
2.5–5 milligrams IV every 2–5 min; maximum total dose 15 milligrams IV over 10–15 min
Effective in terminating narrow QRS complex reentrant tachydysrhythmias involving the AV node and reducing ventricular rate in atrial fibrillation or flutter
Propranolol
1–3 milligrams IV over 1 min; may repeat every 2–5 min up to a total of 5 milligrams
Effective in terminating narrow QRS complex reentrant tachydysrhythmias involving the AV node and reducing ventricular rate in atrial fibrillation or flutter
Procainamide
Initial: 20–50 milligrams/min
100 milligrams every 5 min until arrhythmia is suppressed, hypotension occurs, or the QRS complex is prolonged by 50% from its original duration
(maximum dose:17 milligrams/kg)
Maintenance infusion rate: 1–4 milligrams/min
Used in wide-complex tachydysrhythmias and new-onset atrial fibrillation
Median time to conversion of new-onset atrial fibrillation about 1 h
Caution in patients with AMI and LV dysfunction Infuse initial dose at rate of 20 milligrams/min to reduce adverse effects
Amiodarone
Stable patient: 150 milligrams in 100 mL of D5W over 10 min,
followed by infusion at 1 milligram/min for 6 h
If breakthrough arrhythmia occurs, may give repeat 150-milligram boluses over 10 min
Maximum total daily dose is 2.2 grams
Ventricular fibrillation or pulseless ventricular tachycardia: 300 milligrams IV bolus; may repeat with additional dose of 150 milligrams IV bolus
Used in wide-complex tachydysrhythmias and new-onset atrial fibrillation
Preferred in setting of AMI or LV dysfunction Contraindicated in pregnancy
Lidocaine
Loading dose: 50–100 milligrams over 2–3 min.
May repeat in 5 min (up to 300 milligrams in any 1-h period) Maintenance: 1–4 milligrams/min (start low in patients with liver dysfunction or CHF)
Third-line agent for ventricular tachycardia and ventricular fibrillation
Magnesium sulfate
2 grams IV over 2 min, followed by infusion of 1–2 grams/h
Used in torsades de pointes with long QT interval
Ibutilide
Weight <60 kg: 10 micrograms/kg IV over 10 min Weight >60 kg: 1 milligram IV over 10 min
Used for conversion of new-onset atrial fibrillation or flutter Median time to conversion 20–30 min
