Cardiac Rhythm Disturbances

Question 1

Instability as related to cardiac rhythm d turbances means that the dysrhythmia is

Answer 1

(1) impairing perfusion and threatening vital organ function

( 2) has the potential to deteriorate into cardiac arrest

Question 2

most common bradycardia

Answer 2

1. sinus bradycardia
2. junctional rhythm

less commonly, idioventricular rhythm

Question 3

Atrial fibrillation or flutter with slow ventricular response are uncommon; these rhythms are usually seen in patients

Answer 3

experiencing significant conduction system disease,

ssick sinus syndrome

suffering from excessive AV node blocking medications.

Question 4

If the patient is unstable, the vast majority of AV blocks

Answer 4

third-degree heart block

followed much less frequently by second-degree AV block

Question 5

If the patient is stable, most frequently seen

Answer 5

1. second-degree type I AV block

third-degree AV block is less common

second-degree type II AV block is quite rare.

Question 6

Atropine MOA

Answer 6

enhances the automaticity of the sinoatrial (SA) node and p tiates conduction through the AV node by direct vagolytic activity.

Question 7

β-Adrenergic agents MOA

Answer 7

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

Question 8

Glucagon

Answer 8

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.

Question 9

most appropriate pacing method for the acutely symptomatic patient

Answer 9

Transcutaneous pacing

Question 10

Atropine

Answer 10

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

Question 11

Dopamine

Answer 11

IV infusion at rate 2–20 micrograms/kg/min; titrate to desired heart rate

May precipitate myocardial ischemia and ectopy

Question 12

Epinephrine

Answer 12

IV infusion at rate 2–10 micrograms/min; titrate to desired heart rate

May precipitate myocardial ischemia and ectopy

Question 13

Glucagon

Answer 13

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

Question 14

Adenosine

Answer 14

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

Question 15

Verapamil

Answer 15

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

Question 16

Diltiazem

Answer 16

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

Question 17

Esmolol

Answer 17

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

Question 18

Metoprolol

Answer 18

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

Question 19

Metoprolol

Answer 19

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

Question 20

Propranolol

Answer 20

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

Question 21

Procainamide

Answer 21

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

Question 22

Amiodarone

Answer 22

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

Question 23

Lidocaine

Answer 23

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

Question 24

Magnesium sulfate

Answer 24

2 grams IV over 2 min, followed by infusion of 1–2 grams/h

Used in torsades de pointes with long QT interval

Question 25

Ibutilide

Answer 25

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