This document provides information on arrhythmias and cardiac arrest. It defines normal sinus rhythm and various arrhythmias including sinus bradycardia, heart blocks, sinus tachycardia, supraventricular tachycardia, atrial fibrillation, atrial flutter, asystole, ventricular tachycardia, and ventricular fibrillation. Algorithms for managing bradycardia with a pulse and tachyarrhythmias are presented. The cardiac arrest algorithm reviews CPR, defibrillation, medications, and reversible causes of cardiac arrest known as the "Hs and Ts".

1. Arrhythmias and Cardiac
Arrest

2. Arrhythmias/Cardiac
Arrest
• Normal sinus rhythm:
• Rate 60-100 and regular
• Each P wave is followed by a QRS
• Normal P wave morphology and axis
• Each PR interval is constant
• PR interval: 0.12-0.20 seconds
• QRS interval: 0.04-0.10 seconds
• QT interval: < 0.45 seconds

3. Arrhythmias/Cardiac Arrest
Sinus bradycardia: Rate < 60 and regular. Treat with
anticholinergic agents or pacing if patient is unstable
1st degree heart block: PR interval > 0.02 seconds from
delayed communication between atria and ventricles
2nd degree heart block Mobitz type I (Wenckebach):
progressive lengthening of PR interval until a QRS is dropped
2nd degree heart block Mobitz type II: intermittent dropped
QRS complex. May require a pacemaker
3rd degree heart block (complete heart block): no
relationship between P and QRS waves. Atria and ventricles
act independently. Requires a pacemaker

4. Arrhythmias/Cardiac Arrest
Sinus tachycardia: Rate > 100 and regular. Treatment focuses on
identifying and treating underlying cause
Supraventricular tachycardia: Rate > 100, loss of P waves, and
narrow QRS. Acute treatment with vagal maneuvers and
adenosine. Chronic treatment with beta blockers, drugs that
slow AV conduction, or ablation
Atrial fibrillation: Irregular heart rate and absence of P waves.
Most common atrial tachyarrhythmia. RF: structural heart
disease, HTN, and valvular disease. Control rate, consider rhythm
control, and consider anticoagulation.
Atrial Flutter: Ventricular rate around 150 and saw-toothed
appearance with multiple P waves per QRS

5. Arrhythmias/Cardiac Arrest
Asystole: Flat line. Absence of electrical activity.
Do NOT defibrillate
Ventricular tachycardia: Wide QRS complex,
rate >100. Treat with lidocaine, amiodarone, or
procainamide. If sustained and patient is
unstable, DEFIBRILLATE
Ventricular fibrillation: Polymorphic.
DEFIBRILLATE.

6. Bradycardia with a Pulse Algorithm
Key Points:
• If patient is stable, monitor
• If not stable, administer atropine or
glycopyrrolate
• Atropine and glycopyrrolate are
anticholinergic drugs that inhibit the
parasympathetic nervous system and
therefore allow the sympathetic nervous
system to predominate and increase heart
rate
• If atropine does not work, utilize transcutaneous
pacing

7. Tachyarrhythmia Algorithm
• If patient is unstable synchronized*
cardioversion
• Synchronized: synchronizes shock to
the QRS to avoid R on T phenomenon
• R on T phenomenon: can trigger a
ventricular tachyarrhythmia
• Cardioversion initial recommended doses:
• Narrow regular : 50–100 J
• Narrow irregular : 120–200 J biphasic
or 200 J monophasic
• Wide regular : 100 J
• Wide irregular : Defibrillation dose (not
synchronized)
• Adenosine
• First dose : 6 mg rapid IV push; follow
with NS flush. Second dose : 12 mg if
required

8. Cardiac Arrest Algorithm
• CPR:
• 100-120 compressions per minute > 2”
deep
• Minimize breaks in CPR to < 10 seconds
• Rotate compressors every 2 minutes
• Defibrillate if ventricular fibrillation or
ventricular tachycardia
• 120-200J
• Epinephrine 1gm every 3-5 minutes
• Amiodarone first dose 300mg, second dose
150mg

9. Reversible
Causes of
Cardiac Arrest:
“Hs and Ts”
• Hypovolemia
• Give rapid bolus of IV fluid. If hemorrhage, give blood.
Consider other shock states such as high spinal,
neurogenic shock, or anaphylaxis
• Hypoxemia
• Increase O2 to 100%. Check placement of
endotracheal tube. Obtain CXR
• Hypothermia
• Active warming with forced air blanket
• Hydrogen ion (acidosis)
• Sodium bicarbonate 50mEq as needed
• Hypo- or hyper- kalemia
• Hypokalemia- potassium and magnesium infusion
• Hyperkalemia- Calcium chloride 1 gm + D50 1 amp IV
(25g dextrose) + regular insulin 10 units + sodium
bicarbonate

10. Reversible
Causes of
Cardiac Arrest:
“Hs and Ts”
• Tension pneumothorax
• If suspected by unilateral breath sounds, distended neck
veins, deviated trachea, then perform needle
decompression at 2nd intercostal space at the mid-
clavicular line
• Thrombosis (pulmonary)
• TTE to evaluate right ventricle. Consider fibrinolytics
• Thrombosis (coronary)
• TTE to evaluate for wall motion abnormalities. Consider
emergent coronary revascularization
• Tamponade (cardiac)
• TTE to rule out. Treat with pericardiocentesis
• Toxins
• Consider medication error. Confirm no infusions running

11. References
• ACLS medical training. Rhythm Recognition. 2020.
Retrieved from
https://www.aclsmedicaltraining.com/rhythm-
recognition/
• Haluka, J. ACLS Secondary Survey for a Patient in
Respiratory Arrest, 2020, https://www.acls.net/acls-
secondary-survey.htm
• Haluka, J. Using the ACLS Tachycardia Algorithm for
Managing Unstable Tachycardia, 2017,
https://www.acls.net/acls-tachycardia-algorithm-
unstable.htm
• Liu, L. Using the ACLS Bradycardia Algorithm for
Managing Bradycardia, 2019, https://www.acls.net/acls-
bradycardia-algorithm.htm
• Stanford Anesthesia Cognitive Aid Group*. Emergency
Manual: Cognitive aids for perioperative clinical events.
See http://emergencymanual.stanford.edu for latest
version. Creative Commons BY-NC-ND. 2013 (creative
commons.org/licenses/by-nc-nd/3.0/legalcode). *Core
contributors in random order: Howard SK, Chu LK,
Goldhaber Fiebert SN, Gaba DM, Harrison TK.