Montepara Arrhythmias

Phase 0 of action potential

Rapid Na⁺ influx through fast sodium channels

Phase 1 of action potential

Transient potassium channels open and K⁺ efflux returns membrane potential to 0 mV

Phase 2 of action potential

Influx of Ca²⁺ through L-type calcium channels is electrically balanced by K⁺ efflux through delayed rectifier potassium channels

Phase 3 of action potential

Calcium channels close, but delayed rectifier potassium channels remain open and return membrane potential to -90 mV

Phase 4 of action potential

Sodium and calcium channels close, open potassium rectifier channels keep membrane potential stable at -90 mV

Electrocardiogram (ECG, EKG)

Noninvasive test to evaluate the electrical activity of the heart

With each beat, an electrical impulse or “wave” travels through the heart

EKG P wave

Atrium contracts/depolarizes

EKG QRS complex

Ventricles contract/depolarize, atria repolarize

Can measure how long it takes for the impulse to get through the entire ventricle

EKG T wave

Ventricles repolarize

EKG PR interval

Time from beginning of atrium contraction to beginning of ventricle contraction

EKG QT interval

Measured from the beginning of the QRS complex to the end of the T wave

Represents the period from onset of ventricular depolarization to completioln of ventricular repolarization

Dependent on heart rate

Corrected QT (QTc) interval accounts for changes in heart rate

High QTc interval is associated with higher risk of _____

Torsades de Pointes

Types of bradyarrhythmias

Sinus bradycardia

Atrioventricular (AV) block

Types of tachyarrhythmias

Sinus tachycardia

Supraventricular tachycardia

Ventricular tachycardia

Ventricular fibrillation

Treatment of sinus bradycardia

Only concerning/need to treat if patient is symptomatic

Discontinue aggravating medications

Acute therapy → atropine, dopamine, epinephrine, temporary pacing

Permanent therapy → pacemaker

Dosing of atropine for sinus bradycardia

First dose → atropine 1 mg IV

Repeat every 3-5 minutes, max of 3 mg

First degree AV block

1:1 AV conduction

Least severe

Second degree AV block

<1:1 AV conduction

Mobitz Type I (Wenckebach)

• Progressive PR interval lengthening until a ventricular complex is dropped

Mobitz Type II

• Dropped ventricular beats in a random fashion without progressive PR interval lengthening

Third degree AV block

AKA Complete heart block

No AV conduction (AV dissociation)

Needs a pacemaker

Treatment of Sinus Tachycardia

Remove underlying cause

Do NOT target heart rate

Why should you not target heart rate directly in sinus tachycardia?

Further decrease in cardiac output could send patient into shock and kill them

Types of Supraventricular Tachycardia (SVT)

Atrioventricular nodal reentrant tachycardia (AVNRT)

Atrioventricular reentrant tachycardia (AVRT)

Atrial tachycardia

Atrial fibrillation

Atrial flutter

Initial treatment of regular rhythm SVT

Vagal maneuvers, then IV adenosine

Dosing of adenosine for Regular Rhythm SVT

First dose → 6 mg rapid IV push, follow with NS flush

Second dose → 12 mg if required

What type of arrythmia is described as “irregularly irregular”?

Atrial fibrillation

1:1 ventricular rate is good in normal sinus rhythm, but it is BAD in _____

Atrial flutter

_____ arrythmias are not deadly (can cause deadly complications), while _____ arrythmias are deadly

Atrial; ventricular

Risk factors for QT interval prolongation

Female gender, bradycardia, heart failure, recent cardioversion, congenital long QT syndrome, electrolyte abnormalities (hypokalemia, hypomagnesemia), on QT prolonging medications

Drugs that can cause QT interval prolongation

Class Ia and Class III antiarrythmics

Antibiotics (macrolides, fluoroquinolones)

Antidepressants (TCAs, SSRIs)

Antipsychotics

Azole antifungals

Antiemetics

Methadone

Triptans

Treatment of Torsades de Pointes

Discontinue offending medications and correct exacerbating factors, such as electrolyte abnormalities

Direct cardioversion if unstable, defibrillation if pulseless

Magnesium sulfate is the drug of choice

• If ineffective, either temporary transvenous pacing or pharmacologic pacing can be initiated