Cardiac Arrhythmias for the Nurse Practitioner Licensing Exam
Start your One-Week Free Trial
Already subscribed? Log in »
Mechanisms of Arrhythmias
- Abnormal Automaticity:
- Non-pacemaker cells generate spontaneous impulses, disrupting normal heart rhythms.
- Example: Ectopic atrial or ventricular beats.
- Triggered Activity:
- Afterdepolarizations (early or delayed) induce abnormal contractions.
- Example: Torsades de Pointes, often seen with prolonged QT syndrome.
- Re-Entry Circuits:
- Electrical impulses re-enter previously excited tissue, causing repetitive stimulation.
- Example: AV Nodal Reentrant Tachycardia (AVNRT) in PSVT.
Supraventricular Arrhythmias
- Atrial Fibrillation (AF):
- Irregularly irregular rhythm without distinct P waves.
- Increases stroke risk, requiring anticoagulation (e.g., warfarin, DOACs).
- Rate Control: Beta-blockers (e.g., metoprolol) or calcium channel blockers (e.g., diltiazem).
- Rhythm Control: Amiodarone or electrical cardioversion if unstable.
- Atrial Flutter:
- Rapid atrial contractions with a "sawtooth" ECG pattern.
- Managed similarly to AF with rate control and anticoagulation.
- Paroxysmal Supraventricular Tachycardia (PSVT):
- Sudden-onset tachycardia due to AV nodal re-entry circuits.
- Acute management: Vagal maneuvers or adenosine; long-term management may involve ablation.
Ventricular Arrhythmias
- Premature Ventricular Contractions (PVCs):
- Wide QRS complexes occurring early, not preceded by P waves.
- Generally benign but may signal heart disease if frequent.
- Ventricular Tachycardia (VT):
- Defined by ≥3 consecutive PVCs, with a rate >100 bpm.
- Sustained VT (>30 sec): Requires immediate cardioversion if unstable.
- Chronic management: Amiodarone or ICD in structural heart disease.
- Ventricular Fibrillation (VF):
- Chaotic, disorganized ventricular activity causing cardiac arrest.
- Requires immediate defibrillation and CPR.
Bradyarrhythmias
- Sinus Bradycardia:
- HR <60 bpm, often due to vagal tone or medication use.
- Managed with atropine if symptomatic; pacing for refractory cases.
- Atrioventricular (AV) Blocks:
- First-Degree Block: PR interval >200 ms with no missed beats.
- Second-Degree Block:
- Mobitz I (Wenckebach): Progressive PR lengthening followed by a dropped beat.
- Mobitz II: Dropped QRS without preceding PR prolongation; often requires pacemaker.
- Third-Degree Block: Complete dissociation between atrial and ventricular activity; treated with a pacemaker.
Management of Life-Threatening Arrhythmias
- Advanced Cardiac Life Support (ACLS):
- VF or Pulseless VT: Immediate defibrillation and epinephrine administration.
- Symptomatic Bradycardia: Atropine and, if needed, transcutaneous pacing.
- Torsades de Pointes:
- Polymorphic VT associated with prolonged QT; managed with magnesium sulfate and defibrillation if unstable.
Key Points
- Atrial Fibrillation: Requires anticoagulation and careful rate or rhythm management.
- Ventricular Tachycardia and Fibrillation: Immediate cardioversion or defibrillation is crucial.
- Torsades de Pointes: Treated with magnesium sulfate.
- Bradyarrhythmias: Severe AV blocks often necessitate pacemaker implantation.
- ACLS Protocols: Essential in managing cardiac arrest and hemodynamically unstable arrhythmias.