Cardiac Arrhythmias and Syncope

Vasovagal Syncope

• Preceded by sinus bradycardia and asystole

Arrhythmia and Cardiac Syncope

• Caused by sinus bradycardia, sinus pauses, AV block, and prolonged QTc interval
• Medications that slow conduction through the AV node (adenosine, digoxin, verapamil, beta blockers) are avoided in pre-excited AF

Treatment of Overdose

• Glucagon treats beta blocker and CCB overdose, and insulin overdose
• Glucagon is used after acute hemodynamic instability has been addressed with atropine or temporary pacing

Initial Presentation of Atrial Fibrillation

• May initially present with hyperthyroidism, COPD/OSA, and chronic hypertension
• Age is a strong contributor (paroxysmal palpitations in young is AVNRT/AVRT, but AF in old)

Evaluation of Arrhythmias

• Continuous ECG monitoring is needed for evaluation of arrhythmias (AF) and cardiac syncope if initial ECG is normal

Premature Atrial Beats

• Benign and occur when the atria are prematurely activated from a site other than the SA node
• Management is alcohol/tobacco/caffeine/stress abstinence and beta blockers

Ventricular Arrhythmias

• Most ventricular arrhythmias in acute MI occur within the first hour of symptoms
• Patients with history of MI and HFrEF (≤30%) are at increased risk of death due to ventricular arrhythmia (VTach, VFib, premature ventricular contractions)
• Management is beta-blocker, ACEi/ARB, spironolactone, and implantable cardioverter-debibrillator

Hyperkalemic Emergency

• Treated with calcium gluconate, insulin + glucose, albuterol, NaHCO3, patiromer (K+ stool binder), furosemide, and dialysis
• Urgent calcium gluconate, insulin, and glucose are reserved for ECG change, potassium ≥6.5 mEq/L, or rapidly rising potassium due to tissue breakdown

Digoxin Toxicity

• Causes atrial tachycardia with AV block resulting from increased automaticity of myocardial conduction and increased vagal tone
• Hypokalemia increases digoxin binding and worsens toxicity

ACS with Normal ECG

• Warrants serial ECGs every 15-30 minutes

Cor Pulmonale

• RV failure resulting from hypoxic vasoconstriction and pulmonary HTN (COPD, IPF, asbestosis, OSA, ARDS)
• Presents with SOB, pitting lower extremity edema, anorexia, abdominal pain, hepatomegaly, hepatojugular reflux, ascites, JVD, loud P2, S3, and TR in the absence of LV failure
• Management is echocardiogram and right heart catheterization
• May occur with chronic hypoxia, hypercapnia with compensatory metabolic alkalosis, and secondary erythrocytosis