Tachydysrhythmias

Basics

Description

  • Any disturbance of the heart’s rhythm resulting in a rate >100 bpm
  • Categorized by narrow or wide QRS complex and regular or irregular rhythm
  • Sinus tachycardia:
    • Narrow-complex, regular rhythm, typical rate of 100–150 bpm
    • Max rate typically 220 minus age
    • Functional response to physiologic stress caused by increased catecholamine tone or decreased vagal stimulation
  • Supraventricular tachycardia (SVT):
    • Typically, a narrow-complex tachycardia that originates within or above the atrioventricular (AV) node
    • Can be wide-complex if associated with aberrancy
  • Ventricular tachycardia (VT):
    • Can be monomorphic or polymorphic
    • ≥3 consecutive ventricular ectopic beats at a rate of >100 bpm
    • Most common initiating rhythm in sudden death for patients with previous MI
  • Torsades de pointes:
    • Form of polymorphic VT with undulating axis and prolonged baseline QT interval
    • Secondary to either congenital or acquired abnormalities of ventricular repolarization
    • Often the result of drug therapy or electrolyte disturbances
  • Ventricular fibrillation (VF):
    • Oscillations without evidence of discrete QRST morphology
    • Accounts for 80–85% of sudden cardiac deaths
    • Frequently results from degeneration of sustained VT

Etiology

  • Sinus tachycardia:
    • Acute MI
    • Anemia
    • Anxiety
    • CHF
    • Drug intoxication or withdrawal
    • Hyperthyroidism
    • Hypovolemia
    • Hypoxia
    • Infection/fever
    • Pain
    • Pericardial tamponade
    • Pulmonary embolism
    • Shock
  • Atrial tachycardia:
    • Drug toxicity (eg, theophylline, cocaine)
    • Electrolyte abnormalities
    • Hypoxia
  • Junctional tachycardia:
    • AV nodal reentry
    • Myocardial ischemia
    • Pre-excitation syndromes
    • Structural heart disease
  • Multifocal atrial tachycardia:
    • Hypoxic effects of chronic lung disease
    • Theophylline toxicity
  • Atrial fibrillation (AFib) and atrial flutter:
    • Alcohol intake or withdrawal
    • Cardiomyopathy
    • CHF
    • COPD
    • Coronary artery disease
    • Drugs (eg, sympathomimetics, β-agonists)
    • Electrolyte abnormalities
    • HTN
    • Hyper- or hypothyroidism
    • Hypoxia
    • Hypo- or hypervolemia
    • Myocardial ischemia
    • Myocarditis
    • Pulmonary embolism
    • Sepsis
    • Valvular heart disease (esp. mitral valve)
  • Wolff–Parkinson–White (WPW) syndrome:
    • Drug or alcohol toxicity
    • Intrinsic accessory pathway
  • VT:
    • Cardiac ischemia
    • Cardiac scarring/fibrosis
    • Cardiac surgery or congenital anomaly repair
    • Cardiomyopathy
    • Digoxin toxicity (bidirectional VT)
    • Electrolyte abnormalities
    • Hypoxia
    • Long QT syndrome
  • Torsades de pointes:
    • Congenital QT prolongation
    • Drug toxicity (antiarrhythmic class IA and III agents, antipsychotics, antibiotics, etc.)
    • Electrolyte abnormalities (esp. hypokalemia, hypomagnesemia)
  • VF:
    • Acidosis
    • Acute MI (most common)
    • Blunt trauma (commotio cordis)
    • Brugada syndrome
    • Cardiomyopathy
    • Chronic ischemic heart disease
    • Electrocution
    • Electrolyte abnormalities
    • Hypoxia
    • Shock

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