Tachydysrhythmias

Basics

Description

  • Any disturbance of the heart's rhythm resulting in a rate >100 bpm
  • Sinus tachycardia:
    • Narrow complex regular rhythm at a 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):
    • A narrow complex tachycardia that originates above the His bundle
  • Regular SVT:
    • Atrial tachycardia
    • Junctional tachycardia:
      • Regular tachycardia without preceding depolarization waves
  • Irregular SVT:
    • Atrial fibrillation (AF)
    • Atrial flutter (with variable block)
    • Multifocal atrial tachycardia
  • Ventricular tachycardia (VT):
    • ≥3 consecutive ventricular ectopic beats at a rate of 100 bpm
    • Most common initiating rhythm in sudden death in patients with previous MI
  • Torsades de pointes:
    • Paroxysmal form of 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
  • 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
    • Hyperthyroidism
    • Hypovolemia
    • Hypoxia
    • Infection
    • Pain
    • Pericardial tamponade
    • Pulmonary embolism
  • Atrial tachycardia:
    • Electrolyte disturbances
    • Drug toxicity (e.g., theophylline)
    • Hypoxia
  • Junctional tachycardia:
    • AV nodal re-entry
    • Myocardial ischemia
    • Structural heart disease
    • Pre-excitation syndromes
  • Wolff–Parkinson–White (WPW) syndrome:
    • Intrinsic accessory pathway
    • Drug and alcohol toxicity
  • AF:
    • HTN
    • Coronary artery disease
    • Hyper-/hypothyroidism
    • Alcohol intake
    • Mitral valve disease
    • Chronic obstructive pulmonary disease
    • Pulmonary embolism
    • Hypoxia
    • Digoxin toxicity
    • Chronic pericarditis
    • Idiopathic AF
  • Atrial flutter:
    • Ischemic heart disease
    • Valvular heart disease
    • CHF
    • Myocarditis
    • Cardiomyopathies
    • Pulmonary embolism
    • Electrolyte abnormalities
  • Multifocal atrial tachycardia:
    • Hypoxic effects of chronic lung disease
    • Theophylline toxicity
  • Ventricular tachycardia:
    • Dilated cardiomyopathy
    • Cardiac ischemia
    • Hypoxia
    • Cardiac scarring/fibrosis
    • Cardiac surgery or congenital anomaly repair
    • Digoxin toxicity
    • Long QT syndrome
    • Electrolyte abnormalities
  • Torsades de pointes:
    • Drug toxicity (antiarrhythmic class IA and III agents, antipsychotics, antibiotics, etc.)
    • Hypokalemia
    • Hypomagnesemia
    • Congenital QT prolongation
  • Ventricular fibrillation:
    • Acute MI (most common)
    • Chronic ischemic heart disease
    • Hypoxia
    • Acidosis
    • Anaphylaxis
    • Electrocution
    • Shock
    • Hypokalemia
    • Initiation of quinidine therapy

There's more to see -- the rest of this topic is available only to subscribers.

© 2000–2025 Unbound Medicine, Inc. All rights reserved