Prolonged QRS complex

An intraventricular conduction delay on ECG, characterized by prolonged QRS duration (>100–120 ms), reflecting slowed or abnormal propagation of electrical impulses through the ventricular conduction system or ventricular myocardium.

Causes

• Conduction system abnormalities

  • Right bundle branch block (RBBB)

  • Left bundle branch block (LBBB)

  • Nonspecific intraventricular conduction delay

  • Fascicular block

  • His–Purkinje system disease

• Arrhythmia-related causes

  • Ventricular tachycardia

  • Ventricular pacing rhythms

  • Wolff–Parkinson–White syndrome

• Electrolyte and metabolic causes

  • Hyperkalemia

  • Severe electrolyte disturbances

  • Acid–base abnormalities affecting myocardial conduction

• Structural heart disease

  • Ventricular hypertrophy

  • Cardiomyopathy

  • Myocardial fibrosis

  • Ischemic heart disease

  • Prior myocardial infarction

  • Cardiac amyloidosis

  • Infiltrative cardiomyopathies

• Medication and toxin-related causes

  • Tricyclic antidepressants

  • Sodium-channel blocking medications

  • Class I antiarrhythmic drugs

  • Other cardiotoxic substances affecting ventricular conduction

• Device-related causes

  • Pacemaker rhythm

  • Implantable cardiac device-related ventricular activation patterns

• Other causes

  • Myocarditis

  • Congenital conduction abnormalities

  • Age-related degeneration of the cardiac conduction system

  • Idiopathic intraventricular conduction delay