Bundle of His & branches

Looks like

A short cable of conducting fibres running from the AV node into the septum, then splitting into a left and a right branch.

What it does

Carries the beat fast down both sides of the septum to the ventricles.

Keeping it well

A block in one branch shows on an ECG; a new left-branch block with chest pain is treated like a heart attack. Block of both branches can progress to complete heart block and need a pacemaker.

Related conditions

• 22q11.2 deletion syndrome (DiGeorge)
• Amyloidosis (AL and ATTR)
• Aortic stenosis
• Atrial fibrillation
• Atrial flutter
• Botulism
• Brugada syndrome
• Cardiomyopathy (dilated, restrictive, arrhythmogenic)
• Chagas disease
• Chickenpox (varicella)
• Chronic neuropathic pain
• Chronic pain syndrome
• Congenital heart defects
• Coronary artery disease
• Diphtheria
• Down syndrome (trisomy 21)
• Eating disorders
• Extra heartbeats (ectopics and palpitations)
• Fainting (syncope)
• Fibromyalgia
• Friedreich's ataxia
• Guillain-Barré syndrome
• Heart block & bradycardia
• Heart failure
• Hypertrophic cardiomyopathy
• Hypothermia & frostbite
• Kawasaki disease
• Long QT syndrome
• Lyme disease
• Myasthenia gravis
• Myocarditis
• Orthostatic hypotension & POTS
• Panic disorder
• Pericardial effusion & tamponade
• Pericarditis
• Peripheral neuropathy
• Rabies
• Restless legs syndrome
• Shingles (herpes zoster)
• Shock (circulatory failure)
• Sudden cardiac arrest
• Sudden infant death syndrome
• Supraventricular tachycardia
• Takotsubo (stress) cardiomyopathy
• Tetanus
• Tuberous sclerosis complex
• Ventricular tachycardia
• Vitamin B1, C and other deficiencies
• Wolff–Parkinson–White syndrome