Bachmann's bundle (interatrial band)
Atrial conduction
Broad band of parallel atrial fibres leaving the anterior internodal pathway and crossing the roof of the interatrial groove to the left atrium — the main route by which the sinus impulse reaches the left atrium, keeping the two atria within about 40 ms of each other.
Traced from the start
- Sinoatrial node
- Bachmann's bundle (interatrial band)
Detail
- Conducts to
- Left atrial myocardium; the left atrium activates 30–40 ms after the right and writes the second half of the P wave
- Arterial supply
- Branches of the SA nodal artery and atrial branches of the RCA or LCx
- Alternative routes
- Slower muscular connections across the fossa ovalis rim and the coronary sinus musculature
When it goes wrong
Fibrosis of the bundle from age, hypertension, ischaemia or left atrial dilatation
Interatrial block: P wave 120 ms or longer; partial block gives a notched bifid P in II; advanced block gives a biphasic (positive then negative) P in II, III and aVF because the left atrium is activated retrogradely from below
Advanced interatrial block together with atrial tachyarrhythmias (Bayés syndrome)
Strong association with atrial fibrillation, cardioembolic stroke and cognitive decline — a P wave that predicts AF before it appears
Practise this structure
2 questions in the bank tagged Cardiac Conduction.
A 24-year-old man presents with two hours of palpitations. He is alert, has no chest pain, and his blood pressure is 124/76 mmHg. The radial pulse is regular at…
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A 46-year-old labourer is freed after six hours trapped beneath a collapsed brick wall. Both thighs are tense, swollen and tender, and he cannot move his toes.…
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