Hjerteledningen

Hjerteledningen, or the heart's electrical conduction system, is the network that generates and propagates electrical impulses to coordinate cardiac cycles. Its proper function ensures a regular heart rate and synchronized contraction of atria and ventricles.

Key structures include the sinoatrial (SA) node, the atrioventricular (AV) node, the bundle of His, the right and left bundle branches, and the Purkinje fibers. Internodal pathways connect the SA node to atrial tissue, enabling orderly atrial activation.

Conduction pathway: The SA node fires first, producing an impulse that spreads through atrial muscle, causing atrial contraction. The impulse reaches the AV node, where a brief delay allows ventricular filling. It then travels via the bundle of His and the Purkinje network to the ventricles, triggering ventricular contraction. Conduction velocity and refractory periods influence rhythm and synchrony.

Autonomic regulation: Sympathetic stimulation increases heart rate and conduction velocity; parasympathetic stimulation via the vagus nerve decreases rate. Electrolyte balance and ischemia can affect conduction.

Clinical relevance: Disturbances can cause bradycardia, tachycardia, or blocks (first-, second-, or third-degree AV block) and arrhythmias such as atrial fibrillation, ventricular tachycardia, or fibrillation. Diagnosis primarily uses electrocardiography (ECG); treatments may include medications, lifestyle changes, pacemakers, or ablation in some cases.