The conducting tissue of the heart is a specialised network of cells that generate and transmit the electrical impulses that coordinate each heartbeat. Unlike ordinary heart muscle cells, conducting cells are not primarily contractile; their function is to conduct electricity rapidly and reliably to ensure that the chambers of the heart contract in the correct sequence.
The main components of the cardiac conduction system are: the sinoatrial (SA) node (the heart’s natural pacemaker, located in the right atrium, which generates the electrical impulse initiating each heartbeat at a normal rate of 60 to 100 beats per minute at rest); the atrioventricular (AV) node (located at the junction of the atria and ventricles, which introduces a brief delay allowing the atria to complete contraction before the ventricles activate); the Bundle of His (transmitting the impulse from the AV node into the interventricular septum); the left and right bundle branches (dividing the impulse to supply each ventricle, where disease causes bundle branch block); and the Purkinje fibres (a fine network that delivers the impulse rapidly and simultaneously to all ventricular cells, ensuring coordinated contraction).
Disease or damage to conducting tissue can cause arrhythmias, including heart block, bundle branch block, ventricular tachycardia, and ventricular fibrillation.
Many inherited conditions causing sudden cardiac arrest in young people, such as long QT syndrome and Brugada syndrome, arise from abnormal ion channels in conducting tissue rather than from structural heart disease. This is why echocardiography alone can appear entirely normal in these patients despite their high arrhythmic risk.
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