inside Medicine

The general anatomy of the cardiac conduction system (CCS) has been known for 100 years, but its complex and irregular three-dimensional (3D) geometry is not so well understood.

This is largely because the conducting tissue is not distinct from the surrounding tissue by dissection. The best descriptions of its anatomy come from studies based on serial sectioning of samples taken from the appropriate areas of the heart.

Low X-ray attenuation has formerly ruled out micro-computed tomography (micro-CT) for resolving internal structures of soft tissue, but staining with iodine, which has a high molecular weight, into those tissues enhances the differential attenuation of X-rays and allows visualisation of fine detail in embryos and skeletal muscle.

Here, with the use of a iodine based contrast agent (I2KI), we present contrast enhanced micro-CT images of cardiac tissue. Structures identified include the sinoatrial node (SAN) and the atrioventricular conduction axis: the penetrating bundle, His bundle, the bundle branches and the Purkinje network.

Although the current findings are consistent with existing anatomical representations, the representations shown here offer superior resolution and are the first 3D representations of the CCS within a single intact mammalian heart.


Stephenson RS, Boyett MR, Hart G, et al. (2012) Contrast Enhanced Micro-Computed Tomography Resolves the 3-Dimensional Morphology of the Cardiac Conduction System in Mammalian Hearts. PLoS ONE, 7, e35299.
Jarvis J, Stephenson RS. (2013) Studying the microanatomy of the heart in 3 dimensions: a practical update. Frontiers in Paediatric Cardiology, doi: 10.3389/fped.2013.00026.

Funding - Alder Hey Children's NHS foundation trust: The Cardiac Surgery Research Award