For anaesthetic planning the classification of lesions into the different pathophysiological principles is the most helpful. The four main pathologies are stenotic/obstructive lesions, regurgitant lesions, shunt lesions and mixing lesions. Complex cardiac disease can consist of more than one type of lesion and each needs to be assessed and planned for. An anaesthetist needs to be aware of the haemodynamic changes caused by anaesthetic drugs and techniques, how these changes influence the individual lesion and how to counteract them or change them when needed.