1.5 The principles of electrophysiology
Normal electrical excitation via the specialised conduction pathway within the heart results in co-ordinated myocardial contraction and relaxation and is essential for efficient cardiac function. Control of the system by internal and higher homeostatic mechanisms results in a normal cardiac rhythm and alters heart rate to maintain an appropriate cardiac output. A knowledge of the anatomy of the normal conduction pathway and the basis of excitation of cells is fundamental to understanding normal and abnormal cardiac function and abnormalities of conduction and rhythm. An appreciation of the differences in the activation process in horses compared with humans and small animals is essential in order that the many misconceptions regarding interpretation of equine ECGs (electrocardiograms) are avoided.
1.5.1 Cellular physiology
1.5.2 The action potential
1.5.3 The conduction process
1.5.4 The cardiac electrical field
1.5.5 ECG lead systems
1.5.6 The ventricular depolarisation process