Electrocardiograms (ECGs)

• It is possible to record the waves of excitation as they travel through the heart, place electrodes on the skin over opposite sides of the heart and a recording of the electrical potentials; electrocardiogram (ECG) plotted shows voltage against time
• P wave is atrial systole/contraction, QRS wave represents is ventricular systole/contraction and the T wave is diastole

  
• Sinus rhythm means the heart rate is normal, Tachycardia means heartbeats are closer together (faster-than-normal heart rate) and Bradycardia means heartbeats are further apart (slower-than-normal heart rate)
• Ectopic means n extra heartbeat visible or a single heartbeat that comes quicker/earlier than it should and Atrial Fibrillation means no P wave visible (atria are not contracting properly)
• Ventricular Fibrillation: No P wave, QRS complex or T wave seen, complete disorganisation of contraction; fatal unless electric shocks from a defibrillator can get the heart beating in a normal rhythm again