Electrocardiograms
7.8 iii) Understand how the use of electrocardiograms (ECGs) can aid the diagnosis of cardiovascular
disease (CVD) and other heart conditions.
Electrocardiographs
• Electrocardiograph: A machine that record the electrical activity of the heart.
• Heart muscle depolarises when it contracts and repolarises when it relaxes.
• An electrocardiograph records changes in electrical charge using electrodes placed on the chest.
• A trace produced by an electrocardiograph is called an electrocardiogram (ECG).
Electrocardiograms (ECGs)
• P Wave: Depolarisation/contraction of the atria (atrial systole); initiated by the SAN.
• PR Interval: Time for impulses to be conducted from the SAN across the atria to the ventricles,
through the AVN.
• QRS Complex: Depolarisation/contraction of the ventricles (ventricular systole).
• T Wave: Repolarisation/relaxation of the ventricles (diastole).
Heart Conditions
• Tachycardia: Increased heart rate (>100bpm).
• Bradycardia: Reduced heart rate (<60pbm).
• Fibrillation: Irregular heart beat – atria and ventricles have lost their rhythm.
• Ischaemia: Heart muscle does not receive blood due to atherosclerosis blocking coronary arteries.
15
7.8 iii) Understand how the use of electrocardiograms (ECGs) can aid the diagnosis of cardiovascular
disease (CVD) and other heart conditions.
Electrocardiographs
• Electrocardiograph: A machine that record the electrical activity of the heart.
• Heart muscle depolarises when it contracts and repolarises when it relaxes.
• An electrocardiograph records changes in electrical charge using electrodes placed on the chest.
• A trace produced by an electrocardiograph is called an electrocardiogram (ECG).
Electrocardiograms (ECGs)
• P Wave: Depolarisation/contraction of the atria (atrial systole); initiated by the SAN.
• PR Interval: Time for impulses to be conducted from the SAN across the atria to the ventricles,
through the AVN.
• QRS Complex: Depolarisation/contraction of the ventricles (ventricular systole).
• T Wave: Repolarisation/relaxation of the ventricles (diastole).
Heart Conditions
• Tachycardia: Increased heart rate (>100bpm).
• Bradycardia: Reduced heart rate (<60pbm).
• Fibrillation: Irregular heart beat – atria and ventricles have lost their rhythm.
• Ischaemia: Heart muscle does not receive blood due to atherosclerosis blocking coronary arteries.
15
