Electrocardiograms (ECGs) Flashcards
Electrocardiograms (ECGs)
A trace that records the electrical activity of the heart. Involves attaching sensors (electrodes) to the skin, the sensors pick up electrical activity that spreads out of the heart, through the tissues, and to the skin. The heart depolarises (looses electrical charge) when it contracts and repolarises (gains electrical charge) when it relaxes.
The trace of a healthy persons consists of
a series of waves labelled P, Q, R, S and T.
- P wave shows the excitation of the atria, caused by atrial contraction.
- The QRS complex indicates the stimulation and contraction of the ventricles.
- T waves shows the diastole (relaxation of atria/ventricles).
The height of a wave is bigger when more electrical charge is passing
through the heart (the waves show de/repolarisation of the heart). A bigger wave means a stronger contraction.
Ectopic heartbeat: ‘extra’ heartbeat, can be early atrial contraction (P waves) or ventricular contraction (QRS – as shown above).
Fibrillation: Very irregular heartbeat, atria or ventricle completely lose their rhythm and regular contraction.
