ECG's Flashcards
What is electrocardiography?
Process of recording electrical activity of the heart over a period of time
What is an electrode?
A conductive pad in contact with the body that forms an electric circuit with the ECG
What is a lead?
A connector to the electrode - source of measurement
More than 1 lead to 1 electrode
Describe the sequence of electrical events in the heart
SA node fires/depolarises.
Wave of depolarisation across both atria
AV node delays propagation of signal from atria to ventricles
Down bundle of His, does Purkinje fibres.
Once depolarisation has spread across the ventricles repolarisation starts
What do the P, QRS, T and U waves represent?
P - atrial depolarisation
QRS - ventricular depolarisation
T - ventricular repolarisation
U - Papillary muscle and Purkinje fibre repolarisation
What causes a negative deflection?
Depolarisation away from the positive electrode
Repolarisation towards the negative electrode
How to work out atrial HR from ECG?
Frequency of P waves
How to work out ventricular HR from ECG?
Frequency of QRS complex - distance between R waves
How will a muscle tremor appear on an ECG?
No clear P wave
What causes a sloping baseline on an ECG?
Respiration
What is bradycardia and when will it show symptoms?
Slow heart rate below 60bpm -symptoms below 50bpm
What is tachycardia?
Fast heart rate - above 100bpm
What can cause tachycardia?
Exercise or electrical problems with the heart
What arrhythmia?
Normal increase in HR during inspiration
What is atrial fibrillation how does it appear on ECG?
Abnormal HR
No clear P waves
Still clear R waves but less frequent because most impulses reach AV node in refractory period
