ECGs Flashcards
What does the ECG represent?
Electrical events of the cardiac cycle
What are the steps of heart conduction?
- An action potential is created by the SAN 2. The wave of excitation spreads across the atria, causing them to contract (right to left) 3. AVN 4. Bundle of His, down interventricular septum 5.The bundle of His and the Purkinje fibres spread the wave impulses along the ventricles
What are the pacemakers of the heart?
Sinoatrial node, atrioventricular node and ventricular cells
What is the dominant pacemaker and what is it’s intrinsic rate?
Sinoatrial node, 60-100bpm
What is the backup pacemaker and what is its intrinsic rate?
Atrioventricular node, 40-60bpm
What is the intrinsic rate of ventricular cells?
20-45bpm
What does the P wave represent?
Atrial depolarisation
What does the QRS represent?
Ventricular depolarisation
What does the T wave represent?
Ventricular repolarisation
What does the PR interval represent?
It starts from the P wave to the QRS complex. Atrial depolarisation and delay in AV junction (AV node/Bundle of His)
What does the ST segment represent?
It represent the isoelectric part of repolarisation
What does the QT interval represent?
From ventricular depolarisation to completion of the repolarisation of the ventricles
On ECG paper what time period does one small horizontal box represent?
0.04s (40ms)
On ECG paper what time period does one large horizontal box represent?
0.20s (200ms)
On ECG paper what does 1 large vertical box represent?
0.5mV
