ECG Flashcards
What does the P wave represent?
The P wave is where the atria are full of blood, and the SA mode fires.
The electrical impulses leave the SA node and spread through the Atria causing contraction of the Atria. Blood is pumped through the AV valves and they become depolarised.
What does the PQ segment represent?
In the PQ segment, the impulses arrive at the AV node and are transmitted through the Bundle of His (AV bundle) which divide into left and right bundle branches, conducting impulses towards the Apex of the heart.
These signals are passed onto the Purkinje fibres which turn upwards and spread through the atrioventricular myocardium.
The atria here relax. This is to ensure that all blood is ejected into the ventricles before they can contract.
What happens in the QRS complex?
The atrioventricular valves close here, and the purkinje fibres transmit an impulse to the ventricular myocardium which causes ventricular contraction.
Here, blood is pumped through the semilunar valves which open.
The QRS complex marks the firing of the AV node and represents ventricular depolarisation.
What is an ECG?
An ECG is a composite recording of all of the action potentials that are produced by the nodes and cells of the myocardium.
Each wave or segment of the ECG corresponds to a specific event of the cardiac electrical cycle.
What does the Q wave represent?
The Q wave corresponds to the depolarisation of the inter-ventricular septum.
What is the R wave?
This is produced at the depolarisation of the main mass of the ventricles.
What does the S wave represent?
This represents the last phase of ventricular depolarisation at the base of the heart.
Atrial repolarisation also occurs during this time, but the signal is obscured by the large QRS complex.
What is the ST segment?
The ST segment reflects the plateau in the myocardial action potential. This is when the ventricles contract and pump blood.
What is the T wave?
Here, the ventricles repolarise and prepare for the next contraction.
The T wave report dents ventricular repolarisation immediately before a ventricular relaxation or a ventricular diastole.
When does atrial contraction/systole start?
Around 100 milliseconds after the P wave begins.
What does each cycle of an ECG represent?
One heart beat.
What are the concerns surrounding QT prolongation?
It is a warning of particular arrhythmia such as Torsade de Point.
It is linked with sudden death.
Close monitoring is needed, especially for those on high doses of antipsychotics.
The highest risk antipsychotic with QT prolongation is Thioridazine.
What chemicals in the body are in control of the heart rate?
Sodium and potassium levels determine the heart rate
