Workshop 4: ECG Flashcards
Why is the heart referred to as a dual pump?
It is an organ composed of two pumps.
The right side pumps to the lungs
The left side pumps to the body
Briefly describe Action Potential propagation in the heart
SA node is pacemaker - produces rhythmic action potentials
Contraction spreads through atria
AV node conduction is slow
Conduction through AV bundles & purkinje fibres is fast causing ventricular contraction
What is an ECG?
The electro-cardiogram is a graphic recording of the electrical impulses of the heart.
Tracks the cardiac cycle from depolarisation through reporlarisation
How are action potentials detected?
Electric current generated by myocardial depolarisation is naturally conducted to the surface of the body.
This can be detected by electrodes placed on the patient’s limbs and chest
Why is the electrical activity amplified?
For greater visibility
The waves are then printed on a moving graph paper strip
What can the ECG be used to diagnose?
Coronary artery disease
Myocardial infarction
Pericardial effusion
Pericarditis
Rhythm disturbances - as a result of ischaemia or electrolyte disturbances
disorders of impulse formation and conduction
also used to evaluate effect of certain drugs e.g. digoxin, quinidine, beta blockers
Describe the components of an ECG and what they mean
P wave: Impulse from SA node to atria (atrial depolarisation) Normal P wave indicated by normal size, shape and deflection
PR interval: Time taken from P wave to QRS complex. Normally 0.1-0.2s
QRS complex: indicates depolarisation of the ventricle. Normally <0.12s
ST segment: the interval between depolarisation and repolarisation. Normal if no elevation or depression
T wave: The recovery phase after contraction (venticular repolarisation) Normal if no inverions
In the 12 lead ECG, where do the different leads go?
V1- 4th intercostal space right sternal border
V2- 4th intercostal space left sternal border
V3- between leads V2 and V4
V4- 5th left intercostal space in midclavicular line
V5- horizontally even with V4, but in the anterior axillary line
V6- Horizontally even with V4 and V5 in the midaxillary line.
What is the midaxillary line?
The imaginary line that extends down from the middle of the patient’s armpit
What are heart sounds?
Vibrations created by the closing of the valves
What is the first heart sound?
Lower pitched ‘lub’
Due to closing of the atrioventricular valves (Mitral and Tricuspid)
Occurs in early phase of ventricular contraction
What is the second heart sound?
Higher pitched ‘dub’
Due to closing of semilunar valves (Aortic and pulmonary)
Occurs in relaxation phase of ventricular contraction
