Tut4: ECG Flashcards
(52 cards)
What are the components of the conduction system of the heart
Sino atrial node, Atrioventricular node BUndle of his Bacmann's bundle Left posterior bundle Right bundle Purkinje fibres
List the different waves of the ECG
P wave - atrial depolarisation
QRS complex - ventricular depolarisation
T wave - Ventricular repolarisation
U wave - unknown
Where is the Atrial repolarisation wave?
It is masked by the QRS complex as ventricles have larger mass.
Where does the first heart sound occur?
at the QRS complex
where does the second heart sound occur?
at the end of the t wave
What is the wigger’s diagram?
Diagram that encomapses relative pressures of the aorta, ventricles and atria
Relative ventricular volume
Relative ECG and heart sounds
Relative valve activity
of a cardiac cycle against time.
What is normal sinus rhythm?
Regular rhythm of 60-100bpm
Normal QRS duration
P wave visible before each QRS complex
P-R interval normal (<5 squares)
What does normal sinus rhythm indicate?
That electrical signal is generated by the sinus node and travelling in a normal fashion in the heart
What reason could account for a P-R interval longer than usual (i.e. more than 5 squares)
1st degree block
What is sinus bradycardia?
A heart rate less than 60bpm Rhythm is regular QRS duration is normal P wave is visible before each QRS complex P-R interval - normal
In what situation would sinus bradycardia be normal?
In a healthy athletic person.
What other reasons could cause sinus bradycardia?
Increased vagal tone from drug abuse,
Hypoglycaemia
Brain injury with increase intracranial pressure
What could benign sinus bradycardia be caused by?
patients on beta blockers
What features of the ECG would indicate a myocardial infarction?
S-T element does not go isoelectric which indicates infarction
Otherwise: Regular rhythm Rate: 80bpm normal QRS duration normal p wave
What is sinus tachycardia?
excessive heart rate above 100bpm originating from the SA node Regular rhythm Normal QRS duration P wave visible before each QRS complex normal P-R interval
Impulse generating heart beats are normal but they occur at a faster pace than normal
In what situation would sinus tachycardia be considered normal?
During exercise
What are some other causes of sinus tachycardia?
stress
fright
illness and exercise
Not a surprise if triggered in response to regulatory changes like shock,
but if there is no apparent trigger some medications may be required to suppress the rhythm
What is atrial fibrillation?
Atria fire electrical impulses in an irregular fashion causing irregular heart rhythm.
Irregularly irregular rhythm
Rate: usually 100-160bpm (slower if on medication)
QRS duration usually normal
P wave not distinguishable as atria are firing off all over the place
P-R interval not measureable
What causes atrial fibrillation?
Many sites within atria generate their own electrical impulses, resulting in irregular conduction of impulses to ventricles that generate the heart beat.
Irregular rhythm can be felt when palpating a pulse
What is the significance of QT prolongation
Electrical disturbance of the heart is caused by lengthening of duration of ventricular repolarisation, detected by ECG
Increases risk of TORSADE DE POINTES - type of ventricular tachyarrhythmia which can lead to VT and sudden death
What are the boundaries for QT prolongation in adult males and females?
Adult males:
QTc(ms)
450 PROLONGED
Adult females:
QTc(ms)
470 PROLONGED
QTc >500ms or an increase in the Qtc of >60ms generally considered to confer a high risk of torsade de pointes in an individual patient
What is QTc?
Corrected QT interval
What is torsades de pointes?
A form of ventricular tachycardia where the QRS amplitude varies, and the QRS complexes appear to twist around the baseline
Associated with a prolonged QT interval which may be congenital or acquired (e.g. from medication)
Not usually sustained, terminates spontaenously, but frequently recurs unless the underlying cause is corrected
May degenerate into sustained ventricular tachycardia or ventricular fibrillation
Life threatening arrhythmia and may present as sudden cardiac death in patients with structurally normal hearts
What is the Vaughan Williams Classification of Class I antiarhythmic drugs?
Class I- Sodium channel blockers
Reduces rate of depolarisation in phase 0
e.g. Lignocaine, Mexilitine