ECG Interpretation Flashcards
What are the two atrioventricular valves in the heart?
Mitral and tricuspid valves = open with ventricular diastole, close with ventricular systole
What are the two semilunar valves in the heart?
Aortic and pulmonary valves = open with ventricular systole, close with ventricular diastole
Where do the left and right coronary arteries originate?
From the coronary ostia = openings at the base of the aorta behind the aortic valve leaflets
When does passive filling of the ventricles take place?
During diastole = fill to 70% capacity
What is the normal range for stroke volume?
60-130ml
What is preload?
Volume and stretch of ventricular myocardium at the end of diastole
What is afterload?
Amount of pressure against which the left ventricle must work during systole to open the aortic valve
Where is the brown lead placed?
Lower sternum in the 5th intercostal space
Where is the red lead placed?
Left mid-axillary line in the 5th intercostal space
Where is the black lead placed?
Upper sternum just below the sternal angle
Where is the white lead placed?
Right mid-axillary line in 5th intercostal space
Where is the green lead placed?
Anywhere
How much time does a small square represent on an ECG?
0.04 seconds
How much time does a large square on an ECG represent?
0.2 seconds
What are some features of the U wave?
Usually not visible
Smaller than the T wave when present
May indicate hypovolaemia
What are some reasons for interference during an ECG?
Patient movement, loose or defective electrode, improper grounding, faulty ECG apparatus
Where do all sinus rhythms originate from?
The SA node
What are the variants of sinus rhythm?
Normal sinus rhythm Sinus bradycardia Sinus tachycardia Sinus arrhythmia Sinus pause
What are some examples of circumstances where sinus bradycardia may occur?
In athletes, during sleep or in response to a vagal manoeuvre
What can sinus tachycardia precipitate?
Myocardial ischaemia or infarct
How does respiration impact sinus arrhythmias?
Rate increase with inspiration and decreases with expiration
What is a sinus pause?
Transient absence of P waves that lasts anywhere from 2s to several minutes
What can be used to treat a sinus pause?
Atropine or a pacemaker
Where do impulses originate from to cause atrial rhythms?
Atrial tissues or internodal pathways
