ECG Flashcards
What can an ECG tell us? Advantages?
Structural & perfusion abnormalities. Cheap & easy. Reproducible. Quick results
How is an ECG done? What are leads and what can we see in each?
Electrodes placed on body with cables and wires. Leads are conceptual perspectives of the heart from different angles positions. We can see the electrical activity of the heart from that position
What is a cardiac vector? What happens if no electrical activity? What does steepness of the line show? Upward vs donward deflection? Width of deflection? More deflection?
Cardiac vectors have magnitude and direction. If no electrical activity no deflection - isoelectric. Steepness of line shows velocity of AP. Steeper - faster. Upward deflection is electrical activity towards positive electrode - downwards towards negative. Width shows duration of event. More deflection = more muscle.
P wave meaning?
Atrial depolarisation
QRS?
Ventricular depolarisation
T wave?
Ventricular repolarisation
What direction lead II?
direction of heart
What does SA node do and cause? AV node creates what? Bundle of his? Purkinke fibres?
SA node generates an electrical signal that causes the upper heart chambers (atria) to contract. The signal then passes through the AV (atrioventricular) node to the lower heart chambers (ventricles), causing them to contract, or pump.
AV node bridge between atria and ventricles create delay so they contract with delay between them. -Bundle of his - bundle branches for septal depolarisation. Purkinjke fibres cause ventricular depolarisation, s wave created by purkinje fibres going u[ sides of myocardium (late depolarisation). Repolarisation of heart (other way)
What is S wave?
created by purkinje fibres going up sides of myocardium (late depolarisaiton)
Why is T wave positive deflection if it is repolarisation?
Because it is going in the opposite direction of the heart.
Where are electrodes placed?
V1 right sternal border 4th ICS. V2 left sternal border 4th ICS. V3 between v2 and v4. v4 midclavicular line 5th Ics. V5 anterior axillary line at level of v4. v6 mid-axillary line at level of v4
How to you read polarity? What lead each direction?
Left to right and top to bottom. Lead I right arm to left arm. Lead II right arm to left leg. Lead III left arm to left leg.
View and artery of each lead/electrode?
Lead II, lead III, avF - inferior leads - inferior wall of heart - right coronary artery. Lead I, V5,v6, avl - lateral leads - left circumflex artery. V1 v2 septal leads - left anterior descending artery. V3 and v4 - anterior leads - left anterior descending artery
How to calculate rate from ECG? what is normal?
300/big boxes or 1500/small boxes. Normal is 3-5 big boxes (60-100bpm)
Is asystole shockable?
no
What is normal sinus rhythm?
Regular rate and normal (60-100bpm). Every p wave followed by qrs
What is sinus bradychardia and potential causes?
Slow rate but regular. Less than 60bpm. Can be healthy, due to medications or vagal stimulation.
What is sinus tachycardia and potential causes?
Fast but regular. Above 100bpm. Usually secondary to physiological response.
What is sinus arrythmia?
Rate irregular and nomalish. R-R intervals vary with breathing cycle but each p wave followed by qrs.
What is atrial fibrillation and what is seen on ECG? increased risk of what?
Atrial fibrillation is an oscilating baseline because atria are contracting asynchronously. Rhythm can be irregular and rate may be slow. Turbulent flow pattern increases clot risk.
What is atrial flutter and what is seen on ECG?
Regular saw tooth pattern in baselione (inferior leads). Atrial to ventricular beats may be 2:1 ratio or 3:1 ratio or more
What is a normal PR interval?
0.12-0.2 s (3-5 little boxes)
What is first degree heart block? How is it seen on ECG? Causes?
Prolonged PR segment due to slower AV conduction. All p waves followed by qrs. Regular rhythm. Most benign but progressive disease of ageing
What is second degree heart block mobitz I and what is seen on ECG? Cause?
Gradual prolongation of PR interval until beat skipped. Regylarly irregular. Diseased AV node
What is second degree heart block mobitz II and seen on ECG? Cause?
P waves regular but some not followed by QRS - no PR prolongation. Regularly irregular. Can deteriorate into 3rd degree heart block
What is third degree heart block and ECG? What is needed?
P waves regular qrs regular but no relationship between the 2. p waves can be hidden within bigger vectors. Need back up pacemaker
What is ventricular tachycardia? ECG? Risk of? Shockable?
p waves are hidden. Rate regular and fast. High risk of deteriorating to fibrillation. shockable
What is ventricular fibrillation & ECG? Shockable?
Heart rate irregular and fast (250bpm and above) cant generate output. shockable
What is ST elevation and ECG? Cause?
St elevated >2mm above isoelectric line. Caused by infarction (tissue death caused by hypoperfusion)
What is ST depression and ECG? Cause?
St depression >2mm below isoelectric line. Caused by myocardial ischaemia (coronary insufficiency)
difference between myocardial ischaemia and myocardial infarction?
myocardial ischaemia is decreased blood supply to heart muscle (eg atheroscleorsis). MI is the end-point of this where tissue dies because of lack of blood supply (aca untreated myocardial ischaemia)
What is a normal cardiac axis?
-30 to +90 degrees
