ECG2 Flashcards
What is the clinical relevance of ECG?
- Conduction abnormalities
-
structural abnormalities
- perfusion abnormalities
What are the advantages of using ECGs?
- cheaper
- easy to under take
- reproducible between people and centres
- quick turn around on results
What are leads in ECGS?
representation of electrical activity from a specific heart perspectic
What are cardiac vectors?
Represented by an arrow in the net direction of movement, size reflecting the magnitude
What does the steepness of the line denote?
The velocity
What are downward deflections towards?
Negative electrode
What does the isoelectric line represent?
no change in net voltage i.e vectors are perpendicular to lead
What does the width of the deflection show?
duration of event
What are upward deflections towards?
the positive electrode
Unipolar vs bipolar?
Number of physical electrodes
How are ECGs reported?
- rate and rhythm
- P-wave and PR interval
- QRS duration
- QRS axis
- ST segment
and cardiac axis
How is lead II positioned?
From Right Arm to Left Leg
Right arm being the negative electrode and left leg being the positive electrode
Why on a typical ECG is QRS wave an upwards deflection? (Lead II)
Because it represents electrical stimulation travelling through purkinje fibres towards apex ( downwards towards positive electrode ) = positive deflection
Where is lead I positioned?
Negative E = right arm
Positive E = left arm
Where is lead III positioned?
Negative E = Left arm
Positive E = left leg
Where is the aVR psotioned?
- augmented vector right (unipolar)
Negative E = n/a
Positive E = right wrist
Where is the aVL positioned?
- augmented vector left (unipolar)
Positive E = left wrist
Where is the aVF positioned?
- augmented vector foot
Positive electrode = Left foot
What is the rhythm strip on an ECG?
Lead II along the bottom for comparison
How many chest electrodes are there?
6
Where is V1 electrode placed?
Right sternal border
In the 4th intercostal space
Where is V2 electrode placed?
Left sternal border
In the 4th intercostal space
Where is V3 electrode placed?
Halfway between V2 and V4
Where is V4 electrode placed?
Mid-clavicular line
In the 5th intercostal space
Where is V5 electrode placed?
Anterior axillary line
at the level of V4
Where is V6 electrode placed?
Mid-axillary line
at the level of V4
Which artery corresponds with the aVR lead?
N/A
Which artery corresponds with the aVL lead?
Left circumflex artery
Which artery corresponds with the aVF lead?
Right Coronary artery
Which artery do chest leads V1-V4 correspond with?
Left anterior descending artery
Which leads correspond with the right coronary artery
Leads II + III
also, aVF
Which artery do chest leads V5-V6 correspond with?
Left circumflex artery
On an ECG, how many seconds does a single square correspond to?
5 small squares within a larger square
Small square = 0.04s
Cardiac axis?
///
What is a sinus rhythm?
- each P-wave is followed by QRS
- Rate is regular and normal
What is sinus bradycardia?
- Each P wave followed by QRS
Rate is regular and SLOW
- can be healthy, caused by medication or vagal stimulation
What is sinus tachycardia?
P wave is followed by QRS
rate regular and FAST
often physiological
What is sinus arrhythmia?
each p wave followed by QRS
Rate is IRREGULAR and normal
R-R interval varies with breathing cycle
What is atrial fibrillation?
Oscillating baseline - atria contract asynchonously
- rhythm can be irregular and rate my be slow
turbulent flow pattern increases CLOT RISK
atria not essential for cardiac cycle*
What is atrial flutter?
Regular saw tooth pattern in baseline (II,III,aVF)
atrial to ventricular beats at 2:1 ratio, 3:1 ratio or higher
Saw tooth NOT always visible on all leads
What is first degree hert block?
Prolonged PR segment/ i ntervel caused by slower AAV conduction
regular rhythm
Most benign heart block, but a progressive disease of ageing
What is second degree heart block?
gradual prolongation of PR interval until beat skipped
Most p -waves followed by QRS, some SOME P WAVES ARE NOT
Reguarly irregular, caused by diseased AV node
What is second degree Mobitz II Heart block?
P waves are regular but only some are followed by QRS
no P-R prolongation
reguarly irregular
can rapidly detoriate into 3rd degree heart block
What is 2nd degree heart block also known as ?
Wenckebach (mobitz I)
What is third degree heart block?
P waves are regular,
QRS are regular
No relationship between the two
A non-sinus rhythm
What is ventricular tachycardia?
P waves hidden due to dissociated atrial rhythm
Rate is regular and fast
At high risk of detoriating into fibrillation - cardiac arrest
Shockable rhythm : defibrillators
What is ventricular fibrillation?
Heart rate is irregular and 250 bpm and above
Heart unable to generate an output
Shockable rhythm
What is ST elevation?
P waves visible and always followed by QRS
Rhythm is regular and rate is normal
ST segment is elevated >2mm above isoelectric line
caused by infarction
What is ST depression?
P waves visible and always followed by QRS
ryhthm is regular and rate is normal
ST segment is depressed >2mm below isoelectric line
Caused by myocardial ischaemia
