Electrocardiography Flashcards
what is ECG useful in diagnosing?
- Conduction abnormalities
- Structural abnormalities
- Perfusion abnormalities
what are the benefits of an ECG?
- Relatively cheap and easy to undertake
- Reproducible between people and centres
- Quick turn around on results/report
what is a vector?
- Quantity that has both magnitude and direction
- Represented by arrow in net direction of movement, where size represents magnitude
what are the different elements of an ECG?
draw a normal cardic cycle on an ECG and the changes in pressure in aorta, atrium and ventricle throughout.
what are the different aspects of the heart involved in the cardiac cycle?
where do the electrodes go on an ECG?
what aspect do each lead view on the heart
on an ECG which section corresponds to which view of the heart?
what are the different cardiac vectors?
what time does each square represent on an ECG?
which artery is measured in each section of an ECG?
lateral =Left circumflex artery
inferior and anterior= right coronary artery
septal= left anterior descending artery
how do you calculate the different intervals in an ECG:
what is a normal R-R interval?
0.6-1.2s
what is a normal p wave?
80ms
what is a normal P-R interval?
120-200ms
what is a normal QRS duration?
<120ms
what is a normal QT interval?
<420ms
what is a normal T wave duration?
160ms
what is a normal heart rate?
60-100bpm
what information is required to calculate a QRS axis?
requires an augmented lead perpendicular to it
what is an augmented lead?
uses one fixed lead and one which is half the distance between another
what should a normal cardiac axis be between?
-30 and +90
how do you calculate the cardiac axis?
cardiac axis is reported relative to 0 degrees
so if using lead II which is at 60 deg then subtract answer from 60 deg
what is the sinus rhythm generated by?
sinoatrial node
how do you calculate heart rate?
300/ number of big squares S-S
what is this rhythm and features?
Sinus Rhythm:
- Each p-wave is followed by QRS wave (1:1)
- Rate is regular (even R-R intervals) and normal
what is this rhythm and its features?
Sinus Bradycardia:
- Each p-wave followed by QRS wave (1:1)
- Rate regular (even R-R intervals) and SLOW
Can be healthy (caused by medication or vagal stimulation)
what is this rhythm and its features?
Sinus tachycardia:
- Each p-wave followed by QRS wave (1:1)
- Rate is regular and FAST
- Often physiological response i.e. secondary (medication, excitation)
what is this rhythm and its features?
Sinus arrhythmia:
- Each p-wave followed by QRS wave
- Rate IRREGULAR and normal-ish
- R-R interval varies within breathing cycle
what is this rhythm and its features?
Atrial fibrillation:
- Oscillating baseline- atria contracting asynchronously
- Rhythm can be IRREGULAR and may be SLOW
- Turbulent flow pattern increases clot risk
- Atria not essential for cardiac cycle
what is this wave and its features?
Atrial Flutter:
- Regular saw-toothed pattern in baseline (II, III and aVF)
- Atrial to ventricular beats at 2:1 ratio, 3:1 ratio or higher
- Saw toothed not always visible in all leads
what is this wave and its features?
First degree heart block:
- Prolonged PR segment/ interval caused by slower AV conduction
- Regular rhythm (1:1 ratio P-wave to QRS)
- Most benign heart block but progressive disease or aging)
what is this wave and its features?
Second degree Heart Block: (Mobitz I)
- Gradual prolongation of the PR interval until a beat skipped
- Most P-waves followed by QRS but some p-waves are not
- Regularly irregular, caused by diseased AV node
- Also called Wencheback
what is this wave and its features?
Second degree heart block (Mobitz II)
- P-waves regular, but only some followed by QRS
- No P-R prolongation
- Regularly irregular ratio successes to failures or random
- Can rapidly deteriorate into 3rd degree heart block
- Usually dropped in bundle of His or bundle branches
what is this wave and its features?
Third degree (complete) heart block)
- P-waves regular, QRS regular but independent of each other
- P-waves can be hidden within bigger vectors
- Non-sinus rhythm
- Pumping pf ventricles being determined by ventricles themselves rather than AV node
what is this wave and its features?
Ventricular tachycardia:
- P-waves hidden- dissociated atrial rhythm
- Rate regular and fast
- High risk deteriorating into fibrillation (cardiac arrest)
- Shockable rhythm (defibrillators widely available)
what is this wave and its features?
Ventricular fibrillation:
- Heart rate irregular and 250bpm or above
- Heart unable to generate an output
- Shockable rhythm
what is this wave and its features?
ST elevation:
- P-waves visible and always followed by QRS
- Rhythm is regular and rate is normal (85bpm)
- ST segment is elevated >2mm above isoelectric line
- Caused by infarction (tissue death caused by hypoperfusion)
what is this wave and its features?
ST depression:
- P waves visible and always followed by QRS
- Rhythm regular and rate normal (95bpm)
- ST segment is depressed >2mm below isoelectric line
- Caused by myocardial ischemia (coronary insufficiency)
