ECG Basics to Brilliance- initial pre-reading
ECG interpretation- The basics but in depth
ECG paper
(Passes under the pen at rate of 25mm/sec (so each little box is 1/25 of a second = 0.04 sec)
(1 Little box = 0.04sec
(1 Big box (5 little boxes) = 0.2 sec
(5 big boxes = 1 sec
Calibration box should be 10 mm high (2 big boxes) & 0.20 sec wide (1 big box)
Lead placement
(Limb leads I, II & III must be placed at least 10cm from the heart
Machine does vector manipulation to come up with aVR, aVF & aVL.
(Precordial leads (V1-V6)
Anatomy refresher- Angle of Louis (below manubrium) is next to the 2nd rib.
The space beneath 2nd rib is 2nd intercostal space. Space beneath 4th rib is 4th intercostal space.
|V1 |In the 4th intercostal space just to the right of the sternum |
|V2 |In the 4th intercostal space just to the left of the sternum. |
|V3 |Between leads V2 and V4. |
|V4 |In the 5th intercostal space in the mid-clavicular line. |
|V5 |Horizontally even with V4, in the left anterior axillary line. |
|V6 |Horizontally even with V4 and V5 in the midaxillary line. |
[pic]
Do right sided and posterior leads if patient presents with chest pain and any evidence of STEMI pattern in inferior leads, or ST depression in leads V1-V3.
Right ventricular leads placement
Place the standard leads V1-V6 in a mirror image position on the right side of the anterior chest.
V4R, at 5th right intercostal space in mid-clavicular line, is most useful lead to detect RV ST elevation.
[pic]
[pic]
Isoelectric baseline
(Line between the T wave of previous complex & start of the P wave of the next complex
[pic]
Waves
(= Deflections from the baseline
(Tall or deep waves/deflections in QRS complexes are given capital letters, small waves/deflections are given small letters.
Q wave- 1st negative wave after P wave
R wave- 1st positive deflection after the P
S wave- 1st negative component after an R wave
If another upward component- R’, next negative component is S’.
[pic]
Conduction ratio P:QRS
Number of atrial contractions to ventricular contractions
Eg 3:2 conduction means that for every 3 P waves created, 2 are conducted, and 1 is blocked.
Block ratio P:QRS is different to conduction ratio
Eg 3:2 block means that for every 3 P waves created, 2 are blocked, and only one is conducted.
P waves- in depth
●Ascending limb is RA (right atrium) depolarisation, descending limb is LA (left atrium) depolarisation.
Normal Duration 0.08-0.11sec (so < 3mm in width)
Amplitude 2.5mm), peaked P waves (esp II, III, aVF)
Causes: lung disease eg COPD
P mitrale
Left atrial enlargement
●Double peaked apex. Distance between 2 peaks is > 0.04 sec (> 1 little square)
Most prominent I, aVL, V5/V6 (the leftward leads)
●Duration > 0.11 sec
[pic]
|P wave present & upright in I, II, III, aVF, |P wave present but may be upright OR inverted|P wave may be present but always inverted |
|V5 & V6 | | |
|Sinus brady, SR, sinus tachy, sinus arrythmia|Ectopic atrial rhythm |Junctional rhythm |
| |(rate 100 bpm) | |
| |Wandering atrial pacemaker |Junctional tachycardia |
| |(rate < 100 bpm) | |
| |Multifocal atrial tachycardia |AVNRT |
| |(rate > 100 bpm) | |
| |Premature atrial complexes |AVRT |
| |Escape atrial complexes | |
|PR segment |The line between the end of P wave & start of QRS. |
| |Normally at baseline or depressed (line below baseline) < 0.8mm (< 1 small square) |
| |Pathologically depressed in pericarditis. |
|PR interval |Start of P wave to start of QRS. |
| |From initiation of SA node impulse up to start of ventricular depolarisation. |
| |Normal: 0.12-0.2 sec (3-5 little boxes) |
| | |
| |Short PR: 0.2 sec |
| |●If each PR interval is the same, and followed by a QRS complex- 1st degree AV block |
| | |
| |If PR interval varies (of any duration): |
| |(1) wandering atrial pacemaker (rate < 100) OR multifocal atrial tachycardia (rate > 100) |
| |(2) premature atrial contractions |
| |(3) 2nd degree heart block, 3rd degree block |
|QRS |Indicates ventricular depolarisation |
| |Determined by the widest complex, usually V2/V3. |
| |Normal ................
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