Topic 1 - ECG Flashcards
P-wave
Atrial depolarization
(SA Node Firing)
QRS-Complex
Ventricular depolarization
T-wave
Ventricular repolarization
PQ-Segment
“Conduction time”
Time it takes for signal to go from SA node to the ventricles
ST-Segment
“On isoelectric line”
Myocardial infarctions usually show elevation/depression of ST segment (Low O2 to heart)
RR-Distance
Rhythmicity check
Where is atrial repolarization?
Hidden by the intensity of the QRS-complex
Step 1
Extrasystole
- Extra beats
- During relative refractory period
- Ventricular & Supraventricular
Ventricular: wide QRS + no P-wave
Supraventricular: normal QRS + no P-wave
Step 2
Rhythmicity
- Rhythmic or arrhythmic
- Small boxes * 0.04 seconds
- 60 / one cycle = HR
- Respiratory arrhythmia: HR increase (inhalation) HR decrease (exhalation)
Step 3
HR Calculation
- Rhythmic: HR = 60 / R-R Distance * 0.04s
- Extrasystole: ignore cycle
- Arrhythmic: measure 20cm (8 sec), record cycles, then cross multiply
Step 4
Rhythm generating center
- P-wave present and normal = SA Node
- Pacemaker spike = big spike!
Step 5
P-wave, T-wave, QRS-complex
- Amplitude (1 square = 0.1mv)
- Duration (1 square = 0.04 sec)
- Polarity: +ve up, -nve down
For QRS
- Amplitude start @ isoelectric line to R-wave peak
- Duration: Q to S
- Polarity: Q and S negative, R positive
Step 6
Conduction time (PQ-segment)
- Used clinically to check AV node health
- Duration: from P to Q
- AV node disease: abnormal PQ-segment
Step 7
Eindhoven’s Triangle
- Pick 2 or 3 R-R wave amplitudes from 2 or 3 different leads
- LAD: Left Axis Deviation due to Pregnancy, Obesity, Left Ventricular Hypertrophy
- RAD: Right Axis Deviation due to Situs Invertus or Right Ventricular Hypertrophy
- Find midpoint of leads, measure amp and draw parallel lines to the corner
- Intersection points show direction
