ECG 1 Flashcards
(33 cards)
a vector is
a quantity that has both magnitude and direction
the isoelectric line represents
no net change in voltage
width of the deflection denotes the
duration of the event
the EGC cycle waves and why do they happen? summaries
P = the electrical signal that stimulates contraction of the atria (atrial systole0 QRS = electrical signal that stimulates contraction of the ventricles T = the electrical signal that signifies relaxation of the ventricles
draw the conduction pathway/wave for a sinoatrial node
see example
p wave
Sinoatrial node (SAN)
Autorhythmic myocytes
Atrial depolarisation
horizontal line after P wave
Arioventricular node (AVN)
AVN depolarisation
Isoelectric ECG
Slow signal transduction
very small horizontal line before Q wave
Bundle of His
Rapid conduction
Insulated
downward line of Q wave
Bundle branches
Septal depolarisation
R peak
Purkinje fibres (1) ventricular depolarisation
downward line of S wave
Purkinje fibres (2) Late ventricular depolarisation
horizontal line after S wave
Fully depolarised ventricles
Isoelectric ECG
T wave
Repolarisation
Ventricular repolarisation
size of electrocardiogram squares
each mini square:
-0.04s wide and 0.5 mV tall
each big square;
-each 0.2s wide and 0.1mV tall
summarise the conduction system
- role of SA node
- role of AV node
- role of Bundle of His
The SA node spontaneously depolarises to trigger cardiac cycle
Specialist conductive pathways conduct through atria and to AV node
AV node slows transmission
Bundle of His & branches (composed of Purkinje fibres) insulate signal and carry to bottom of ventricles
Purkinje fibres then spread through myocardium (from endocardium to epicardium) to apex then up to base of ventricles
- which limbs are the sticky electrodes placed on
Sticky electrodes need special placement on limbs (RA, LA and LL; Einthoven’s triangle) and chest (V1-V6; using anatomical landmarks)
Cables attach to electrodes to transmit signal to recorder
Leads are visual representations of cardiac activity in the coronal and horizontal planes
All leads have a fixed cathode (+ve) and some have a fixed anode (I, II, III) and some have a virtual anode (aVR, aVL, aVF, V1-V6)
- which is the most commonly used lead
- what is the single largest electrical event
Lead II is the most commonly used single lead
Specific durations and amplitudes of specific waveforms can provide information about the heart
Cardiac axis gives the net vector of the R-wave, which is usually the largest electrical event as it is the biggest amount of muscle – normal range is -30 to +90 degrees
electrode placement
- the rule of L’s
Lead I: right arm to Left arm
Lead II: right arm to Left Leg
Lead III: Left arm to Left Leg
Where are the following nodes attached V1 V2 V3 V4 V5 V6
V1 = right sternal border of the 4th intercostal space V2 = left sternal border in the 4th intercostal space V3 = halfway between V2 and V4 V4 = mid clavicular line in the 5th intercostal space V5 = anterior axillary line at the level of V4 V6 = mid-axillary line at the level of V4
R-R interval
0.6 - 1.2 s
P wave duration
80 ms
P-R interval
120-200 ms
QRS duration
<120 ms (80 -120 ms)
QT interval
420 ms
