Electrocardiography Flashcards
describe pathway of limb lead I
between L and R arms
describe pathway of limb lead II
along the long axis of the heart, between L foot and R arm
describe pathway of limb lead III
between L foot and L arm
Which plane are the limb leads in?
frontal plane
Which plane are the augmented vector leads in?
frontal plane
Which plane are the precordial/chest leads in?
horizontal plane
Where are the electrodes placed for the standard limb leads?
L foot, L and R arms
Where are the electrodes placed for the augmented vector leads, and how does it work?
positive electrodes at L foot, L and R arms
negative central terminus calculated mathematically, near centre of heart
Where are the electrodes placed for the precordial/chest leads, and how does it work?
six positive electrodes placed: RA to apex, and around lateral left ribs
negative central terminus calculated mathematically, near centre of heart
electrical event associated with P wave
atrial depolarization
mechanical event occurring during P wave
end of diastasis
PR interval
less than 200 ms
electrical events associated with PR segment
atrial depolarization, impulse continues through the AV node, stops at Bundle of His
QRS interval
less than 100 ms
electrical event associated with the QRS complex
ventricular depolarization (bundle branches and Purkinje fibres)
component of ECG associated with bundle branch stimulation
QRS complex
component of ECG associated with atrial depolarization only
P wave
component of ECG associated with atrial contraction
PR segment
factors that affect QRS amplitude/height
directly related: muscle thickness
inversely related: body mass, pericardium (thickness and amount of fluid)
affect of body mass on QRS amplitude
larger body habitus = greater distance from electrodes = poor through-energy/muffled conduction
affect of pericardial effusion on QRS amplitude
more paricardial fluid = greater distance from electrodes = poor through-energy/muffled conduction
affect of thickened pericardium on QRS amplitude
poor through-energy/muffled conduction
affect of hypertrophic cardiomyopathy on QRS amplitude
more muscle = more impulses = more intensity
component of ECG associated with ventricular depolarization
QRS complex
component of ECG associated with Purkinje fibre stimulation
QRS complex
electrical event associated with the ST segment
ventricular electrical plateau before repolarization, and atrial repolarization
mechanical event occurring during QRS complex
atrial contraction (late filling)
electrical event associated with the T wave
ventricular repolarization and atrial resting phase
mechanical event occurring during ST segment
ventricular contraction
mechanical event occurring during T wave
end of ventricular contraction and IVRT
When does early filling occur on the ECG?
during the ventricular resting phase, in the electrical plateau between the T and the P waves
QT interval
less than 440 ms
includes QRS and ST segments, QRS=100ms, systole=300ms
ST interval
variable (though systole/ventricular contraction is about 300 ms)
Which lead is used to diagnose rhythms in most echocardiography labs?
limb lead II
