(cardioresp) ecgs & rhythm disturbances Flashcards
name the 6 limb leads
lead I lead II lead III aVR aVL aVF
what is the angle of lead I?
0 degrees
what is the angle of lead II?
+60 degrees
what is the angle of lead III?
+120 degrees
what is the angle of lead aVF?
+90 degrees
what is the angle of lead aVR?
-150 degrees
bit random, excluded from the ECG artery territories
what is the angle of lead aVL?
-30 degrees
what is the normal cardiac axis?
-30 to 90 degrees
what is left axis deviation?
between -30 to -90 degrees
what is right axis deviation?
between 90 to 180 degrees
which leads are compared to work out cardiac axis?
!! perpendicular !! leads
- lead I + aVF
- lead II + aVL
- lead III + aVR
give two reasons why the heart would deviate from normal axis further to the right
1) increased muscle density on the right = right ventricular hypertrophy
2) infarction on the left (more disabled muscle = less healthy muscle on right)
why does COPD cause right ventricular hypertrophy?
COPD
= reduced lung ventilation
= reduced pO2
= regional vasoconstriction (hypoxic pulmonary vasoconstriction)
= increased pulmonary blood pressure
= the heart has to eject blood against a higher pressure
(hypoxic pulmonary vasoconstriction (HPV) is a homeostatic mechanism that is intrinsic to the pulmonary vasculature - normally hypoxia would cause vasodilation)
why is cardiac axis important?
tells us about the functional myocardium
how is an ECG reported?
1) rate & rhythm
2) P wave (presence, duration, P:QRS ratio)
3) P-R interval
4) QRS complex (duration)
5) S-T segment (elevation/depression)
6) T wave (duration, QT)
what does ST elevation in leads II, III and aVF indicate?
obstruction of RCA leading to a ST-elevated myocardial infarction (STEMI)
what does third-degree heart block look like on an ECG?
1) regular P waves and QRS complex (may not be in normal amounts)
2) no relationship bw P waves and QRS complexes
3) some P waves may be hidden in bigger vectors (!!! - classic, tell-tale sign)
what is characteristic of P waves in third-degree heart block on an ECG?
some P waves may be hidden in bigger vectors
when the line should be isoelectric but is not
what is a coronary angiogram and when is it done?
using X-ray imaging to study coronary vessels
by injecting a dye into them
for an individual with ST elevation in leads II, III, and aVF, what are the expected coronary angiogram results?
obstruction of the RCA
for a patient with an obstruction of the RCA, what treatment options are available?
1) coronary angioplasty
2) coronary artery bypass graft
what is a coronary angioplasty?
using a stent to widen the arterial lumen of the coronary arteries occluded by an atherosclerotic plaque
what is coronary artery bypass surgery?
taking a blood vessel from another part of the body and attaching it to the coronary artery above and below the narrowed area or blockage
= providing another path for blood flow
how does second-degree heart block (Mobitz I) look like on an ECG?
1) P-R elongation until a QRS complex is dropped
2) regularly irregular
how does second-degree heart block (Mobitz II) look like on an ECG?
1) no P-R elongation
2) random QRS complexes are dropped either in a regular pattern (2:1 etc) or randomly = regularly irregular
how can Mobitz II and third degree heart blocks be differentiated on an ECG?
both have regularity and no PR prolongation
BUT
- QRS complexes dropped regularly in Mobitz II but not in third-degree
- third-degree usually has P waves hidden in bigger vectors
which two aspects of the ECG are looked at the differentiate between Mobitz II and third degree?
1) P waves and P:QRS ratio
Mobitz II:
- P-wave with every QRS; but not vice versa
- rate will usually be regular
- PR interval regular
3rd Degree Block:
- may not be a P-wave with each QRS
- PR interval not regular with each PQRS
