CVS Flashcards
Normal range for axis?
-30 to +90
Lead I (0), II (60), and III (120) all positive
Lead II most positive
AVR most negative
Right axis deviation suggested by?
I (0) and AVL (-30) -ve
III (120) and AVF (90) +ve
Left axis deviation suggested by?
RVF (90) and II and III -ve
I and AVL +ve
What is the pathological significance of R and L axis deviation?
L axis deviation isn’t significant unless II is negative
Then suggests LVH??
R axis deviation is always pathological and suggests RVH, COPD, PE
Pacemaker change to ECG?
Spikes before each complex AND:
If ventricular PM, wide QRS as “ectopic”
If atrial PM, spike before P and narrow QRS
Cause of syncope?
TLOC due to global cerebral hypoperfusion
Use of tilt table test?
Syncope and dysautomnia e.g. DM, AIDS, PD, GBS, ETOH
Reflex / neurally mediated / vasovagal syncope?
Low BP e.g. due to standing up, low NaCl diet, heat, and then a stressor causes sympathetic activation to match the “fight or flight” requirement for cardiac output.
The CO rise fails as CBV is low, and then vagal response to dampen down the sympathetic outflow causes decreased HR, CO and fainting.
ABNORMAL TTT
Cardiac syncope?
NORMAL TTT
Heart beats too slow, too fast or too irregularly to supply blood to the brain
Brady e.g. heart blocks
Tachy e.g. SVT (wpw), VT (HR>100 + 3 consecutive premature beats)
Slow and fast arrythmias alternating due to SAN dysfunction
“tachy-brady syndrome”
Presyncopal symptoms + syncope
Sick sinus syndrome
Sudden TLOC +/- seizures without warning; around 30s LOC and negative TTT.
ECG shows AV BLOCK, asystole or VF during attacks
Stokes-Adams attack
Subclavian steal syndrome
Subclavian artery is resistanct to blood flow so reroutes up via vertebrals of carotics and back down into subclavian via collaterals - decreased perfusion to brain
Cervical rib or atherosclerosis
BP different in both arms
Wolf-parkinson Whyte syndrome (WPW)
SHORT PR
WIDENED QRS
SLURRED QRS UPSTROKE
ECG: “delta wave”
Due to some electrical activity skipping down the bundle of Kent and avoiding usual AVN delay, but some still being delayed the normal way.
Tx by cardioversion / catheter RFA
Syncope first line ix?
ECG
Ambulatory ECG
TTT if autonomic /vasovagal suspected
Where do you place ECG leads?
V1 = 4th IC space R side V2 = 4th IC space L side v3 = between V2 and V4 V4 = 5th IC space MCL V5 = half way V4 to V6 V6 = level with V4 MAL
P wave
Depolarisation of atria from SAN down
Upward in lead 2
PR interval
Delay of depolarisation at AVN + atrial depolarisation
QRS complex
Q = first negative; not in all leads R = first positive S = always follows R
Q = due to septum depolarising first after AV from L to R hence down in L2
R = depolarisation down bundles toward L2
S = depolarisation up the buncles
T wave
Ventricular repolariation
Always positive in healthy heart
QT interval
Prolonged QRS suggests?
Blockage or lack of use of bundles of His
Atrial flutter loosk like and caused by?
Saw tooth
Depolarisation chasing itself around FO
Decreased PR likely cause?
WPW (accessory bundle)
Increased PR likely cause?
1st degree block
2nd degree type 1 block
Normal PR pathology?
2nd degree type 2
Complete heart block
Bundle branch blocks
RBBB or LBBB pathologies?
RBBB can be normal
LBBB always pathological
Ventricular fibrillation looks like?
No discernable P, QRS, or T waves
Needs defib or death!
VT
Broad complex tachycardia originating in ventricles
May present as decreased BP, collapse, cardiac arrest
Requires cardioversion
Can degenerate to VF which is life threatening
Atrial flutter
Supra-ventricular narrow-complex tachycardia
“re-entry circuit” - depolarisation chasing itself around PO
Atrial rate around 300 and vent rate commonly around 150 (2:1)
Atrial fibrillation
Lack of P waves
Irregularly irregular
Narrow QRS complexes
TdP
“R on T”
