ECG tutorials Flashcards
What are the 2 causes of wide QRS?
- bundle branch block (due to cell to cell conduction instead of Purkinje system)
- Ventricular origin (not along the conducting system and hence cell to cell conduction): ventricular premature beat, ventricular tachycardia, ventricular escape beat
What does right axis deviation look like in the ECG?
Negative lead I & aVL
Positive lead III & aVF
What are the 5 causes of narrow QRS tachycardia?
- atrial fibrillation (10% of population >80yo)
- sinus tachycardia
- ## atrioventricular nodal reentrant tachycardia
Describe atrial fibrillation
- irregularly irregular pulse (c.f. regularly irregular pulse may be due to ectopic beats)
- no p waves (atrium is not depolarised in an organised fashion)
- fast & chaotic within atria
- high frequency signals around pulmonary veins (pulmonary vein isolation by electrophysiology; electrocuting all around pulmonary veins & will cure AF)
- conduction via AV node is selective as it is hit irregularly by the atria & due to refractory period (AV node has a longer refractory period than atria)
- ventricular rhythm is determined on the refractory period of AV node
- Px: palpitation, dyspnoea (due to reduced filling time -> high end diastolic pressure in atria -> back flow into pulmonary veins & high pressure -> fluid out of pulmonary capillaries; congestion & poor diffusion)
- mostly asymptomatic. Only symptomatic with tachycardia
- worse symptoms in anyone who already have trouble filling the heart e.g. left ventricular hypertrophy, mitral stenosis, HOCM
Rate control (by working on the AV node)
- Non-dihydropyridine, verapamil, diltiazem
- beta blockers
- digoxin
Rhythm control:
- amiodarone
- sotalol
What is the scoring system for major bleeding risk in pt who are anticoagulated?
HAS-BLED score
- Hypertension history (>160mmHg systolic)
- Abnormal renal/liver function
- Stroke Hx
- Bleeding Hx (anaemia/predisposition to bleeding)
- Labile INRs
- Elderly (>65yo)
- Drug therapy (antiplatelet agent, NSAID)
- Alcohol intake (>8 drinks/week)
Early beat, Wide QRS & funny looking T wave is likely to be:
Ventricular ectopic/premature beat
What are the group of leads?
- inferior
- anterior
- lateral
Inferior: II, III, aVF (right coronary artery)
Anterior: V1-5 (LAD)
Lateral: I, aVL, V5, V6 (circumflex)
What does ST elevation mean?
Myocardial infarction directly underneath the group of leads (a lead above the part of infarction receives the current going through the infarction). There’s reciprocal depression as the current going through the infarction at another site is perceived as going away from it.
- Transmural infarction
- Pericarditis
- Physiological
What often blocks/occludes a coronary artery?
Thrombus (NOT atheroma) due to a plaque rupture (fibrous cap destruction exposing the underlying collagen, cholesterol etc, aggregating platelets).
1% of MI due to emboli
1% of MI due to artery dissection
Unknown mechanisms:
- why the plaques rupture.
- why the person has a plaque at that particular point.
Is there a screening test for CAD?
No. You cannot pick up CAD early.
If you are not symptomatic, exercise tests will not detect the small plaques.
What is the side effect of tPA as a Rx for AMI?
Major bleeding. E.g. 1% intracerebral bleeding
It reduces morbidity by >5% in MI. Benefit far outweights than the SE. Hence only give if you’re really sure if the pt is having an AMI (not an angina) by looking at the ECG STEMI. (not in a NSTEMI)
When does T inversion occur (in STEMI & NSTEMI)?
24 hours post STEMI.
NSTEMI: Might have normal ECG, ST depression or T wave inversion.
(3) Rx of NSTEMI
This could be unstable angina. Rx: - antianginal -anti coagulant - antipaltelet
(1) Rx of STEMI
Definite diagnosis of AMI
Rx:
Urgent reperfusion; thrombolysis or PCI
Where does the right bundle run? Hence what area infarct will cause RBBB?
In the septum.
Anterior septal infarct will cause right bundle branch block
