ECG Pro Flashcards
What are you likely to see on an ECG in someone with atrial fibrillation? What causes this?
Chaotic atria - no p waves, ‘wavy baseline’
SA node inactive, chaotic atrial activity acting as pacemaker - no p waves, wavy baseline
Irregular pulse as AV node receiving/conducting random signals from atria
What are 3 features on an ECG that can be seen during an MI?
- ST-elevation (dying tissue, T wave may have inverted)
- Pathological Q waves > 2mm deep
- Inverted T waves
What does the tombstone sign on an ECG indicate?
ST-elevation, MI
Why would a T wave invert?
dead myocytes repolarize the wrong way
What typically causes a R axis deviation? What does this mean?
R ventricular hypertrophy and pulmonary conditions
Depolarisation distorted tp R
What usually causes a L axis deviation?
Conduction defects (not increased LV mass)
What are the features of RBBB on an ECG? Which leads should you look at?
- Bunny ears: V1, maybe V2 and 3
- slurred S wave in lateral leads: 1, aVL and V6
- QRS duration>120 ms
What defines ST elevation?
S starts 2 small squares above isoelectric baseline in 2 consecutive chest leads
What does a ‘tented’ T wave indicate?
When is it normal to see an inverted T wave?
Hyperkalemia (bigger repolarisation)
Inverted T wave can be normal in V1
What is a common symptom of 2nd-degree heart block?
Syncope
What is characteristic of Mobitz 1 Wenckebach?
The P-R interval gets continually longer until the AV node cannot conduct electricity QRS complex disappears.
“Wencke-wencke-wencke-bach (drop)”
What is characteristic of Mobitz 2?
RANDOM blocked QRS (no PR prolongation); erratic relationship between P and R waves
What causes heart block and what kind of heart rate is typically associated?
Problems with AV node: Bradycardia
What is the definition of 2nd-degree heart block and what are the 2 types called?
Some P waves produce QRS: Mobitz 1: wenckebach Mobitz 2
What causes atrial flutter and how does this appear on an ECG?What is one diagnostic criterion?
Single re-entry loop causing many atria contractions, “Sawtooth” of P waves (250-300 bpm)
Regularly irregular rhythm: AV node picks which P waves to conduct at regular intervals
Purkinje fibres normal: QRS complex narrow/normal
Why can’t an AV node conduct every P wave?
Hit AV node during its refractory period
How does a ventricular tachycardia appear on an ECG? What symptoms might the patient experience?
Abnormal depolarization/Beats originate in ventricular muscle >100 bpm
Shortens diastole -> SV reduces and heart fills less -> FOC reduces -> reduces CO
Wide QRS; Basically no AV node conduction, P waves, ABSENT PR interval
What are some common causes of ventricular tachycardia?
Coronary disease, previous heart attacks, HF and heart valvular disease
What causes ventricular fibrillation? How does this appear on an ECG and how would you treat it?
Abnormal firings of electrical signals -> STOPS beating
ECG is wavy chaotic baseline (no QRS or P waves) -> cardiac arrest
*require CRP, IV meds and defibrillation
What does supraventricular tachycardia mean?
any tachycardia that is NOT ventricular
What causes a bundle branch block?
Post MI dead myocardium, delayed conduction on affected side’s bundle of HIS
-> QRS on dead side is broad (electricity passes slower through myocardium)
What defines a sinus bradycardia? When is this common?
SA node generates <60 bpm,
Everything else is normal
*Common in athletes and during sleep
What defines sinus tachycardia? When is this normal?
SA node generates >100 bpm,
On ECG: may have shorter/steeper S wave, everything else normal exercise and anxiety
What are some causes of R bundle branch blocks?
Congenital, MI, hypertension, PE
