ECG Flashcards
Normal HR for sinus rhythm
60-100bpm
P wave axis for sinus rhythm
Upright in leads 1 and 2 and inverted in aVR
QRS complex length for sinus rhythm
<100ms
Normal PR interval
120-200ms and constant
How does the QT interval vary with HR
Inversely proportional
Main ECG change on STEMI
ST elevation
Anterior STEMI ECG
Precordial leads V1-6 ST elevation
Reciprocal ST depression in inferior leads 3 and aVF
Lateral STEMI ECG
ST elevation in leads 1 aVL and V5-6
Reciprocal ST depression in inferior leads 3 and aVF
High lateral STEMI ECG
ST elevation localised to leads 1 and aVL
Inferior STEMI ECG
ST elevation in leads 2 3 and aVF
Reciprocal ST depression in aVL
Progressive development of Q waves in 2 3 aVF
ECG NSTEMI findings
Regional ST depression
T wave inversion or flattening
Dynamic or new Q or T wave changes
Define atrial fibrillation
Dysrhythmia characterised by disorganised atrial activity and contraction resulting in an irregularly irregular ventricular response
Key ECG features of AF (5)
- no p wave
- irregularly irregular rhythm
- no isoelectric baseline
- variable ventricular rate
- QRS<120 ms (unless existing BBB or accessory pathway)
ECG features of complete heart block
Severe bradycardia due to no AV conduction
Complete AV dissociation - independent atrial and ventricular rates
What is left bundle branch block?
Conduction delay which means impulses travel first via RBBB to RV and then to LV via the septum (r to l instead of l to r). This reverses septal activation so Q waves eliminated
Normal conduction through bundle branches
Impulses travel equally through R and L bundles, septum activated from left to right and formation of small Q waves in lateral leads
ECG findings for LBBB (4)
- Broad monophasic R waves in lateral leads (1, aVL, V5-6)
- deep S waves in right precordial leads (V1-3)
- QRS> 120ms
- No Q waves in lateral leads
What is right bundle branch block?
Delayed activation of right ventricle causing a secondary R wave
ECG findings in RBBB (3)
- QRS> 120 ms
- RSR’ pattern in V1-3
- wide slurred S wave in lateral leads (1, aVL, V5-6)
What is ventricular fibrillation
- shockable arrest rhythm
Ventricles attempt to contract at rates of up to 500bpm, rapid and irregular activity results in loss of cardiac output
Prolonged VF results in asystole
ECG findings in VF (4)
- chaotic irregular deflections of varying amplitude
- no identifiable P waves, QRS complexes or T waves
- rate 150-500bpm
- amplitude decreases with duration
ECG findings in VT ( 5)
- regular, broad complex tachycardia
- uniform QRS complexes in each lead
MAY - very broad complexes (>160ms)
- AV dissociation
- extreme axis deviation
What is sinus arrhythmia?
Normal phenomenon commonly seen in young healthy people. HR varies due to change in vagal tone during respiratory cycle
ECG findings in sinus arrhythmia
- variation in P-P interval of more than 120ms
- P-P interval gradually lengthens and shortens in cyclical fashion
- normal P waves
- constant PR interval
Sinus bradycardia
HR<60bpm
Sinus tachycardia
HR >100bpm
Atrial flutter vs atrial fibrillation
AFib is irregular atrial contraction, atrial flutter is regular atrial activity but more often than ventricles
Atrial flutter ecg findings (5)
-Narrow complex tachycardia
- atrial activity ~300bpm
- loss of isoelectric baseline
- sawtooth inverted waves in 2,3, aVF
- upright in V1 may resemble P waves
Atrial ectopics ECG findings
- abnormal p wave followed by normal QRS
- may not be conducted
First degree AV Block ecg
PR>200ms
2nd degree AV block (mobitz 1, wenckebach)
Progressive prolonging of PR until p wave is dropped
What is SVT?
Any tachydysrhythmia originating above the bundle of his.
Includes regular atrial, irregular atrial and regular AV tachycardia
Atrioventricular re entry tachycardia
Form of SVT arising in patients with accessory pathways. Can be orthodromic (through av then accessory) or antidromic (through accessory then AV)
AVRT vs AVNRT
avrt has an anatomical reentry circuit, in avnrt there is a functional reentry within AV node
