ECGs - normal Flashcards
<p>Big square</p>
<p>5mm
| 0.2s</p>
<p>Small square</p>
<p>1mm
| 0.04s</p>
<p>Estimating rate</p>
<p>NORMAL: 60-100
Regular: 300/number of big squares in between each R
Very fast: 1500/number of small squares between each R
Slow or irregular: Number of Rs on rhythm strip x 6
Note: calculate atrial and ventricular rates separately if they are different</p>
<p>Rhythm</p>
<p>Look at rhythm strip - confirm by looking at other leads
1) Rate - tachy or brady?
2) Pattern of QRS - regular, regularly irregular or irregularly irregular?
3) Each p followed by QRS?</p>
<p>Axis - using I, II and III</p>
<p>Positive, positive, positive - Normal
Positive, euphasic, negative - LAD (physiological)
Positive, negative, negative - LAD (pathological)
Negative, positive, positive - RAD</p>
<p>P wave</p>
<p>Atrial depolarisation
Upright - inversion normal in aVR
Duration <120ms (3 small squares)
Amplitude <2.5mm limb/1.5 chest
Atrial abnormalities most easily seen in I, II, aVF and V1 was p wave most prominent
Tall P wave - RA enlargement
Broad P wave (+/-mitrale) - LA enlargement</p>
<p>PR interval</p>
<p>START of P wave to START of QRS
120-200ms (3-5 small squares)
>200ms - delayed conduction through AV node - first degree HB
<120ms - pre-excitation (accessory pathway eg WPW) or AV nodal (junctional) rhythm</p>
<p>PR segment</p>
<p>END of P to START of QRS Pericarditis - PR depression Atrial ischaemia: PR elevation or depression in pts with MI</p>
<p>Q waves</p>
<p>Any negative deflection before an R wave
Pathological: >40ms (1 small square) wide, >2mm deep, >25% depth of QRS, present in V1-3
Usually indicate current or prior MI
Absent Q waves in V5-6 most commonly LBBB</p>
<p>R wave progression</p>
<p>R wave ≤3mm in V3
| Caused by prior anteroseptal MI, LVH, inaccurate lead placement, normal variant</p>
<p>QRS</p>
<p>Narrow <100ms (2.5 small squares) - supraventricular origin - Sinus, AF/flutter, junctional tachycardia
Broad >100ms (2.5 small squares) - ventricular origin or aberrant conduction
Broad complex QRS: Bundle branch block, hyperkalaemia, TCA overdose (sodium channel blockers), pre-excitation (WPW), ventricular pacing, hypothermia, VT</p>
ST segment
END of S waves to START of T wave
ST elevation: >1mm limb lead or 2mm chest lead
ST elevation: MI, coronary vasospasm, pericarditis, LBBB, LVH, ventricular aneurysm, brugada syndrome, raised ICP, ventricular paced rhythm
ST depression: NSTEMI, myocardial ischaemia, post MI, reciprocal in STEMI, digoxin, hypokalaemia, SVT, RBBB, LBBB, RVH, LVH, ventricular paced rhythm
QT interval
START of Q to END of T
Inversely proportional to HR (fast=short)
Abnormally prolonged = risk of TdP
Measure in II, V5 or V6
Normal: >350ms/9ish small squares and <440ms/11 small squares (men) or <460ms/11.5 small squares (women) if 60bpm
To correct: QT/(root of(60/HR)) if 60-100 bpm; QT/((60/HR)/3) if outside of that range
Prolonged QT: hypokalaemia, hypomagnesia, hypocalcaemia, hypothermia, MI, post-cardiac arrest, raised ICP, congenital long QT syndrome, Drugs: antipsychotics, antiarrhythmics, TCAs, some other antidepressants, some antihistamines (loratidine), quinine and other quines, macrolides (erythromycin, clarithromycin)
Short QT: Hypercalcaemia, congenital short QT syndrome, digoxin effect
T waves
Ventricular repolarisation
Upright in all leads except aVR and V1
Amplitude <5mm limbs and <15mm chest
Hyperacute, inverted, biphasic, camel hump, flattened
