Standard ECG settings are 25mm/s and 10mm/mV.  Beware small complexes, which may indicate someone has adjusted the Y-axis to 5mm/mV.

Axis @ birth 60-180, @ 1 yr 10-100, @ >1yr 30-90 (NB prems have LESS Rt dominance!). So you expect QRS to be positive in both I and aVF. Under 1, I can be negative but aVF should still be positive.

RVH defined as:

• Dominant RV1 +/- Q after 1 yr,
• Upright TV1 over 1 week and under 7-8 yr,
• SV6 over 15mm if under 1yr or over 5mm if over 1 yr.

Brugada syndrome – genetic arrhythmia. Persistent or intermittent right sided ST elevation and RBBB, leading to VF and sudden death.

QTc is normally under 0.490 up to 6 months, or 0.425 if over 6 months. Calculation = QT/SQR(RR), where QT is time from beginning of Q to end of T. Easiest way to calculate it is to count small squares: QTc is then QT/5 divided by SQR(RR) (where default is 25mm/sec). Over 450ms with history of syncope is a red flag; otherwise over 460ms. Consider family history of sudden death or “epilepsy”, too.

PR 80-160ms (so 3-5 small squares), QRS less than 75ms. Look for delta wave if PR short.

RV1 less than 20-26mm (trough at 1 year), SV6 less than 10mm at birth falling to 4 mm at 10 year.

LVH – deep Q waves in V6 are a clue (upper limit is 0.54mV, ie 5 small squares). The SV1+RV6 upper limit ranges from 3.1mV (newborns) through to 5.7 (older children), staying at around 5 for most children (ie 50 small squares, my calculations). Glasgow guideline says if V5 (rather than V1) and V6 complexes overlap but this depends on how the ECG is printed and can very between 20 and 40 squares!!

For adults, there are many different criteria for LVH eg:

• Sokolow + Lyon (Am Heart J, 1949;37:161)
  • S V1+ R V5 or V6 > 35 mm
• Cornell criteria (Circulation, 1987;3: 565-72)
  • SV3 + R avl > 28 mm in men
  • SV3 + R avl > 20 mm in women

But sensitivity of ECG criteria less than 20% at specificity levels of 88% to 92%. Obesity affects chest lead voltage, for example.  Better in patients with a specific cardiac disease. An elevated LVM (left ventricular mass) index is taken as the reference for LVH. In kids the SV3R + RV7 Sokolow-Lyon parameter performs best, but who does V7 routinely? (and still only 25.3% sensitivity).

So you can say voltage criteria for LVH met, but can’t say diagnostic of LVH.  More likely when other features such as left axis deviation, ST and T wave changes. ST elevation under 2 squares not significant. T wave inversion in V5/6 most suspicious (Glasgow guideline). When clinical evidence is also taken into account, the sensitivity improves considerably (but still under 50%).

[Normal ranges – European Heart Journal (2001) 22, 702–711]

LVM (as estimated from echocardiographic measurements) is itself vulnerable to measurement error and may oversimplify the geometry of the left ventricle. Alternatively, a combination of increased LVM and clinical evidence of volume or pressure overload of the left ventricle may be a better reference standard.