ECG

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!)

RVH defined as:

  • Dominant RV1 +/- Q after 1 yr,
  • Upright TV1 over 1 week and under 7 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).

PR 80-160ms, QRS less than 75ms, 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).

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.  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.

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