Today I added z-score calculations for the neonatal RV, based on data presented in the December 2014 JASE article, A comprehensive echocardiographic protocol for assessing neonatal right ventricular dimensions and function in the transitional period: normative data and z scores.

There are a few exceptions to the data available here as compared to that presented in the article. Namely, I have omitted the z-score calculations of the following measurements:

  • IVCV'
  • IVRT'
  • MPI
  • S'/D' ratio

Things like the tissue Doppler-derived IVCV' (isovolumic contraction velocity) and IVRT (isovolumic relaxation time) are notoriously difficult to measure1 (particularly so in my hands). The tissue Doppler-derived MPI and S'/D' ratio suffer from the same fate as the preceding, I am afraid. To wit: the wide range of normal values of the MPI (± 2 SD = 0.1 - 0.7).

I struggled with the idea of including calculated Doppler ratios. The ratios of the inflow and tissue Doppler vary wildly: according to the data, it is normal for the ratio to exhibit a reversed E/A— like that of a "normal" newborn, or a "big E, little A" like that of an adult (inflow Doppler E/A ratio ± 2 SD = 0.6 - 1.2). If the morphology of the E and A waves can normally vary that much, I am not sure if a ratio z-score has much benefit. I am deeply skeptical about diastolic function z-scores you see, but I included them anyhow for the less skeptical among us.

If you feel strongly that these omissions are glaring and must be remedied, you can petition for their inclusion by adding a feature request.