Saturday, December 15, 2007

Ebstein's Anomaly: Measuring the Spectrum

Ebstein's anomaly is a malformation of the tricuspid valve and right ventricle. The classic description is something along the lines of: a tethered and displaced septal (and posterior) leaflet, a "sail-like" anterior leaflet, and a variable "atrialized" portion of the right ventricle. Echocardiographically, it is important to understand the measurable parameters that help describe the spectrum of disease, and thus help guide the management.

At one end of the spectrum is a tricuspid valve that is apically displaced just slightly more than normal:

Tricuspid Valve Offset Calculator:

At the other end of the spectrum are the critically ill neonates whose biventricular circulation— and very survival— are not certain:

Great Ormond Street Ebstein Index Calculator:

Ultimately, it is the actual leaflet and right ventricle morphology which dictates just how much and what kind of repair can be attempted, and 3D echo seems best suited to describing these.

Source: Ebstein's Anomaly
Attenhofer Jost et al. Circulation.2007; 115: 277-285

Saturday, December 8, 2007

Fetal Echo Z-Scores: the SGA conundrum

actual size! The fetal echo z-score calculator was initially a proof-of-concept project (as were all of the calculators at It has since proven itself to be quite useful, and I refer to it for nearly all fetal echos now.

However, a shortcoming of the current calculator is highlighted by this common referral:

  • SGA (Small for Gestational Age)
  • RV > LV
  • LV measures lower limits of normal for EGA

The real difficulty here of course, is the SGA baby. Based purely on dates, the baby is known to be small- and all measures of her cardiac structures are sure to be small as well.

But can't her heart still be relatively normal

In the article Development of Z-scores for fetal cardiac dimensions from echocardiography, regressions are presented based on three independent variables: femur length, biparietal diameter, and EGA. According to the authors, "femur length gave the better correlation coefficient with fetal cardiac dimensions" though admittedly, all the independent variable gave good correlations. And a good discussion is made over EGA as a surrogate for fetal size, the importance of considering fetal size, fetal growth and fetal size, fetal size, fetal size, ...

So why don't I build the calculator based on the femur length- ergo the fetal size?

Because: I have now become an advocate of measuring the fetus:

  • measuring the BPD
  • measuring the head circumference
  • measuring the abdominal circumference
  • measuring the femur length

Now, I measure the fetal size and, taking advantage of the OB calculation package on the ultrasound machine, use the size-determined EGA- rather than the date-determined EGA.


The new and improved fetal echo worksheet allows you to edit the EGA and automatically update all of the z-scores based on your measurements. And, just for fun, makes estimations of the EDC and LMP.


Users of the Pediatric Cardiac Valve Z-Score calculator might be interested to know about an erratum to the reference article:

The tricuspid valve nomograms have been re-published.

In the process of refining the calculator on, it was noted that tricuspid valve z-scores calculated by the supplied formula differed considerably from the result when using the nomogram. I contacted the lead author, he contacted their statistician, and it was discovered that the original nomograms were in error.

Fortunately, the error involved only the nomograms themselves- the formulae are (still) correct and thus, none of our calculations were affected.