JASE Feature: Ped echo cards create consensus to measure standards
In an effort to standardize the way echo measurements are made in the pediatric population, a group of experts have developed a consensus statement with recommendations on how to accurately quantify the effect of diseases on the size of cardiovascular structures. The document appears in the May issue of the Journal of the American Society of Echocardiography.

Due to the need for consensus on how to measure the size of each cardiovascular structure, the document describes the recommended protocols for the morphometric evaluation of the heart in children with or without congenital heart disease.

While adult echo cardiology has a standard methodology to measure cardiac structures, pediatric cardiology does not. "The goal of this document was to establish uniform ways to measure various structures of pediatric cardiac anatomy," lead author Leo Lopez, MD, of Children's Hospital at Montefiore in Bronx, N.Y., told Cardiovascular Business News. "Ultimately, once we all agree on how measurements can be made, we can then go to the next stage of adjusting all of those values for size, age and other patient characteristics, and that will also make it easier for us to distinguish normal from abnormal values."

Lopez and eight colleagues developed the consensus document over a two-year period. "Consensus was not easy," he said. "It was a little like herding cats."

They reviewed the literature to determine, for example, all the different ways people measure left ventricular (LV) function, and decided among themselves which are the ones that most people use, why they use those particular techniques and what the exact methodology is for each measurement.

"We vetted every piece of information that we wanted to put in the paper. Not everyone agreed with the final decisions, but they needed to feel comfortable about them," he said.

After the writing group finished its work, the document went to the Pediatric Council at the American Society of Echocardiography (ASE), a group of about 10 people. The recommendations then were submitted to the ASE standards committee, comprised mostly of adult echo people, and then to the board of directors of the ASE.

The authors explained the importance of adjusting measurements of cardiovascular structures for the effects of body size. Also, they addressed the following:
  • How to identify the pediatric quantification protocols for the pulmonary veins, systemic veins, atria and atrioventricular valves.
  • How to recognize and apply the recommended echocardiographic methods for the evaluation of left and right ventricular size and function.
  • The optimal views and the appropriate anatomic sites for correct measurement of the ascending aorta, proximal and distal arch, and descending aorta.
  • Appropriate transducer position and Doppler technique for the anatomic and hemodynamic interrogation of the aorta and aortic valve and the pulmonary artery and the pulmonary valve.

"For example, to measure the size of the valves, part of what we needed to do was decide exactly when during the cardiac cycle the measurement should be made and where it should be made. Should it be made at the muscular area where the valves are attached or should we measure at the tip of the leaflet edge? That is the type of detail we needed to make," Lopez said.

Two recommendations that might potentially create controversy, according to Lopez, are of the aorta and LV size.

"The timing of the measurement of the pediatric aorta is different than from general adult guidelines. Our recommendation created a lot of controversy when it was undergoing the review process by the adult echo experts. We outline exactly why we differed in our paper from previous guidelines and why we think it's important to measure it at a different time of cardiac cycle," he said.

Regarding measuring the LV, in pediatrics, it has traditionally been done in M-mode. The adult guidelines published in 2005 moved away from M-mode, suggesting the measurement be done in 2D only. "We concurred with the adult guidelines, in that we thought 2D measurements were good, but we differed from them in that we decided it was better to make those measurements in a different plane of orientation. There is already a lot of discussion about moving away from M-mode and there will be more discussion to follow about why we're using a different orientation than the adult guidelines," Lopez said.

"The most important point of our paper is that children are not little adults and adults are not big children. The measurements and the rationale behind the measurements are very different from adult echo and that's why we felt the need to create this document for pediatrics," he said.

The next step is to establish a big project that involves collecting normal values using these standard methodologies outlined in the document. The normal values will then be used as the control group for all other measurements that echocardiographers want to make in their daily clinical activities.

With a database of normative values, generated by using the same measurement methodology, echocardiographers will be able to generate z-scores to determine the number of standard deviations from the mean value. "It's Important to know whether the size of the aorta, for example, is greater than two standard deviations from the mean value of that particular size of the patient—and the only way to do that is to have a big control population to compare your measurement against," Lopez said.

Many digital echo systems automatically calculate the z-score. The problem is they all use different z-scores. "We want everybody to use same z-score and ideally it would be incorporated into all of these echo systems. The process of getting that done is something we haven't begun to think about," he said.

In the mean time, there are normative databases that people have created over the years (available here), but the data collection techniques often differ, as does the way the analysis is performed.

"A collection of quantitative data from a normal pediatric population is required to function as the standard against which all measurements are compared," Lopez explained. "We hope the recommendations will lead to the creation of a normative database of pediatric measurements."