Ultrasound: four dimensions for pediatric cardiac diagnostics

Interview with Jan-Pit Horst, Heart and Diabetes Center North Rhine-Westphalia, Bad Oeynhausen

Fortunately, only a handful of newborns are affected by them, though this determines if not the rest of their lives then, at least, the first few years of affected children: congenital heart defects. After the necessary surgeries, the small patients repeatedly need to return for checkups. Until now, these were conducted using MRI scans. 4D ultrasound can be an alternative.

03/01/2016

Photo: Young smiling physician with white coat in the hallway of a hospital - Jan-Pit Horst

Jan-Pit Horst; ©HDZ NRW

In this interview with MEDICA-tradefair.com, Jan-Pit Horst talks about 4D ultrasound in pediatric cardiac diagnostics. He explains why the right ventricle is so difficult to assess using 2-dimensional ultrasound images and how reference ranges for heart size are able to support future treatment decisions.

Mr. Horst, you examined the hearts of children using a 4D ultrasound system in a study. What kind of technology is this?

Jan-Pit Horst: 3D ultrasound imaging is well-known and by now very well established in hospital facilities and larger medical practices. It lets us picture and record the heart in all three dimensions with a single image.

4D ultrasound enables us to determine the commonly used 2D parameters, such as the heart cavity diameter for example. In addition, this type of program can calculate the left and right ventricular volumes from 3D images. We are also able to measure functional parameters such as the motion of the tricuspid annular plane systolic excursion (TAPSE) or assess the so-called longitudinal strain. This program shows us the heart in motion since the images are being generated almost in real time. This is the fourth dimension.

For which types of concerns in research and diagnostics can this type of system be utilized?

Horst: We have to distinguish between adult and pediatric patients in this case. This system works great for adults in cases of pulmonary hypertension and all issues pertaining to right ventricular insufficiency.

In the pediatric realm, it is primarily helpful with progress assessments after surgical procedures for congenital heart disease. Normally, this would require frequent MRI scans that previously made a much better assessment of the right ventricle possible.

Photo: Collage from six ultrasound images

All dimensions of the right and left ventricle in the 2D image. Shown are also all markings that are necessary to create a four-dimensional image; ©HDZ NRW

Until now, it was very difficult for us to picture and map the right ventricle with 2D ultrasound because it has a very irregular shape. So far, an accurate quantitative assessment of the ventricle’s size and performance was not possible this way. We can cut down on MRI scans for these patients using 3D or 4D ultrasound machines. At this point, these types of systems are already being used for initial assessments of children with congenital heart defects.

You introduced a study on examining children's hearts with 4D ultrasound technology and received an award for the accompanying poster presentation at the recent annual meeting of the German Society of Pediatric Cardiology. What exactly did you research?

Horst: The study consisted of two parts. First, we investigated whether this program is actually able to deliver reliable data. To do this, we examined patients using MRI scanning. This is the gold standard for assessing the right ventricle. We subsequently compared the results of the MRI scan to the ultrasound exam. We discovered that the results of the ultrasound are comparable with the test results of the MRI scan.

During the second part of the study, we examined 394 children between 0 and 18 years of age in collaboration with the University Medical Centers of Bonn and Munich. Based on these exams, we established reference ranges for the size and function parameters of the right side of children’s hearts for specific age groups. These can assist colleagues who are uncertain whether the measured values match the age of the patient or whether they are already too extensive. This is meant to support them in deciding whether further treatment is needed.

Photo: Three-dimensional image of the right ventricle

A model of the right ventricle that has been calculated from 2D images. Also shown are two 2D images that were the basis for this and some of the resulting measurements; ©HDZ NRW

You just talked about the initial assessment of congenital heart defects and the follow-up exams after surgeries. What disease patterns are you faced with when it comes to the right ventricle?

Horst: There are two areas in particular. On the one hand, it pertains to diseases where the right ventricle itself is affected, as is the case with tetralogy of Fallot. This involves a narrowing of the pulmonary artery, a connection between the two large heart ventricles due to a ventricular septal defect, an overriding aorta, and hypertrophy, an enlargement of the heart muscle in the right ventricle. After the surgical repair of the defect, the pulmonary artery valve often becomes leaky. This causes the right ventricle to enlarge over time. We need to assess the rate and scale of this enlargement. Beyond a specific ventricle size, heart function can slow down, potentially leading to insufficiency. This is why the leaky valve needs to be replaced by an artificial valve at the right moment.

On the other hand, there are heart defects where the right ventricle has to take over the job of the left one, as is the case with a so-called congenitally corrected transposition of the great arteries where - among other things - the aorta originates from the right instead of the left heart ventricle. Hypoplastic left heart syndrome is a very particular case. Essentially, these children are born with only half a heart. Due to a displacement of the mitral valve, their left heart ventricle is so small, it is unable to ensure proper blood supply to the body. A series of three surgeries converts the right ventricle to where it no longer supplies pulmonary circulation but supports the systemic circulation instead. This means considerable more work for it which can become too much since there is much higher blood pressure in systemic circulation than there is in pulmonary circulation. This is why we subsequently need to carefully monitor the right ventricle.

In conclusion, can you assess what benefits your findings might have for diagnostic investigation, treatment and research?

Horst: 4D diagnostic ultrasound is a widely spread technique at this point. It is quick and everyone who is trained in ultrasound technology is able to conduct the procedure. Unlike an MRI scan that would otherwise be required in this case, it is very cost-effective and less stressful for the children. Thanks to our reference values, our colleagues will be able to better assess their readings and analyze their patients - and determine whether they require surgery or if it is still sufficient to continue monitoring them.

Photo: Timo Roth; Copyright: B. Frommann

© B. Frommann

The interview was conducted by Timo Roth and translated from German by Elena O'Meara.
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