As echocardiography systems have been able to increase frame rates over the past decade, it has enabled additional information to be collected from cardiac ultrasound imaging studies. This includes the development of vector flow and speckle tracking imaging that can trace the paths taken by individual blood cells inside the heart to show energy loss and visualization of vortices. These factors are believed to play a crucial role in disease development and may act as early indicators for disease detection.
These technologies were developed nearly a decade ago and are still in the process of being investigated and validated, but are available on a couple commercially available echo systems.
Cardiovascular Business spoke with Luc Mertens, MD, section head of echocardiography at The Hospital for Sick Children in Toronto, at the American Society of Echocardiography (ASE) 2023 meeting about his research in this area for pediatric cardiac assessments.
"This allows you to track the blood as it flows through the heart, and that allows you to do a very detailed assessment of flow characteristics. That offers the opportunity to look at new flow characteristics like vortices and energy losses as the blood flows through the heart and it gives insight into understanding physiology and how the blood flow changes in different disease conditions. If we can quantify energy losses better in congenital heart disease, we can better understand the effect of certain therapies on blood flow within the heart," Mertens explained.
Assessment of congenital heart and valve disease using vortex imaging
In the pediatric cardiology realm, Mertens and his team have been actively collaborating with the Trondheim University Hospital in Norway to develop and implement quantification tools for assessing energy losses in congenital heart diseases. One of the major applications of this technology lies in diastolic function assessment, particularly challenging in pediatrics using traditional methods. The ability to characterize pressure differences during diastole using flow information opens new avenues for understanding and detecting diastolic abnormalities early on in various heart conditions.
In recent years, he said they have been using the technology to look at diastolic function assessment, which is very difficult to do using the traditional echo methods. The technology can characterize pressure differences during diastole. "I believe the future of this technology really is using that for characterizing diastolic abnormalities very early on in congenital heart disease or any type of heart diseases," Mertens explained.
The technology can also clearly show the swirling of blood in vortices, which has long been assumed to play a role in valve disease progression and in uses when valve replacements fail. This echo toll now makes it easier to visualize and assess the turbulent hemodynamics inside the ventricles and how this may play a role in valve disfunction.
"I think for valve function, you see when the flow gets into the heart, you develop those vortices around lateral to the mitral valve leaflets. Those are likely very important for having normal physiologic inflow. When you put in any type of valve, whether it's a bioprosthesis or a mechanical valve, obviously that changes very dramatically the flow within the heart, which probably negatively impacts how you fill the heart or how you affect cardiac function in the long run. So now we have quantification techniques, but that took a long time to actually develop and validate because one thing is to develop something, but then you also have to validate it. And that's not always easy to do," Mertens said.
Development of speckle tracking technology
While this technology has been around for five to 10 years, early limitations, such as accuracy influenced by echo penetration depth, initially led to its development for pediatric use. Mertens noted that recent advancements have overcome those limitations, making the methodology more applicable to adult patients as well.
For reliable velocity assessments using speckle tracking, Mertens said you need ultrafast ultrasound systems with frame rates between 500-800. This enables tracking of the blood flow through the heart, and that allows a very detailed assessment of flow characteristics in two dimensions.
Hitachi (now owned by Fujifilm) was the first to developed vector flow imaging. GE HealthCare followed with blood speckle tracking. Mertens said they take different approaches, but show the same thing, with the ability to quantify energy loss, flow velocity and direction.
Looking ahead, he said the technology holds promise and may offer a significant leap forward in understanding and assessing cardiac conditions.
Dave Fornell has covered healthcare for more than 17 years, with a focus in cardiology and radiology. Fornell is a 5-time winner of a Jesse H. Neal Award, the most prestigious editorial honors in the field of specialized journalism. The wins included best technical content, best use of social media and best COVID-19 coverage. Fornell was also a three-time Neal finalist for best range of work by a single author. He produces more than 100 editorial videos each year, most of them interviews with key opinion leaders in medicine. He also writes technical articles, covers key trends, conducts video hospital site visits, and is very involved with social media. E-mail: dfornell@innovatehealthcare.com