麻豆传媒

SAN DIEGO -- Three-dimensional echocardiography has won many supporters but not everyone is convinced that it's ready for widespread clinical use.

Debate here at the American Society of Echocardiography meeting centered around image quality and how much the technology adds to clinical decision-making.

Self-described 3D ultrasound promoter Natesa G. Pandian, MD, of Tufts Medical Center in Boston, argued that the technology should be an integral part of every echo lab.

"[The heart is] a three-dimensional organ and should be viewed and examined in a three-dimensional manner," he told attendees at a session devoted to 3D echocardiography.

The traditional 2D method shows slices of the heart in a single plane whereas the newer method uses a different transducer to cast a pyramid of ultrasound waves that encompasses the heart, which can be analyzed by the slice if desired or in a variety of other ways.

"Even for a trained eye, even for a good echocardiographer, still when you see it in 3D, a picture is worth a thousand words," Pandian said.

There is a learning curve, he acknowledged. But the accurate quantification of volumes and ejection fraction with 3D makes it worthwhile for most patients, he said. "We make big, big decisions on numbers."

Seeing the whole heart in real-time is a powerful method for assessing left ventricular morphology and function, noted Mark Monaghan, PhD, of King's College Hospital in London, who also spoke at the session.

This is particularly true with regard to dyssynchrony since all segments and papillary muscles can be compared during a single heart beat -- making it useful for assessment of cardiac resynchronization therapy, he said.

Monaghan pointed to studies linking dyssynchrony to CRT response and showing that following 3D echo criteria jointly maximizes the number of patients considered appropriate for CRT and their outcomes.

However, one problem in using it for CRT evaluation is that the temporal resolution is not as good as for 2D, speckle tracking, or tissue Doppler imaging, he cautioned.

The most universally agreed application for 3D is in mitral valve surgery.

Stanton K. Shernan, MD, of Harvard and Brigham and Women's Hospital in Boston, explained at the session that 3D transesophageal echocardiography may allow more efficient and complete evaluation of the anatomy and functional geometry of the mitral valve for a more accurate diagnosis, particularly for patients with complex lesions.

However, it has yet to be proven that this results in superior and more durable repair, he noted.

Nevertheless, this "killer application" makes 3D transesophageal echo ready for routine use, said Harry Rakowski, MD, of Toronto General Hospital in Toronto.

But this is the exception, Rakowski argued at the session, because the data just isn't there yet for 3D overall despite the pretty pictures.

"Clearly 3D is the future of echocardiography -- there is no doubt about it," he told attendees. "There will be a time when we get there."

He pointed to the evolution of CT which looked exciting in 1995 but didn't really come into major application until image quality was robust and easy enough.

The most common use of echocardiography is to assess left ventricular function.

But Rakowski cited one recent study showing that end-systolic and end-diastolic volume and ejection fraction assessed by 3D were no different than with 2D and that differences in paired comparisons were not enough to change clinical management.

Other challenges for clinical use are the high cost, tedious image manipulation of enormous data files that are harder to store and retrieve, and extra scanning time, Rakowski said.

In an informal show of hands in the room, most had a 3D echo machine but almost no one used 3D exclusively or surface 3D almost all the time.

"I'll use it routinely when its easy and robust, and that day hopefully isn't too far off," Rakowski said.

Comment