Advances in 3D Echo Bring the Technique Closer to Clinical Routine
Two dimensional transthoracic and transesophogeal echo (TTE and TEE, respectively) are limited in their reproducibility because they rely on geometrical assumptions. Advances in 3D TTE and TEE not only seek to solve the reproducibility problem, but also allow immediate delivery of reconstructed 3D data, making the techniques optimal for heart failure patients and those with valvular pathologies.
“Accuracy is a fool’s gold after a certain point,” says Mani Vannan, MBBS, chair of cardiovascular medicine and director of cardiovascular imaging at Ohio State University Medical Center in Columbus. “With so many variations in 2D echo measurements, cardiologists can’t be certain if the variations are those of a reader or of the technology.”
Vannan says real-time 3D TTE derives left ventricular (LV) volume and ejection fraction, as well as mitral regurgitant flow, “without any user interaction.” Today’s systems use pattern recognition software to quantify data immediately. The technology is particularly useful in heart failure patients with irregular heart cycles. “Because each data acquisition is a complete heartbeat, and not an image of five or seven beats stitched together, clinicians can accurately quantify LV volume and ejection fraction, irrespective of the cardiac rhythm,” he says.
Three-dimensional color flow Doppler had been limited by gated acquisition (which potentially results in stitching artifacts) and geometric assumptions. At ACC.10, Vannan and colleagues presented two studies demonstrating the ability of real-time 3D color flow Doppler imaging (Siemens Healthcare) to quantify the regurgitant orifice volume and the ability of 3D TEE (Siemens) to model and quantify the aortic valve and root in patients with aortic regurgitation.
PARTNER & EVEREST IICardiologists at the Cedars-Sinai Medical Center in Los Angeles are involved in the PARTNER trial, which is assessing the Sapien transcatheter valve (Edwards Lifesciences) in patients with severe aortic stenosis, and the EVEREST II trial, which is testing the MitraClip (Abbott) in patients with mitral regurgitation. “The use of 3D TEE results in improved accuracy and reduced procedure time,” says Robert J. Siegel, MD, director of the cardiac noninvasive laboratory at Cedars-Sinai.
For a successful deployment of the MitraClip, the use of real-time 3D TEE helps identify patients who are better candidates for the procedure, and also adds value intra-operatively. Siegel et al presented a study at ACC.10 showing that real-time 3D TEE (Philips Healthcare) better identified trajectory of the catheter delivery system, alignment of the clip and mitral leaflet coaptation. In addition, the technique identified mechanisms of residual mitral regurgitation, which helped in deciding whether to use a second clip or not. Overall, 3D TEE reduced procedure time by 40 minutes.
Bhan et al from Kings Health Partners in London also presented a study at ACC.10, finding the use of 3D TEE (Philips) is “uniquely placed to provide detailed anatomical information, spatial orientation and continuous real-time imaging during transcatheter aortic valve implantation in patients with severe aortic stenosis.”
Siegel and colleagues have found that 3D TEE color flow Doppler, compared to 2D Doppler, adds unique information in patients with mitral prosthesis paravalvular leaks (Am J Cardiol 2010;105(7):984-9). They also use real-time 3D TEE when deploying closure devices for atrial septal defects, as well as the Watchman device (Atritech), which seals off the left atrial appendage.
Regarding cost, Siegel says, “Three-dimensional echo techniques are time saving, and they improve patient care because they allow us to make better and more sensitive and specific diagnoses more quickly. That is the biggest cost issue.”