Real-time magnetic resonance-guided aortic valve replacement using Engager valve

Measurement of the Aortic Annulus Area and Diameter by Three-Dimensional Transesophageal Echocardiography in Transcatheter Aortic Valve Replacement

OBJECTIVES

Sizing of the aortic valve is crucial for transcatheter aortic valve replacement (TAVR). Multidetector computed tomography (MDCT) is used for sizing. Recently, three-dimensional transesophageal echocardiography (3DTEE) has enabled accurate measurement of the aortic annulus area and diameter in cases that are difficult to measure. The authors compared measurements of aortic annulus areas and diameters acquired by MDCT and 3DTEE.

DESIGN

Retrospective observational study.

SETTING

Single national center.

PARTICIPANTS

Sixty-eight patients who underwent TAVR replacement between September 2015 and March 2017.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The authors extracted and compared preoperative measurements of the aortic annulus area, as well as the long- and short-axis diameter, measured by MDCT and 3DTEE. There was no significant difference in the aortic annulus area (409 ± 74 v 414 ± 70 mm², p = 0.15) or short-axis diameter (20.4 ± 2.0 v 20.6 ± 1.9 mm, p = 0.103) between 3DTEE and MDCT, but the long-axis diameter differed significantly (25.0 ± 2.4 v 25.8 ± 2.0 mm, p < 0.001), respectively. Prosthesis sizes based on 3DTEE and MDCT were the same, except in 3 patients who could not stay still during MDCT measurement; in those cases, prosthesis sizes based on 3DTEE were adopted.

CONCLUSIONS

Measurements of the aortic annulus area and diameter in TAVR were similar between 3DTEE and MDCT. Patients who have difficulty remaining still during MDCT measurement because of dementia should have their prostheses sized based on 3DTEE measurements.

Is intra-procedure three-dimensional transesophageal echocardiogram an alternative to preprocedure multidetector computed tomography for the measurement of the aortic annulus in patients undergoing transcatheter aortic valve replacement?

BACKGROUND

The role of three-dimensional transesophageal echocardiography (3DTEE) vs multidetector computed tomography (MDCT) in aortic annular sizing has been poorly defined in patients undergoing transcatheter aortic valve replacements (TAVR). We set to determine the correlation between 3DTEE and MDCT in measuring the aortic annulus prior to TAVR.

METHODS

In an observational, retrospective study, we compared aortic annular areas measured by MDCT and 3DTEE in TAVR patients. The aortic annular area was measured by planimetry of images obtained by MDCT pre-TAVR and by intra-TAVR TEE using 3D rendering of the aortic annulus followed by planimetry. Our primary outcome was degree of correlation between mean aortic annulus area by 3DTEE and MDCT.

RESULTS

Of the 111 consecutive patients undergoing TAVR who had measurements from both modalities available for comparison between February 2012 and April 2015, 87 met inclusion criteria. The mean aortic annular area by MDCT was 4.44±0.88 cm² and by 3DTEE was 4.33±0.78 cm² . There was a strong positive linear correlation between aortic annular area measurements obtained from these two modalities with mild relative underestimation by 3DTEE (ρ=.833). This relationship can be estimated using the predictive formula: [Formula: see text] CONCLUSIONS: Three-dimensional transesophageal echocardiography measurements have a high degree of correlation with MDCT measurements and thus can assist in proper valve prosthesis selection for TAVR. Our study thus supports use of 3DTEE as a reasonable alternative imaging modality in patients undergoing TAVR.

Robot-assisted real-time magnetic resonance image-guided transcatheter aortic valve replacement

BACKGROUND

Real-time magnetic resonance imaging (rtMRI)-guided transcatheter aortic valve replacement (TAVR) offers improved visualization, real-time imaging, and pinpoint accuracy with device delivery. Unfortunately, performing a TAVR in a MRI scanner can be a difficult task owing to limited space and an awkward working environment. Our solution was to design a MRI-compatible robot-assisted device to insert and deploy a self-expanding valve from a remote computer console. We present our preliminary results in a swine model.

METHODS

We used an MRI-compatible robotic arm and developed a valve delivery module. A 12-mm trocar was inserted in the apex of the heart via a subxiphoid incision. The delivery device and nitinol stented prosthesis were mounted on the robot. Two continuous real-time imaging planes provided a virtual real-time 3-dimensional reconstruction. The valve was deployed remotely by the surgeon via a graphic user interface.

RESULTS

In this acute nonsurvival study, 8 swine underwent robot-assisted rtMRI TAVR for evaluation of feasibility. Device deployment took a mean of 61 ± 5 seconds. Postdeployment necropsy was performed to confirm correlations between imaging and actual valve positions.

CONCLUSIONS

These results demonstrate the feasibility of robotic-assisted TAVR using rtMRI guidance. This approach may eliminate some of the challenges of performing a procedure while working inside of an MRI scanner, and may improve the success of TAVR. It provides superior visualization during the insertion process, pinpoint accuracy of deployment, and, potentially, communication between the imaging device and the robotic module to prevent incorrect or misaligned deployment.

Real-time magnetic resonance imaging-guided transcatheter aortic valve replacement

OBJECTIVES

To demonstrate the feasibility of Real-time magnetic resonance imaging (rtMRI) guided transcatheter aortic valve replacement (TAVR) with an active guidewire and an MRI compatible valve delivery catheter system in a swine model.

METHODS

The CoreValve system was minimally modified to be MRI-compatible by replacing the stainless steel components with fluoroplastic resin and high-density polyethylene components. Eight swine weighing 60-90 kg underwent rtMRI-guided TAVR with an active guidewire through a left subclavian approach.

RESULTS

Two imaging planes (long-axis view and short-axis view) were used simultaneously for real-time imaging during implantation. Successful deployment was performed without rapid ventricular pacing or cardiopulmonary bypass. Postdeployment images were acquired to evaluate the final valve position in addition to valvular and cardiac function.

CONCLUSIONS

Our results show that the CoreValve can be easily and effectively deployed through a left subclavian approach using rtMRI guidance, a minimally modified valve delivery catheter system, and an active guidewire. This method allows superior visualization before deployment, thereby allowing placement of the valve with pinpoint accuracy. rtMRI has the added benefit of the ability to perform immediate postprocedural functional assessment, while eliminating the morbidity associated with radiation exposure, rapid ventricular pacing, contrast media renal toxicity, and a more invasive procedure. Use of a commercially available device brings this rtMRI-guided approach closer to clinical reality.