Role of Multimodality Imaging in Transcatheter Aortic Valve Replacement

How to Image and Manage Prosthesis-Related Complications After Transcatheter Aortic Valve Replacement

PURPOSE OF REVIEW

In this review, we provide an overview of potential prosthesis - related complications after transcatheter aortic valve replacement, their incidences, the imaging modalities best suited for detection, and possible strategies to manage these complications.

RECENT FINDINGS

Therapy for severe aortic valve stenosis requiring intervention has increasingly evolved toward transcatheter aortic valve replacement over the past decade, and the number of procedures performed has increased steadily in recent years. As more and more centers favor a minimalistic approach and largely dispense with general anesthesia and intra-procedural imaging by transesophageal echocardiography, post-procedural imaging is becoming increasingly important to promptly detect dysfunction of the transcatheter valve and potential complications. Complications after transcatheter aortic valve replacement must be detected immediately in order to initiate adequate therapeutic measures, which require a profound knowledge of possible complications that may occur after transcatheter aortic valve replacement, the imaging modalities best suited for detection, and available treatment options.

Modified continuity equation using left ventricular outflow tract three-dimensional imaging for aortic valve area estimation

PURPOSE

Aortic valve area (AVA) is usually estimated by the continuity equation (CE) in which the left ventricular outflow tract (LVOT) area is calculated assuming a circular shape. This study aimed to compare measurements of LVOT area using standard 2D transthoracic echocardiography (2DTTE), 3D transesophageal echocardiography (3DTEE), and multidetector computed tomography (MDCT) and assess their relative impact on AVA estimated by the CE.

METHODS AND RESULTS

We prospectively enrolled 60 patients with severe aortic stenosis (AS) referred for transcatheter aortic valve replacement (TAVR) who systematically underwent 2DTTE, 3DTEE, and MDCT. Mean LVOT areas obtained by 2DTTE (3.28±0.66 cm² ) and 3DTEE (3.95±0.90 cm² ) were significantly underestimated when compared to the mean MDCT LVOT area (4.31±0.99 cm² ). LVOT was rather elliptical than round, with a mean eccentricity index of 1.47 (ratio of maximum to minimum LVOT diameters) assessed by MDCT. Mean TTE AVA estimated by the CE was 0.62±0.20 cm² . Substitution of 2DTTE LVOT area by 3DTEE LVOT area in the CE resulted in AVA of 0.74±0.24 cm² , while using MDCT LVOT area held an AVA of 0.80±0.24 cm² . MDCT-derived AVA was similar to MDCT planimetric AVA and allowed 24% of patients to be reclassified from severe to moderate AS.

CONCLUSIONS

2DTTE and 3DTEE underestimate LVOT area when compared to MDCT with significant impact on AVA estimation. Assessment through MDCT fusion AVA may be of incremental value in patients with discrepant severity criteria for AS.

Ferumoxytol MRA for transcatheter aortic valve replacement planning with renal insufficiency

BACKGROUND

Computed tomography angiography (CTA) is the test of choice for pre-procedure imaging of transcatheter aortic valve replacement (TAVR) candidates. The iodinated contrast required, however, increases the risk of renal dysfunction in patients with pre-existing renal failure. Ferumoxytol is a magnetic resonance imaging (MRI) contrast agent that can be used with renal failure. Its long vascular resonance time allows gated MRA sequences that approach CTA in image quality. We present respiratory and cardiac gated MRA enabled by ferumoxytol that can be post-processed in an analogous fashion to CTA.

METHODS

Seven patients with renal failure presenting for TAVR were imaged with respiratory and cardiac gated MRA at 3T using ferumoxtyol for contrast. Aortic annulus, root and peripheral access dimensions were calculated in a fashion identical to that used for CTA. Of these, 6 patients underwent a TAVR procedure and 5 had intraoperative valve assessment with transesophageal echocardiograph (TEE) using standard clinical protocols that employed both two- and three-dimensional techniques.

RESULTS

Good correlation between MRA aortic annulus measurements and those from TEE were shown in 5 patients with mean annulus area of 392.4mm² (290-470 range) versus 374.1mm² (285-440 range), with a pairwise correlation coefficient of 0.92, p=0.029. All patients received Sapien valve implants (one 20mm, three 23mm, and two 26mm valves). Access decisions were guided by MRA with no complications. Annulus sizing resulted in no greater than trace/mild aortic regurgitation in all patients.

CONCLUSIONS

Ferumoxytol MRA is a safe alternative to CTA in patients with renal failure for pre-TAVR analysis of the aortic root and peripheral access.

On the Mechanics of Transcatheter Aortic Valve Replacement

Transcatheter aortic valves (TAVs) represent the latest advances in prosthetic heart valve technology. TAVs are truly transformational as they bring the benefit of heart valve replacement to patients that would otherwise not be operated on. Nevertheless, like any new device technology, the high expectations are dampened with growing concerns arising from frequent complications that develop in patients, indicating that the technology is far from being mature. Some of the most common complications that plague current TAV devices include malpositioning, crimp-induced leaflet damage, paravalvular leak, thrombosis, conduction abnormalities and prosthesis-patient mismatch. In this article, we provide an in-depth review of the current state-of-the-art pertaining the mechanics of TAVs while highlighting various studies guiding clinicians, regulatory agencies, and next-generation device designers.

Double trouble: A case of periprocedural detection of intracardiac thrombus and aortic root dissection during emergent transfemoral TAVR

We report a case of emergency transcatheter aortic valve replacement (TAVR) in a 65-year-old patient presenting with decompensated severe aortic stenosis. Transesophageal echocardiography (TEE) was used effectively to obtain measurements of the aortic annulus and for intra-procedural guidance. At baseline, we detected a left atrial appendage thrombus and a localized aortic root dissection after balloon valvuloplasty. The case highlights the important role that TEE may play during TAVR procedures.

Significant Reduction in Mitral Regurgitation Volume Is the Main Contributor for Increase in Systolic Forward Flow in Patients with Functional Mitral Regurgitation after Transcatheter Aortic Valve Replacement: Hemodynamic Analysis Using Echocardiography

BACKGROUND

Reduction in mitral regurgitation (MR) after transcatheter aortic valve replacement (TAVR) has previously been reported. However, the hemodynamic effects of TAVR in patients with MR have not been previously evaluated.

METHODS

We analyzed 571 patients who underwent TAVR from December 2010 to December 2013. We studied 20 patients with moderate or severe preprocedural functional mitral regurgitation (FMR) who also had a follow-up transthoracic echocardiography (TTE) examination between 90 and 360 days (median 213 days) after TAVR (Significant FMR Group). We also studied age- and gender-matched 20 patients with mild or lesser MR (Nonsignificant MR Group). Left ventricular functional measurements were assessed using echocardiography before and after TAVR. Left ventricular outflow tract stroke volume measurements using pulsed-wave Doppler (SVLVOT ) were calculated as a representative of systolic forward flow, and stroke volume by the Simpson's method (SVSimpson ) was calculated as a parameter of degree of LV contraction.

RESULTS

MR grade improved in 22 of 40 patients after TAVR. In both groups, BNP level decreased, left ventricular ejection fraction increased, and SVLVOT increased after TAVR. SVSimpson increased in the Nonsignificant MR Group and remained unchanged in the Significant FMR Group. Vena contracta width of MR (MRVC) decreased in the Significant FMR Group. Using multivariable analysis in the Significant FMR Group, the increase in SVLVOT significantly correlated with the decrease in MRVC (P < 0.05).

CONCLUSIONS

SVLVOT increased significantly after TAVR in patients with FMR. In these patients, increase in SVLVOT after TAVR was associated with decrease in severity of MR.