Cardiac MRI for Post-TAVR Paravalvular Leak Assessment
Condition: Paravalvular Leak
Study type: Observational

Summary: 
      The objectives of this study are to: a) evaluate and correlate the severity of paravalvular
      leak (PVL) assessed by both cardiac MRI and transthoracic echocardiography (TTE) after
      transcatheter aortic valve replacement (TAVR) with Medtronic Evolut-R or Evolut PRO
      bioprostheses; b) assess the inter and intraobserver variability of both imaging methods; and
      c) correlate the severity of PVL with post-TAVR changes in LV remodeling and clinical
      outcomes.
    

Detailed description: 
      Paravalvular leak (PVL) represents the most common complication post-transcatheter aortic
      valve replacement (TAVR). Presence of even mild PVL has been associated with unfavorable
      outcomes including late mortality, which is physiologically and hemodynamically hard to be
      reconciled.

      Although transthoracic echocardiogram (TTE) is the first line test for the PVL
      quantification, it can be flawed due to poor acoustic windows, eccentricity of PVL, image
      degradation associated with the implanted prosthesis, irregular orifices, subjectivity and
      inconsistency of the assessment and grading. Furthermore, to date, most published studies do
      not use a uniform standardized way of quantifying the PVL. The Valve Academic Research
      Consortium (VARC) published the VARC II definitions and suggested the use of TAVR-specific
      criteria for the assessment of PVL. However, there has been no validation of this proposed
      criteria and how their selected cutoffs correlate to patient outcomes. All these issues
      contribute to uncertainty and imprecision of the current method, leading to difficulties and
      subjectivity in the assessment and quantification of PVL severity.

      Cardiac MRI (CMR) is able to directly quantify aortic regurgitation with high accuracy and
      reproducibility by using the technique of phase-contrast velocity mapping when compared to
      TTE. CMR had lower intraobserver and interobserver variabilities for regurgitant volume
      assessment, suggesting that CMR may be superior for serial measurements. In addition, CMR
      quantification of aortic regurgitant fraction allows risk-stratification identifying patients
      at risk for development of heart failure and need for aortic valve surgery.

      However, despite these advantages, the use of CMR for PVL assessment post-TAVR has been
      limited. A recent single center prospective pilot study (n=16) showed that CMR assessment of
      PVL was feasible using CoreValve prosthesis. In addition, CMR rather than TTE, correlated
      better with intra-procedural aortography. TTE underestimated the degree of PVL compared to
      CMR suggesting the opportunity of this modality to more reliably and accurately quantify PVL
      after TAVR. Another recent small and single-center CMR study (n=43) compared immediate
      post-TAVI CMR findings with those at 6-month follow-up. There were 32 patients (74%) treated
      with Medtronic CoreValve prosthesis and 11 (26%) treated with Edwards Sapien XT valve. The
      authors noted significant favorable LV remodeling at 6 months, but not in patients with >
      mild PVL. Furthermore, PVL quantified by CMR did not decrease over time. Given the small
      number of patients, the authors could not compare the temporal changes between the two
      prosthesis. In addition, the mechanisms associated with the changes in PVL severity were not
      able to be ascertained given the study design.

      CMR provides exquisite tissue characterization using late-gadolinium enhancement imaging.
      Adverse myocardial response to pressure-overload causes maladaptive myocardial hypertrophy
      with increased LV mass and also myocardial fibrosis (MF), which has been associated with
      adverse outcomes despite aortic valve replacement. Newer CMR techniques such as T1 mapping
      and extracellular volume fraction quantification can now non-invasively quantify the extent
      of diffuse MF supported by histological validation. The interplay between PVL and MF and
      their impact of on the LV reverse remodeling is unknown. It is possible that PVL might exert
      its detrimental effects by slowing LV reverse remodeling, hampering the regression of LV
      hypertrophy and myocardial fibrosis post-TAVR.

      Lastly, gated multi-detector computed tomography (MDCT) which has a critical role in the
      pre-procedural planning of patients undergoing TAVR evaluation, also has been found important
      in identifying predictors of PVL post-TAVR. However, the role of MDCT in the post-TAVR
      setting, for PVL evaluation, has not been yet established. Gated MDCT post-TAVR might be
      relevant to determine the interplay between the native aortic valve/annulus and the TAVR
      prosthesis aiding in the evaluation of possible mechanism(s) behind PVL changes over time.
    

Intervention name(s): Multimodality Imaging and Biomarkers
Intervention type(s): Diagnostic Test
Intervention description(s): Cardiac MRI, Cardiac MDCT, Echocardiography and Biomarkers Testing
Observational model: Cohort
Time perspective: Prospective
Sampling method: Probability Sample
Study population: 
        55 men and women aged 60 or above who received Medtronic Evolut-R or Evolut PRO and have at
        least mild paravalvular leak on transthoracic echocardiogram performed 25-45 days after
        TAVR procedure.
      
Biospecimen description: 
      Samples for future
    
Keywords: post TAVR quantification; cardiac MRI; echocardiography; biomarkers