Page 25 - Journal of Structural Heart Disease Volume 5, Issue 3

Original Scientific Article
64
Despite the constraints to which patients are eli- gible for percutaneous pulmonary valve replacement (PPVR), there is still no consensus about whom to recommend for PPVR rather than surgery. The main reason for replacing the pulmonary valve in this pop- ulation is the deleterious effects of pulmonary regur- gitation, including arrhythmia risk, decline in right ventricular function, exercise intolerance, and risk of sudden death [2, 5]. Cardiac MRI is considered to be the gold standard in evaluating right ventricular size and function in patients with repaired RVOT lesions. Cardiac MRI is also considered the most reliable mo- dality in clinical decision making regarding timing of pulmonary valve replacement; thus many of these patients will undergo this procedure as part of rou- tine management [5, 6]. However, there are few stud- ies evaluating the effectiveness of cardiac MRI as a screening tool for PPVR candidacy and no studies to our knowledge that evaluated the ability of cardiac MRI to determine candidacy based on RVOT size.
Balloon waist diameter (BWD) is still the gold stan- dard measurement that determines if a PPVR can be performed, but this requires an invasive procedure. While the risk of diagnostic catheterization is low, it is not negligible [7]. The aim of this study is to de- termine the correlation and agreement of the RVOT minimal diameter between pre-procedural cardiac MRI and the measured BWD of the RVOT in patients undergoing attempted or successful PPVR.
Methods
This was a single center, retrospective study of pa- tients undergoing PPVR who had a cardiac MRI per- formed within one year prior to the procedure. The Institutional Review Board at the Medical University of South Carolina approved the project. All patients who underwent catheterization for attempted PPVR were eligible. Patients were excluded if they did not have a cardiac MRI within one year prior to the cath- eterization at this institution, the PPVR was done via perventricular technique, or BWD measurements were not available.
The cardiac MRI studies were performed using a 1.5 T system (Magnetom Avanto, Siemens Healthineers, Erlangen, Germany), following a standard institution- al clinical protocol. Measurements were made from
three different MRI sequences: stacked cine steady- state free-precession imaging (cSSFP) through the RVOT in two planes, contrast-enhanced magnetic resonance angiography (MRA), and a self-navigat- ed three-dimensional steady-state free-precession (3D-SSFP) technique. The cSSFP planes were select- ed for measurement from stacked “4-chamber” slices (oblique coronal plane) and slices taken through the RVOT perpendicular to the “4 chamber” view (oblique sagittal plane). The MRA and 3D-SSFP images were uploaded to a separate workstation for 3D recon- struction (Aquarius iNtuition, TeraRecon, San Mateo, Calif.) Cardiac cycle was gated for cSSFP and 3D-SSFP protocols. cSSFP images were retrospectively gated with 25 phases per cardiac cycle taken during an ex- piratory breath hold. The field of view was adjusted for body size. All cardiac MRI measurements were per- formed by a single investigator (JDK). Measurements from cSSFP images were made during peak systo- le at the narrowest diameter of the RVOT (Figure 1). MRA and 3D-SSFP measurements were made of the cross-sectional diameter at the narrowest portion of the RVOT. Two measurements of the cross sectional diameter were taken perpendicular to each other. BWD was measured at the time of catheterization and was defined as the narrowest point in the sizing bal- loon at full inflation within the RVOT (Figure 1). This was done using a compliant sizing balloon, with few exceptions AmplatzerTM sizing balloon II (St. Jude, St. Paul, MN), which was expanded using hand inflation until a waist was seen in the RVOT. Volumetric data was extracted from cardiac MRI reports.
Categorical variables are described as counts and percentages; continuous variables are described us- ing means and standard deviations. Measurements of the BWD diameter in the anteroposterior (AP) and lateral views were plotted against the cardiac MRI measurements in each protocol. Correlation analysis was done using Pearson’s “r”. Agreement was detect- ed using Bland-Altman plots.
Results
There were 23 patients who met inclusion criteria. Of those, 18 (78%) had BWD measurements available in both AP and lateral orientation, 22 (96%) had lat- eral BWD measurements available for comparison.
Journal of Structural Heart Disease, June 2019
Volume 5, Issue 3:62-69