• CMR May Help Assess Risk for Coronary Artery Compression Prior to TPVi

    Cardiac magnetic resonance (CMR) can be a “useful tool” in assessing risk for coronary artery (CA) compression in patients undergoing transcatheter pulmonary valve implantation (TPVi) for treatment of dysfunctional RV-PA conduits, according to a new multi-center retrospective analysis.

    The study, published online Monday and in the May 9 issue of JACC: Cardiovascular Interventions, evaluated the accuracy of CMR in predicting CA compression during TPVi – a widely available option to treat dysfunctional right ventricle (RV)–to–pulmonary artery (PA) conduits, for which CA compression is an absolute contraindication.

    Led by Ryan A. Romans, MD, from Ward Family Heart Center at Children’s Mercy Kansas City, Missouri, the team noted that computed tomography (CT) has been shown to predict the risk for CA compression prior to attempted TPVi, with patients whose CAs are in closer proximity to the right ventricular outflow tract (RVOT) and those with abnormal coronary anatomy being higher risk.

    “However, computed tomography requires radiation, and many patients undergo CMR to assess RV volumes and function,” they said, noting that the utility of CMR in predicting CA compression during TPVi “remains unclear.”

    Indeed, they said that despite the routine use of CMR, CA compression precluding TPVi still occurs in approximately 5% to 10% of patients.

    “If CMR were able to accurately predict CA compression, those patients could avoid unnecessary cardiac catheterization, attempted TPVi procedures, and potential serious adverse events,” said Romans and colleagues.

    “Alternatively, if CMR were unable to predict risk for CA compression, it would be unnecessary if being done only to evaluate CA anatomy.”

    Study details

    The multicenter retrospective cohort study included all patients who underwent attempted TPVi between 2007 and 2016 at nine centers in the United States. Patients were included if they had RV-PA conduits, underwent attempted TPVi, and underwent CMR in the 12 months prior to attempted TPVi. TPVi in patients with native RVOTs and those who previously underwent surgical bioprosthetic pulmonary valve replacement were excluded.

    Patients were excluded if the CMR was not of adequate quality to evaluate CA position relative to the conduit, noted Romans and his colleagues.

    A total of 240 patients met inclusion criteria for the study. At baseline, the patients identified to have CA compression were of similar age (mean 19.3 years old with CA compression vs. a mean 19.0 years for no compression), the majority were male (70.8% vs. 60.9% respectively), received a homograft RV-PA conduit (79.2% vs 81,6%), and had similar RV-PA conduit size at implantation (both 21).

    The majority of patients were reported to have normal coronary anatomy, said the authors, adding that the most common diagnoses were tetralogy of Fallot (TOF) variants and aortic valve disease status post Ross procedure.

    There was a relatively even distribution of conduit dysfunction types of pulmonary stenosis (PS) (36%), PI (23%), and both PS and PI (40%).

    Key findings

    Among 231 patients, TPVi was successful in 198 (86%), said the team, noting that in 24 (10%), balloon testing precluded implantation (documented CA compression or high risk).

    A univariate analysis found that anomalous coronary anatomy, severe conduit calcification, and intermediate or greater risk on qualitative assessment were associated with CA compression.

    When controlling for abnormal coronary anatomy or conduit calcification in the multivariable analysis, both distance to the RV-PA conduit ≤2.1 mm (area under the curve [AUC]: 0.70) and distance to most stenotic area ≤13.1 mm (AUC: 0.69) predicted CA compression (P <0.05 for all).

    Subjective assessment had the highest AUC (0.78), with 96% negative predictive value, noted Romans and colleagues.

    “This multicenter study showed that CMR can be a useful tool in assessing risk for CA compression in patients undergoing TPVi for treatment of dysfunctional RV-PA conduits,” they said.

    “This study is also the first to demonstrate that severe conduit calcification is a risk factor for CA compression,” they said. “This is not surprising, as the calcified portions of the conduit are pushed outward by the stents that are placed to restore the lumen of the conduit to an adequate size for a transcatheter valve to be placed.”

    “The heavily calcified conduits thus take up more space within the mediastinum when displaced, increasing the risk for CA compression.”

    The team noted that TPVi may still be successful even in patients thought to be high risk, adding that CA compression cannot be completely ruled out noninvasively.

    “CMR may assist in patient selection and counseling families prior to TPVi, although balloon testing remains essential,” they said.

    Stepwise approach

    Writing in an accompanying editorial, Philipp Lurz, MD, PhD, and Anne Rebecca Schöber, MD, from the University of Leipzig and Leipzig Heart Institute, Germany, noted that a stepwise approach is recommended to reduce the risk of CA compression to a minimum.

    “First, the proximity of the proximal CA to the RVOT should be assessed, they said, noting that CMR should be used to visualize the anatomical relationship of the coronary arteries and the proposed implantation site.

    “As a second step, aortic root angiography should be performed in all patients at the time of catheterization,” they noted. “On biplane projection, the relationship between the CA and the pulmonary artery can be assessed.”

    “If these 2 investigations cannot fully rule out the risk for coronary compression, selective coronary angiography and simultaneous balloon inflation in the implantation site is performed.”

    The editorialists added that it is important to continue the work set out in the new study, and to further refine objective CMR criteria, but noted that in the meantime, invasive assessment and testing for CA compression “remain irreplaceable.”

    “Hopefully in the future, with the advancement of noninvasive imaging and the establishment of objective criteria, which this study has importantly contributed to, physicians will be able to spare patients unnecessary treatment attempts and optimize individual patient selection and treatment,” they said.

    Sources:

    Romans RA, Lu JC, Balasubramanian S, et al. Cardiac Magnetic Resonance to Predict Coronary Artery Compression in Transcatheter Pulmonary Valve Implantation Into Conduits. JACC Cardiovasc Interv 2022;15:979-988.

    Lurz P, Schöber AR. Coronary Artery Compression in Percutaneous Pulmonary Valve Implantation: Go the Distance. JACC Cardiovasc Interv 2022;15:989-991.

    Image Credit: samunella – stock.adobe.com

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