JACC: CT can help prevent undersizing of aortic valves

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Multidetector CT (MDCT) 3D aortic annular dimensions are predictive of valve leakage following transcatheter aortic valve replacement (TAVR), according to a study published online Feb. 22 in the Journal of the American College of Cardiology.

Approximately one in nine patients undergoing TAVR experiences moderate to severe paravalvular aortic regurgitation (PAR), explained Jonathon Leipsic, MD, of St. Paul’s Hospital, University of British Columbia in Vancouver, and colleagues. PAR is associated with increased morbidity and mortality and one of the main causes of PAR is undersizing of the transcatheter heart valve (THV).

“Accurate and reproducible measurements of the aortic annulus are crucial for optimum sizing of THVs,” wrote the authors.

Included in the study were 102 patients who underwent MDCT prior to TAVR. Differences in THV size and measurements of annular size from MDCT were analyzed to determine their ability to predict PAR. MDCT was repeated after TAVR in a group of 50 patients to assess THV eccentricity and expansion.

Moderate or severe PAR occurred in 13 of the 102 patients. Results showed that PAR was associated with THV undersizing (THV diameter – mean diameter = -0.7 mm vs. 0.9 mm for trivial to mild PAR) and the difference between THV size and MDCT annular size was predictive of PAR. Annular eccentricity, however, was not associated with PAR.

The authors also reported that 35.3 percent and 45.1 percent of THVs were undersized relative to MDCT mean diameter and area, respectively.

“This study demonstrates that MDCT annular measurements have good predictive value of moderate or severe PAR following TAVR. Differences between nominal THV size and MDCT mean annular diameter and area demonstrated the strongest relationship,” wrote the authors. “Importantly, these findings were consistent across multiple MDCT readers from different institutions and countries using a variety of workstations, suggesting that these findings are generalizable.”

Leipsic and colleagues said their data suggest that the implanted THV size should be greater than the 3D annular size assessed by MDCT to reduce the risk of PAR. THVs oversized by at least 1 mm by diameter or 10 percent by area had a significantly reduced risk of moderate or severe PAR, they explained, but oversizing has its own risks. Coronary occlusion or annular rupture can occur with THV oversizing and future studies are needed before intentional oversizing should be performed.

The authors wrote that annular diameters identified with 2D transesophageal echocardiography (TEE) are on average 1.4 mm less than the mean diameters on MDCT, suggesting that TEE underestimates the true annular size.

“We do not intend to suggest that MDCT is superior to TEE but rather that MDCT with 3-dimensional measures can provide complementary and additive information in the assessment of patients undergoing TAVR,” they wrote.

A second study published the same day in the Journal of the American College of Cardiology, however, suggested that CT become the new gold standard for annular evaluation. Researchers in that study, led by Raj. R. Makkar, MD, of Cedars-Sinai Heart Institute in Los Angeles, argued that the 3D measures of CT provided superior information to traditional 2D TEE.