Aliased Flow Signal Planimetry by Cardiovascular Magnetic Resonance Imaging for Grading Aortic Stenosis Severity: A Prospective Pilot Study

Objectives: Transthoracic echocardiography (TTE) is the standard technique for assessing aortic stenosis (AS), with effective orifice area (EOA) recommended for grading severity. EOA is operator-dependent, influenced by a number of pitfalls and requires multiple measurements introducing independent and random sources of error. We tested the diagnostic accuracy and precision of aliased orifice area planimetry (AOA(cmr)), a new, simple, non-invasive technique for grading of AS severity by low-VENC phase-contrast cardiovascular magnetic resonance (CMR) imaging. Methods: Twenty-two consecutive patients with mild, moderate, or severe AS and six age- and sex-matched healthy controls had TTE and CMR examinations on the same day. We performed analysis of agreement and correlation among (i) AOA(cmr); (ii) geometric orifice area (GOA(cmr)) by direct CMR planimetry; (iii) EOA(echo) by TTE-continuity equation; and (iv) the “gold standard” multimodality EOA (EOA(hybrid)) obtained by substituting CMR LVOT area into Doppler continuity equation. Results: There was excellent pairwise positive linear correlation among AOA(cmr), EOA(hybrid), GOA(cmr), and EOA(echo) (p < 0.001); AOA(cmr) had the highest correlation with EOA(hybrid) (R(2) = 0.985, p < 0.001). There was good agreement between methods, with the lowest bias (0.019) for the comparison between AOA(cmr) and EOA(hybrid). AOA(cmr) yielded excellent intra- and inter-rater reliability (intraclass correlation coefficient: 0.997 and 0.998, respectively). Conclusions: Aliased orifice area planimetry by 2D phase contrast imaging is a simple, reproducible, accurate “one-stop shop” CMR method for grading AS, potentially useful when echocardiographic severity assessment is inconclusive or discordant. Larger studies are warranted to confirm and validate these promising preliminary results.