Planimetric and continuity equation assessment of aortic valve area: Head to head comparison between cardiac magnetic resonance and echocardiography

PURPOSE: To compare the accuracy of planimetric and continuity equation measurements of aortic valve area (AVA) by cardiac MR (cMR) to each other and against transthoracic (TTE) and transesophageal (TEE) echocardiography. MATERIALS AND METHODS: A total of 31 patients (21 men, mean age = 67 +/- 13 years) with aortic stenosis (AS) and 16 controls (12 men, mean age = 57 +/- 14 years) underwent measurement of AVA by planimetric and continuity equation cMR. Measurements were compared to TEE planimetry and continuity equation TTE. RESULTS: AVA by continuity equation cMR correlated highly to continuity equation TTE (r = 0.98) and was not significantly different (1.8 +/- 1.3 cm2 vs. 1.8 +/- 1.4 cm2, P = 0.62). Similarly, AVA by cMR planimetry was not statistically different from TEE planimetry (2.1 +/- 1.7 cm2 vs. 2.1 +/- 1.6 cm2, P = 0.34) and correlated highly (r = 0.98). Yet planimetric measurements of AVA by cMR and TEE were significantly higher than AVA by continuity equation cMR (P < 0.001 and P < 0.001, respectively) and TTE (P < 0.001 and P < 0.001, respectively). CONCLUSION: Both planimetry and continuity equation-based measurements of AVA by cMR are equally accurate. However, similar to TEE, cMR AVA is larger by planimetry than by continuity equation. This is consistent with the contention that the anatomical maximum opening of a stenotic aortic valve is larger than the size of the functional vena contracta.