Correlation of aortic valve area obtained by the velocity-encoded phase contrast continuity method to direct planimetry using cardiovascular magnetic resonance.

BACKGROUND: Aortic stenosis (AS) is the most common valvular heart disease resulting in surgical intervention. Transthoracic echocardiography (TTE) utilizing the continuity equation is commonly used to determine aortic valve area (AVA). However, sometimes TTE can be limited by poor acoustic windows, heavy valvular calcification, or eccentric jet morphology. Cardiovascular magnetic resonance (CMR) provides an alternative non-invasive method for the evaluation of AVA using direct planimetry. Prior studies have shown good correlation between CMR and other modalities, such as TTE, TEE, and cardiac catheterization. CMR can also assess AVA by using the continuity equation employing velocity-encoded phase contrast (VEPC) imaging. We sought to assess whether velocity-encoded phase-contrast MRI can provide an alternate means of quantifying AVA by CMR.
METHODS: Twenty-two consecutive AS patients were imaged with CMR. AVA was determined by VEPC imaging and by direct planimetry.
RESULTS: Mean AVA by planimetry was 1.05+/-0.41 cm2 and 1.00+/-0.4 cm2 by VEPC, with a strong correlation (R2=0.86, p<0.0001) between the two methods. The mean difference of AVA was 0.05+/-0.15 (95% CI=[0.02-0.08]), and the limits of agreement were -0.26 to 0.36 cm2. The mean difference between 2 observers for planimetry was 0.030+/-0.07 (95% CI=[0.02-0.04]) with limits of agreement of -0.11 to 0.16 cm2 and for VEPC was 0.008+/-0.085 (95% CI=[-0.01-0.026]) with limits of agreement of -0.16 to 0.18 cm2.
CONCLUSIONS: VEPC CMR is an alternative method to direct planimetry for accurately determining AVA. Both techniques can be easily incorporated into a single CMR exam to increase the confidence of AVA determination utilizing cardiac magnetic resonance imaging.