Three-dimensional surface area of the aortic valve orifice by three-dimensional echocardiography: Clinical validation of a novel index for assessment of aortic stenosis

Background A direct and accurate method of assessing aortic valve area (AVA) in patients with aortic stenosis (AS) is desirable because of the well-known theoretical and practical limitations of the currently available methods. We assessed the clinical feasibility and accuracy of a novel index, the 3-dimensional surface area (3-DSA) of the aortic valve orifice by 3-dimensional transesophageal echocardiography (3-DTEE) in patients with AS. Methods Intraoperative 3-DTEE was performed in 23 consecutive patients (mean age 58 ± 15 years) with valvular AS using a Toshiba SSA-380A system with a multiplane TEE probe and a TomTec EchoScan system. The 3-DTEE acquisition, processing and reconstruction were conducted and the aortic valve orifice presented using a “surgeon’s aortotomy view” (aortic valve orifice as if viewed through an open aortic root). The 3-D images were videotaped and calibrated and the 3-DSA measured by planimetry of the inner surface of the aortic valve leaflets at the maximal systolic opening using the dynamic 3-D images. For comparison, the 2-D cross sectional area (2-DCSA) of the aortic valve was also determined by 2-DTEE. The 3-DSA and 2-DCSA were compared with the AVA by the invasive Gorlin formula and the Doppler continuity equation method by transthoracic echocardiography. Results The 3-DSA and 2-DCSA measurements were feasible in all but one patient. Both 3-DSA and 2-DCSA correlated moderately well with the AVA by the Gorlin formula (n = 17, r = 0.66, standard error of the estimate [SEE] = 0.3 cm2 , P < .05 for 3-DSA and r = 0.61, SEE = 0.5 cm2 P < .05 for 2-DCSA, respectively). They also correlated well with the AVA by Doppler continuity equation method (n = 22, r = 0.90, SEE = 0.1 cm2 , P < .05 for 3-DSA and r = 0.83, SEE = 0.3 cm2 , P < .05 for 2-DCSA, respectively). There was no statistically significant difference between the 3-DSA and AVA by both the Gorlin formula (Δ = 0.1 ± 0.3 cm2 , P = .3) and the Doppler continuity equation (Δ = –0.0 ± 0.3 cm2 , P = .7). In contrast, the 2-DCSA significantly overestimated AVA by the Gorlin formula (Δ = 0.5 ± 0.5 cm2 , P < .005) and by the Doppler continuity equation (Δ = 0.5 ± 0.6 cm2 , P < .0001). Conclusions Planimetry of 3-DSA of the aortic valve orifice by 3-DTEE is a clinically feasible and relatively accurate technique for assessment of AVA and is superior to 2-DCSA by 2-DTEE. (Am Heart J 1998;136:1042-50.)