Measurement of Aortic Valve Area by Simplified Continuity Equation in Aortic Stenosis With Atrial Fibrillation

Gwon, Hyeon Cheol; Zo, Ju Hee; Kim, Hyo Soo; Sohn, Dae Won; Oh, Byung Hee; Lee, Myoung Mook; Park, Young Bae; Choi, Yoon Sik; Seo, Jung Don; Lee, Young Woo

Abstract

BACKGROUND
When aortic stenosis is associated with atrial fibrillation, estimation of the aortic valve area(AVA) by continuity equation refuires averaging of 8-12 beats of LVOT-TVI and AV-TVI to calculate mean LVOT-TVI and mean AV-TVI. Since this method labour intensive, we therefore propose a new simplified method.
METHODS
We studied 9 patients of aortic stenosis with atrial fibrillation. We recorded LVOT velocity and aortic valve velocity in 4-chamber view and measure the LVOT area in the parasternal long axis view. We measured RR interval(RR) and diastolic filling time(DFT) of preceding beat in ECG recorded simultaneously. AVA(mean)was defined as the aortic valve area calculated from the mean LVOT-TVI and mean AV_TVI of 10 veats by using continuity equation. AVA)RR), AVA(DFT), AVA(rTT) and AVA-rDDFT) were defined as the aortic valve area calculated from the 1 beat of LVOT-TVI and AV_TVI normalized by RR, DDFT, rRR and rDFT respectively. 20 sets of AVA(mean), AVA(RR), AVA(DFT),AVA(rTT) and AVA(DFT) were calculated in each patient and their means and standard deviations are compared.
RESULTS
1) R values of the correlation of RR, DFT, rTT, rDFT is 0.87, 0.87, 0.89 with LVOT-TVI and 0.91, 0.93, 0.94 with AV-TVI. 2) Averages of AVAs are AVA(mean) 0.76+/-0.35cm2, AVA(rRR) 0.75+/-0.04cm2, AVA(RR) 0.76+/-0.11cm2, AVA(DFT) 0.82+/-0.35cm2, AVA(rRR) 0.75+/-0.15cm2, AVA(rDFP) 0.76+/-0.10cm2. 3) Averages of AVAs showed no significant difference. Standard deviation of AVA(mean) was significantly smaller than other new AVAs(p<0.01). THe standard deviation of AVA(rDFT) was significantly smaller than that of AVA(RR), AVA(DFT) and AVA(RR)(p=0.35, p=0.05,p=0.008).
CONCLUSION
When aortic stenosis is associated with atrial fibrillation, newly derived AVA(rDFT) could be more easily calculated compared to conventional AVA(mean) and was also a reproducibe and precise estmate of aortic valve area.