At what flow rate does aortic valve gradient become severely elevated? Implications for guideline recommendations on aortic valve area cutoffs

IntroductionSince many patients with AVA < 1.0 cm2 do not manifest a mAVG > 40 mmHg, we sought to determine the AVA at which mAVG tends to exceed 40 mmHg in a sample of subjects with varied transvalvular flow rates.Material and methodsWe selected 200 subjects with an AVA< 1.0 cm2. The sample was selected to include subjects with a varied mean systolic flow (MSF) rates. Linear regression was performed to determine the relationship between MSF and mAVG. Since this relationship varied by AVA, the regression was stratified by AVA (critical <0.6 cm2, severe 0.6-0.79 cm2 , moderately severe 0.8-0.99 cm2)ResultsThe study sample was 79 ± 12 years-old and was 60% female. The MSF rate at which mAVG tended to exceed 40 mmHg was 120 ml/s for critical AVA, 183 ml/s for severe AVA and 257 ml/s for moderately severe AVA. Those with moderately severe AVA rarely (8%) had a mAVG > 40 mmHg at a wide range of MSF. In contrast, those with severe AVA typically (75%) had mAVG > 40 mmHg when MSF was normal (>200 ml/s). Those with critical AVA frequently (44%) had mAVG > 40 mmHg, even when MSF was reduced.ConclusionsAVA > 0.8 cm2 was rarely associated with mAVG > 40 mmHg, even when transvalvular flow rate was normal. Consideration should therefore be given to either raising the cutoff AVA or lowering the mAVG at which aortic stenosis is considered severe.