Strata of Aortic Stenosis Severity vs. Survival Benefit of AVR
Is there an effect of different echocardiographic strata of aortic stenosis (AS) severity (with special interest in patients with an effective orifice area [EOA] between 0.8 and 1.0 cm2) on survival benefit associated with aortic valve replacement (AVR)?
A cohort of 1,710 patients with moderate to severe AS by echocardiography/Doppler were separated into four strata of AS severity based alternatively on EOA, indexed EOA, mean gradient, or peak aortic jet velocity (Vmax). The survival rates of medically vs. surgically treated patients were compared. To eliminate covariate differences that may have led to biased estimates of treatment effect, propensity matching with a greedy 5-to-1 digit-matching algorithm was used.
Mean EOA was 0.9 ± 0.3 cm2, mean gradient 33 ± 18 mm Hg, and mean Vmax 3.6 ± 0.9 m/s. A total of 1,030 (60%) patients underwent AVR within 3 months following echocardiographic evaluation. During a mean follow-up of 4.4 ± 3.0 years, there were 469 deaths. Patients with an EOA between 0.8 and 1.0 cm2 had a significant observed survival benefit with AVR (hazard ratio, 0.37; 95% confidence interval, 0.21-0.63; p = 0.0002). AVR also was associated with improved survival in patients with mean gradient between 25 and 40 mm Hg or Vmax between 3 and 4 m/s, but only in patients with concomitant EOA ≤1.0 cm2 (p = 0.001 vs. p = 0.46 in patients with EOA >1.0 cm2).
These results do not support decreasing the EOA threshold value for severity to 0.8 cm2, and they confirm that AVR is associated with improved survival in a substantial number of patients with discordant aortic grading.
Discrepancies between mean gradient and EOA on echocardiography (perhaps most commonly EOA ≤1.0 cm2 but mean gradient <40 mm Hg) has led to uncertainty as to whether the criterion for severe AS on echo/Doppler should be changed from EOA ≤1.0 cm2 to EOA ≤0.8 cm2. As is cogently discussed in the accompanying editorial, what constitutes truly severe AS should not be oversimplified to any one single measure; but rather should take into consideration a skilled physical examination, measurement of valve hemodynamics (including Vmax, mean gradient, dimensionless valve index, EOA, and indexed EOA), exercise hemodynamics, biological markers, evidence of myocardial fibrosis, and—most importantly—sound clinical judgment. However, this work provides evidence that the echo/Doppler threshold of EOA ≤1.0 cm2 is a potent predictor of clinical benefit from AVR, and therefore, should continue to be considered a criterion for severe AS.
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