Measures Of Aortic Stenosis Severity Research Articles

Flow Dependence of Measures of Aortic Stenosis Severity During Exercise

Flow Dependence of Measures of Aortic Stenosis Severity During Exercise

Flow dependence of measures of aortic stenosis severity during exercise

Objectives. This study was designed to investigate the effect of altering transvalvular volume flow rate on indexes of aortic stenosis severity (valve area, valve resistance, percent left ventricular stroke work loss) derived by using Doppler echocardiography.Background. Assessment of hemodynamic severity in aortic stenosis has been limited by the absence of an index that is independent of transvalvular flow rate. The traditional measurement of valve area by the Gorlin equation has been shown to vary with alterations in transvalvular flow. Recently, valve resistance and percent stroke work loss have been proposed as indexes that are relatively independent of flow. Although typically derived with invasive measurements, valve resistance and percent stroke work loss (in addition to continuity equation valve area) can be determined noninvasively with Doppler echocardiography.Methods. We performed 110 symptom-limited exercise studies in 66 asymptomatic patients with valvular aortic stenosis. Continuity equation valve area, valve resistance (the ratio between mean transvalvular pressure gradient and mean flow rate) and the steady component of percent stroke work loss (the ratio between mean transvalvular pressure gradient and left ventricular systolic pressure) were assessed by Doppler echocardiography at rest and immediately after exercise.Results. Mean transvalvular volume flow rate increased 24% (from [mean ± SD]319 ± 80 to 400 ± 140 ml/s, p < 0.0001); mean pressure gradient increased 36% (from 30 ± 14 to 41 ± 18 mm Hg, p < 0.0001); continuity equation aortic valve area increased 14% (from 1.38 ± 0.50 to 1.58 ± 0.69 cm2, p < 0.0001); valve resistance increased 13% (from 137 ± 81 to 155 ± 97 dynes · s · cm−5, p < 0.0001); and percent stroke work loss increased 17% (from 17.4 ± 6.9% to 203 ± 8.5%, p < 0.0001). The effects of flow on valve area, valve resistance and percent stroke work loss were independent of the presence of an aortic valve area ⪯ or > 1.0 cm2or reduced transvalvular flow rate (rest cardiac output < 4.5 liters/min).Conclusions. In patients with asymptomatic aortic stenosis, Doppler echocardiographic measures of valve area, valve resistance and percent stroke work loss are flow dependent. Flow dependence is observed with valve area ⪯ or > 1.0 cm2and in the presence of both normal and low transvalvular flow states. The potential effects of transvalvular flow should be considered when interpreting Doppler measures of aortic stenosis severity.

Doppler echocardiographic findings in adults with severe symptomatic valvular aortic stenosis

Baseline echocardiographic data in 680 adults (mean age 78 years) undergoing balloon aortic valvuloplasty at 24 medical centers were analyzed to describe the degree of outflow obstruction in patients with symptomatic aortic stenosis. Maximal aortic jet velocity ranged from 2.3 to 6.6 m/s (mean 4.4 ± 0.8) and continuity equation valve area ranged from 0.1 to 1.4 cm 2 (mean 0.6 ± 0.2). Of note, 36% had a jet velocity ≤4.0 m/s but only 3% had a valve area >1.0 cm 2 due to a high prevalence of impaired systolic function (54%). Outflow tract diameter was poorly correlated with body surface area (p = 0.26), although the group mean diameter was smaller in women than in men (1.9 ± 0.2 vs 2.1 ± 0.3 cm, p = 0.0001). Mean pressure gradient was related closely to maximal gradient (r = 0.92) and to maximal jet velocity (mean ΔP = 2.4 V 2 +0.75 mm Hg). Simpler measures of aortic stenosis severity were correlated with Doppler and invasive valve area as follows: maximal jet velocity (r = −0.36 and −0.32), mean gradient (r = −0.33 and −0.29), outflow tract to jet velocity ratio (r = 0.67 and 0.40), and the fractional shortening velocity ratio (r = 0.29 and 0.22). This study demonstrates marked variability in stenosis severity in symptomatic adults referred for balloon aortic valvuloplasty. The absence of a predictable relation between outflow tract diameter and body size emphasizes the importance of this measurement in each patient if definition of valve area is needed. The correlations between mean pressure gradient and maximal jet velocity, and between valve area and the velocity ratio support the potential use of these simpler measures of stenosis severity.

Hemodynamic progression of aortic stenosis in adults assessed by doppler echocardiography

Doppler echocardiography was used to follow the hemodynamic severity of aortic stenosis. First, the reproducibility of repeat recordings (mean interval 28 ± 36 days) of aortic jet velocity, made by two independent observers, was tested in 38 adults with aortic stenosis and unchanged clinical status. The two recordings of maximal velocity correlated well (r = 0.96, y = 0.88x + 0.46m/s, SEE = 0.21 m/s) with a mean coefficient of variation of 3.2%. Repeat recording of left ventricular outflow tract velocity by two independent observers in 10 other patients with aortic stenosis also correlated well (r = 0.94, y = 1.06x + 0.0 m/s, SEE = 0.06 m/s) with a mean coefficient of variation of 4.6%.Next, Doppler echocardiography was used to study 42 patients with aortic stenosis (mean age 66 years) over a follow-up interval of 6 to 43 months (mean 20). Maximal aortic jet velocity increased by 0.36 m/s per year (range −0.3 to +1.0 m/s per year). Mean transaortic pressure gradient changed by −7 to +23 (mean 8) mm Hg/year. Aortic valve area by the continuity equation (n = 25) decreased by 0 to 0.5 cm2/year (mean decrease 0.1 cm2/year). year patients had a worsening of stenosis (decrease in valve area) even though they had no change or a decrease in pressure gradient, because of concurrent decreases in transaortic volume flow.Twenty-one patients (50%) developed new or progressive symptoms of aortic stenosis necessitating valve replacement. These patients had a higher maximal aortic jet velocity at follow-up (4.5 versus 3.9 m/s, p < 0.01) and a greater rate of increase in mean pressure gradient (15 versus 7 mm Hg/year, p < 0.01) than did those who remained asymptomatic; however, there were no significant differences in age, follow-up interval or maximal aortic jet velocity at entry.It is concluded that Doppler echocardiographic measures of aortic stenosis severity are reproducible. The rate of change of transaortic pressure gradient varies among patients and the gradient may not increase even when stenosis severity worsens. Although stenosis severity progresses more rapidly in patients who develop symptoms requiring valve replacement, these patients cannot be identified at the initial study.