Validation of the severity index by cardiac catheterization and Doppler echocardiography in patients with aortic sclerosis and stenosis

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Abstract

Abstract
The severity index is a new echocardiographic measure that is thought to be an accurate indicator of aortic leaflet pathology in patients with AS. However, it has not been validated against cardiac catheterization or Doppler echocardiographic measures of AS severity nor has it been applied to patients with aortic sclerosis. The purposes of this study were to compare the severity index to invasive hemodynamics and Doppler echocardiography across the spectrum of calcific aortic valve disease, including aortic sclerosis and AS. 48 patients with aortic sclerosis and AS undergoing echocardiography and cardiac catheterization comprised the study population. The aortic valve leaflets were assessed for mobility (scale 1 to 6) and calcification (scale 1 to 4) and the severity index was calculated as the sum of the mobility and calcification scores according to the methods of Bahler et al. The severity index increased with increasing severity of aortic valve disease; the severity indices for patients with aortic sclerosis, mild to moderate AS and severe AS were 3.38 ± 1.06, 6.45 ± 2.16 and 8.38 ± 1.41, respectively. The aortic jet velocity by echocardiography and the square root of the maximum aortic valve gradient by cardiac catheterization correlated well with the severity index (r = 0.84, p < 0.0001; r = 0.84, p < 0.0001, respectively). These results confirm that the severity index correlates with hemodynamic severity of aortic valve disease and may prove to be a useful measure in patients with aortic sclerosis and AS.

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Background
Aortic stenosis (AS) and aortic sclerosis are common findings in elderly patients, affecting 50% of those over the age of 84 years [1]. Echocardiography provides an accurate noninvasive assessment of disease severity and progression [2,3]. Studies have found that the presence of aortic valve calcium is associated with increased disease severity and predicts more rapid disease progression [4]. Bahler et. al. proposed that the severity index, a measure of both aortic valve leaflet calcium and mobility, was an accurate indicator of aortic leaflet pathology in patients with AS [5]. However, this new echocardiographic score has not been validated against cardiac catheterization measures of AS severity. Moreover, this index has not been validated against either cardiac catheterization or Doppler echocardiography in patients with aortic sclerosis. Therefore, the purposes of this study were to compare the severity index to invasive hemodynamics and Doppler echocardiography across the spectrum of calcific aortic valve disease, including aortic sclerosis and AS.

Methods A. Study population
48 patients with aortic valve disease (aortic sclerosis and AS) identified by echocardiography with subsequent referral for invasive hemodynamic assessment of AS severity comprised the study population. All patients were referred for echocardiography by their treating physicians after a systolic murmur was detected. Patients underwent standard left and right heart catheterization for assessment of AS severity within one month of the echocardiogram. The institutional review board of Harbor-UCLA Research and Education Institute approved the study protocol. At the time of cardiac catheterization, information was obtained regarding the presence of traditional cardiovascular risk factors, including hypertension, family history of premature coronary artery disease, hyperlipidemia, smoking, and diabetes mellitus. Patients were classified as having hypertension if they were receiving anti-hypertensive medications or had known but untreated hypertension (systolic blood pressure >140 mm Hg or diastolic blood pressure > 90 mm Hg). Family history of coronary artery disease was defined as premature coronary artery disease (occurring in men age less than 45 years and women age less than 55 years) in a first-degree relative. Hyperlipidemia was defined as use of cholesterol lowering medication or, in the absence of cholesterol lowering medication use, as having a total serum cholesterol >240 mg/dL. Smoking was defined as the use of >10 cigarettes/day. Patients receiving insulin or oral hypoglycemic agents were classified as having diabetes mellitus.

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References
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