Evaluation and Clinical Implications of Aortic Valve Calcification Measured by Electron-Beam Computed Tomography

Abstract

Background-Electron-beam computed tomography (EBCT) is used to measure coronary calcification but not for aortic valve calcification (AVC). Its accuracy, association with aortic stenosis (AS) severity, and diagnostic and prognostic value with respect to AVC are unknown. Methods and Results-In 30 explanted aortic valves, the AVC score by EBCT (1125Ϯ1294 Agatston units [AU]) showed a strong linear correlation (rϭ0.96, PϽ0.0001) with valvular calcium weight (653Ϯ748 mg) by pathology that allowed estimation of calcium weight as AVC score/1.7, with a small standard error of the estimate (53 mg). In 100 consecutive clinical patients, we measured AVC by EBCT and AS severity by echocardiographic aortic valve area (AVA). The AVC score was 1316Ϯ1749 AU (range 0 to 7226 AU). Intraobserver and interobserver variabilities were excellent (4Ϯ4% and 4Ϯ10%, respectively). AVC and AVA were strongly associated (rϭ0.79, PϽ0.0001) but had a curvilinear relationship that suggested that AVC and AVA provide complementary information. AVC score Ն1100 AU provided 93% sensitivity and 82% specificity for diagnosis of severe AS (AVA Ͻ1 cm 2 ), with a receiver operator characteristic curve area of 0.89. AVC assessment by echocardiography was often more severe than by EBCT (PϽ0.0001). During follow-up, 22 patients either died, developed heart failure, or required surgery. With adjustment for age, sex, symptoms, ejection fraction, and AVA, the AVC score was independently predictive of event-free survival (risk ratio 1.06 per 100-AU increment [1.02 to 1.10], PϽ0.001), even after adjustment for echocardiographic calcifications. Conclusions-AVC is accurately and reproducibly measured by EBCT and shows a strong association and diagnostic value for severe AS. The curvilinear relationship between AVC and AVA suggests these measures are complementary, and indeed, AVC provides independent outcome information. Thus, AVC is an important measurement in the evaluation of patients with AS.

Sex Differences in Aortic Valve Calcification Measured by Multidetector Computed Tomography in Aortic Stenosis

“…AVC measurement by MDCT is a fast, simple, noninvasive, highly feasible, widely available, and highly reproducible technique. 15,16 In these studies, intraobserver and interobserver variabilities were <7%. Moreover, for visualization of calcification, CT does not require contrast and can be performed in patients with arrhythmias.…”

“…13,[23][24][25] In the present large, prospective, cross-sectional study with simultaneous CT scans and Doppler echocardiograms, we observed excellent correlations between hemodynamic severity of AS and severity of AVC load determined by MDCT. 15,23,26,27 However, although the general mechanism of more calcification associated with more severe AS holds true, this large series of patients provides the power to detect for the first time that the relation between AS severity and AVC load in men and women is significantly different (Figure 1). As expected, in patients with mild AVC and less severe AS, the difference between sexes is smaller (Figure 2), and obviously, at that relatively benign end of the spectrum, AVC load, peak aortic velocity, mean gradient, and indexed aortic valve area should be equal in men and women with normal or minimally affected aortic valves.…”

“…However, Doppler echocardiographic measurements are routinely used clinically, and methods of measurement are well defined. The MDCT quantification of calcification has been the subject of longstanding collaboration among our institutions 15,16,49 and is achieved by software that leaves limited operator interventions in defining calcification of interest. As shown, variability is low, and ANCOVA showed that the slope of the regression of velocity-AVC is similar between institutions in men (P=0.40) and women (P=0.61) and between scanners used in men (P=0.34) and women (P=0.52).…”

“…6 However, the analogy to atherosclerosis suggests that there may be important, yet thus far undefined, sex-related differences in the development of AVC and the transition to AS. This issue can now be analyzed because cardiac computed tomography (CT) provides accurate and reproducible quantification of AVC load, 15 and multidetector CT (MDCT) may prove to be a useful adjunct tool for the evaluation of AS severity. However, previous studies suggested a single set of cutoff values for detecting severe AS regardless of sex, 16 so the impact of sex on the relation between aortic cusp calcification measured by MDCT and hemodynamic severity of AS remains uncertain.…”

Evaluation of valvular disease by cardiac computed tomography assessment

“…16 On the basis of these data, MDCT can be considered the preferred imaging technique for both diagnosis and prognosis in patients with poor acoustic windows or left ventricular (LV) dysfunction. 17 …”