Clinical validation semi-automatic quantification score for AV calcifications with TTE: The Global Calcium score

Introduction: Increased calcification of the aortic valve (AV) is associated with worse prognosis and faster progression of AV stenosis. An ultrasound (US) scoring system has recently been validated in vitro to quantify the amount of calcium compared to computed tomography (CT). Purpose: We aimed to validate this new US calcium scoring method in patients with AV calcification, compared to CT Agatston score of the AV. Methods: We prospectively enrolled 25 patients (mean age 71 ±15) years, 32% were male) with various degrees of AV calcification. All patients underwent both a cardiac CT and transthoracic echocardiography (TTE). The CT Agatston AV calcium score was determined . TTE parasternal long axis (PLAx) and short axis (PSAx) images were obtained, maintaining all US settings constant. The US global calcium (GC) score was calculated using imaging software OsiriX. Multiple regions of interest (ROIs) were applied in end-diastole. Three ROIs in PLAx view: at the anterior and posterior annulus and at the leaflets. Five ROIS in PSAx view: one delineating the annulus, one for every leaflet, and one delineating the cusps free edges. Three heart cycles were recorded. A calcium score was calculated by calibrating the mean grayscale value of those ROIs, to the adjacent blood-pool. The GC score was calculated as the mean of the PLAx and PSAx calcium scores. CT and US analysis were blinded for the results of the other imaging modality. Results: There is a significant linear correlation between the US GC score and the CT Agatston score for the quantification of AV calcifications (R2 0.4, p=0.0013). (Figure 1A). The GC score was 64 +/- 25AU (range 26 to 119 AU). A GC score > 47 AU provided 82% sensitivity and 75% specificity for diagnosis of severe calcification (CT Agatston score >1100 AU). The GC score threshold allowed semi-automatic selection of valvular regions with severe calcification. (Figure 1B)