Kimberly S Yan

Publications (2)4.55 Total impact

• Article: Correlation of calcification on excised aortic valves by micro-computed tomography with severity of aortic stenosis.

  Sam Chitsaz, Namrata Gundiah, Charlie Blackshear, Nebiyu Tegegn, Kimberly S Yan, Ali N Azadani, Michael Hope, Elaine E Tseng
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  ABSTRACT: The quantification of incidentally found aortic valve calcification on computed tomography (CT) is not performed routinely, as data relating to the accuracy of aortic valve calcium for estimating the severity of aortic stenosis (AS) is neither consistent nor validated. As aortic valve calcium quantification by CT is confounded by wall and coronary ostial calcification, as well as motion artifact, the ex-vivo micro-computed tomography (micro-CT) of stenotic aortic valves allows a precise measurement of the amounts of calcium present. The study aim, using excised aortic valves from patients with confirmed AS, was to determine if the amount of calcium on micro-CT correlated with the severity of AS. Each of 35 aortic valves that had been excised from patients during surgical valve replacement were examined using micro-CT imaging. The amount of calcium present was determined by absolute and proportional values of calcium volume in the specimen. Subsequently, the correlation between calcium volume and preoperative mean aortic valve gradient (MAVG), peak transaortic velocity (V(max)), and aortic valve area (AVA) on echocardiography, was evaluated. The mean calcium volume across all valves was 603.2 +/- 398.5 mm3, and the mean ratio of calcium volume to total valve volume was 0.36 +/- 0.16. The mean aortic valve gradient correlated positively with both calcium volume and ratio (r = 0.72, p < 0.001). V(max) also correlated positively with the calcium volume and ratio (r = 0.69 and 0.76 respectively; p < 0.001). A logarithmic curvilinear model proved to be the best fit to the correlation. A calcium volume of 480 mm3 showed sensitivity and specificity of 0.76 and 0.83, respectively, for a diagnosis of severe AS, while a calcium ratio of 0.37 yielded sensitivity and specificity of 0.82 and 0.94, respectively. A radiological estimation of calcium amount by volume, and its proportion to the total valve volume, were shown to serve as good predictive parameters for severe AS. An estimation of the calcium volume may serve as a complementary measure for determining the severity of AS when aortic valve calcification is identified on CT imaging.
  The Journal of heart valve disease 05/2012; 21(3):320-7. · 0.81 Impact Factor
• Article: Operative risks and survival in veterans with severe aortic stenosis: surgery versus medical therapy.

  Sam Chitsaz, Nicolas Jaussaud, Edward Chau, Kimberly S Yan, Ali N Azadani, Mark B Ratcliffe, Elaine E Tseng
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  ABSTRACT: Transcatheter aortic valves were developed as an alternative to surgery for the one third to two thirds of patients with severe aortic stenosis who do not undergo aortic valve replacement. In this study, we examined reasons for medical management of aortic stenosis in relation to operative risks and outcomes for veterans with and without valve replacement. The echocardiography database was screened from 2000 to 2007 for severe aortic stenosis. The Society of Thoracic Surgeons risk scores and survival were determined for patients with and without aortic valve replacement. Of 132 severe aortic stenosis patients included, 42% were medically managed. Predicted operative mortality risk was lower for surgical patients than for medical patients (4.5%±4.2% versus 6.8%±5.1%, p=0.002). Overall, the most common reason for medical management of aortic stenosis was assumption that the patient was high risk for surgery (30.4%). The surgery group had significantly higher median survival (92.2 versus 32.4 months) and 5-year survival (71% versus 37%, p<0.001) than the medical group. Cardiac surgery was not consulted in 61% of medically managed patients, of whom only 18% had Society of Thoracic Surgeons risk score of 10 or greater. Aortic valve replacement was an independent predictor of lower mortality (hazard ratio 0.43, p=0.008). Although operative risk was higher among patients who did not undergo surgery, most were not the 10% or greater required for transcatheter valves. Given the significantly lower survival with medical therapy, aortic valve replacement should be carefully considered for most severe aortic stenosis patients whereas transcatheter aortic valves should be reserved for patients with high operative risks.
  The Annals of thoracic surgery 09/2011; 92(3):866-72. · 3.74 Impact Factor