Effective echo screening and inter modality agreement in the assessment of ascending thoracic aorta dimension (2020)

Type of publication:
Conference abstract

Author(s):
*Botley S.; *Challinor E.; *Ingram T.; *Lee E.; *Pakala V.

Citation:
Heart; Jul 2020; vol. 106

Abstract:
Introduction: Accurate measurement and interval monitoring of the ascending aorta for at risk individuals are crucial for prevention of life-threatening complications. Echocardiography (echo) is the first line screening test. Positive results are referred for computed tomography (CT) or magnetic resonance imaging (MRI), both are considered gold standard methods for imaging the whole aorta. These tests involve radiation (CT) and contrast (CT & MRI) exposure. An effective screening echo streamlines subsequent referrals to CT and MRI. Several published references (1,2,3) are in clinical use. Measurements are normalised to body surface area (1,3), height (2), gender (2,3) and age (3). The aims of this study were: Assess the inter-modality agreement of ascending aorta measurements between echo and CT. Compare the rate of ‘dilated aorta’ using the existing references (1,2,3). Methods Between Sep 2018 and Sep 2019, 107 patients underwent gated CT thoracic aorta at our institute as per clinically indicated. We retrospectively examined these records. We used Bland Altman plot to assess inter-modality agreement (echo & CT) of ascending aorta measurements. We reported inter and intra-observer variability for echo measurements as coefficient of variation. Echo aorta measurements were coded into ‘dilated’ or ‘normal’ after normalising for age, sex, height and weight as per the existing references (1,2,3). The rates of ‘dilated aorta’ using the three reference methods (1,2,3) were compared using Chi-squared test with Bonferroni adjustment. Statistical analysis was performed using SPSS 25 (IBM). Results Data were excluded from analysis due to incomplete biometrics (9), poor echo images (27). 71 subjects were included for analysis (age 68 +/- 14 years, BSA 1.9 +/- 0.2 m2, 52.1% male). 16 had bicuspid aortic valves. Intra- and interobserver variability for echo measurements were 1.2% and 1.4% respectively. Figure 1 shows the inter-modality agreement of ascending aorta measurements. Echo underestimated ascending aorta dimensions by a mean of 1.4 +/- 2.7 mm (95% CI 0.7-2.0 mm). There was a significant difference in the rates of ‘dilated aorta’ using the existing reference ranges (1,2,3): 59% (1), 27% (3) and 59% (2) of subjects had ‘dilated aorta’, c2 = 15.3, p=0.00. Conclusion Echo is an effective screening test for detecting ascending aorta dilatation. In our department, it has excellent intra- and inter- observer variability and good measurement agreement with CT. Normalising aortic dimension (3) resulted in the fewest ‘positive test’ requiring further imaging; potentially improving clinical efficacy of the service and avoiding contrast and radiation exposure for the patients.

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