1. Extent of Thoracic Aortic Atheroma Burden and Long- term Mortality after Cardiothoracic Surgery. A Computed Tomography Study. Vikram Kurra, Michael L. Lieber, Srikanth Sola, Vidyasagar Kalahasti, Donald Hammer, Stephen Gimple, Scott D Flamm, Michael A Bolen, Sandra S Halliburton, Tomislav Mihaljevic, Milind Y Desai, Paul Schoenhagen Cleveland Clinic, Cleveland, Ohio, USA

2. Disclosures Dr. Mihaljevic is a consultant for Edwards Lifesciences, St. Jude Medical, and Intuitive Surgical. Dr. Flamm reports indirect departmental research support from Phillips Healthcare and Siemens Medical Solutions. Dr. Halliburton serves on the Medical Advisory Board, Philips Medical Systems.

3. Background and Objectives Background: In patients evaluated for cardiothoracic surgery, presence of severe aortic atheroma is associated with adverse short- and long-term post-operative outcome. However, the relationship between aortic plaque burden and mortality remains unknown. Objectives: We hypothesized that the extent of aortic atheroma of the entire thoracic aorta, determined by pre- operative multi-detector row computed tomographic angiography (MDCTA), is associated with long-term mortality following non-aortic cardiothoracic surgery.

4. Methods We reviewed clinical and imaging data from all patients, who underwent ECG-gated contrast- enhanced MDCTA prior to coronary bypass or valvular heart surgery at our institution between 2002-2008. MDCTA studies were analyzed for thickness and circumferential extent of aortic atheroma in 5 segments of the thoracic aorta and a semi- quantitative total plaque-burden score (TPBS) was calculated (Table 1, Figure 1,2). The primary endpoint was all-cause mortality during long-term follow-up.

5. Table 1: Total plaque-burden score (TPBS) Atheroma Thickness 0absent 1 = mild<3 mm 2 = moderate3-5 mm 3 = severe> 5 mm Atheroma Circumferential Extent 0< 1/3 circumferential aortic diameter 1 = mild1/3- 2/3 circumferential aortic diameter 2= moderate>2/3 circumferential aortic diameter 3 = severe

6. Figure 1: Measurement of Plaque Thickness and Circumferential Extent

7. Figure 2: Segments of the Aorta Included in the Total Plaque Burden Score

8. Results A total of 862 patients (71% males, 67.8 years) were included and followed over a mean period of 25 ± 16 months. The mean TPBS was 8.6. The TPBS was a statistically significant predictor of mortality (p < 0.0001), while controlling for baseline demographics, cardiovascular risk factors, and type of surgery including re-operative status. The estimated hazard ratio for TPBS was 1.08 (95% CI: 1.045-1.12). Other independent predictors of mortality were GFR (p=0.015), type of surgery (p=0.007), and PAD (p=0.03).

9. Figure 3: Example of the Calculation of the Total Plaque Burden Score

10. Table 2: Predictors of All-cause Mortality in Multivariate Analysis Variablep Hazard Ratio (95% CI) TPBS<0.0001 1.08 (1.04-1.12) GFR0.01 0.989 (0.980-0.998) PAD0.03 1.54 (1.05, 2.27) Surgery Type0.01 Combined: 1.44 (0.94, 2.19)* CABG: 0.62 (0.33, 1.16)* *These hazard ratios refer to the risk of mortality for each surgery type compared to the risk of mortality for valvular surgery alone.

11. Figure 4: Kaplan-Meier Analysis of Survival

12. Conclusion Extent of thoracic aortic atheroma burden is independently associated with increased long-term mortality in patients following cardiothoracic surgery. Our data demonstrates that thoracic aortic atherosclerosis is a marker of atherosclerotic events and mortality after cardiothoracic surgery. It is an attractive hypothesis that this relationship is not limited to patients after surgery, but describes general atherosclerotic disease patterns of the aorta, with impact for prevention of cardiovascular events. This requires further evaluation in non-surgical patient populations.