Between EVENTS and matched CONTROLS, mean absolute differences in propensity score was 0.035±0.025. Our matching technique resulted in no significant differences in age, logarithm-adjusted CCS, and prevalence of traditional risk factors between EVENTS and CONTROLS (univariable analysis results are shown in ). Hypercholesterolemia (66% in EVENTS, 64% in CONTROLS) and hypertension (81% in EVENTS, 80% in CONTRLS) were the most frequently found risk factors in both groups. Mean FRS in EVENTS was higher than that in CONTROLS at the time of NCT (15±8 vs. 12±7, p=0.012), though both mean scores predicted intermediate risk.
Characteristics of 58 patients with MACE (EVENTS) and 174 matched event-free controls (CONTROLS). Matched variables are shown in italics.
Detection of pericardial and thoracic fat and quantification of PFV and TFV was successful in all cases. Analysis of the typical NCT required 5–10 minutes of user time to fully contour the pericardium. PFV and TFV were highly correlated to each other (r2=0.74).
Overall mean PFV was 89.1 ± 41.4 cm3 (range 18.2–259.2 cm3) and mean TFV was 183.9 ± 83.6 cm3 (range 34.1–518.4 cm3). EVENTS had greater mean PFV and TFV than CONTROLS (102±49 vs. 85±38 cm3, p=0.007 and 205±90 vs. 177±80 cm3, p=0.029, respectively). EVENTS had greater frequencies of PFV > 125 cm3 (33% vs. 14%, p=0.002) and TFV > 250 cm3 (31% vs. 17%, p=0.025). and each shows representative examples of pericardial and thoracic fat analysis in an EVENT and one of the corresponding controls.
Figure 2 A representative example of pericardial fat volume (PFV) and thoracic fat volume (TFV) quantification in matched patients with a coronary calcium score (CCS) of 0. Within each panel, the top row shows standard coronal, axial, and sagittal (left to right) (more ...)
Figure 3 A representative example of pericardial fat volume (PFV) and thoracic fat volume (TFV) quantification in matched patients with very high coronary calcium scores (CCS). Within each panel, the top row shows standard coronal, axial, and sagittal (left to (more ...)
Results from multivariable analyses are shown in and . In multivariable analyses that adjusted for age, CCS, and all traditional risk factors, PFV was associated with MACE (OR 1.91, 95% CI 1.14–3.19 per doubling of PFV), as was TFV (OR 1.83, 95% CI 1.08–3.09 per doubling of TFV). As expected from matching, none of the other variables showed a significant association. In multivariable analyses that adjusted for BMI, CCS, and FRS, PFV (OR 1.74, 95% CI 1.03–2.95 per doubling) and TFV (OR 1.78, 95% CI 1.01–3.14 per doubling) remained significantly associated with MACE. In these analyses, FRS was a concurrent independent predictor of MACE when adjusting for PFV (OR 1.10, 95% CI 1.03–1.17) or TFV (OR 1.10, 95% CI 1.03–1.17). Addition of PFV and TFV to the model containing BMI, CCS, and FRS significantly increased the deviance chi-square statistic (15.3 vs 10.8 for PFV, p=0.03; 14.9 vs 10.8 for TFV, p=0.04), indicating improved model fit. Extra-pericardial thoracic fat volume (TFV-PFV) did not exhibit a significant relationship to MACE when adjusting for BMI, CCS, and FRS (OR 1.44, 95% CI 0.91–2.28, p=0.12).
Results of conditional multivariable regression analyses adjusting for age, traditional risk factors, and CCS
Results of conditional multivariable regression analyses adjusting for BMI, CCS, and FRS
ROC analysis using FRS and CCS ≥ 400 resulted in an AUC of 0.68 and using FRS, CCS ≥ 400, and PFV ≥125 cm3 resulted in an AUC of 0.73 (see ), a difference that trended towards significance (p = 0.058). Estimated sensitivity for predicting MACE when PFV ≥ 125 cm3 was added to FRS and CCS ≥ 400 was not different than using FRS and CCS ≥ 400 only (0.65 vs 0.61, p=0.48). However, estimated specificity (0.72 vs 0.66, p = 0.009) and accuracy (0.70 vs 0.65, p =0.009) improved. ROC analysis using TFV ≥ 250 cm3 in place of PFV did not show any significant difference (AUC 0.68 vs 0.68, p=0.7).
Figure 4 Receiver-operator-characteristic curves for major adverse cardiovascular event (MACE) prediction using Framingham Risk Score (FRS) and coronary calcium score greater than 400 (CCS≥400) only and using FRS, CCS≥400, and pericardial fat volume (more ...)