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Novel Computed Tomography Angiography Parameter Is Associated with Low Cardiac Index in Patients with Chronic
Estefania Oliveros1, Michel Ibrahim2, Carlos Manuel Romero3
1Heart and Vascular Institute, Temple University Hospital, Philadelphia, PA 19140, USA.
Insights
Chronic thromboembolic pulmonary hypertension (CTEPH) patients with higher CT Hounsfield Unit gradient (HU-Δ) values show a correlation with lower cardiac index (CI). This imaging metric may help identify reduced cardiac function in CTEPH.
Area of Science:
- Radiology
- Cardiology
- Pulmonary Medicine
Background:
- Chronic thromboembolic pulmonary hypertension (CTEPH) is a serious condition resulting from unresolved pulmonary embolism.
- Assessing cardiac index (CI) is crucial for managing CTEPH, but invasive methods can be burdensome.
- Novel imaging techniques are needed to non-invasively evaluate hemodynamic status in CTEPH.
Purpose of the Study:
- To investigate the correlation between CT Hounsfield Unit gradient (HU-Δ) and invasively measured cardiac index (CI) in CTEPH patients.
- To determine if HU-Δ can serve as a non-invasive marker for low CI in CTEPH.
Main Methods:
- Retrospective analysis of 237 CTEPH patients undergoing pulmonary CTA.
- Calculation of absolute and fractional HU-Δ by comparing contrast opacification in the main pulmonary artery (MPA) to the left atrium (LA) and left ventricle (LV).
- Comparison of HU-Δ values between patients with low CI (<2.2 L/min/m²) and normal CI.
Main Results:
- Patients with low CI exhibited significantly higher HU-Δ values (MPA-LA and MPA-LV) compared to those with normal CI.
- Specific HU-Δ thresholds demonstrated moderate sensitivity and specificity in detecting low CI.
- Fractional HU-Δ reductions also showed potential for identifying low CI, with AUCs up to 0.65.
Conclusions:
- Elevated HU-Δ between the MPA and cardiac chambers is associated with reduced CI in CTEPH.
- CT-derived HU-Δ represents a reproducible and potentially valuable non-invasive imaging biomarker for assessing cardiac function in CTEPH.
Abstract:
Chronic thromboembolic pulmonary hypertension (CTEPH) is a complication of incomplete resolution of acute pulmonary embolism. We hypothesize changes in CT Hounsfield Unit gradient (HU-Δ) created by the dispersion of IV contrast through the downstream blood pool correlate with cardiac index (CI). We sought to compare HU-Δ with invasively obtained CI.
Methods:
We completed a retrospective analysis of CTEPH patients in which individuals with low CI (<2.2-L/min/m2) were identified. Both absolute and fractional HU-Δ were derived from pulmonary CTA by subtracting the HU value of the left atrium (LA) and left ventricle (LV) from the main pulmonary artery (MPA) (absolute) and expressing them as a percentage of MPA-HU (fractional) on static axial images. These were compared between low and normal CI.
Results:
Of the 237 patients, 50.2% were female, 53.2% were White, 36.7% were Black. Hemodynamics were mean pulmonary artery (PA) pressure = 45.4 ± 11.2-mmHg, pulmonary vascular resistance = 9.2 ± 4.4-WU, CI = 2.05 ± 0.48-L/min/m2. There was a higher mean MPA-HU = 391.1 ± 113.6 than LA-HU = 251.6 ± 81. In patients with low CI, the HU-Δ was higher, HU-ΔMPA-LA was 148.9 ± 78.4 vs. 124.5 ± 77.2 (p = 0.02), and HU-ΔMPA-LV was 170.7 ± 87 vs. 140 ± 82 (p = 0.009). A HU-ΔMPA-LA = 118 had a sensitivity of 75.6% and specificity of 77% to detect low CI, AUC 0.61, p = 0.003. A HU-ΔPA-LV = 156 had a sensitivity of 77% and specificity of 53% to detect low CI, AUC = 0.62, p = 0.001. A fractional reduction HU-ΔMPA-LA of 35% had a sensitivity and specificity of 79% and 53%, respectively, to detect low CI (AUC 0.65, p < 0.001). A fractional reduction of the HU-ΔMPA-LV of 40% had a sensitivity and specificity of 80% and 55%, respectively, to detect low CI (AUC 0.65, p < 0.001). HU Δ were highly reproducible (Kappa = 0.9, p < 0.001, 95% CI 0.86-0.95).
Conclusions:
High HU Δ between MPA-LA and MPA-LV were associated with low CI in patients with CTEPH.
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