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Computed tomography-derived Hounsfield units for the differentiation between thrombosis and leaflet fibrosis in
Ramona Schmitt1, Jonas Hein1, Jan Minners1
1Department of Cardiology and Angiology, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Südring 15, 79189, Bad Krozingen, Germany.
Insights
Computed tomography angiography (CTA)-derived Hounsfield units (HU) can differentiate bioprosthetic heart valve thrombosis from fibrosis. A threshold of 105 HU on CTA accurately distinguishes between these conditions, aiding treatment decisions.
Area of Science:
- Cardiology
- Radiology
- Biomedical Engineering
Background:
- Bioprosthetic heart valve (BHV) dysfunction diagnosis can be challenging.
- Distinguishing between leaflet thrombosis and fibrosis is crucial for appropriate management.
- Subclinical leaflet thrombosis (HALT) may be detected via computed tomography angiography (CTA).
Purpose of the Study:
- To determine if CTA-derived Hounsfield units (HU) can differentiate between thrombosis and leaflet fibrosis in patients with BHV dysfunction.
- To establish a HU threshold for distinguishing thrombosis from fibrosis.
Main Methods:
- Retrospective assessment of valvular leaflet HU in 95 patients (derivation cohort) with HALT signs post-BHV implantation.
- Validation in a cohort of 46 patients undergoing CTA for suspected BHV dysfunction.
- Analysis of HU values in relation to treatment response (oral anticoagulation).
Main Results:
- Median HU was 87 in the derivation cohort.
- In the validation cohort, the "thrombosis" subgroup (n=19) had a median HU of 87, while the "fibrosis" subgroup (n=27) had a median HU of 137 (p < 0.001).
- A threshold of 105 HU demonstrated 84% sensitivity and 91% specificity for differentiating thrombosis from fibrosis (AUC 0.94 ± 0.02).
Conclusions:
- CTA-derived HU can effectively differentiate between leaflet thrombosis and fibrosis in BHV dysfunction.
- A HU value of 105 provides good discriminatory power.
- This finding may assist in selecting optimal treatment strategies for BHV dysfunction.
Purpose:
Our hypothesis was that computed tomography angiography (CTA)-derived Hounsfield units (HU) can differentiate between thrombosis and leaflet fibrosis (defined by a lack of response to oral anticoagulation) in patients with bioprosthetic heart valve dysfunction.
Materials And Methods:
Valvular leaflet HU were retrospectively assessed in 95 patients (derivation cohort) undergoing CTA 35 days after bioprosthetic heart valve (BHV) implantation showing signs of subclinical leaflet thrombosis (hypoattenuated leaflet thickening, HALT). A second (validation) cohort included 46 patients undergoing CTA for suspected BHV dysfunction 2 years [interquartile range IQR 1.5-5.0] after valve replacement. This study included CTA between May 2012 and December 2017.
Results:
In the derivation cohort, the median HU (95 patients) was 87 (IQR 77; 96). In the validation cohort, patients with resolution of findings in a follow-up CTA after newly initiated anticoagulation ("thrombosis" subgroup, 19 patients) similarly demonstrated HU of 87 (IQR 74; 100) (p = 0.816). In contrast, patients without improvement under oral anticoagulation ("fibrosis" subgroup, 27 patients) exhibited a median of 137 HU (IQR 116, 164; p < 0.001 vs. thrombosis subgroup). In multivariable Cox regression analysis, lower HU were an independent predictor of thrombosis. C-statistics demonstrated an area under the receiver operating characteristic curve of 0.94 ± 0.02 (CI 0.897-0.983, p < 0.001) with a value of 105 HU resulting in a sensitivity of 84% and a specificity of 91% for the differentiation between thrombosis and fibrosis.
Conclusion:
A value of 105 HU on CTA provides good discriminatory power to distinguish between leaflet fibrosis (as defined by a lack of response to oral anticoagulation) and thrombosis after bioprosthetic valve replacement and may help in choosing optimal treatment.
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