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Development and validation of a novel method to derive central aortic systolic pressure from the MR aortic distension
Michael A Quail1, Jennifer A Steeden, Daniel Knight
1Center for Cardiovascular Imaging, Institute of Cardiovascular Science, University College London and Great Ormond Street Hospital for Children, London, United Kingdom.
Insights
Central aortic systolic pressure (CASP) can be accurately measured using magnetic resonance imaging (MRI) methods. The arctangent and exponential models provide superior results for assessing cardiovascular risk compared to brachial pressure.
Area of Science:
- Cardiovascular imaging and hemodynamics.
- Biomedical engineering and medical physics.
Background:
- Central aortic systolic pressure (CASP) is a critical indicator of cardiovascular risk, superior to brachial pressure.
- Current methods for measuring CASP are invasive or technically challenging.
- Magnetic resonance imaging (MRI) offers a non-invasive approach to assess cardiovascular parameters.
Purpose of the Study:
- To develop and validate non-invasive methods for determining CASP using MRI-derived aortic area curves.
- To compare the accuracy of different pressure-area relationship models (linear, exponential, arctangent) for CASP estimation.
- To evaluate the potential of MRI-derived CASP for improved assessment of systemic arterial hypertension.
Main Methods:
- Utilized a high temporal resolution spiral phase-contrast MRI sequence in 20 volunteers.
- Derived aortic area curves and calibrated them using brachial mean and diastolic pressures.
- Applied linear, exponential, and arctangent models to estimate CASP, with the arctangent model also calibrated by pulse wave velocity.
- Validated estimated CASP against carotid tonometry CASP as the reference standard.
Main Results:
- Brachial systolic pressure showed only moderate correlation with carotid CASP (r²=0.46).
- Arctangent, exponential, and linear models derived from MRI demonstrated strong correlations with carotid CASP (r²=0.90, 0.86, 0.85, respectively).
- Excellent agreement was observed between carotid CASP and arctangent (bias 1.5; SD 3.3) and exponential (bias 0.6; SD 3.6) MRI-derived CASP.
Conclusions:
- CASP can be reliably derived from MRI data using various pressure-area relationship models.
- The arctangent and exponential models are superior to the linear model for MRI-based CASP estimation.
- MRI-derived CASP offers a more comprehensive assessment of systemic arterial hypertension compared to traditional brachial pressure measurements.
Purpose:
Central aortic systolic pressure (CASP) is a more accurate measure of load and cardiovascular risk than brachial pressure. Unfortunately, CASP is difficult to measure using current methods. In this study we report three methods of determining CASP by combining MR-derived aortic area curves with different models of the pressure-area relationship.
Materials And Methods:
CASP was derived by calibrating aortic area curves to the brachial mean and diastolic pressure, using: linear, exponential, and arctangent models in 20 volunteers using a high temporal resolution spiral PC-MR flow sequence. The arctangent model also required calibration with pulse wave velocity. Carotid tonometry CASP was used as the reference standard.
Results:
Brachial systolic pressure correlated only moderately with carotid CASP r(2) = 0.46 (P = 0.01). However, arctangent, exponential, and linear CASP correlated strongly with carotid CASP, r(2) = 0.90, r(2) = 0.86, r(2) = 0.85, respectively (P < 0.0001). There was excellent agreement between carotid CASP and both arctangent (bias 1.5; SD 3.3) and exponential CASP (bias 0.6; SD 3.6). There was a slight underestimation using the linear model (bias -2.3; SD 3.8) and poor agreement and overestimation using brachial systolic pressure (bias 12.9; SD 8.0).
Conclusion:
We have shown that CASP can be derived from MR data: arctangent and exponential methods being superior to the linear method. The superior correlation of MR derived CASP over brachial systolic BP suggests these measures will allow more comprehensive assessment of systemic arterial hypertension.
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