Abstract 13640: Development and Validation of a Novel Method to Derive Central Aortic Systolic Pressure From the MRI Aortic Distension Curve
Background: CMR is already used to assess cardiac sequelae of systemic arterial hypertension (LV hypertrophy, systolic & diastolic dysfunction). However, this data is limited without a measure of cardiac load such as central aortic systolic pressure (CASP). Unfortunately, current methods of determining CASP, such as tonometry, are difficult to perform during CMR. Therefore, we developed 3 methods of measuring CASP, which combine CMR derived aortic area curves with different models of the pressure area relationship.
Methods: Ascending aorta area curves were obtained in 20 volunteers (24-50yrs) using a high temporal resolution (10ms) spiral PC-MR flow sequence. CASP was derived by calibrating the area curves to the brachial oscillometric MAP and DAP, using linear (LIN), exponential (EXP) and arctangent (ARC) models. The ARC model also required pulse wave velocity, which could be measured in a single slice (QA method) because of the high temporal resolution of the PC-MR sequence. Carotid tonometry CASP was used as the standard comparator.
Results: Brachial systolic BP ranged 104-143mmHg and only moderately correlated with carotid CASP r^2=0.46 (p=0.01). However, ARC, EXP and LIN 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 ARC CASP (bias 1.5, SD 3.3) and EXP CASP (bias 0.6, SD 3.6). There was a slight underestimation using the LIN model (bias -2.3, SD 3.8) and poor agreement and overestimation using brachial systolic BP (bias 12.9, SD 8.0).
Conclusion: We have shown that it is possible to derive CASP from CMR data: ARC and EXP methods being superior to the LIN method. The superior correlation of CMR derived CASP over brachial systolic BP suggests these measures are useful in accurately defining cardiac load. Therefore, we believe that CMR derived CASP will allow more comprehensive assessment of the causes and consequences of systemic arterial hypertension.
- © 2013 by American Heart Association, Inc.