Author + information
- Received February 23, 2012
- Revision received July 3, 2012
- Accepted July 9, 2012
- Published online January 1, 2013.
- Petter Dyverfeldt, PhD⁎,⁎ (, )
- Michael D. Hope, MD⁎,
- Elaine E. Tseng, MD†,‡ and
- David Saloner, PhD⁎,†,‡
- ↵⁎Reprint requests and correspondence:
Dr. Petter Dyverfeldt, IMH/KVM/KlinFys, Linköping University, SE-581 83, Linköping, Sweden
Objectives The authors sought to measure the turbulent kinetic energy (TKE) in the ascending aorta of patients with aortic stenosis and to assess its relationship to irreversible pressure loss.
Background Irreversible pressure loss caused by energy dissipation in post-stenotic flow is an important determinant of the hemodynamic significance of aortic stenosis. The simplified Bernoulli equation used to estimate pressure gradients often misclassifies the ventricular overload caused by aortic stenosis. The current gold standard for estimation of irreversible pressure loss is catheterization, but this method is rarely used due to its invasiveness. Post-stenotic pressure loss is largely caused by dissipation of turbulent kinetic energy into heat. Recent developments in magnetic resonance flow imaging permit noninvasive estimation of TKE.
Methods The study was approved by the local ethics review board and all subjects gave written informed consent. Three-dimensional cine magnetic resonance flow imaging was used to measure TKE in 18 subjects (4 normal volunteers, 14 patients with aortic stenosis with and without dilation). For each subject, the peak total TKE in the ascending aorta was compared with a pressure loss index. The pressure loss index was based on a previously validated theory relating pressure loss to measures obtainable by echocardiography.
Results The total TKE did not appear to be related to global flow patterns visualized based on magnetic resonance–measured velocity fields. The TKE was significantly higher in patients with aortic stenosis than in normal volunteers (p < 0.001). The peak total TKE in the ascending aorta was strongly correlated to index pressure loss (R2 = 0.91).
Conclusions Peak total TKE in the ascending aorta correlated strongly with irreversible pressure loss estimated by a well-established method. Direct measurement of TKE by magnetic resonance flow imaging may, with further validation, be used to estimate irreversible pressure loss in aortic stenosis.
- aortic stenosis
- magnetic resonance imaging
- pressure loss
- transvalvular pressure gradient
- turbulent kinetic energy
Dr. Dyverfeldt was supported by the Fulbright Commission, the Swedish Heart-Lung Foundation, and the Swedish Brain Foundation. Dr. Hope was supported by an RSNA Research Scholar grant. Dr. Tseng was supported by a grant from the Coulter Foundation and an American Heart Association Grant-in-Aid, administered by the Northern California Institute for Research and Education using resources from the San Francisco VA Medical Center. Dr. Saloner was supported by a VA MERIT review grant and NIH grant NS 059944. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose.
- Received February 23, 2012.
- Revision received July 3, 2012.
- Accepted July 9, 2012.
- American College of Cardiology Foundation