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      Assessing cardiac function in the single ventricle circulation: Kinetic energy ejection fraction

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          Abstract

          Background Those with single ventricle circulations often have a normal ventricular volumetric ejection fraction (VV EF) which is not in keeping with their symptoms and prognosis. Recently four-dimensional flow (4Dflow) magnetic resonance imaging (MRI) has been used to extract parameters of intra-cardiac kinetic energy (KE). There has been recent interest in measuring ventricular KE in health and disease to see if this could provide an additional tool in the assessment of ventricular function. We propose a new simple measure of ventricular function based on kinetic energy, the kinetic energy ejection fraction (KE EF), and assess its usefulness in patients with single ventricle circulation. Methods Kinetic energy measured by 4D flow MRI was prospectively quantified in 41 patients with a single ventricle circulation (aged 0.5 - 28 years) and compared to 43 healthy volunteers (aged 1.5 - 62 years) who acted as negative controls, and 14 patients with left ventricular (LV) dysfunction (aged 28 - 79 years) who acted as positive controls. The ratio of ejected kinetic energy to total kinetic energy was used to devise KE EF. Results Figure 1 shows the MRI derived volumetric and kinetic energy parameters. The KE EF has a smaller range than VV EF in healthy subjects (97.3 +/- 0.8% vs. 60.1 +/- 5.5%). LV dysfunction causes a fall in KE EF (90.0 +/- 6.7; p = 0.0001). Although VV EF in healthy LVs and single ventricle hearts did not differ (p = 0.99) the respective KE EF was significantly lower (91.0 +/- 8.0%; p < 0.0001) with a wider range. Those reporting the greatest symptomatic impairment (NYHA II) had lower KE EF than asymptomatic (NYHA I) subjects (p= 0.0067) whilst in comparison VV EF remained unchanged (p = 0.54). Figure 1 Box and whisker plots showing relationship between patient group and ejection fraction (kinetic and volumetric) for all patients. P values are shown for inter-group comparisons, and are calculated post hoc from the Generalized Linear Model Conclusions Kinetic energy parameters offer new insight into the function of the heart. KE EF is a marker of healthy cardiac function displaying a very small range of values in comparison to the broader range shown in VV EF. In those with single ventricle circulations it identifies a spectrum of diminished cardiac performance corresponding to a patient's perceived exercise tolerance. This is particularly useful in conditions such as single ventricle physiology where standard ejection fraction values are often normal. Further work to determine its relationship with other prognostic outcomes would allow full implementation as a clinical tool. Funding N/A.

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          Author and article information

          Journal
          J Cardiovasc Magn Reson
          J Cardiovasc Magn Reson
          Journal of Cardiovascular Magnetic Resonance
          BioMed Central (London )
          1097-6647
          1532-429X
          3 February 2015
          2015
          : 17
          : 1
          : O57
          Affiliations
          KCL, London, UK
          Article
          4084
          10.1186/1532-429X-17-S1-O57
          4328423
          b57f6eb2-80c3-41b5-adcf-365946aaacd6
          © Wong et al; licensee BioMed Central Ltd. 2015

          This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The Creative Commons Public Domain Dedication waiver ( http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

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          © The Author(s) 2015

          Cardiovascular Medicine
          Cardiovascular Medicine

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