- Technologist presentation
- Open Access
Exercise CMR: real-time assessment of cardiac performance with phase contrast imaging
© Quinlan et al. 2016
- Published: 27 January 2016
- Main Pulmonary Artery
- Cardiac Performance
- Bland Altman Plot
- Flow Mapping
- Phase Contrast Imaging
Exercise CMR is an emerging technique for understanding the effects of physiological stress on the cardiovascular system in health and disease. Accurate assessment of cardiovascular performance during exercise is challenging due to high heart rates and respiratory motion therefore new imaging tools are required for real-time measurement of biventricular function. In this study we evaluated the accuracy of high-temporal resolution real-time phase contrast imaging to measure cardiac performance during progressive exercise stress.
CMR was performed at rest and throughout exercise in 8 healthy volunteers (5 females, mean age 31 years) using a Philips 1.5T Achieva (Best, Netherlands) with a 32-channel cardiac coil. Conventional breath-hold retrospectively gated phase contrast imaging of the main pulmonary artery (MPA) and ascending thoracic aorta were acquired at rest. Exercise was performed using an MR-compatible cycle ergometer (Lode, Netherlands). Subjects were exercised in the supine position with rotational movement of pedals at a rate of 60 revolutions per minute to 40% of their maximal power output determined by prior cardiopulmonary exercise testing.
An ungated real-time echo-planar phase contrast sequence of the MPA and aorta was acquired using the following parameters: field-of-view = 300 × 300 mm; repetition time= 12 ms; echo time= 4.0 ms; flip angle = 20°; velocity encoding 200 cm/s (aorta) and 100 cm/s (MPA); temporal resolution of 50 ms.
Automated correction of voxel aliasing was performed in Matlab if required. Stroke volume index (SVI) was measured using Art Fun (Inserm, Paris) with automated in-plane vessel tracking of the MPA and aorta. Cardiac output (CO) was calculated as stroke volume × HR. Comparisons between methods were made with Bland Altman plots, differences between rest/stress conditions with the Wilcoxon signed-rank test and the agreement between MPA/Aortic flow with the correlation coefficient.
Real-time flow mapping offers a novel approach for measuring cardiac performance during exercise which is straightforward to acquire and analyse. Our pilot data indicates that this could be a valuable tool in the expanding role of exercise CMR.
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.