Objective We previously described lower leg lean mass Z-scores (LLMZ) in Fontan patients associated with worse peak oxygen consumption on metabolic exercise testing. We hypothesised that LLMZ correlates with indexed systemic flow (Qsi) and cardiac index (CI) on exercise cardiac magnetic resonance (eCMR).
Methods Thirteen patients had LLM measured by dual-energy X-ray absorptiometry within mean 40 (range 0–258) days of eCMR. LLM was converted to sex and race-specific Z-scores based on healthy reference data. Ventricular volumes and flow measurements of the ascending and descending (DAO) aorta and superior vena cava (SVC) were obtained by CMR at rest and just after supine ergometer exercise to a heart rate associated with anaerobic threshold on prior exercise test. Baseline and peak exercise measures of Qsi (SVC+DAO/BSA) and CI, as well as change in Qsi and CI with exercise, were compared with LLMZ by linear regression.
Results LLMZ was not correlated with resting flows, stroke volume or CI. There was a strong linear correlation between LLMZ and change in both CI (r=0.77, p=0.002) and Qsi (r=0.73, p=0.005) from rest to exercise. There was also a significant correlation between LLMZ and Qsi at exercise (r=0.70, p=0.008). The correlation between LLMZ and CI at exercise did not reach significance (r=0.3, p=0.07).
Conclusions In our cohort, there was a strong linear correlation between LLMZ and change in both CI and Qsi from rest to exercise, suggesting that Fontan patients with higher LLMZ may be better able to augment systemic output during exercise, improving performance.
- fontan physiology
- cardiac magnetic resonance (cmr) imaging
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Contributors CA planned and administered the body composition study, performed data analysis, interpreted study results and wrote the manuscript. DG and ML participated in planning the body composition study, interpreted study results, and contributed to and edited the manuscript. AW and ET performed data analysis and edited the manuscript. SP interpreted study results and edited the manuscript. AY developed the exercise CMR protocol. MF developed the exercise CMR protocol, administered the exercise CMR study, and reviewed the manuscript. KW developed the exercise CMR protocol, administered the exercise CMR study, performed data analysis, interpreted study results and edited the manuscript. CA and KW are responsible for the overall content as guarantors.
Funding Funding was provided by a Children’s Hospital of Philadelphia Cardiac Center Grant as well as support from the Robert S. and Dolores Harrington Endowment in Pediatric Cardiology at The Children’s Hospital of Philadelphia and by NIH grants T32 HL007915 (CA), K23 HL089647 (KKW), K24 DK0768084 (MBL), R01 HL098252-01 (MBL), R01 HL098252 (APY, MAF) and Clinical and Translational Science Award UL1 RR024134 and UL1 TR000003.
Provenance and peer review Not commissioned; externally peer reviewed.