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Exercise-Induced Alterations in Lung Water Density in Heart Failure Using Single-Breath-Hold 3D Ultrashort Echo Time
Hang Chen1, Manuel A Morales1, Alexander Schulz1
1Department of Medicine (Cardiovascular Division), Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, USA.
Background:
Evaluating pulmonary congestion after exercise in heart failure (HF) may reveal perturbations not apparent at rest and provide insight into dyspnea and exercise intolerance.
Purpose:
To investigate the reproducibility and exercise-induced alterations in lung water density (LWD) using 3D ultrashort echo time (UTE) MRI.
Study Type:
Prospective.
Field Strength/Sequence:
3-T MRI with a prototype 3D stack-of-spirals UTE Volumetric Interpolated Breath-hold Examination (VIBE) sequence.
Population:
Sixty-nine HF patients (59 ± 12 years; 39 males) across a range of left ventricular ejection fraction (23 HFpEF, 16 HFmrEF, 18 HFimpEF, and 12 HFrEF); 34 healthy subjects.
Assessment:
UTE MRI was performed at rest and after exercise. Images were normalized to yield relative LWD (%). LWD was quantified as the mean normalized pixel intensity within the segmented parenchyma, and lung volume was also measured. Reproducibility was evaluated in a separate scan/rescan study.
Statistical Tests:
Shapiro-Wilk test; one-way ANOVA or Kruskal-Wallis test with FDR correction; Student's t-test or Wilcoxon signed-rank test; χ2 test or Fisher's exact test; Bland-Altman analysis. p < 0.05 was considered significant.
Results:
In healthy controls, LWD decreased significantly after exercise with an absolute change of -1.25% (interquartile range [IQR]: -2.92% to 0.38%) and relative change of -4.35% (IQR: -9.55% to 1.30%). Compared with controls, HFpEF showed a significantly greater absolute change (0.47%, IQR: -0.91% to 2.10%) and relative change in LWD (1.46%, IQR: -2.65% to 6.45%), not apparent in other HF subgroups (p = 0.053-0.821). Changes in lung volume did not differ between each HF subgroup and healthy controls (p = 0.056-0.498). Bland-Altman analysis demonstrated good agreement for LWD and lung volume.
Data Conclusion:
Single-breath-hold 3D UTE MRI provides reproducible LWD measurements at rest and enables detection of exercise-induced LWD alterations. This approach captures pulmonary fluid changes following exercise and identifies greater LWD response in HFpEF.
Technical Efficacy:
Stage 1.
