Evaluation of Exercise-Induced Changes in Lung Water Density in Heart Failure with Preserved Ejection Fraction.

The primary chronic symptom of heart failure with preserved ejection fraction (HFpEF) is severe exercise intolerance, often associated with dyspnea upon exertion. Here we examine the role of pulmonary congestion, by measuring lung water density (LWD, %) using a previously validated magnetic resonance imaging (MRI) approach. First, in 6 healthy reference controls (3 M/3 F, BMI: 23 ± 3 kg/m , age: 24 ± 4 years) LWD was measured at rest and in response to six minutes of moderate intensity dynamic leg exercise, using an MRI compatible exercise ergometer. LWD decreased in all six healthy reference controls immediately following exercise (from 24.8 ± 3.0% to 18.9 ± 4.2%, p=0.003), while returning to baseline ten minutes after exercise cessation. Next, we assessed exercise-induced changes in LWD in 10 individuals with HFpEF (4 M/6 F, BMI: 35 ± 6 kg/m , age: 69 ± 5 years), following the same experimental protocol. In contrast to the reference control participants, LWD remained unchanged from baseline immediately after exercise (22.8 ± 4.1% vs. 21.9 ± 5.2%, respectively), and tended to increase above baseline ten minutes after exercise cessation (25.2 ± 7.7%). Together, the data support the use of cardiovascular MRI in evaluating LWD at rest and in response to exercise. More work is needed to determine whether changes in LWD contribute to exercise intolerance in HFpEF.