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Effects of Exercise on Thoracic Blood Volumes, Lung Fluid Accumulation, and Pulmonary Diffusing Capacity in Heart Failure with Preserved Ejection Fraction.

Background- Heart failure with preserved ejection fraction (HFpEF) patients experience symptoms of exertional dyspnea which may be related to lung fluid accumulation during exercise. A CT-based method was used to measure exercise-induced changes in extravascular lung fluid content and thoracic blood volumes and determine the effect of lung fluid on lung diffusing capacity for carbon monoxide (DLCO) in stable HFpEF subjects and healthy controls. Methods- Nine subjects with HFpEF (Age 68±8y, BMI 32.1±2.6kg/m2) and eight healthy controls (62±9y, 23.8±2.4kg/m2) performed triplicate re-breathe DLCO/DL-NO tests in a supine position at rest and duplicate measurements during two 5 min submaximal exercise stages (15 and 35W) and recovery. Subjects subsequently performed a 5 min exercise bout (35W) inside a CT scanner, and extravascular lung fluid content and thoracic blood volumes were quantified at rest and immediately following exercise from thoracic and contrast perfusion scans, respectively. Results-Subjects with HFpEF had a higher lung fluid content at rest compared to controls (Mean±SD, HFpEF: 14.4±1.7%, Control: 12.8±1.7%, p=0.043) and a higher lung fluid content following exercise (15.2±2.0% vs. 12.6±1.5%, p=0.009). Higher lung fluid content was associated with a lower DLCO and alveolar-capillary membrane conductance (Dm) in subjects with HFpEF (DLCO: R=-0.57, p=0.022, Dm: R=-0.61, p=0.012), but not in controls. Pulmonary blood volume was not altered by exercise and was similar between groups. Conclusions-Submaximal exercise elicited a greater accumulation of lung fluid in HFpEF compared to controls, and lung fluid content was negatively correlated with lung diffusing capacity and alveolar-capillary membrane conductance in HFpEF.