Subclinical Pulmonary Congestion and Abnormal Hemodynamics in Heart Failure With Preserved Ejection Fraction

Abstract

Objectives: The authors hypothesized that quantitative computed tomography (QCT) imaging would reveal subclinical increases in lung congestion in patients with heart failure and preserved ejection fraction (HFpEF) and that this would be related to pulmonary vascular hemodynamic abnormalities.

Background: Gross evidence of lung congestion on physical examination, laboratory tests, and radiography is typically absent among compensated ambulatory patients with HFpEF. However, pulmonary gas transfer abnormalities are commonly observed and associated with poor outcomes.

Methods: Patients referred for invasive hemodynamic exercise testing who had undergone chest computed tomography imaging within 1 month were identified (N = 137). A novel artificial intelligence QCT algorithm was used to measure pulmonary fluid content.

Results: Compared with control subjects with noncardiac dyspnea, patients with HFpEF displayed increased mean lung density (-758 HU [-793, -709 HU] vs -787 HU [-828, -747 HU]; P = 0.002) and a higher ratio of extravascular lung water to total lung volume (EVLWV/TLV) (1.25 [0.80, 1.76] vs 0.66 [0.01, 1.03]; P < 0.0001) by QCT imaging, indicating greater lung congestion. EVLWV/TLV was directly correlated with pulmonary vascular pressures at rest, with stronger correlations observed during exercise. Patients with increasing tertiles of EVLWV/TLV demonstrated higher mean pulmonary artery pressures at rest (34 ± 11 mm Hg vs 39 ± 14 mm Hg vs 45 ± 17 mm Hg; P = 0.0003) and during exercise (55 ± 17 mm Hg vs 59 ± 17 mm Hg vs 69 ± 22 mm Hg; P = 0.0003).

Conclusions: QCT imaging identifies subclinical lung congestion in HFpEF that is not clinically apparent but is related to abnormalities in pulmonary vascular hemodynamics. These data provide new insight into the long-term effects of altered hemodynamics on pulmonary structure and function in HFpEF.

Keywords: computed tomography; congestion; exercise; heart failure; hemodynamics.

Figure 1:. Correlations between Lung Congestion and Invasive Hemodynamics

Heat map displaying correlations between extravascular lung water (Log [EVLWV/TLV]) with invasive hemodynamic measures. The left column displays correlation for all patients at rest and the right column displays correlations for all patients at peak exercise. Abbreviations: EVLWV/TLV = extravascular lung water volume indexed to total lung volume; PA = pulmonary artery; PCWP = pulmonary capillary wedge pressure; PVR = pulmonary vascular resistance; RAP = right atrial pressure

Figure 2:. Pulmonary Artery Pressures at Rest and Exercise and Lung Water

Pulmonary artery systolic pressure (PASP) measured at catheterization increased from patients in the lowest tertile of extravascular lung water volume indexed to total lung volume (black) to the middle (green) and highest tertile (red) at rest (left panels) and during exercise (right panels).

Central Illustration:. Quantitative CT Analysis for Lung Congestion

The top left figure displays the distribution of mean lung density for controls (black) and for patients with HFpEF (red). The rightward shift, shorter peak, and wider curve are consistent with increased mean lung density and increased extravascular lung water in patients with HFpEF. Patients with HFpEF also displayed higher extravascular lung water volume (EVLWV, top right) and EVLWV/TLV (bottom left). Cumulative frequency distribution shows higher extravascular lung water as indicated by EVLWV to total lung volume (TLV) ratio in those with HFpEF (bottom right). Abbreviations: AU = arbitrary units; CT = computed tomography; EVLWV = extravascular lung water volume; EVLWV/TLV = extravascular lung water volume indexed to total lung volume; HFpEF = heart failure with preserved ejection fraction; HU = Hounsfield units