Different Determinants of Ventilatory Inefficiency at Different Stages of Reduced Ejection Fraction Chronic Heart Failure Natural History

Figures

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  Figure 1. Flow chart showing study population selection. CHF indicates reduced ejection fraction chronic heart failure; CPET, cardiopulmonary exercise test; LVEF, left ventricular ejection fraction; RER, respiratory exchange ratio; VCO2, volume of exhaled carbon dioxide; VE, ventilation.

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  Figure 2. Changes in ventilation, VCO 2, and work rate at lowest VE/VCO 2 between different VE/VCO 2 slope tertile pairs. Tertile pairs are represented as circle pairs connected by lines. Data are expressed as mean±SD. The x‐axis and symbols on the right side of the graphs show average values per tertile. In the presence of a step‐wise work rate and VCO 2 decrease with increasing tertile in all tertile pairs, ventilation progressively and counterintuitively increased. This highlights the role played by ventilatory overactivation in determining increased VE/VCO 2 slope over a wide range of chronic heart failure pathophysiology stages. VCO2 indicates volume of exhaled carbon dioxide; VE, ventilation. *P<0.01 versus tertile 1; † P<0.01 versus tertile 2; ‡ P<0.01 versus tertiles 1 and 2.

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  Figure 3. Ventilation, VCO 2, and cardiac output as a function of work rate in the study population. Black, gray, and white shapes represent tertiles 1, 2, and 3, respectively. Triangles, squares, circles, and diamonds represent start of exercise phase, first ventilatory threshold (1st VT), lowest VE/VCO 2, and peak exercise, respectively. Data are expressed as mean±SD. The VE/W slope and 1st VT VE/W slope (A) progressively increase across VE/VCO 2 slope tertiles, whereas the VCO 2/W slope does not (B). On the contrary, both 1st VT VCO 2/W slope (B) and cardiac output/W slope (C) are significantly lower in tertile 3 than in tertile 1 or 2, which indicates reduced hemodynamic efficiency, in addition to ventilatory overactivation, in patients with moderately/severely increased VE/VCO 2 slope. CO indicates cardiac output; VCO2, volume of exhaled carbon dioxide; VE, ventilation. *P<0.05 versus tertiles 2 and 3 for both VE/W and 1st VT VE/W slopes; † P<0.05 versus tertile 3 for both VE/W and 1st VT VE/W slopes; ‡ P<0.05 versus tertile 1 and 2 for 1st VT VCO 2/W slope (B) and CO/W slope (C).

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  Figure 4. ΔVE/VCO 2 slope as a function of ΔVE/W slope, ΔVCO 2/W slope, and ΔCO/W slope in the study population. ΔVE/VCO 2 slope is directly related to ΔVE/W slope (A) and inversely to ΔCO/W slope (C). Conversely, no correlation at all is detected between ΔVE/VCO 2 slope and ΔVCO 2/W slope (B). CO indicates cardiac output; VCO2, volume of exhaled carbon dioxide; VE, ventilation; W, work rate.