Affiliation:
1. Department of Respiratory Medicine, Beijing Friendship Hospital Capital Medical University, Beijing, China
2. Division of Respiratory and Critical Care Physiology and Medicine, Rehabilitation Clinical Trials Center, Los Angeles Biomedical Research Institute at Harbor‐UCLA Medical Center, Torrance, CA
3. Faculty of Biological Sciences, University of Leeds, United Kingdom
4. Faculty of Medicine, University of Leeds, United Kingdom
Abstract
Background
Peak ratios of pulmonary gas‐exchange to ventilation during exercise (
V
˙
O
2
/
V
˙
E
and
V
˙
CO
2
/
V
˙
E
, termed “circulatory equivalents”) are sensitive to heart failure (
HF
) severity, likely reflecting low and/or poorly distributed pulmonary perfusion. We tested whether peak
V
˙
O
2
/
V
˙
E
and
V
˙
CO
2
/
V
˙
E
would: (1) distinguish
HF
patients from controls; (2) be independent of incremental exercise protocol; and (3) correlate with lactate threshold (
LT
) and ventilatory compensation point (
VCP
), respectively.
Methods and Results
Twenty‐four
HF
patients (61±11 years) with reduced ejection fraction (31±8%) and 11 controls (63±7 years) performed ramp‐incremental cycle ergometry. Eighteen
HF
patients also performed slow (5±1 W/min), medium (9±4 W/min), and fast (19±6 W/min) ramps. Peak
V
˙
O
2
/
V
˙
E
and
V
˙
CO
2
/
V
˙
E
from X‐Y plot, and
LT
and
VCP
from 9‐panel plot, were determined by 2 independent, blinded, assessors. Peak
V
˙
O
2
/
V
˙
E
(31.2±4.4 versus 41.8±4.8 mL/L;
P
<0.0001) and
V
˙
CO
2
/
V
˙
E
(29.3±3.0 versus 36.9±4.0 mL/L;
P
<0.0001) were lower in
HF
than controls. Within individuals, there was no difference across 3 ramp rates in peak
V
˙
O
2
/
V
˙
E
(
P
=0.62) or
V
˙
CO
2
/
V
˙
E
(
P
=0.97). Coefficient of variation (
CV
) in peak
V
˙
O
2
/
V
˙
E
was lower than for
LT
(5.1±2.1% versus 8.2±3.7%;
P
=0.014), and coefficient of variation in peak
V
˙
CO
2
/
V
˙
E
was lower than for
VCP
(3.3±1.8% versus 8.7±4.2%;
P
<0.001). In all participants, peak
V
˙
O
2
/
V
˙
E
was correlated with, but occurred earlier than,
LT
(
r
2
=0.94; mean bias, −0.11 L/min), and peak
V
˙
CO
2
/
V
˙
E
was correlated with, but occurred earlier than,
VCP
(
r
2
=0.98; mean bias −0.08 L/min).
Conclusions
Peak circulatory equivalents during exercise are strongly associated with (but not identical to)
LT
and
VCP
. Peak circulatory equivalents are reliable, objective, effort‐independent indices of gas‐exchange abnormality in
HF
.
Publisher
Ovid Technologies (Wolters Kluwer Health)
Subject
Cardiology and Cardiovascular Medicine
Cited by
5 articles.
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