Elsevier

Progress in Cardiovascular Diseases

Volume 68, September–October 2021, Pages 12-18
Progress in Cardiovascular Diseases

Cardiorespiratory optimal point during exercise testing and sudden cardiac death: A prospective cohort study

https://doi.org/10.1016/j.pcad.2021.09.001Get rights and content
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open access

Abstract

Background

Cardiorespiratory optimal point (COP) during exercise, a potentially useful submaximal cardiopulmonary exercise testing (CPET) variable, may be an independent risk factor for cardiovascular disease outcomes. However, the relationship of COP with risk of sudden cardiac death (SCD) has not been previously investigated. We sought to evaluate the association between COP during exercise and SCD risk and determine whether COP improves SCD risk prediction.

Methods

COP, the minimum value of the ventilatory equivalent for oxygen (VE/VO2) in a given minute of a CPET, was ascertained in 2190 men who underwent clinical exercise testing. Hazard ratios (HRs) (95% confidence intervals [CIs]) and measures of risk discrimination for SCD were calculated.

Results

A total of 240 SCDs death occurred during a median follow-up of 28.8 years. COP was linearly associated with SCD in a dose-response manner. In a multivariable model comprising several established and emerging CVD risk factors, the HR (95% CI) for SCD was 2.51 (1.36–4.62) per standard deviation increase in COP. This was minimally attenuated to 2.36 (1.27–4.37) on further adjustment for high sensitivity C-reactive protein. The association did not vary importantly in several relevant clinical subgroups. Addition of COP to a SCD risk score was associated with a C-index change of 0.0086 (0.0005 to 0.0167; p = .038) and difference in −2 log likelihood (p = .017).

Conclusions

COP during exercise is strongly, inversely and independently associated with SCD in a graded fashion. COP during exercise may potentially be used for the prediction of the long-term risk for SCD beyond established CVD risk factors.

Keywords

Cardiorespiratory optimal point
Cardiopulmonary exercise testing
Sudden cardiac death
Cohort study
Prognosis

Abbreviations

BMI
body mass index
CHD
coronary heart disease
CI
confidence interval
COP
cardiorespiratory optimal point
CO2
carbon dioxide
CPET
cardiopulmonary exercise testing
CRF
cardiorespiratory fitness
CVD
cardiovascular disease
FPG
fasting plasma glucose
hsCRP
high-sensitivity C-reactive protein
HDL-C
high-density lipoprotein cholesterol
HR
hazard ratio
KIHD
Kuopio Ischaemic Heart Disease risk factor study
IQR
interquartile range
LVEF
left ventricular ejection fraction
VO2
oxygen uptake
OUES
oxygen uptake efficiency slope
NRI
net-reclassification-improvement
SBP
systolic blood pressure
SCD
sudden cardiac death
SD
standard deviation
SES
socioeconomic status
STROBE
STrengthening the Reporting of OBservational studies in Epidemiology
VE
ventilation
VE/VCO2
ventilatory equivalent for carbon dioxide
VE/VO2
ventilatory equivalent for oxygen
VO2peak
peak oxygen uptake

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