Associations of cardiovascular and all-cause mortality events with oxygen uptake at ventilatory threshold.

Int J Cardiol. 2017 Feb 10. pii: S0167-5273(16)32158-1.

Kunutsor SK(1), Kurl S(2), Khan H(3), Zaccardi F(4), Laukkanen JA(5).

BACKGROUND: Oxygen uptake (VO2) at ventilatory threshold (VT), is a
cardiopulmonary exercise testing parameter which may be a proxy for peak VO2. We
aimed to assess the associations of VO2 at VT with sudden cardiac death (SCD),
fatal coronary heart disease (CHD) and cardiovascular disease (CVD), and
all-cause mortality.
METHODS AND RESULTS: VO2 at VT was assessed during a submaximal exercise test
using respiratory gas analyzers in the Kuopio Ischemic Heart Disease cohort of
1639 middle-aged men. Hazard ratios (HRs) (95% CIs) were assessed. During a
median follow-up of 25.6years, 121 SCDs, 202 fatal CHDs, 312 fatal CVDs, and 703
all-cause mortality events occurred. VO2 at VT was correlated with peak VO2
(r=0.90) and linearly associated with each outcome. Comparing extreme quartiles
of VO2 at VT, the HRs (95% CIs) for SCD, fatal CHD, fatal CVD, and all-cause
mortality on adjustment for established risk factors were 0.37 (0.18-0.78), 0.32
(0.18-0.57), 0.45 (0.30-0.69), and 0.50 (0.38-0.64) respectively. The HRs were
1.02 (0.36-2.91), 1.43 (0.63-3.25), 1.46 (0.79-2.71), and 1.02 (0.69-1.51)
respectively on further adjustment for peak VO2. Addition of VO2 at VT to a CVD
mortality risk prediction model containing established risk factors significantly
improved risk discrimination and reclassification at 25years.
CONCLUSIONS: There are linear and inverse associations of VO2 at VT with fatal
cardiovascular and all-cause mortality events, which are dependent on peak VO2.
Inclusion of VO2 at VT in the standard established risk factors panel
significantly improves the prediction and classification of long-term CVD
mortality risk.