Article

The first (VT1) and second (VT2) ventilatory thresholds are landmarks
to tailor exercise rehabilitation in coronary artery disease (CAD)
or chronic
heart failure (CHF).
Methods - allowing VT1 and VT2 determination based on heart
rate variability (HRV) have been proposed but not yet evaluated in these patients. DESIGN: To determine the heart rate (HR) associated with VT1 and VT2 by
three methods of HRV analyses. METHODS: Fourteen CHF and 24 CAD patients
performed an exercise test on a cycle ergometer (10 -W every minute until
exhaustion). VT1 and VT2 were determined with the 'respiratory equivalent'
method. HR at VT1 was determined with the standard deviation (SD) of R minus sign
in boxR intervals (VT(SD)) and of the instantaneous beat-to-beat variability of
the Poincare plot method (VT(Poincare)). HR at VT1 and VT2 was determined through
a time-varying HRV analysis method (VT(TV1) and VT(TV2), respectively). RESULTS:
HR at VT(SD) was significantly higher than HR at VT1. No significant differences
were observed between HR at VT(Poincare), VT(TV1), and at VT1, nor between HR at
VT(TV2) and VT2. HR at VT(SD), VT(Poincare),
and VT1 were significantly
correlated, but with a low r (2) value and a large mean HR difference. With the
time-varying method, the mean HR difference was lower than 5% and the correlation
coefficients were higher (especially for VT(TV2)). CONCLUSIONS: SD and Poincare
plot methods lead to substantial inaccuracy in HR estimates.
The time-varying HRV
analysis led to strong correlation coefficients and low limits of agreement.
Therefore, this method may be a promising, low-cost tool for non-invasive
assessment of the ventilatory thresholds in cardiac disease.

Langue : ANGLAIS