Prognostic power of ventilatory responses during submaximal exercise in patients with chronic heart disease.
BACKGROUND
Although parameters obtained during submaximal exercise are known to be useful for predicting mortality in cardiac patients, it has been a matter of debate whether the submaximal parameters are superior to peak oxygen uptake (VO(2)). For this purpose, we aimed to determine the best index among exercise variables in predicting long-term mortality in patients with chronic heart disease.


METHODS
The study population consisted of 385 consecutive patients with chronic heart disease who performed a symptom-limited incremental exercise test on a cycle ergometer. Breath-by-breath respiratory gas analysis was used to estimate the peak VO(2), the ratio of the increase in VO(2) to the increase in work rate (WR) [VO(2)/Delta WR], and the ratio of the increase in minute ventilation E to the increase in carbon dioxide output (VCO(2)) [Delta VE/Delta VCO(2)].


RESULTS
After 1,899 +/- 495 days of follow-up (mean +/- SD), 33 cardiovascular-related deaths occurred. Nonsurvivors achieved lower peak VO(2), lower VO(2)/Delta VWR, and higher Delta VE/Delta VCO(2) compared to the survivors. In the univariate Cox proportional hazards analysis, peak VO(2), VO(2)/Delta VWR, and Delta VE/Delta VCO(2) were found to be significant prognostic indexes of survival. However, multivariate analysis revealed O(2)/Delta VWR as an independent predictor of mortality and Delta VE/delta VCO(2) as a slightly weaker predictor. In this analysis, the prognostic power of peak O(2) was insignificant.


CONCLUSIONS
Submaximal respiratory gas indexes are very likely to be more sensitive than peak VO(2) for predicting poor survival in ambulatory patients with chronic heart disease.
Koike
Akira
A
Cardiovascular Institute, Tokyo, Japan. koike@cepp.ne.jp
Itoh
Haruki
H
Kato
Makoto
M
Sawada
Hitoshi
H
Aizawa
Tadanori
T
Fu
Long Tai
LT
Watanabe
Hiroshi
H
D002245:Carbon Dioxide / Q000097:blood; D002908:Chronic Disease; D005080:Exercise Test; D005260:Female; D006331:Heart Diseases / Q000097:blood / Q000401:mortality / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D010100:Oxygen / Q000097:blood; D010101:Oxygen Consumption; D011379:Prognosis; D016016:Proportional Hazards Models; D011659:Pulmonary Gas Exchange; D012123:Pulmonary Ventilation; D012189:Retrospective Studies; D012307:Risk Factors; D016019:Survival Analysis
D002245:Carbon Dioxide; D010100:Oxygen