title: Usefulness of non-invasive measurement of cardiac output during sub-maximal exercise to predict outcome in patients with chronic heart failure.
abstract: Peak oxygen consumption (Vo(2)) is a powerful prognostic predictor of survival in patients with chronic heart failure (CHF) because it provides an indirect assessment of a patient's ability to increase cardiac output (CO). However, many patients with CHF who undergo cardiopulmonary exercise testing are unable to perform maximal exercise. New metabolic carts coupled with the inert gas rebreathing technique provide a noninvasive measurement of CO. Whether the noninvasive measurement of CO at a fixed submaximal workload can predict outcome is unknown. This study's population comprised 259 patients (mean age 54 +/- 14 years, mean left ventricular ejection fraction 27 +/- 14%) with CHF who underwent symptom-limited incremental cardiopulmonary exercise testing. Vo(2) and CO were measured at rest, at 25 W, and at peak exercise. Submaximal exercise was defined as <80% peak Vo(2). Among 259 patients, 145 had Vo(2) at 25 W <80% of peak. Vo(2) at 25 W averaged 9.3 +/- 1.8 ml/kg/min. This Vo(2) represented 62 +/- 11% of peak Vo(2), which averaged 15.4 +/- 4.4 ml/kg/min. Prospective follow-up averaged 521 +/- 337 days. In this cohort, there were 15 outcome events (death, urgent heart transplantation, or implantation of a left ventricular assist device as a bridge to transplantation). On univariate Cox hazard analysis, CO at 25 W (hazard ratio 0.64, 95% confidence interval 0.48 to 0.84, p = 0.002) was found to be significant predictor of events of outcome. In conclusion, CO at 25 W measured noninvasively during submaximal exercise may have potential value as a predictor of outcomes in patients with CHF.
authors.affiliation: Division of Cardiology, College of Physicians and Surgeons, Columbia University, New York, New York, USA.
authors.forename: Ayumi
authors.initials: A
authors.lastname: Goda
authors.forename: Chim C
authors.initials: CC
authors.lastname: Lang
authors.forename: Paula
authors.initials: P
authors.lastname: Williams
authors.forename: Margaret
authors.initials: M
authors.lastname: Jones
authors.forename: Mary Jane
authors.initials: MJ
authors.lastname: Farr
authors.forename: Donna M
authors.initials: DM
authors.lastname: Mancini
mesh_terms: D000328:Adult; D000368:Aged; D001795:Blood Pressure Determination; D002302:Cardiac Output; D002908:Chronic Disease; D015331:Cohort Studies; D016001:Confidence Intervals; D005080:Exercise Test / Q000379:methods*; D017079:Exercise Tolerance; D005260:Female; D005500:Follow-Up Studies; D006333:Heart Failure / Q000175:diagnosis* / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption; D011237:Predictive Value of Tests; D011379:Prognosis; D016016:Proportional Hazards Models; D011446:Prospective Studies; D012129:Respiratory Function Tests; D018570:Risk Assessment; D012720:Severity of Illness Index