Cardiovascular Diseases ; diagnosis ; Exercise Test ; Heart Failure ; diagnosis ; Humans

OBJECTIVETo observe oxygen uptake efficiency plateau (OUEP, i.e.highest V˙O2/V˙E) and carbon dioxide output efficiency (lowest V˙E/V˙CO2) parameter changes during exercise in normal subjects.

METHODSFive healthy volunteers performed the symptom limited maximal cardiopulmonary exercise test (CPET) at Harbor-UCLA Medical Center. V˙O2/V˙E and V˙E/V˙CO2 were determined by both arterial and central venous catheters. After blood gas analysis of arterial and venous sampling at the last 30 seconds of every exercise stage and every minute of incremental loading, the continuous parameter changes of hemodynamics, pulmonary ventilation were monitored and oxygen uptake ventilatory efficiency (V˙O2/V˙E and V˙E/V˙CO2) was calculated.

RESULTSDuring CPET, as the loading gradually increased, cardiac output, heart rate, mixed venous oxygen saturation, arteriovenous oxygen difference, minute ventilation, minute alveolar ventilation, tidal volume, alveolar ventilation and pulmonary ventilation perfusion ratio increased near-linearly (P < 0.05-0.01, vs.resting); arterial oxygen concentration maintained at a high level without significant change (P > 0.05); stroke volume, respiratory rate, arterial partial pressure of carbon dioxide, arterial blood hydrogen ion concentration and dead space ventilation ratio significantly changed none-linearly (compare resting state P < 0.05-0.01).OUE during exercise increased from 30.9 ± 3.3 at resting state to the highest plateau 46.0 ± 4.7 (P < 0.05 vs.resting state), then, declined gradually after anaerobic threshold (P < 0.05-0.01, vs.OUEP) and reached 36.6 ± 4.4 at peak exercise. The V˙E/V˙CO2 during exercise decreased from the resting state (39.2 ± 6.5) to the minimum value (24.2 ± 2.4) after AT for a few minutes (P > 0.05 vs.earlier stage), then gradually increased after the ventilatory compensation point (P < 0.05 vs.earlier stage) and reached to 25.9 ± 2.7 at peak exercise.

CONCLUSIONSCardiac and lung function as well as metabolism change during CPET is synchronous.In the absence of pulmonary limit, appearing before and after anaerobic threshold, OUEP and lowest V˙E/V˙CO2 could be used as reliable parameters representing the circulatory function.

Arteries ; Blood Gas Analysis ; Blood Pressure ; Carbon Dioxide ; metabolism ; Cardiac Output ; Exercise ; physiology ; Exercise Test ; Heart ; Heart Rate ; Hemodynamics ; Humans ; Lung ; Oxygen ; metabolism ; Oxygen Consumption

OBJECTIVETo assess peak oxygen consumption (peak VO₂) derived from cardiopulmonary exercise testing (CPET), concentrations of NT-proBNP and echocardiographic changes in patients with chronic heart failure (CHF) and reduced left ventricular ejection fraction (LVEF, <40%).

METHODSSeventy patients were included and divided into two groups according to the New York Heart Association (NYHA) classification: NYHA II group (17 cases) and NYHA III-IV group (53 cases). The basic clinical information, plasma concentration of NT-proBNP at rest, echocardiographic parameters and peak VO₂from CPET were compared between two groups. Correlation among peak VO₂, NT-proBNP and echocardiographic parameters in this patient cohort was assessed and their abilities to discriminate the NYHA III-IV grade were analyzed through c-Statistic.

RESULTSLeft atrial diameter ((51.3 ± 7.2) mm vs. (44.0±7.4) mm, P<0.001) was larger, plasma concentration of NT-proBNP (1 379-4 399 pmol/L vs. 1 109-2 356 pmol/L, P<0.01) was higher and peak VO₂((13.4 ± 3.5) ml·kg⁻¹·min⁻¹ vs. (18.2 ± 3.7) ml·kg⁻¹·min⁻¹, P<0.001) were significantly lower in NYHA III-IV group than those in NYHA II group. However, left ventricular end-diastolic diameter (LVEDD) and LVEF were similar between two groups. Peak VO₂correlated significantly with NT-proBNP (r=-0.311, P<0.01), but neither peak VO₂nor NT-proBNP correlated with echocardiographic parameters (LA, LVEDD and LVEF). ROC analysis showed that peak VO₂had the strongest discriminatory power for detecting NYHA III-IV grade patients (AUC=0.835, P<0.001), followed by the NT-proBNP (AUC=0.723, P<0.01).

CONCLUSIONPeak VO₂is a more sensitive parameter to detect the disease aggravation (NYHA III-IV grade) of the CHF patients with reduced LVEF compared to plasma NT-proBNP and echocardiographic parameters (LA, LVEDD, LVEF).

Chronic Disease ; Echocardiography ; Exercise Test ; Heart ; Heart Failure ; Humans ; Natriuretic Peptide, Brain ; Oxygen Consumption ; Peptide Fragments ; ROC Curve ; Ventricular Function, Left