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Mechanisms of exercise intolerance in heart failure with preserved ejection fraction: the role of abnormal peripheral oxygen extraction.

ABSTRACT: BACKGROUND:Exercise capacity as measured by peak oxygen uptake (Vo2) is similarly impaired in patients with heart failure with preserved ejection fraction (HFpEF) and heart failure with reduced ejection fraction (HFrEF). However, characterization of how each component of Vo2 changes in response to incremental exercise in HFpEF versus HFrEF has not been previously defined. We hypothesized that abnormally low peripheral o2 extraction (arterio-mixed venous o2 content difference, [C(a-v)o2]) during exercise significantly contributes to impaired exercise capacity in HFpEF. METHODS AND RESULTS:We performed maximum incremental cardiopulmonary exercise testing with invasive hemodynamic monitoring on 104 patients with symptomatic NYHA II to IV heart failure (HFpEF, n=48, peak Vo2=13.9±0.5 mL?kg(-1)?min(-1), mean±SEM, and HFrEF, n=56, peak Vo2=12.1±0.5 mL?kg(-1)?min(-1)) and 24 control subjects (peak Vo2 27.0±1.7 mL?kg(-1)?min(-1)). Peak exercise C(a-v)o2 was lower in HFpEF compared with HFrEF (11.5±0.27 versus 13.5±0.34 mL/dL, respectively, P<0.0001), despite no differences in age, hemoglobin level, peak respiratory exchange ratio, Cao2, or cardiac filling pressures. Peak C(a-v)o2 and peak heart rate emerged as the leading predictors of peak Vo2 in HFpEF. Impaired peripheral o2 extraction was the predominant limiting factor to exercise capacity in 40% of patients with HFpEF and was closely related to elevated systemic blood pressure during exercise (r=0.49, P=0.0005). CONCLUSIONS:In the first study to directly measure C(a-v)o2 throughout exercise in HFpEF, HFrEF, and normals, we found that peak C(a-v)o2 was a major determinant of exercise capacity in HFpEF. The important functional limitation imposed by impaired o2 extraction may reflect intrinsic abnormalities in skeletal muscle or peripheral microvascular function, and represents a potential target for therapeutic intervention.

SUBMITTER: Dhakal BP

PROVIDER: S-EPMC5771713 | biostudies-literature | 2015 Mar

REPOSITORIES: biostudies-literature

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Mechanisms of exercise intolerance in heart failure with preserved ejection fraction: the role of abnormal peripheral oxygen extraction.

Dhakal Bishnu P BP Malhotra Rajeev R Murphy Ryan M RM Pappagianopoulos Paul P PP Baggish Aaron L AL Weiner Rory B RB Houstis Nicholas E NE Eisman Aaron S AS Hough Stacyann S SS Lewis Gregory D GD

Circulation. Heart failure 20141024 2

<h4>Background</h4>Exercise capacity as measured by peak oxygen uptake (Vo2) is similarly impaired in patients with heart failure with preserved ejection fraction (HFpEF) and heart failure with reduced ejection fraction (HFrEF). However, characterization of how each component of Vo2 changes in response to incremental exercise in HFpEF versus HFrEF has not been previously defined. We hypothesized that abnormally low peripheral o2 extraction (arterio-mixed venous o2 content difference, [C(a-v)o2]) ...[more]

PMID: 25344549

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Project description:BackgroundThe correlation between echocardiographic parameters and hemodynamics data in patients with heart failure with preserved ejection fraction (HFpEF) is unclear. It is important to find a non-invasive echocardiographic parameter for predicting exercise pulmonary capillary wedge pressure (PCWP).AimThis study sought to determine the correlation between echocardiographic parameters and hemodynamics data at rest and during exercise in HFpEF patients.Methods and resultsThis study was a cross-sectional cohort exploratory analysis of baseline data from the ILO-HOPE trial. A total of 34 HFpEF patients were enrolled. The average age was 70 ± 12 years, and most (74%) were women. The patients underwent invasive cardiac catheterization and expired gas analysis at rest and during exercise. Echocardiography including tissue Doppler imaging was performed, and global longitudinal strain and other novel diastolic function indexes were analyzed at rest and during exercise. At rest, no significant correlation was noted between resting PCWP and echocardiographic parameters. However, a significant correlation was observed between post-exercise PCWP and stress E/e' (septal, lateral, and mean) ratio (p = 0.003, 0.031, 0.012). Moreover, post-exercise ΔPCWP showed a good correlation with stress E/e' (septal, lateral, and mean; all p ≤ 0.001) and global longitudinal strain (GLS) during exercise (p = 0.03). After multivariate regression analysis with adjustment for possible confounding factors including age and sex, there was still a significant correlation between post-exercise ΔPCWP and E/e' (r = 0.62, p < 0.001 for E/e'mean).ConclusionOnly stress echocardiography derived tissue Doppler E/e' ratio is closely correlated with abnormal exercise hemodynamics (PCWP and post-exercise ΔPCWP) in HFpEF. This echocardiographic marker is substantially more sensitive than other novel echocardiographic parameters during exercise, and may have significant diagnostic utility for ambulatory HFpEF patients with dyspnea.Clinical trial registrationhttps://www.clinicaltrials.gov, identifier NCT03620526.

Project description:BACKGROUND:Heart failure with preserved ejection fraction (HFpEF) is a common syndrome with a pressing shortage of therapies. Exercise intolerance is a cardinal symptom of HFpEF, yet its pathophysiology remains uncertain. METHODS:We investigated the mechanism of exercise intolerance in 134 patients referred for cardiopulmonary exercise testing: 79 with HFpEF and 55 controls. We performed cardiopulmonary exercise testing with invasive monitoring to measure hemodynamics, blood gases, and gas exchange during exercise. We used these measurements to quantify 6 steps of oxygen transport and utilization (the O2 pathway) in each patient with HFpEF, identifying the defective steps that impair each one's exercise capacity (peak Vo2). We then quantified the functional significance of each O2 pathway defect by calculating the improvement in exercise capacity a patient could expect from correcting the defect. RESULTS:Peak Vo2 was reduced by 34±2% (mean±SEM, P<0.001) in HFpEF compared with controls of similar age, sex, and body mass index. The vast majority (97%) of patients with HFpEF harbored defects at multiple steps of the O2 pathway, the identity and magnitude of which varied widely. Two of these steps, cardiac output and skeletal muscle O2 diffusion, were impaired relative to controls by an average of 27±3% and 36±2%, respectively (P<0.001 for both). Due to interactions between a given patient's defects, the predicted benefit of correcting any single one was often minor; on average, correcting a patient's cardiac output led to a 7±0.5% predicted improvement in exercise intolerance, whereas correcting a patient's muscle diffusion capacity led to a 27±1% improvement. At the individual level, the impact of any given O2 pathway defect on a patient's exercise capacity was strongly influenced by comorbid defects. CONCLUSIONS:Systematic analysis of the O2 pathway in HFpEF showed that exercise capacity was undermined by multiple defects, including reductions in cardiac output and skeletal muscle diffusion capacity. An important source of disease heterogeneity stemmed from variation in each patient's personal profile of defects. Personalized O2 pathway analysis could identify patients most likely to benefit from treating a specific defect; however, the system properties of O2 transport favor treating multiple defects at once, as with exercise training.

Dataset Information

Mechanisms of exercise intolerance in heart failure with preserved ejection fraction: the role of abnormal peripheral oxygen extraction.

Publications

Mechanisms of exercise intolerance in heart failure with preserved ejection fraction: the role of abnormal peripheral oxygen extraction.

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