Ryan M. Murphy

Mechanisms of Exercise Intolerance in Heart Failure With Preserved Ejection Fraction The Role of Abnormal Peripheral Oxygen Extraction

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.

Pulmonary Vascular Response Patterns During Exercise in Left Ventricular Systolic Dysfunction Predict Exercise Capacity and Outcomes

Background— Elevated resting pulmonary arterial pressure (PAP) in patients with left ventricular systolic dysfunction (LVSD) purports a poor prognosis. However, PAP response patterns to exercise in LVSD and their relationship to functional capacity and outcomes have not been characterized. Methods and Results— Sixty consecutive patients with LVSD (age 60±12 years, left ventricular ejection fraction 0.31±0.07, mean±SD) and 19 controls underwent maximum incremental cardiopulmonary exercise testing with simultaneous hemodynamic monitoring. During low-level exercise (30 W), LVSD subjects, compared with controls, had greater augmentation in mean PAPs (15±1 versus 5±1 mm Hg), transpulmonary gradients (5±1 versus 1±1 mm Hg), and effective pulmonary artery elastance (0.05±0.02 versus −0.03±0.01 mm Hg/mL, P<0.0001 for all). A linear increment in PAP relative to work (0.28±0.12 mm Hg/W) was observed in 65% of LVSD patients, which exceeded that observed in controls (0.07±0.02 mm Hg/W, P<0.0001). Exercise capacity and survival was worse in patients with a PAP/watt slope above the median than in patients with a lower slope. In the remaining 35% of LVSD patients, exercise induced a steep initial increment in PAP (0.41±0.16 mm Hg/W) followed by a plateau. The plateau pattern, compared with a linear pattern, was associated with reduced peak VO2 (10.6±2.6 versus 13.1±4.0 mL · kg−1 · min−1, P=0.005), lower right ventricular stroke work index augmentation with exercise (5.7±3.8 versus 9.7±5.0 g/m2, P=0.002), and increased mortality (hazard ratio 8.1, 95% CI 2.7 to 23.8, P<0.001). Conclusions— A steep increment in PAP during exercise and failure to augment PAP throughout exercise are associated with decreased exercise capacity and survival in patients with LVSD, and may therefore represent therapeutic targets. Clinical Trial Information— URL: http://www.clinicaltrials.gov. Unique identifier: NCT00309790.

Exercise Oscillatory Ventilation in Systolic Heart Failure An Indicator of Impaired Hemodynamic Response to Exercise

Background— Exercise oscillatory ventilation (EOV) is a noninvasive parameter that potently predicts outcomes in systolic heart failure (HF). However, mechanistic insights into EOV have been limited by the absence of studies relating EOV to invasive hemodynamic measurements and blood gases performed during exercise. Methods and Results— Fifty-six patients with systolic HF (mean±SEM age, 59±2 years; left ventricular ejection fraction, 30±1%) and 19 age-matched control subjects were studied with incremental cardiopulmonary exercise testing. Fick cardiac outputs, filling pressures, and arterial blood gases were measured at 1-minute intervals during exercise. We detected EOV in 45% of HF (HF+EOV) patients and in none of the control subjects. The HF+EOV group did not differ from the HF patients without EOV (HF−EOV) in age, sex, body mass index, left ventricular ejection fraction, or origin of HF. Univariate predictors of the presence of EOV in HF, among measurements performed during exercise, included higher right atrial pressure and pulmonary capillary wedge pressure and lower cardiac index (CI) but not Paco2 or Pao2. Multivariate logistic regression identified that low exercise CI is the strongest predictor of EOV (odds ratio, 1.39 for each 1.0-L · min−1 · m−2 decrement in CI; 95% confidence interval, 1.14–1.70; P =0.001). Among HF patients with EOV, exercise CI was inversely related to EOV cycle length ( R =−0.71) and amplitude ( R =−0.60; both P <0.001). In 11 HF+EOV subjects treated with 12 weeks of sildenafil, EOV cycle length and amplitude decreased proportionately to increases in CI. Conclusion— Exercise oscillatory ventilation is closely related to reduced CI and elevated filling pressures during exercise and may be an important surrogate for exercise-induced hemodynamic impairment in HF patients. Clinical Trial Registration— URL: . Unique identifier: [NCT00309790][1]. # Clinical Perspective {#article-title-46} [1]: /lookup/external-ref?link_type=CLINTRIALGOV&access_num=NCT00309790&atom=%2Fcirculationaha%2F124%2F13%2F1442.atomBackground— Exercise oscillatory ventilation (EOV) is a noninvasive parameter that potently predicts outcomes in systolic heart failure (HF). However, mechanistic insights into EOV have been limited by the absence of studies relating EOV to invasive hemodynamic measurements and blood gases performed during exercise. Methods and Results— Fifty-six patients with systolic HF (mean±SEM age, 59±2 years; left ventricular ejection fraction, 30±1%) and 19 age-matched control subjects were studied with incremental cardiopulmonary exercise testing. Fick cardiac outputs, filling pressures, and arterial blood gases were measured at 1-minute intervals during exercise. We detected EOV in 45% of HF (HF+EOV) patients and in none of the control subjects. The HF+EOV group did not differ from the HF patients without EOV (HF−EOV) in age, sex, body mass index, left ventricular ejection fraction, or origin of HF. Univariate predictors of the presence of EOV in HF, among measurements performed during exercise, included higher right atrial pressure and pulmonary capillary wedge pressure and lower cardiac index (CI) but not PaCO2 or PaO2. Multivariate logistic regression identified that low exercise CI is the strongest predictor of EOV (odds ratio, 1.39 for each 1.0-L · min−1 · m−2 decrement in CI; 95% confidence interval, 1.14–1.70; P=0.001). Among HF patients with EOV, exercise CI was inversely related to EOV cycle length (R=−0.71) and amplitude (R=−0.60; both P<0.001). In 11 HF+EOV subjects treated with 12 weeks of sildenafil, EOV cycle length and amplitude decreased proportionately to increases in CI. Conclusion— Exercise oscillatory ventilation is closely related to reduced CI and elevated filling pressures during exercise and may be an important surrogate for exercise-induced hemodynamic impairment in HF patients. Clinical Trial Registration— URL: http://www.clinicaltrials.gov. Unique identifier: NCT00309790.

Exercise Oscillatory Ventilation in Heart Failure

Irregular breathing characterized by cyclic variation of ventilation with a period of approximately 1 min has been recognized in patients with heart failure for almost two centuries. Periodic breathing during exercise is a noninvasive parameter that is easily recognizable during submaximal cardiopulmonary exercise testing. Recent studies have established that periodic breathing during exercise not only signals significant impairment in resting and exercise hemodynamic parameters but also potently predicts adverse events in heart failure patients. This article reviews the mechanistic basis of periodic breathing and the clinical utility of discerning patterns of irregular breathing in patients with heart failure.

Prolonged Mean VO2 Response Time in Systolic Heart Failure: An Indicator of Impaired Right Ventricular-Pulmonary Vascular Function

Background— In patients with left ventricular systolic dysfunction (LVSD), the rate at which oxygen uptake (VO2) increases on initiation of exercise is inadequate to match metabolic demands. To gain mechanistic insights into delayed VO2 kinetics in LVSD, we simultaneously assessed hemodynamic measurements, ventilatory parameters, and peripheral oxygen usage during exercise. Methods and Results— Forty-two patients with symptomatic LVSD (age, 59±2 years [mean±SEM]; LV ejection fraction, 30±1%) and 17 controls (LV ejection fraction, 68±1%) underwent maximum upright cycle ergometry cardiopulmonary exercise testing. Hemodynamic monitoring and first-pass radionuclide ventriculography were performed at rest and during exercise. VO2 kinetics were quantified by mean response time (MRT), which was significantly longer in patients with LVSD compared with controls (64±3 versus 45±5 s; P =0.004). In LVSD patients, MRT was associated with higher biventricular filling pressures and reduced cardiac output during early exercise. LVSD patients with MRT ≥60 s, compared with LVSD subjects with MRT <60 s, demonstrated greater impairment in right ventricular-pulmonary vascular function during exercise as evidenced by lower right ventricular ejection fraction (35±2 versus 45±2%; P =0.03), steeper increment in transpulmonary gradient relative to cardiac output (3.7 versus 2.2 mm Hg/L; P <0.001), and increased ventilatory dead-space fraction (17±1 versus 12±2%; P =0.03). In contrast, MRT was not associated with LV ejection fraction (rest, exercise), PaO2, hemoglobin, or resting pulmonary function test results. Conclusions— Delayed oxygen uptake on initiation of exercise (ie, MRT ≥60 s) in LVSD is closely related to impaired right ventricular-pulmonary vascular function and may represent an important surrogate for inability to augment RV performance during physical activity in patients with heart failure.Background—In patients with left ventricular systolic dysfunction (LVSD), the rate at which oxygen uptake (VO2) increases on initiation of exercise is inadequate to match metabolic demands. To gain mechanistic insights into delayed VO2 kinetics in LVSD, we simultaneously assessed hemodynamic measurements, ventilatory parameters, and peripheral oxygen usage during exercise. Methods and Results—Forty-two patients with symptomatic LVSD (age, 59±2 years [mean±SEM]; LV ejection fraction, 30±1%) and 17 controls (LV ejection fraction, 68±1%) underwent maximum upright cycle ergometry cardiopulmonary exercise testing. Hemodynamic monitoring and first-pass radionuclide ventriculography were performed at rest and during exercise. VO2 kinetics were quantified by mean response time (MRT), which was significantly longer in patients with LVSD compared with controls (64±3 versus 45±5 s; P=0.004). In LVSD patients, MRT was associated with higher biventricular filling pressures and reduced cardiac output during early exercise. LVSD patients with MRT ≥60 s, compared with LVSD subjects with MRT <60 s, demonstrated greater impairment in right ventricular-pulmonary vascular function during exercise as evidenced by lower right ventricular ejection fraction (35±2 versus 45±2%; P=0.03), steeper increment in transpulmonary gradient relative to cardiac output (3.7 versus 2.2 mm Hg/L; P<0.001), and increased ventilatory dead-space fraction (17±1 versus 12±2%; P=0.03). In contrast, MRT was not associated with LV ejection fraction (rest, exercise), PaO2, hemoglobin, or resting pulmonary function test results. Conclusions—Delayed oxygen uptake on initiation of exercise (ie, MRT ≥60 s) in LVSD is closely related to impaired right ventricular-pulmonary vascular function and may represent an important surrogate for inability to augment RV performance during physical activity in patients with heart failure.

Prolonged Mean Vo2 Response Time in Systolic Heart FailureClinical Perspective

Background— In patients with left ventricular systolic dysfunction (LVSD), the rate at which oxygen uptake (VO2) increases on initiation of exercise is inadequate to match metabolic demands. To gain mechanistic insights into delayed VO2 kinetics in LVSD, we simultaneously assessed hemodynamic measurements, ventilatory parameters, and peripheral oxygen usage during exercise. Methods and Results— Forty-two patients with symptomatic LVSD (age, 59±2 years [mean±SEM]; LV ejection fraction, 30±1%) and 17 controls (LV ejection fraction, 68±1%) underwent maximum upright cycle ergometry cardiopulmonary exercise testing. Hemodynamic monitoring and first-pass radionuclide ventriculography were performed at rest and during exercise. VO2 kinetics were quantified by mean response time (MRT), which was significantly longer in patients with LVSD compared with controls (64±3 versus 45±5 s; P =0.004). In LVSD patients, MRT was associated with higher biventricular filling pressures and reduced cardiac output during early exercise. LVSD patients with MRT ≥60 s, compared with LVSD subjects with MRT <60 s, demonstrated greater impairment in right ventricular-pulmonary vascular function during exercise as evidenced by lower right ventricular ejection fraction (35±2 versus 45±2%; P =0.03), steeper increment in transpulmonary gradient relative to cardiac output (3.7 versus 2.2 mm Hg/L; P <0.001), and increased ventilatory dead-space fraction (17±1 versus 12±2%; P =0.03). In contrast, MRT was not associated with LV ejection fraction (rest, exercise), PaO2, hemoglobin, or resting pulmonary function test results. Conclusions— Delayed oxygen uptake on initiation of exercise (ie, MRT ≥60 s) in LVSD is closely related to impaired right ventricular-pulmonary vascular function and may represent an important surrogate for inability to augment RV performance during physical activity in patients with heart failure.Background—In patients with left ventricular systolic dysfunction (LVSD), the rate at which oxygen uptake (VO2) increases on initiation of exercise is inadequate to match metabolic demands. To gain mechanistic insights into delayed VO2 kinetics in LVSD, we simultaneously assessed hemodynamic measurements, ventilatory parameters, and peripheral oxygen usage during exercise. Methods and Results—Forty-two patients with symptomatic LVSD (age, 59±2 years [mean±SEM]; LV ejection fraction, 30±1%) and 17 controls (LV ejection fraction, 68±1%) underwent maximum upright cycle ergometry cardiopulmonary exercise testing. Hemodynamic monitoring and first-pass radionuclide ventriculography were performed at rest and during exercise. VO2 kinetics were quantified by mean response time (MRT), which was significantly longer in patients with LVSD compared with controls (64±3 versus 45±5 s; P=0.004). In LVSD patients, MRT was associated with higher biventricular filling pressures and reduced cardiac output during early exercise. LVSD patients with MRT ≥60 s, compared with LVSD subjects with MRT <60 s, demonstrated greater impairment in right ventricular-pulmonary vascular function during exercise as evidenced by lower right ventricular ejection fraction (35±2 versus 45±2%; P=0.03), steeper increment in transpulmonary gradient relative to cardiac output (3.7 versus 2.2 mm Hg/L; P<0.001), and increased ventilatory dead-space fraction (17±1 versus 12±2%; P=0.03). In contrast, MRT was not associated with LV ejection fraction (rest, exercise), PaO2, hemoglobin, or resting pulmonary function test results. Conclusions—Delayed oxygen uptake on initiation of exercise (ie, MRT ≥60 s) in LVSD is closely related to impaired right ventricular-pulmonary vascular function and may represent an important surrogate for inability to augment RV performance during physical activity in patients with heart failure.

DETERMINANTS OF VE/VCO2 SLOPE IN NORMAL INDIVIDUALS – VENTILATORY EFFICIENCY IS MODIFIABLE WITH ENDURANCE TRAINING

Ventilatory efficiency, as indicated by the increment in minute ventilation (VE) relative to CO2 production (VCO2), reflects right ventricular-pulmonary vascular (RV-PV) function during exercise. In patients with heart failure (HF), a VE/VCO2 slope greater than 34 purports a poor prognosis. Less is

Mechanisms of Exercise Intolerance in Heart Failure With Preserved Ejection FractionCLINICAL PERSPECTIVE: The Role of Abnormal Peripheral Oxygen Extraction

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.

Mechanisms of Exercise Intolerance in Heart Failure With Preserved Ejection FractionCLINICAL PERSPECTIVE

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.

Prolonged Mean Vo2 Response Time in Systolic Heart Failure

Background— In patients with left ventricular systolic dysfunction (LVSD), the rate at which oxygen uptake (VO2) increases on initiation of exercise is inadequate to match metabolic demands. To gain mechanistic insights into delayed VO2 kinetics in LVSD, we simultaneously assessed hemodynamic measurements, ventilatory parameters, and peripheral oxygen usage during exercise. Methods and Results— Forty-two patients with symptomatic LVSD (age, 59±2 years [mean±SEM]; LV ejection fraction, 30±1%) and 17 controls (LV ejection fraction, 68±1%) underwent maximum upright cycle ergometry cardiopulmonary exercise testing. Hemodynamic monitoring and first-pass radionuclide ventriculography were performed at rest and during exercise. VO2 kinetics were quantified by mean response time (MRT), which was significantly longer in patients with LVSD compared with controls (64±3 versus 45±5 s; P =0.004). In LVSD patients, MRT was associated with higher biventricular filling pressures and reduced cardiac output during early exercise. LVSD patients with MRT ≥60 s, compared with LVSD subjects with MRT <60 s, demonstrated greater impairment in right ventricular-pulmonary vascular function during exercise as evidenced by lower right ventricular ejection fraction (35±2 versus 45±2%; P =0.03), steeper increment in transpulmonary gradient relative to cardiac output (3.7 versus 2.2 mm Hg/L; P <0.001), and increased ventilatory dead-space fraction (17±1 versus 12±2%; P =0.03). In contrast, MRT was not associated with LV ejection fraction (rest, exercise), PaO2, hemoglobin, or resting pulmonary function test results. Conclusions— Delayed oxygen uptake on initiation of exercise (ie, MRT ≥60 s) in LVSD is closely related to impaired right ventricular-pulmonary vascular function and may represent an important surrogate for inability to augment RV performance during physical activity in patients with heart failure.Background—In patients with left ventricular systolic dysfunction (LVSD), the rate at which oxygen uptake (VO2) increases on initiation of exercise is inadequate to match metabolic demands. To gain mechanistic insights into delayed VO2 kinetics in LVSD, we simultaneously assessed hemodynamic measurements, ventilatory parameters, and peripheral oxygen usage during exercise. Methods and Results—Forty-two patients with symptomatic LVSD (age, 59±2 years [mean±SEM]; LV ejection fraction, 30±1%) and 17 controls (LV ejection fraction, 68±1%) underwent maximum upright cycle ergometry cardiopulmonary exercise testing. Hemodynamic monitoring and first-pass radionuclide ventriculography were performed at rest and during exercise. VO2 kinetics were quantified by mean response time (MRT), which was significantly longer in patients with LVSD compared with controls (64±3 versus 45±5 s; P=0.004). In LVSD patients, MRT was associated with higher biventricular filling pressures and reduced cardiac output during early exercise. LVSD patients with MRT ≥60 s, compared with LVSD subjects with MRT <60 s, demonstrated greater impairment in right ventricular-pulmonary vascular function during exercise as evidenced by lower right ventricular ejection fraction (35±2 versus 45±2%; P=0.03), steeper increment in transpulmonary gradient relative to cardiac output (3.7 versus 2.2 mm Hg/L; P<0.001), and increased ventilatory dead-space fraction (17±1 versus 12±2%; P=0.03). In contrast, MRT was not associated with LV ejection fraction (rest, exercise), PaO2, hemoglobin, or resting pulmonary function test results. Conclusions—Delayed oxygen uptake on initiation of exercise (ie, MRT ≥60 s) in LVSD is closely related to impaired right ventricular-pulmonary vascular function and may represent an important surrogate for inability to augment RV performance during physical activity in patients with heart failure.