Clinical significance of respiratory compensation during exercise testing in cardiac patients.

Ventilation (VE) increases linearly with the increase of carbon dioxide output (VCO2) during cardiopulmonary exercise testing. VE-VCO2 slope rises in parallel with exercise intensity, reaches a turning point (called the RC point), then steepens because of respiratory compensation for lactic acidosis. While this RC point can be identified universally, it is undetectable in some patients. In this study we evaluated whether the respiratory compensation during exercise testing has clinical significance in cardiac patients. In total, 152 cardiac patients with a respiratory exchange ratio at peak exercise (peak R) of between 1.10 and 1.20 were enrolled. Cardiopulmonary parameters were compared between patients who manifested the RC point (n = 118) and those who did not (n = 34). The peak R did not significantly differ between these two groups. Compared to the patients without the RC point, those with the RC point had a higher oxygen uptake at peak exercise (peak VO2) (20.2 ± 5.3 vs 13.6 ± 3.4 mL/min/kg, p < 0.001), higher anaerobic threshold (AT) (12.4 ± 3.2 vs 9.2 ± 2.3 mL/min/kg, p < 0.001), and lower VE-VCO2 slope (31.7 ± 5.8 vs 37.8 ± 9.6, p = 0.001). Brain natriuretic peptide (BNP) tended to be lower in the patients with the RC point (175.4 ± 364.7 vs 327.9 ± 381.1 pg/mL, p = 0.067). Peak VO2, the marker of cardiopulmonary function, was found to be the independent predictor of the presence of the RC point. The present findings suggest that the phenomenon of respiratory compensation during heavy exercise indicates better cardiopulmonary function in cardiac patients within a prescribed range of effort.

Clinical Significance of the Presence of Oscillatory Breathing Both at Rest and During Exercise in Cardiac Patients.

Cardiac patients often experience nocturnal and daytime oscillatory breathing (OB). OB noted at rest sometimes becomes unclear or even disappears during exercise. We evaluated the physiological significance of OB by comparing the clinical characteristics of cardiac patients who manifested OB only at rest (group A), only during exercise (group B), and both at rest and during exercise (group C).Among 3,432 cardiac patients who underwent cardiopulmonary exercise testing (CPX), 114, 94, and 65 patients were identified as group A, B, and C, respectively. Left ventricular ejection function was 57 ± 17% in group A, 49 ± 20% in group B, and 41 ± 21% in group C (P < 0.05 for all comparisons among the 3 groups). The level of brain natriuretic peptide (BNP) was significantly higher in group C than in groups A and B. The peak VO2 was lower and the VE-VCO2 slope was higher in groups B and C than in group A.The present findings suggest that cardiac function is more impaired in cardiac patients who manifest OB both at rest and during exercise than in cardiac patients who manifest OB only at rest or only during exercise.

Relationship between the prognostic value of ventilatory efficiency and age in patients with heart failure.

Background Ventilatory efficiency decreases with age. This study aimed to investigate the prognostic significance and cut-off value of the minute ventilation/carbon dioxide production (VE/VCO2) slope according to age in patients with heart failure. Methods and results We analysed 1501 patients with heart failure from our observational cohort who performed maximal symptom-limited cardiopulmonary exercise testing and separated them into three age groups (≤55 years, 56-70 years and ≥71 years) in total and according to the three ejection fraction categories defined by European Society of Cardiology guidelines. The endpoint was set as heart failure events, hospitalisation for heart failure or death from heart failure. The VE/VCO2 slope increased with age. During the median follow-up period of 4 years, 141 heart failure (9%) events occurred. In total, univariate Cox analyses showed that the VE/VCO2 slope (cont.) was significantly related to heart failure events, while on multivariate analysis, the prognostic significance of the VE/VCO2 slope (cont.) was poor, accompanied by a significant interaction with age ( P < 0.0001). The cut-off value of the VE/VCO2 slope increased with the increase in age in not only the total but also the sub-ejection fraction categories. Multivariate analyses with a stepwise method adjusted for estimated glomerular filtration rate, peak oxygen consumption, atrial fibrillation and brain natriuretic peptide, showed that the predictive value of the binary VE/VCO2 slope separated by the cut-off value varied according to age. There was a tendency for the prognostic significance to increase with age irrespective of ejection fraction. Conclusion The prognostic significance and cut-off value of the VE/VCO2 slope may increase with advancing age.

Clinical significance of the overshoot phenomena of respiratory gas indices during recovery from maximal exercise testing.

BACKGROUND: Overshoot phenomena of the gas exchange ratio (R:VCO2/VO2), ventilatory equivalent for O2 (VE/VO2), and end-tidal O2 pressure (PETO2) are commonly observed during recovery from maximal cardiopulmonary exercise testing (CPX). We investigated the clinical significance of the overshoots of these indices by comparing their magnitudes between healthy subjects and cardiac patients with left ventricular dysfunction. METHODS: In total, 121 subjects (73 healthy subjects and 48 cardiac patients with left ventricular ejection fraction<40%) who underwent CPX and achieved peak R≥1.10 were enrolled. We evaluated and calculated the presence and magnitude of the overshoot phenomena of R, VE/VO2, and PETO2. RESULTS: The overshoot phenomena of R, VE/VO2, and PETO2 were observed in all the subjects. The magnitudes of the R (21.4±12.4% vs. 29.3±10.0%, p<0.001), VE/VO2 (45.5±23.5% vs. 77.5±28.5%, p<0.001), and PETO2 (5.3±3.4% vs. 10.1±4.2%, p<0.001) overshoots were significantly lower in cardiac patients than in healthy subjects. In cardiac patients, the magnitude of the PETO2 overshoot showed significant positive correlations with the peak O2 uptake (VO2) (r=0.52, p<0.001), anaerobic threshold (r=0.43, p=0.003), and ratio of the increase in VO2 to the increase in the work rate (r=0.41, p=0.005), and a negative correlation with the slope of the increase in ventilation versus the increase in CO2 output (r=-0.50, p<0.001). The magnitudes of the R and VE/VO2 overshoots showed the same patterns of significant correlation with the CPX indices. CONCLUSIONS: We concluded that the overshoots of R, VE/VO2, and PETO2 during recovery from maximal exercise reflect the natural cardiopulmonary adaptation after exercise and are more prominent in subjects with better cardiopulmonary function.

The relationship between resting heart rate and peak VO2: A comparison of atrial fibrillation and sinus rhythm.

BACKGROUND: Resting heart rate is a surrogate marker associated with achieved exercise capacity, which has been observed in patients with sinus rhythm. The aim of this study was to examine and compare the relationships between resting heart rate and peak oxygen consumption in atrial fibrillation and sinus rhythm. METHODS AND RESULTS: A total of 2160 consecutive patients undergoing cardiopulmonary exercise testing in our single-hospital cohort were divided into two groups according to rhythm status: an atrial fibrillation group (N = 320) and a sinus rhythm group (N = 1840). In the total cohort and sinus rhythm group, resting heart rate was negatively correlated with percentage of predicted peak oxygen consumption (Ptrend < 0.0001); in atrial fibrillation patients, this correlation was apparently positive (Ptrend = 0.032). Multivariate analysis of the total cohort showed a significant interaction between resting heart rate and rhythm status for peak oxygen consumption after adjustments for age, sex, ejection fraction, structural heart diseases and heart rate-lowering drugs. In the sinus rhythm group, resting heart rate was an independent, negative contributing factor for peak oxygen consumption, even after the adjustments for patient background. However, in the atrial fibrillation group, resting heart rate was a weak positive or non-independent contributing factor for peak oxygen consumption after the same adjustments. CONCLUSIONS: The impact of resting heart rate on exercise capacity differed completely between atrial fibrillation and sinus rhythm, suggesting that heart rate control may need to be managed differently for atrial fibrillation and sinus rhythm, in light of exercise capacity that is related to quality of life and prognosis.

Clinical significance of a spiral phenomenon in the plot of CO2 output versus O2 uptake during exercise in cardiac patients.

A spiral phenomenon is sometimes noted in the plots of CO2 output (VCO2) against O2 uptake (VO2) measured during cardiopulmonary exercise testing (CPX) in patients with heart failure with oscillatory breathing. However, few data are available that elucidate the clinical significance of this phenomenon. Our group studied the prevalence of this phenomenon and its relation to cardiac and cardiopulmonary function. Of 2,263 cardiac patients who underwent CPX, 126 patients with a clear pattern of oscillatory breathing were identified. Cardiopulmonary indexes were compared between patients who showed the spiral phenomenon (n = 49) and those who did not (n = 77). The amplitudes of VO2 and VCO2 oscillations were greater and the phase difference between VO2 and VCO2 oscillations was longer in the patients with the spiral phenomenon than in those without it. Patients with the spiral phenomenon also had a lower left ventricular ejection fraction (43.4 ± 21.4% vs 57.1 ± 16.8%, p <0.001) and a higher level of brain natriuretic peptide (637.2 ± 698.3 vs 228.3 ± 351.4 pg/ml, p = 0.002). The peak VO2 was lower (14.5 ± 5.6 vs 18.1 ± 6.3, p = 0.002), the slope of the increase in ventilation versus VCO2 was higher (39.8 ± 9.5 vs 33.6 ± 6.8, p <0.001), and end-tidal PCO2 both at rest and at peak exercise was lower in the patients with the spiral phenomenon than in those without it. In conclusion, the spiral phenomenon in the VCO2-versus-VO2 plot arising from the phase difference between VCO2 and VO2 oscillations reflects more advanced cardiopulmonary dysfunction in cardiac patients with oscillatory breathing.

Relation between oscillatory breathing and cardiopulmonary function during exercise in cardiac patients.

BACKGROUND: Oscillatory breathing, alternating between hyperpnea and hypopnea, has been recognized in cardiac patients, especially in those with heart failure. We evaluated whether the cycle length and amplitude of oscillatory breathing correlate with impaired cardiopulmonary function during exercise. METHODS AND RESULTS: We analyzed respiratory gas data during cardiopulmonary exercise testing (CPX) in 17 cardiac patients (68 ± 12 years) who showed clear oscillatory ventilation during CPX. The cycle length (time from peak to peak) and the amplitude (difference between peak and nadir) for both oscillating ventilation (VE) and oscillating O(2) uptake (VO(2)) were calculated from several consecutive oscillations noted at rest, and compared with indices of CPX. Oscillating VO(2) preceded oscillating VE in 16 of the 17 patients. Peak VO(2) (10.3 ± 3.1 ml min(-1)kg(-1)) correlated significantly negatively with the cycle length of the VE oscillation (r=-0.60, P=0.010), and of the VO(2) oscillation (r=-0.61, P=0.008), and the difference in time between the peak of oscillating VE and the corresponding peak of VO(2) (r=-0.58, P=0.012). Similarly, the slope of the increase in VE to the increase in CO(2) output (45.6 ± 11.5) correlated significantly positively with the cycle length of the VE and VO(2) oscillations (r=0.68, P=0.002; r=0.67, P=0.003, respectively). CONCLUSIONS: The cycle length of oscillatory breathing is closely related to impaired cardiac reserve during exercise in cardiac patients.

Prognostic value of cardiopulmonary exercise testing in cardiac patients with atrial fibrillation.

Parameters obtained from cardiopulmonary exercise testing (CPX) are recognized for their high prognostic value in predicting future cardiac events in cardiac patients. Our group compared the prognostic value of CPX parameters between patients with sinus rhythm (SR) and patients with atrial fibrillation (AF).Peak O2 uptake (VO2), the ratio of the increase in VO2 to the increase in work rate (ΔVO2/ΔWR), and the slope of the increase in ventilation to the increase in CO2 output (VE-VCO2 slope) were obtained from CPX in 72 AF patients and 478 SR patients. The prognostic values of these indices were compared between the two groups.Six cardiac deaths and 25 cardiac events were observed in the AF group and 9 cardiac deaths and 96 cardiac events were observed in the SR group, over a prospective follow-up period of 1,192 days. The percentages of cardiac deaths and cardiac events were higher in the AF group than in the SR group. In a multivariate Cox proportional hazards analysis, peak VO2 was identified as a sole significant predictor of cardiac death and cardiac events in SR patients and VE-VCO2 slope was identified as a sole significant predictor of cardiac death and cardiac events in AF patients.Our results suggest that the VE-VCO2 slope is strongly predictive of future cardiac events in patients with AF and that peak VO2 is strongly predictive of future cardiac events in SR patients.

Role of cardiopulmonary dysfunction and left atrial remodeling in development of acute decompensated heart failure in chronic heart failure with preserved left ventricular ejection fraction.

BACKGROUND: The presence of heart failure (HF) with preserved ejection fraction (HFPEF) is increasingly recognized. However, prognostic factors for HFPEF remain unclear. METHODS AND RESULTS: The data were derived from Shinken Database 2004-2010, a prospective cohort study (n=15,227). We examined 301 consecutive HFPEF patients (New York Heart Association Class II or greater) and tracked them for an average 3.5 years. Cardiopulmonary exercise testing (CPX), blood exams, and ultrasound cardiogram (UCG) were performed at the first medical examination. Acute decompensated HF (ADHF) admission was observed in 19 patients (6.3%). CPX showed that the anaerobic threshold was lower (7.3±4.8mL/min/kg vs. 9.7±4.3mL/min/kg, p=0.02) and slope of the increase in ventilation to the increase in CO(2) output (VE-VCO(2) slope) was higher (40.6±8.5 vs. 34.6±7.9, p<0.01) in patients with ADHF admission than those without. Serum brain natriuretic peptide (BNP) tended to be higher and left atrial (LA) dimension was significantly greater (47.0±15.8mm vs. 41.0±9.9mm, p=0.01) in patients with ADHF admission than those without. Multivariate analysis showed that higher VE-VCO(2) slope and greater LA dimension were independent determinants of ADHF admission. CONCLUSION: An aggravated CPX parameter and LA dilatation were associated with ADHF admission in patients with symptomatic HFPEF, suggesting the prognostic role of cardiopulmonary dysfunction during exercise and LA remodeling in the pathogenesis of decompensated HF development in HFPEF.

Overshoot phenomena of respiratory gas variables during exercise recovery in cardiac patients.

BACKGROUND: Transient increases (overshoot) in respiratory gas variables have been observed during exercise recovery, but their clinical significance is not clearly understood. Our group evaluated the relationship between the presence of overshoot of respiratory gas variables and the parameters obtained from cardiopulmonary exercise testing (CPX). METHODS AND RESULTS: In total, 227 patients with various cardiac diseases underwent CPX. The overshoot phenomena of O2 uptake (·VO2), ·VO2/heart rate (O2-pulse), and CO2 output (·VCO2) were analyzed by respiratory gas analysis during recovery after maximal exercise. The overshoot of ·VO2, O2-pulse, and ·VCO2 were recognized in 11 (5%), 43 (19%), and 12 (5%) patients, respectively. Compared with the patients without a ·VO2 overshoot, those with a ·VO2 overshoot had a significantly lower peak ·VO2 (12.3±3.7 vs. 17.9±6.2ml·min⁻¹·kg⁻¹, P=0.003), lower anaerobic threshold (9.4±1.7 vs. 12.4±3.3 ml·min⁻¹·kg⁻¹, P=0.001), higher ·VE-·VCO2 slope (38.0±5.2 vs. 33.2±9.6, P=0.013), and lower left ventricular ejection fraction (LVEF) (39.9±22.8 vs. 55.8±16.8%, P=0.003). Similar findings were obtained for the patients with an O2-pulse overshoot and those with a ·VCO2 overshoot. CONCLUSIONS: The overshoot phenomena of respiratory gas variables during recovery after maximal exercise are correlated with impaired cardiopulmonary function during exercise in cardiac patients.

Abnormal end-tidal PO(2) and PCO(2) at the anaerobic threshold correlate well with impaired exercise gas exchange in patients with left ventricular dysfunction.

BACKGROUND: The aim of the present study was to compare the end-tidal O(2) pressure (PETO(2)) to end-tidal CO(2) pressure (PETCO(2)) in cardiac patients during rest and during 2 states of exercise: at anaerobic threshold (AT) and at peak. The purpose was to see which metabolic state, PETO(2) or PETCO(2), best correlated with exercise limitation. METHODS AND RESULTS: Thirty-eight patients with left ventricular (LV) ejection fraction <40% underwent cardiopulmonary exercise testing (CPX). PETO(2) and PETCO(2) were measured during CPX, along with peak O(2) uptake (VO(2)), AT, slope of the increase in ventilation (VE) relative to the increase in CO(2) output (VCO(2)) (VE vs. VCO(2) slope), and the ratio of the increase in VO(2) to the increase in work rate (ΔVO(2)/ΔWR). Both PETO(2) and PETCO(2) measured at AT were best correlated with peakVO(2), AT, ΔVO(2)/ΔWR and VE vs. VCO(2) slope. PETO(2) at AT correlated with reduced peak VO(2) (r=-0.60), reduced AT (r=-0.52), reduced ΔVO(2)/ΔWR (r=-0.55) and increased VE vs. VCO(2) slope (r=0.74). PETCO(2) at AT correlated with reduced peak VO(2) (r=0.67), reduced AT (r=0.61), reduced ΔVO(2)/ΔWR (r=0.58) and increased VE vs. VCO(2) slope (r=-0.80). CONCLUSIONS: PETCO(2) and PETO(2) at AT correlated with peak VO(2), AT and ΔVO(2)/ΔWR, but best correlated with increased VE vs. VCO(2) slope. PETO(2) and PETCO(2) at AT can be used as a prime index of impaired cardiopulmonary function during exercise in patients with LV failure.

Overshoot phenomenon of oxygen uptake during recovery from maximal exercise in patients with previous myocardial infarction.

The overshoot in oxygen uptake (VO2 overshoot) during recovery from maximal exercise is thought to reflect an overshoot in cardiac output. We investigated whether this phenomenon is related to cardiopulmonary function during exercise in cardiac patients. A total of 201 consecutive patients with previous myocardial infarction underwent cardiopulmonary exercise testing (CPX). An apparent VO2 overshoot during the recovery from CPX (6.5+/-8.1% increase relative to the peak VO2) was observed in ten patients. A comparison of patients with the VO2 overshoot to those without the VO2 overshoot revealed that the former had a significantly lower left ventricular ejection fraction (40.1+/-19.1 vs. 55. 2+/-14.9%, respectively, p = 0.002) and larger left ventricular diastolic and systolic dimensions. Patients with the VO2 overshoot also had a significantly lower peak VO2 (13.1+/-6.1 vs. 18.1+/-4.5 ml/min/kg, p < 0.001), lower DeltaVO2/DeltaWR (work rate) (6.6+/-3.8 vs. 9.5+/-1.7 mL/min/W, p < 0.0001), and a higher E (minute ventilation)/VCO2 (carbon dioxide output) slope (45.0+/-18.6 vs. 32.6+/-6.6, p < 0.0001) than those without the overshoot. A VO2 overshoot during recovery from maximal exercise was found in 5% of patients with previous myocardial infarction. This condition, which suggests a transient mismatch between cardiac contractility and afterload reduction, was found to be related to impaired cardiopulmonary function during exercise.

Prognostic value of end-tidal CO2 pressure during exercise in patients with left ventricular dysfunction.

We compared the prognostic power of end-tidal CO(2) pressure (PETCO(2)) during exercise, an index of arterial CO(2) pressure, with those of established respiratory gas indexes during exercise testing in patients with left ventricular dysfunction. Seventy-eight consecutive patients with a left ventricular ejection fraction (LVEF)

Prognostic value of heart rate profiles during cardiopulmonary exercise testing in patients with cardiac disease.

Earlier studies have demonstrated that an impaired capacity to increase heart rate (HR) and a slowed HR recovery following exercise are both associated with cardiovascular mortality. We sought to determine whether HR profiles during exercise testing are superior to respiratory gas parameters in predicting mortality among patients with cardiac disease. Five-hundred and fifty stable cardiac patients (63.4 +/- 9.9 years) underwent a symptom-limited incremental exercise test. Measurements included peak VO(2), VE/VCO(2) slope, HR increase (HR difference from rest to peak exercise), and HR recovery (HR difference from peak to 2 minutes after exercise). Twenty-eight cardiovascular-deaths occurred during 4 years of prospective follow-up. In multivariate analysis, the CPX parameters were found to be significant predictors of cardiovascular-death; peak VO(2) (relative risk (RR), 3.44; 95% CI 1.37 to 8.62; P = 0.008), VE/VCO(2) slope (RR, 1.52; 95% CI 1.11 to 2.08; P = 0.009), while HR increase and HR recovery were determined not to be independent predictors. Although HR profiles during exercise testing are easy to perform and useful as prognostic predictors in patients with cardiac disease, they are not superior to respiratory gas analysis.

Clinical significance of cerebral oxygenation during exercise in patients with coronary artery disease.

BACKGROUND: Recent investigations have demonstrated that cerebral oxyhemoglobin (O(2)Hb) decreases during exercise in patients with left ventricular dysfunction, reflecting a cerebral hypoxia. We sought to establish a prognostic value of decreased cerebral O(2)Hb during exercise in cardiac patients, and to compare it with those of indexes obtained from cardiopulmonary exercise testing (CPX). METHODS AND RESULTS: A total of 344 consecutive patients with coronary artery disease were enrolled in the study. All the patients performed CPX, during which cerebral O(2)Hb was continuously monitored using near-infrared spectroscopy. There were 13 cardiac deaths and 78 cardiovascular events during the prospective follow-up period of 1,231+/-538 days. The change of O(2)Hb measured at the forehead from rest to peak exercise (DeltaO(2)Hb) was significantly lower in non-survivors than in survivors (-1.5+/-3.3 vs 1.7+/-3.2 micromol/L, p=0.0004). By multivariate Cox proportional hazards analysis, DeltaO(2)Hb and left ventricular ejection fraction (LVEF) were found to be independent prognostic markers for cardiac deaths. The DeltaO(2)Hb, LVEF and peak oxygen uptake were found to be significant prognostic markers for cardiovascular events, mainly for heart failure worsening and sudden cardiac death. CONCLUSION: The present findings suggest that a decrease in cerebral O(2)Hb during exercise predicts future cardiovascular events in patients with coronary artery disease.

Determination of the V.E/V.CO2 slope from a constant work-rate exercise test in cardiac patients.

Incremental exercise testing to a symptom-limited maximum has been used to measure the ratio of the increase in ventilation (V.E) to the increase in CO(2) output (V.CO(2)) during exercise (V.E/V.CO(2) slope), a valuable index reflecting the severity of the ventilation-perfusion mismatch in heart failure. Here we studied whether this same value for the slope of V.E/V.CO(2) could be determined from a short constant work-rate exercise test of moderate intensity. Twenty-three patients with a previous myocardial infarction underwent moderate-intensity (69+/-15 W) constant work-rate exercise for 6 min and an incremental work-rate exercise test to the max. The V.E/V.CO(2) slope was calculated from the incremental exercise test from the start of increasing the work-rate to the ventilatory compensation point. The V.E/V.CO(2) slope was similarly calculated from the start of constant work-rate exercise until the 4th minute, when V.E and V.CO(2) changed minimally. The V.E/V.CO(2) slope determined from incremental exercise was 33.8+/-5.9, ranging from 20.9 to 42.8. The slope obtained from constant work-rate exercise was 32.9+/-5.7. The V.E/V.CO(2) slopes obtained from the two exercise tests did not differ significantly. The slope obtained from constant work-rate exercise was significantly positively correlated with the slope obtained from the incremental exercise (r=0.84, p<0.0001). The V.E/V.CO(2) slope can be determined from constant work-rate exercise at a moderate intensity. This indicates that the relationship between ventilation and CO(2) output is consistent and independent of the mode of exercise testing.

Effects of supplemental O2 inhalation on cerebral oxygenation during exercise in patients with left ventricular dysfunction.

BACKGROUND: It has been recently reported that cerebral oxyhemoglobin (O(2)Hb) decreases during exercise in nearly 50% of patients with dilated cardiomyopathy. The present study evaluated whether the inhalation of supplemental O(2) diminishes the decrease in cerebral O(2)Hb during exercise. METHODS AND RESULTS: Ten patients with a left ventricular ejection fraction <50% and a clearly observable decrease in cerebral O(2)Hb during preliminary exercise testing underwent 2 additional symptom-limited incremental exercise tests: 1 while breathing room air (control) and the other while breathing 50% O(2). In the latter test, the switch from room air to 50% O(2) was performed, on average, at 43.0+/-14.2 W. Cerebral O(2)Hb was continuously monitored during exercise using near-infrared spectroscopy. In the control exercise test, cerebral O(2)Hb gradually decreased as the work rate increased in all the subjects. When the subjects breathed 50% O(2), this decrease in cerebral O(2)Hb was diminished. The change in cerebral O(2)Hb from rest to peak exercise during the test under 50% O(2) was significantly higher than that during the control test (-0.23 +/-1.89 vs -2.47+/-1.57 micromol/L, p=0.002). Similarly, the change in the cerebral tissue oxygenation index was significantly higher in the test under 50% O(2) (0.45 +/-4.46 vs -3.33+/-3.06%, p=0.023). CONCLUSIONS: Impaired cerebral oxygenation during moderate to heavy intensity exercise in patients with left ventricular dysfunction can be offset by breathing supplemental O(2).

Influence of cerebrovascular arteriosclerosis on cerebral oxygenation during exercise.

BACKGROUND: Although it is assumed that cerebral oxygenation during exercise is influenced by both cardiopulmonary function and cerebrovascular arteriosclerosis, the latter factor has not been fully clarified. In the present study the relationship between the degree of cerebrovascular arteriosclerosis and cerebral oxygenation during exercise was investigated. METHODS AND RESULTS: A total of 109 patients (69 patients with coronary artery disease, 40 patients with hypertensive heart disease) (61.7+/-9.7 years) performed a symptom-limited exercise test with respiratory gas measurements (CPX). From the respiratory gas analysis, peak O(2) uptake (VO(2)), the slope of the increase in VO(2) to the increase in work rate (DeltaVO (2)/DeltaWR), and the slope of the increase in ventilation to the increase in CO(2) output (VE/VCO(2) slope) were calculated. Oxyhemoglobin (O(2)Hb) at the forehead was monitored using near-infrared spectroscopy. The brain ischemic score was counted based upon fluid-attenuated inversion recovery images of magnetic resonance imaging and expressed from 0 to 4. When compared with patients with a lower ischemic score (<2, n=67), those with a higher ischemic score (> or =2, n=42) had a lower increase in brain O(2)Hb during exercise (-1.08 +/-2.7 vs 0.77+/-4.1 micromol/L, p=0.011). Of brain ischemic score, left ventricular ejection fraction, peak VO(2), DeltaVO(2)/DeltaWR, and the VE/VCO(2) slope, DeltaVO(2)/ DeltaWR was found to be the sole independent index determining cerebral O(2)Hb during exercise. The CPX parameters were also significantly related to the degree of cerebrovascular arteriosclerosis. CONCLUSIONS: Although cerebral oxygenation during exercise is mainly related to cardiopulmonary function, the degree of cerebrovascular arteriosclerosis partly influences cerebral oxygenation in patients with risk factors for atherosclerosis.

Critical level of cerebral oxygenation during exercise in patients with left ventricular dysfunction.

BACKGROUND: In a recent study the indexes of cerebral oxygenation decreased during maximal exercise in nearly half of all patients with left ventricular dysfunction. Whether these levels decrease severely enough to influence mental status or level of consciousness was evaluated in the present study. METHODS AND RESULTS: Forty-two patients with idiopathic dilated cardiomyopathy (IDC) and 29 healthy subjects underwent a symptom-limited maximal exercise test. The cerebral oxyhemoglobin (O(2)Hb) and tissue oxygenation index (TOI) were continuously monitored using near-infrared spectroscopy. The changes in O(2)Hb and TOI were also measured in 7 subjects: 2 who experienced episodes of reduced consciousness caused by sudden decreases in blood pressure during exercise recovery and 5 who exhibited sustained ventricular tachycardia during an electrophysiological study. The change in cerebral O(2)Hb during exercise in patients with IDC averaged 0.38+/-3.39 micromol/L, significantly lower than in the normal subjects (4.30+/-4.47 micromol/L, p<0.0001). The cerebral O(2)Hb decreased during exercise in 18 of 42 patients with IDC. The change in cerebral TOI in the IDC patients during exercise was significantly less than that in the normal subjects (-2.0+/-4.7 vs 2.1+/-5.8%, p=0.002). The mean decreases in cerebral O(2)Hb and TOI were -5.34 micromol/L and -9.7%, respectively, in the patients with reduced consciousness during exercise recovery, and -2.52 micromol/L and -16.5%, respectively, in those with ventricular tachycardia. CONCLUSION: The indexes of cerebral oxygenation may drop severely enough during maximal exercise in some patients with severe IDC that consciousness is affected.

Does the severity of central sleep apnea correlate with respiratory gas indexes during cardiopulmonary exercise testing?

Central sleep apnea (CSA) is thought to arise as a consequence of chronic heart failure. We have attempted to determine the relationship between the severity of CSA and the respiratory gas indexes during cardiopulmonary exercise testing (CPX), indexes well-known to reflect the severity of heart failure. Twenty consecutive cardiac patients (59.0 +/- 15.3 years) with CSA underwent CPX. End-tidal PCO(2)(PETCO(2)) was measured at rest and at peak exercise as a substitute for PaCO(2), along with the peak oxygen uptake (V(.)O(2)) and the ratio of the increase in ventilation to the increase in CO(2)output (V(.)E/V(.)CO(2) slope). Peak VO(2), % peak VO(2), and the VE/V(.)CO(2) slope of the subjects were 15.5 +/- 5.8 mL/min/kg, 52.8 +/- 16.7%, and 37.9 +/- 12.5, respectively, showing moderate to severely decreased exercise capacity. While PETCO(2) at both rest and peak exercise significantly correlated with peak VO(2) (r = 0.63 and r = 0.51, respectively) and the VE/V(.)CO(2) slope (r = -0.77 and r = -0.91, respectively), none of these 3 parameters correlated with the apnea-hypopnea index. The apnea-hypopnea index in the subjects with lower resting PETCO(2) was not notably different from that in the subjects with relatively high PETCO(2). Although the severity of CSA is assumed to correlate with the severity of heart failure, and a lowering of PaCO(2) during wakefulness is considered to be one of the mechanisms behind CSA, the severity of CSA does not correlate with the respiratory gas indexes of CPX or the level of PETCO(2) in cardiac patients with moderate to severely decreased exercise capacity.