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PubMed1999

Physiological response to a short period of exercise training in patients with chronic heart failure.

BACKGROUND AND PURPOSE: Whilst cardiac rehabilitation is regularly offered to patients recovering from a myocardial infarction, people with chronic heart failure are often excluded from exercise training programmes. This study was designed to investigate the effects of eight weeks' exercise training in patients with moderate chronic heart failure. METHOD: Eight male patients entered a 16-week randomized, controlled, crossover study of two months' exercise training versus a control period. They performed supervised training three times a week and measures of indices of aerobic function and exercise tolerance were performed monthly throughout the study period. RESULTS: After training, the time walked on a treadmill during an exercise tolerance test increased from 14.8 min (95% CI; range 10.4-18.1 min) to 15.9 min (range 12.1-15.9 min). Significant changes at peak exercise levels (p < 0.05) were seen in oxygen uptake increasing from 3.4 metabolic equivalents (METs) (95% CI; range 2.6-4.2 METs) to 4.0 METs (range 3.2-4.9 METs), and in cardiac index, improving from 5.0 l/min-1/m-2 (95% CI; range 2.9-8.1 l/min-1/m-2) to 5.5 l/min-1/m-2 (range 3.0-9.4 l/min-1/m-2). Resting heart rate decreased significantly (p < 0.05), from 84 beats/min-1 (95% CI; range 73-105 beats/min-1) to 76 beats/min-1 (range 64-90 beats/min-1). Blood flow measurements by venous occlusion plethysmography showed a 21.5% decrease (range 58.5-238.9%) in resting blood flow to the lower leg and a 31.6% increase (range -7.2% to 52.5%) after submaximal exercise, but these changes were not significant (p > 0.05). All benefits were lost within two months of ceasing regular exercise. CONCLUSION: This study demonstrated that patients with moderate chronic heart failure derived beneficial physiological responses from eight weeks' exercise training, but these were soon lost after cessation of regular exercise.

Adult↗

PubMed2006

Caffeine prolongs exercise duration in heart failure.

BACKGROUND: Caffeine increases submaximal exercise performance in healthy young subjects; its effects on exercise tolerance in heart failure (HF) have not been characterized. METHODS AND RESULTS: To determine whether caffeine increases exercise tolerance in HF, caffeine (4 mg/kg intravenously, equivalent to 2 cups of coffee) or vehicle were infused into 10 treated HF patients (left ventricular ejection fraction 25 +/- 2 %), and 10 age-matched normal subjects (N) on 2 separate days in a double-blind, randomized, crossover design. We measured heart rate, blood pressure, and ventilation at rest and during graded cycling (15 W/minute) to peak effort. Peak oxygen consumption was unaffected in either group. Mean exercise time was unchanged in N (1,013 +/- 87 versus 988 +/- 107 seconds; P = .86) but was significantly increased by caffeine in HF (from 511 +/- 28 to 560 +/- 37 seconds; P = .004) despite an increase in peak minute ventilation (P < .05). Resting and peak blood pressures were higher after caffeine (P < .05) in HF, not N. CONCLUSION: Caffeine allows HF patients to exercise longer at peak effort.

Adult↗

PubMed1990

Cardiac sports rehabilitation for patients with ischemic heart disease.

This paper summarizes data gathered from an 8 years sports cardiac rehabilitation program at Kyoto University and satellite hospital (Takeda Hospital). In total, 185 patients were rehabilitated under our original program with no serious cardiac accidents. Compliance was 58.2% after 6 months of this rehabilitation. In patients selected to evaluate the value of rehabilitation, exercise study with treadmill and 201Tl scintigraphic study showed improvement in exercise tolerance (in 58% of patients) and in perfusion on exercise (in 40%). Coronary angiographic study showed regression of arterial narrowing in 16% of the patients studied. We conclude that in addition to emotional and psychological support, our sports cardiac rehabilitation is safe and effective in improving exercise tolerance and cardiac perfusion.

Coronary Angiography↗

PubMed1997

[The possibility of the development of isosorbide dinitrate and nifedipine withdrawal syndromes in patients with stable stenocardia of effort].

Exercise tests were performed in 18 patients with stable angina of effort treated with isosorbide dinitrate (ID) or nifedipine (NF) to see whether sharp discontinuation of the above drugs may entail withdrawal syndrome. Exercise tolerance declined 21 and 24 hours after the last administration of NF, 13 and 18 hours after that of ID. Compared to NF, ID tolerance decreased in a less degree. Some of the patients experienced myocardial ischemia in the course of the exercise tolerance tests, there were more frequent anginal episodes, arterial pressure rose. For ID withdrawal syndrome manifested weaker than for NF.

Adult↗

PubMed1992

[A case of congenital long QT syndrome associated with T wave alternans].

A case was presented in which a rare T wave alternans occurred in association with congenital long QT syndrome. A 71-year-old woman, who had experienced several syncopal attacks per year for the previous forty years, was admitted for further evaluation of the syncope. She had a family history of sudden death (sister) and QT prolongation (son). Electrocardiogram showed a corrected QT interval of 0.68 seconds. Treadmill exercise-tolerance test revealed both T wave alternans immediately after exercise and torsades de pointes 150 seconds after exercise. The syncope was induced by the mental excitation. A prolonged corrected QT interval reduced from 0.70 seconds to 0.58 seconds by the correction of her serum potassium and magnesium. The effect of propranolol, verapamil, phenytoin or mexiletine on T wave alternans and ventricular arrhythmia was evaluated by the treadmill exercise-tolerance test. The treatment with propranolol was most effective.

Adrenergic beta-Antagonists↗

PubMed2006

Differential effect of troponin T mutations on the inotropic responsiveness of mouse hearts--role of myofilament Ca2+ sensitivity increase.

Troponin T (TnT) mutations that cause familial hypertrophic cardiomyopathy (FHC) and sudden cardiac death frequently increase myofilament Ca2+ sensitivity, suggesting that their Ca2+-sensitizing effect contributes importantly to the FHC pathogenesis. To test this hypothesis, we compared transgenic mice expressing the Ca2+-sensitizing TnT-I79N mutant (I79N), which causes a high rate of sudden cardiac death in patients, with mice expressing the more benign TnT-R278C mutant (R278C) that does not affect myofilament Ca2+ sensitivity. Acutely increasing myofilament Ca2+ sensitivity with EMD57033 served as a positive control. Isovolumically contracting hearts were compared over a range of loading conditions (Frank-Starling curve). Consistent with their increased myofilament Ca2+ sensitivity, I79N-Tg hearts demonstrated significantly higher systolic performance at low perfusate [Ca2+] compared with R278C-Tg hearts, which were not statistically different from control hearts expressing either human wild-type TnT or no transgene (CON). Diastolic function was impaired in both FHC mutants (time to 90% relaxation: I79N 48 +/- 1.0 ms, n = 10 or R278C 47 +/- 0.4 ms, n = 7, versus CON 44 +/- 1.0 ms, n = 20, P < 0.05). In the presence of isoproterenol, almost all contractile parameters of R278C hearts became indistinguishable from control hearts, whereas both systolic and diastolic function of I79N hearts significantly worsened (end-diastolic pressure: I79N 20 +/- 4 mmHg versus CON 13 +/- 2 mmHg or R278C 11 +/- 2 mmHg, P < 0.05). The Ca2+ sensitizer EMD57033 produced an even greater contractile dysfunction than the I79N mutation at fast pacing rates. In vivo, maximal exercise tolerance was significantly impaired only in I79N mice. Pretreatment with beta-adrenergic receptor antagonists abolished differences in exercise tolerance. In conclusion, the Ca2+-sensitizing effects of TnT mutations may reduce the responsiveness of mouse hearts to inotropic stimuli.

Actin Cytoskeleton↗

PubMed1992

Efficacy of a single dose of slow-release isosorbide dinitrate in the treatment of silent or painful myocardial ischemia in stable angina pectoris.

A double-blind study was performed in 32 patients with stable angina pectoris to assess the effects of slow-release isosorbide dinitrate (ISDN) (a single dose of 120 mg/day) on the frequency and duration of painless and painful ischemic episodes, and on electrocardiographic changes and exercise tolerance. Forty-eight-hour electrocardiographic monitoring and treadmill exercise tests were performed before, and at 20 and 21 days of therapy. Holter monitoring showed a significant decrease in the frequency of painful and silent episodes (p less than 0.001), and in the duration of painful (1,623 +/- 664 seconds vs 323 +/- 161 seconds; p less than 0.001) and silent episodes (2,818 +/- 1,496 seconds vs 223 +/- 102 seconds; p less than 0.001). The magnitude of painful and silent ST-segment depression was significantly reduced (2.7 +/- 0.9 mm to 0.7 +/- 0.7 mm and 2.0 +/- 1.1 mm to 0.7 +/- 0.5 mm, respectively; p less than 0.001). Time of exercise testing to the onset of ST-segment depression (442 +/- 137 seconds vs 858 +/- 110 seconds; p less than 0.001) or anginal pain was doubled (461 +/- 128 seconds vs 830 +/- 130 seconds; p less than 0.001). The work load increased from 6 to 10 METs (p less than 0.001). ISDN in a single dose of 120 mg/day is a valuable drug for stable angina pectoris, decreasing the frequency of silent and painful ischemic episodes and the magnitude of ST-segment depressions, and increasing exercise tolerance. It particularly shortened the duration of silent episodes. For patients' compliance, a once-daily dose of ISDN could be advantageous.

Adult↗

PubMed2007

A stress echocardiography study of cardiac function during progressive exercise in pediatric oncology patients treated with anthracyclines.

BACKGROUND: Anthracycline-treated patients (AP) are at risk for cardiac dysfunction years after treatment. Cardiac function has not been evaluated during exercise in AP. The purpose of this study was to assess exercise tolerance, left ventricular (LV) function, and hemodynamics during progressive exercise. PROCEDURE: We studied 47 AP (cumulative dose: 36-504 mg/m(2)) who were in complete remission and 12 healthy controls (CON). AP were further grouped by cumulative dose (LOW or= 260 mg/m(2)) and resting echocardiographic function. All subjects performed 3-min incremental stages on a semi-recumbent cycle ergometer until volitional fatigue. Using echocardiography and Doppler, LV dimensions, posterior wall thickness (LVPWs), peak aortic velocity (PAoV), shortening fraction (SF), rate-corrected mean velocity of fiber shortening (MVCFc), wall stress at peak systole (sigmaPS), stroke volume index (SVI), and cardiac index (CI) were determined. Measurements were performed at rest, during each stage of exercise, and in recovery. RESULTS: AP did less work than CON (P < 0.050). CON and LOW had similar resting function, while HIGH had a lower SF and MVCFc (P < 0.050) and a higher sigmaPS (P < 0.001). Resting SVI and CI were also lower in HIGH. At peak exercise, MVCFc and sigmaPS remained different in HIGH, and both AP groups had a lower SF, SVI, and CI (P < 0.001). AP had an abnormal SVI response to exercise. AP showed a smaller initial increase in SVI that was not maintained throughout exercise. CONCLUSIONS: AP have reduced exercise tolerance. There also appears to be a dose-related effect on myocardial contractility and SVI. These findings may help to guide treatment.

Adolescent↗

PubMed1997

[Common and current measurement parameters].

The different parameters used in cardiopneumologic exercise tests allow an assessment of exercise tolerance on the basis of the subject's ventilatory response, cardiac and metabolic adaptation and gas exchanges during exercise. VO2max and dyspnea are indicators of good or poor exercise tolerance. Normal values established for adults in three reference articles depend on age, body weight and height. In a 20-year-old non sedentary subject, VO2max is approximately 45 ml/mn/kg and decreases to 25 ml/mn/kg at 65 years of age. Dyspnea is measured on two types of scales, categorical and visual analogue scales. "Minimal dyspnea" at maximal effort is normal in a healthy subject but becomes "very severe" in diseased subjects. A dyspnea threshold can be determined from the evolution of dyspnea during the test and is useful for retraining in patients with chronic obstructive lung disease. The normal ventilatory response always leaves a ventilatory reserve equal to 30% of the theoretical maximal ventilatory output. If the reserve is diminished, exercise is limited by ventilatory capacity. Gas exchanges reflect muscle adaptation to exercise and the homogeneous nature of alveolar ventilation compared with pulmonary perfusion (VA/Q). This depends on the physiological dead space (VD/VT) which is approximately 1/3 at rest decreasing to 1/4 or 1/5 at maximal exercise. VD/VT is high at rest and stays high during exercise in interstitial lung disease and vascular lung disease. VA/Q also depends on the alveo-arterial oxygen differential (P(A-a)O2) which increases two-fold during exercise. Expired gas and arterial gas must be measured simultaneously for the calculation. To measure cardiac adaptation, the ECG, heart rate and oxygen pulse (VO2/HR) must be recorded. The kinetics of oxygen pulse is more important than its maximal value, a decrease with unchanged heart rate suggests early-stage cardiomyopathy. Finally, blood lactate, the metabolic response to exercise, is used to determine the lactate threshold or the anaerobic threshold. Measurement of the ventilatory threshold is less invasive, ventilatory outflow increasing with increasing lactate level as described by the Beaver or Wassermann model. These thresholds indicate the subject's aerobic capacity. The exercise test has diagnostic value but can also be useful for individual patient management, particularly cardiorespiratory rehabilitation.

Adult↗

PubMed1984

[Changes in the physical load tolerance of stenocardia patients taking obzidan, korinfar and izoptin separately and together].

Changes in exercise tolerance under the impact of obsidan, corinfar, isoptin and their combinations were studied in 12 angina patients with the help of bicycle ergometry. The most marked increase in exercise tolerance following the use of a single drug was observed with obsidan (85.1 +/- 35.1%), although corinfar and isoptin also led to a significant elevation in the patients' working capacity (67.4 +/- 14.4% and 49.8 +/- 6.3%, respectively). Combination of isoptin and obsidan brought about no increase in tolerance as compared with obsidan alone whereas the combination of corinfar with obsidan showed the maximal antianginal effect.

Adult↗

PubMed1994

Effect of beta blockade on the neurohumoral and cardiopulmonary response to dynamic exercise in cardiac transplant recipients.

OBJECTIVE: To determine the effects of a small dose of beta blocker on neurohumoral and cardiopulmonary responses after cardiac transplantation. BACKGROUND: Cardiac transplant recipients have a reduced exercise capacity and abnormal cardiovascular responses to exercise. The sympathoadrenal response to exercise has been shown to be abnormal with high venous noradrenaline. The effect of beta blockade on these neurohumoral mechanisms has not been defined. METHODS: 10 non-rejecting cardiac transplant recipients were studied. Patients carried out graded exercise to a symptom limited maximum. Blood samples were taken during exercise. Concentrations of noradrenaline, adrenaline, and atrial natriuretic peptide and plasma renin activity were measured. The next day, the exercise and sampling procedure were repeated after an oral dose of propranolol (40 mg). RESULTS: Patients tolerated exercise poorly after beta blockade, which was reflected in the maximum workload reached. Heart rate and blood pressure were significantly higher at rest and during exercise before beta blockade. Although there was no significant difference when resting, mean (SEM) noradrenaline concentrations during peak exercise were higher after beta blockade (16.2 (2) v 23.6 (2.9) nmol/l, p = 0.001). Adrenaline concentrations at peak exercise were also greater after beta blockade (0.89 (0.31) v 1.18 (0.38) nmol/l, p = 0.055). Atrial natriuretic peptide concentrations tended to be higher after beta blockade (118.75 (50.2) v 169.79 (39.3) pmol/l, p = 0.36). There was no significant change in plasma renin activity. CONCLUSIONS: A small oral dose of a competitive beta blocker such as propranolol has an adverse effect on exercise tolerance and cardiovascular response to exercise in cardiac transplant recipients. There are also increased concentrations of circulating noradrenaline and therefore, sympathetic activity during exercise. beta blockers should be used with caution in cardiac transplant recipients.

Administration, Oral↗

PubMed2005

Exercise outcomes after pulmonary rehabilitation depend on the initial mechanism of exercise limitation among non-oxygen-dependent COPD patients.

STUDY OBJECTIVES: Pulmonary rehabilitation (PR) that includes exercise training can improve exercise tolerance and quality of life for patients with COPD. However, the degree of benefit from PR is variable. We hypothesized that the exercise response to PR varies depending on the initial factors that limit exercise. DESIGN, SETTING, PARTICIPANTS, AND MEASUREMENTS: We retrospectively analyzed the change in exercise capacity after PR in 290 nonhypoxemic patients with COPD. We classified patients into the following subgroups based on the primary limitation seen on initial exercise testing: (1) ventilatory-limited (VL); (2) cardiovascular-limited (CVL); (3) mixed ventilatory/cardiovascular-limited (VLCVL); and (4) non-cardiopulmonary-limited (NL). We compared outcomes among subgroups. RESULTS: In the entire study population, PR led to increased timed walk distance (30.3%; p < 0.0001) and maximal oxygen consumption (VO2max) [84.8 mL/min; p < 0.0001]. Stepwise multiple regression selected age, ventilatory reserve at peak exercise, and exercise arterial oxygen pressure as individual predictors of improvement in VO2max. VO2max increased in the VL subgroup (30.4 mL/min; p = 0.008), the CVL subgroup (109.0 mL/min; p < 0.0001), the mixed VLCVL subgroup (61.3 mL/min; p < 0.0001), and NL subgroups (110.5 L/min; p < 0.0001). The improvement in VO2max was greater in the CVL subgroup than in the VL subgroup (p < 0.0001). Timed walk distance improved to a similar degree in all subgroups (26 to 36%). CONCLUSIONS: Patients with nonventilatory exercise limitations experience the greatest increase in VO2max after PR. However, even patients with severe ventilatory limitation can improve exercise tolerance with PR.

Aged↗

PubMed1999

[Effect of exercise therapy on oxygen consumption in patients with chronic heart failure].

The effect of exercise training on delta Vo2/delta WR was studied in 12 patients(11 men, one woman, mean age 62 +/- 9 yr)with chronic heart failure(old myocardial infarction, dilated cardiomyopathy, patients after coronary arterial bypass graft surgery and patients after aortic valve replacement). Cardiopulmonary exercise testing was performed to decide the exercise tolerance and assess the delta Vo2/delta WR. Patients underwent physical training at the anaerobic threshold for 3 months. Cardiopulmonary exercise testing was performed after the second week and after the third month. The anaerobic threshold increased at the third month compared with before exercise testing and the second week(p < 0.05, respectively) (before exercise testing: 13.6 +/- 2.0 ml/min/kg, the second week: 14.7 +/- 2.5 ml/min/kg, the third month: 16.2 +/- 2.1 ml/min/kg). The delta Vo2/delta WR increased at the second week compared with before exercise testing(before exercise testing: 8.9 +/- 1.9 ml/min/W, the second week: 10.6 +/- 1.9 ml/min/W, p < 0.05), but significantly decreased at the third month compared with the second week(the third month: 9.4 +/- 1.7 ml/min/W, p < 0.05). Serial increase of the anaerobic threshold and the peak Vo2/heart rate suggests that the exercise tolerance and cardiac function of the patients improved significantly. The increase of the delta Vo2/delta WR after the first 2 weeks seemed to depend on the luxury blood supply to both working and non-working muscles. The decrease of delta Vo2/delta WR at the third month may be due to the redistribution of the blood flow to the working muscles.

Chronic Disease↗

PubMed1987

[Functional shifts in the respiratory and circulatory systems of bronchial asthma patients during exertion].

A total of 56 patients aged 40-59 were examined for bronchial asthma of infectious-allergic etiology and moderate severity. Exercise-related bronchospasm (EB) was detected in 46 of them. Exercise tolerance was studied using bicycle ergometry, ventilometric changes with threshold exercise test and central hemodynamics was assessed in response to standard exercise with chest tetrapolar rheography. BE was associated with an additional decrease in the working capacity of patients with bronchial asthma with moderately expressed ventilation disturbances at rest. These patients were also demonstrated to have hypoergic-nature response of central hemodynamics to a standard motor test. BE-free patients with the same degree of ventilation disturbances exhibited the response close to normoergic. The evidence suggests the involvement of the hemodynamic mechanisms in the formation of an exercise tolerance threshold in bronchial asthma complicated by BE.

Adult↗

PubMedDate not supplied

Results of an 8-week, outpatient pulmonary rehabilitation program on patients with and without chronic obstructive pulmonary disease.

PURPOSE: To determine whether there is any difference in the effect of pulmonary rehabilitation (PR) on outcomes in patients with and without chronic obstructive pulmonary disease (COPD). METHODS: Retrospective analysis of medical records of all patients enrolling in PR over a 5-year period. RESULTS: A total of 422 patients enrolled in a multidisciplinary PR program from August 1999 to April 2004. Three hundred nine patients had COPD and 113 patients had diagnoses other than COPD. Three hundred seventy-nine patients completed the program. PR was conducted according to currently accepted guidelines. Measurements included the 6-minute walk distance (6MW) performed at the beginning and end of the program and quality of life as determined by the Chronic Respiratory Questionnaire (CRQ) at the beginning and end of the program. Both groups had significant improvements in the 6MW and all domains of the CRQ following PR. There was no significant difference in any of these outcomes between the 2 groups. The baseline forced expiratory volume in 1 second (FEV1) was not correlated with improvement in the 6MW in either group. CONCLUSIONS: There is no significant difference in improvement in exercise tolerance or quality of life following PR in COPD versus non-COPD patients. Baseline lung function does not predict improvement in exercise tolerance. PR is effective for patients with disability due to any chronic respiratory disease and not just COPD.

Aged↗

PubMed1994

Respiratory muscle function and exercise capacity in multiple sclerosis.

Patients with multiple sclerosis (MS) show a poor exercise tolerance. A reduction in respiratory muscle strength has also been reported. The purpose of this study was to evaluate whether reduction in exercise tolerance was related to respiratory muscle dysfunction. Twenty four multiple sclerosis patients (mean +/- SD age: 48 +/- 9 yrs, duration of illness 12.2 +/- 6 yrs, severity of illness as assessed by Expanded Disability Scale Score (EDSS) 5.3 +/- 2), underwent detailed evaluation of lung function tests, arterial blood gas analysis, respiratory muscle strength and endurance, and exercise test on an arm ergometer. Sixteen of the 24 patients were able to perform the exercise test (Group I), whilst the other eight were not (group II). Arterial blood gases and lung function tests were normal for both groups. Respiratory muscle strength as assessed both by maximal inspiratory pressure (MIP) and maximal expiratory pressure (MEP) was significantly reduced (MIP 18-76 cmH2O; MEP 16-82 cmH2O) compared to predicted values. Inspiratory muscle endurance time was significantly reduced in Group II in comparison to Group I (247 +/- 148 vs 397 +/- 154 s, respectively). Both MIP and MEP were significantly related to inspiratory muscle endurance time. Endurance time, MIP and MEP were inversely significantly related to duration of illness, whilst only endurance time was significantly related to Expanded Disability Scale Score.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Gas Analysis↗

PubMedDate not supplied

[A comparative analysis of the effect of low-intensity physical training on a bicycle ergometer, graded walking and drug therapy on the cardiovascular system of patients with stage-II hypertension].

In contrast to standard bicycle exercise with moderate or submaximal effort, low-effort exercises were employed by the author who studied their effect on cardiovascular system of stage II hypertension patients. They were males (n-126) aged 47.2 +/- 3.6 with the disease history of 8.4 +/- 1-9 years. Associated coronary heart disease was diagnosed in 82% of the patients. The test subjects were divided randomly into three groups: group 1 patients received drugs only, group 2 received drugs and exercised walking, group 3 received drugs and exercised on bicycle ergometer in the nonstrenuous regimen. It was found that exercise tolerance of the patients was different and depended on the hemodynamic type. Hypokinetic circulation patients showed the lowest exercise tolerance. Low-effort bicycle exercise in addition to drugs is indicated for hyper- and eukinetic circulation patients. Walking is inferior to the bicycle exercise and can be recommended as a variety of nonpharmacological treatment of hypertension stage II. The combined effect of walking and chemotherapy produced the rise in cardiac capacity in the absence of the adequate increment in coronary blood flow, whereas bicycle exercise seems to enhance cardiac coronary circulation in hypertensive subjects.

Antihypertensive Agents↗

PubMed2005

Heart rate response to graded exercise correlates with aerobic and ventilatory capacity in patients with heart failure.

BACKGROUND: Autonomic dysfunction and reduced exercise tolerance are typical features of patients with congestive heart failure (CHF). Baro-chemoreflex balance and organ response may have a common role in conditioning exercise tolerance, ventilation, and chronotropic competence in patients with CHF. HYPOTHESIS: We tested the hypothesis that there is a relationship between functional capacity and chronotropic competence to exercise in CHF. METHODS: In all, 48 stable outpatients with CHF (age 65 +/- 10 years, 41 men, NYHA class 2.1 +/- 0, ejection fraction 31 +/- 7%, peak VO2 16 +/- 4 ml/kg/min) performed cardiopulmonary exercise testing (CPX). Heart rate (HR) response to exercise was assessed by the chronotropic index (CRI). The CRI was calculated by the following formula: CRI = peak HR - rest HR/220 - age - rest HR x 100 (normal value > 80%). The relationship of CRI to peak oxygen consumption (VO2) and ventilation/carbon dioxide production (VE/VCO2) ratio was examined. A group of 33 healthy controls underwent CPX as well. RESULTS: The CRI correlated directly with peak VO2 (r = 0.638, p < 0.001) and inversely with VE/VCO2 (r = -0.492, p < 0.001) in patients with CHF. A CRI < 78% identified patients with CHF and a peak VO2 < 20 ml/kg/min, area under the receiver operating curve (AUROC): 0.76, 95% confidence interval (CI) 0.60-0.92. A CRI < 74% predicted exercise hyperventilation in CHF (AUROC: 0.71 for VE/VCO2 > 30, 95% CI 0.53-0.88). The CRI was not significantly related either to peak VO2 or to VE/VCO2 in the control group. CONCLUSIONS: In patients with mild to moderate CHF, CRI correlates with functional capacity. This relationship adds new data on pathophysiologic grounds and supports the routine incorporation of CRI into CPX interpretation.

Aged↗