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A combined hemodynamic and radionuclide approach was used to evaluate right ventricular contractility in 16 adolescent and adult patients with cystic fibrosis (CF). Nine patients had normal resting pulmonary artery pressure, and seven had resting pulmonary artery hypertension (PH). Right ventricular ejection fraction (RVEF) was observed by radionuclide angiocardiography, and stroke volume index (SVI) by thermodilution techniques. By combination of these measures right ventricular end-diastolic and end-systolic volumes were derived. RVEF was normal in CF patients without PH (58.9 +/- 7.2%) but was reduced in those with PH (45.4 +/- 2.3%). There was a strong inverse linear correlation between RVEF and afterload, as assessed by mean pulmonary artery pressure (r = -0.76), indicating RVEF being afterload-dependent. Right ventricular contractility, however, as assessed by right ventricular end-systolic pressure-volume relations was even higher in CF patients with PH, indicating preserved or even increased contractility in the face of an increased afterload stress. The acceleration time, evaluated by pulsed Doppler echocardiography, was normal in CF patients without PH (117.3 +/- 5.5 msec) and significantly reduced in those with PH (85.1 +/- 6.4 msec). Both RVEF and AT were efficient in estimating pulmonary artery pressure in these patients.
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PMID:Right ventricular contractility is preserved in patients with cystic fibrosis and pulmonary artery hypertension. 316 17

A combined haemodynamic and radionuclide approach was used to evaluate right ventricular performance in 16 adolescent and adult patients with cystic fibrosis (CF). There were nine patients with mild arterial hypoxaemia (PaO2 greater than 80% of predicted) and normal resting pulmonary artery pressure and seven patients with severe arterial hypoxaemia (PaO2 less than 70% of predicted) and resting pulmonary arterial hypertension (PH). The right ventricular ejection fraction (RVEF) by equilibrium angiocardiography using krypton 81m as a tracer and stroke volume index (SVI) by thermodilution techniques were measured simultaneously and right ventricular end-diastolic and end-systolic volumes were derived. RVEF was normal in CF patients without PH (58.9 +/- 7.2%) but was reduced in those with PH (45.4 +/- 2.6%). There was a statistically significant inverse linear correlation between RVEF and afterload as assessed by mean pulmonary artery pressure (Pap: r = -0.76) and pulmonary vascular resistance (PVR: r = -0.78), indicating that RVEF ist afterload-dependent. Right ventricular function, however, as assessed by right ventricular end-systolic pressure-volume relations was even higher in CF patients with PH, indicating preserved or even increased right ventricular function in the face of an increased afterload stress.
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PMID:Right ventricular performance and pulmonary haemodynamics in adolescent and adult patients with cystic fibrosis. 321 93

The influence of altered lung mechanics on cardiac performance in cystic fibrosis (CF) was examined in an analysis of cardiorespiratory performance during exercise. The stroke volume (SV) response to exercise, derived from an indirect Fick (CO2) determination of cardiac output during submaximal steady-state exercise served as the index of cardiac performance. The relationship between exercising SV and forced expiratory volume in one second (FEV1), inspiratory duty cycle during exercise (Tl/Ttot) and exercising systemic arterial oxygen tension (PaO2) was examined in 15 studies involving 11 individuals with CF. The subjects were 12 to 25 yr of age and the FEV1 ranged from 15 to 72% predicted. Although a relationship existed between the SV expressed as a percentage of the mean predicted from height and gender (SV%) and PaO2 (r = 0.61, p less than 0.02), a more striking relationship was noted between SV% and either FEV1 or Tl/Ttot (r = 0.79 and 0.73, p less than 0.002). A multiple regression analysis of SV% identified an element of the relationship between FEV1 or Tl/Ttot and cardiac performance which was distinct from the influence of the coexisting hypoxia (p less than or equal to 0.05). The limitation in the SV response to exercise was noted to be in part reversible, coincident with an improvement in ventilatory mechanics that had occurred in 2 of the 4 persons in whom repeated studies were available. These observations suggest that in individuals with CF and a moderately severe degree of expiratory airflow limitation, there is a mechanical element of cardiopulmonary interdependence.
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PMID:The mechanical effects of expiratory airflow limitation on cardiac performance in cystic fibrosis. 333 53

While deficient exercise performance of sick children results from hypoactivity and detraining, it can also be caused by specific pathophysiological factors. These can affect one or more components of physical fitness. A low maximal aerobic power will result from a low maximal stroke volume, as in aortic stenosis or cardiomyopathy; a low maximal heart rate, as in congenital complete heart block or intake of beta-blockers; a low O2 content of the arterial blood, as in anemia or advanced cystic fibrosis; and a high O2 content of mixed-venous blood, as in muscle atrophy or severe malnutrition. A high O2 cost of locomotion, as in advanced obesity or cerebral palsy, will cause the patient to exert at a high percentage of his maximal aerobic power and thus fatigue easily. A subnormal muscle strength, as in progressive muscular dystrophy or juvenile rheumatoid arthritis, is sometimes the primary factor that limits the walking ability or other daily functions. Recent data suggest that local muscle endurance, as assessed by the Wingate anaerobic test, is particularly deficient in some neuromuscular diseases. Examples are muscular dystrophies and spastic cerebral palsy. The ratio of peak anaerobic power to peak aerobic power seems lower in such patients than in able-bodied controls.
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PMID:Pathophysiological factors which limit the exercise capacity of the sick child. 372 7

Initial evaluation of 22 patients with cystic fibrosis (CF) on entry into a trial of home oxygen therapy was used to elucidate the possible effects of poor nutritional status on exercise performance in CF. The patients had advanced lung disease (mean FEV1, 36 percent predicted) and all had a stable resting PaO2 less than or equal to 65 mm Hg. Nutritional status was determined by calculating weight as a percentage of ideal for height (Wt/Ht) for each subject. Exercise testing consisted of a progressive exercise test on a cycle ergometer to measure maximum work capacity (Wmax), and a steady state test at 50 percent of baseline Wmax. During the steady state test, cardiac output (Q) and stroke volume (SV) were computed by the indirect Fick (CO2) method. Wmax, SV, Q and lung function results are expressed as percent predicted. Mean (+/- SD) Wmax was 58 +/- 15 percent predicted. Wmax correlated with both FEV1 and Wt/Ht, but FEV1 and Wt/Ht were not related. During steady state exercise, 12 of 22 patients had a SV less than 80 percent predicted. SV correlated with Wt/Ht, but not with lung function. Thirteen of the 22 patients had a Wt/Ht less than or equal to 90 percent and were considered malnourished. When compared with the well-nourished patients (Wt/Ht greater than 90%), these malnourished subjects had significantly lower mean values for Wmax%, SV% and Q% predicted, but not for lung function parameters. We conclude that: in patients with CF and advanced lung disease, nutritional status plays a significant role in determining exercise capacity; lower exercise tolerance of malnourished patients is an independent effect, as nutritional status and lung function were not related; and malnourished patients with CF have an altered cardiac performance on exercise testing which is due to a reduced SV rather than an impaired heart rate response.
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PMID:Effects of nutritional status on exercise performance in advanced cystic fibrosis. 374 50

Exercise testing was performed in 50 patients with cystic fibrosis to determine whether hemodynamic factors limit exercise capacity in the disease. Prior to exercise testing, lung function and blood gas values were measured. Nutritional status was determined by calculating a weight for height (Wt for Ht) ratio for each subject. A progressive exercise test was used to determine maximum work capacity (Wmax). Cardiac output (Q) (indirect Fick method), and stroke volume (SV) were computed during steady-state exercise at 50% Wmax in 21 of 50 patients. Wmax, SV, Q, and lung function results are expressed as per cent predicted. The mean (+/- SD) Wmax was 75 +/- 23%. Multiple regression analysis showed that maximum voluntary ventilation, resting PaO2, and Wt for Ht accounted for 84% of the variance in Wmax. Although some patients had a reduced SV (mean = 96%) during steady-state exercise, all patients achieved a normal cardiac output (mean = 115%). SV correlated with resting PaO2 but not with lung function. We conclude that exercise capacity in cystic fibrosis is influenced by lung function, nutritional status, and resting hypoxemia, but not by cardiac function; the SV limitation noted in some patients may be due to increased pulmonary vascular resistance related to hypoxemia.
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PMID:Multiple factors limit exercise capacity in cystic fibrosis. 377 84

The ability of digoxin to increase exercise capacity and stroke volume (SV) during exercise was evaluated in ten patients with cystic fibrosis (CF) ages 12 to 20 years with moderate to severe degrees of airway obstruction but no history of heart failure. A double-blind crossover trial of digoxin versus placebo was carried out. An evaluation of exercise performance was undertaken upon entry into the study, and after each of the one-week periods in which digoxin 0.25 mg/day or placebo was taken. Exercise testing consisted of a progressive exercise test on a cycle ergometer to measure maximum work capacity (Wmax) and a steady state test at 2/3 of the baseline Wmax. During the steady state test, the oxygen consumption and carbon dioxide production were measured and cardiac output (Q) was calculated by the indirect Fick (CO2) method. From Q and heart rate (HR), SV was derived. After digoxin, Wmax was unchanged. On steady state exercise HR was unchanged, but there was a slight but significant fall in Q due to a fall in SV. The decrease in SV was associated with exercising hypoxemia. We conclude that digoxin did not increase exercise capacity or improve exercising cardiac function in patients with moderate to severe airway obstruction due to CF.
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PMID:The effect of digoxin on exercise capacity and exercising cardiac function in cystic fibrosis. 712 21

A variety of mechanisms have been implicated in the development of left ventricular dysfunction in patients with chronic cor pulmonale. A two-dimensional echocardiographic study of cystic fibrosis (CF) patients with severe cor pulmonale was undertaken to evaluate the effects of long-term pulmonary abnormalities on right and left ventricular geometry. Ten patients with severe obstructive pulmonary disease secondary to CF underwent evaluation by a mechanical sector scanner from the long axis, short axis, and four chambered views. All patients manifested right heart failure. Eight had clinical scores less than 40 and died within six months of the initial examination. All patients were receiving diuretics, and six were taking digoxin at the time of the study. The most striking echographic feature was flattening or compression of the left ventricle along its minor dimension by a massively dilated right ventricle. Compression of the left ventricle and additional abnormalities of interventricular septal motion resulted in dyskinetic contraction and relaxation that could contribute to a diminished stroke volume. Massive right ventricular enlargement appears to be a major factor producing left ventricular dysfunction in chronic cor pulmonale.
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PMID:Ventricular interdependence in severe cystic fibrosis. A two-dimensional echocardiographic study. 727 91

The two common forms of heat illness in the Services are heatstroke and heat exhaustion. Biochemical predisposing factors are considered for each. Susceptibility to malignant hyperthermia should be tested for in cases of heat stroke. The heterozygote status for cystic fibrosis should be established in cases of heat exhaustion.
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PMID:The biochemistry of heat illness. 856 56

Previous studies comparing cardiac output (Q) and stroke volume (SV) between cystic fibrosis (CF) patients and control subjects have shown conflicting results: some found lower SV in CF patients with severe airflow limitation, and others showed no difference between CF and control subjects. Methodologic problems could explain these discrepant findings. The aim of this study was to better characterize Q and SV with exercise in CF patients with mild as well as severe airflow obstruction. Subjects included 18 CF patients with FEV1 ranging from 28 to 80% of predicted without pulmonary hypertension, and 16 matched control subjects. Cardiac output was measured at three levels of upright cycle exercise using the indirect Fick (CO2) method with blood gas sampling. Q on exercise was similar among control and CF subjects. SV was lower in CF patients, particularly those with FEV1 < or = 55% predicted, than in control subjects. Stepwise regression of SV on height, percent ideal body weight, and FEV1 showed a significant effect of relative underweight on SV. Despite this, well-nourished patients with FEV1 56 to 80% of predicted also had lower SV. As these findings were consistent across the range of severity of lung disease and age, even in the absence of malnutrition, they imply that another mechanism accounts for SV limitation during exercise in CF.
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PMID:Stroke volume during exercise in cystic fibrosis. 863 May 52


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