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J Defoor

Publications and source records attributed to J Defoor.

8 recordsLinked to original sources
PubMed2006

Oxygen uptake efficiency slope in coronary artery disease: clinical use and response to training.

The Oxygen Uptake Efficiency Slope (OUES), a new parameter derived from respiratory gas analysis, has been suggested as a submaximal index of cardiopulmonary functional reserve. We evaluated the clinical application and the effect of physical training on the OUES in patients with coronary artery disease (CAD). Maximal cycle-ergometer testing with respiratory gas analysis (breath-by-breath) was performed in 590 patients with CAD and again after three months of physical training in 425 patients. OUES was determined from the linear relation of oxygen uptake (V.O (2)) vs. the logarithm of pulmonary ventilation (V (E)) during exercise, i.e. V.O (2) = a log (10) V (E) + b, where a is the OUES. The ventilatory anaerobic threshold (VAT) and the slope of the relation of V (E) nu carbon dioxide production (V.CO (2)) (V (E)-V.CO (2) slope) were also determined. Correlation coefficients of the relation from which OUES was derived in individuals averaged 0.975 +/- 0.024 (mean +/- SD) when calculated from data up to a respiratory gas exchange ratio of 1.0. Submaximal OUES was marginally lower (5.4 +/- 7.9 %, p < 0.05) than the OUES calculated from 100 % of respiratory exercise data. Of all submaximal parameters, submaximal OUES (r = 0.837, p < 0.001) and VAT (r = 0.860, p < 0.001) correlated best with peak V.O (2), followed by V (E)-V.CO (2) slope (r = - 0.469, p < 0.001). OUES was lower in patients who underwent coronary artery bypass grafting as compared with patients after coronary angioplasty (p < 0.05). Peak V.O (2) and OUES increased significantly (p < 0.001) after training with 24 +/- 19.2 % and 20.9 +/- 19.3 %, respectively. Changes in peak V.O (2) correlated better with changes in OUES and in VAT (r = 0.61 and r = 0.55, p < 0.001, respectively) than with changes in V (E)-V.CO (2) slope (r = - 0.171, p < 0.001). The submaximal OUES is clinically useful for the quantification of exercise performance and is sensitive to physical training in patients with CAD.

Coronary Artery Disease↗
PubMed2001

Exercise performance and training in patients with implantable cardioverter-defibrillators and coronary heart disease.

The aim of this preliminary study was to compare exercise performance and the effect of exercise training in cardiac patients with and without an implantable cardioverter-defibrillator (ICD). There are few data on exercise performance and on the effect of exercise training in patients with an ICD. Data in patients with an ICD (n = 8) were compared with those from a matched control group (n = 16). Patients performed maximal cycle-ergometer testing before and after 3 months of exercise training. All patients had to stop the exercise test for reasons of exhaustion. The predetermined heart rate threshold in ICD patients, set at the detection rate of the ICD minus 30 beats/min, was not reached. Before training, peak oxygen uptake was not different in the ICD patients compared with the control group (21.0 +/- 6.9 vs 21.9 +/- 5.0 ml oxygen standard temperature pressure dry/min/kg). Exercise training increased peak oxygen uptake to a similar extent in both groups, 20% and 24%, respectively. One ICD patient developed uneventful ventricular tachycardia at the end of the post-training exercise test, and another during training. Thus, exercise performance and the favorable response to a 3-month exercise training program are comparable in patients with ICD and matched control patients. However, tachyarrhythmias may occur during exercise testing or training and require special attention. Selected patients with ICD can be encouraged to participate in medically supervised exercise training programs. The results of this study should be confirmed with additional studies on larger numbers of subjects.

Coronary Disease↗
PubMed2001

Cardiorespiratory exercise function after the arterial switch operation for transposition of the great arteries.

AIMS: This study compares the functional outcome and cardiorespiratory response to exercise, in patients who have undergone arterial switch for transposition of the great arteries, with normal controls and patients who have undergone atrial switch operation. METHODS AND RESULTS: Fifteen patients who had undergone arterial switch (mean age 8.5+/-2.9 years) were compared to 32 patients who had undergone atrial switch (9.2+/-1.8 years) and 27 normal controls (8.5+/-2.1 years). Exercise testing was performed on a treadmill and gas exchange measured breath-by-breath. Aerobic capacity, assessed by determination of the ventilatory anaerobic threshold, averaged 91+/-7.8% of normal (95% confidence limits: 92-108%) for arterial switch and 75.1+/-13.1% for atrial switch (P<0.001 patients vs normals). Aerobic exercise function was evaluated by calculation of the slope of oxygen uptake vs exercise intensity. The mean value for this slope was 2.0+/-0.25 for arterial switch, 2.5+/-0.46 for normals and 1.7+/-0.80 for atrial switch (P<0.05; patients vs normals). Efficiency of the pulmonary gas exchange was assessed by calculation of the slope of ventilation vs carbon dioxide output during exercise. This averaged 38.7+/-14.7 for arterial switch, 48.1+/-14.1 for atrial switch and 30.3+/-7.6 for normals (P<0.001; patients vs normals). CONCLUSION: Cardiorespiratory exercise function is at, or slightly below, the lower limit of normal in patients with arterial switch, while the lowest values were observed for those who had undergone atrial switch.

Child↗
PubMed2000

Comparison of cardiac output measured by two automated methods of CO2 rebreathing.

PURPOSE: The aim of the present study was to investigate the reproducibility of the exponential method of CO2 rebreathing with the use of automated curve fitting and to determine whether this method is superior to the equilibrium method in terms of reproducibility and clinical practicability. METHODS: Repeated measurements of cardiac output were performed using the automated equilibrium and exponential methods. These measurements were compared in 12 healthy male subjects at rest and during incremental exercise tests. RESULTS: Estimated cardiac output was not significantly different between duplicate measurements at rest nor at any level of exercise with either method. At rest the exponential method showed a tendency toward larger variability than the equilibrium method. The exponential method produced significantly higher (P < or = 0.001) estimates at rest (averaging up to 9.8 L x min(-1)) compared with the equilibrium method (averaging up to 6.5 L x min(-1)). Reproducibility improved for both methods with increasing workloads, and a second measurement at rest also seemed more reproducible and valid than the first. During exercise, both methods produced comparable values for cardiac output, and highly significant relations between cardiac output and oxygen uptake were observed for both methods (ranging from r2 = 0.79 to r2 = 0.88, P < or = 0.001). The equilibrium method produced unpleasant side effects more frequently (75% vs 21%, P < or = 0.001) compared with the exponential method and lead more subjects to premature interruption of the exercise test because of the rebreathing maneuver (42% vs 17%, P = 0.058). CONCLUSIONS: Automated curve fitting for the exponential method gave reproducible and valid results during submaximal and maximal exercise but not at rest. The equilibrium method on the other hand interfered with exercise. Therefore, the equilibrium method is recommended at rest and at lower levels of exercise and the exponential method at higher intensities.

Adolescent↗
PubMed2000

Oxygen uptake versus exercise intensity: a new concept in assessing cardiovascular exercise function in patients with congenital heart disease.

OBJECTIVE: To assess the relation between exercise intensity and oxygen uptake during graded exercise in paediatric patients who underwent surgical repair of congenital heart disease, and to compare it with conventional measures of aerobic exercise function. DESIGN: Cross sectional study. Exercise testing was performed on a treadmill and gas exchange was measured on a breath by breath basis. PATIENTS: 29 patients who underwent an atrial switch operation for transposition of the great arteries (TGA) (mean (SD) age at testing 10.3 (2.5) years) and 30 patients who underwent total repair of tetralogy of Fallot (TF) (age 12.1 (3.3) years) performed graded exercise testing. Exercise responses were compared with data obtained in 24 normal controls (age 11.4 (2.6) years). RESULTS: The slope of oxygen uptake versus exercise intensity averaged 1.50 (0. 64) ml O(2)/min(2)/kg in the patients with TGA and 1.68 (0.75) ml O(2)/min(2)/kg after TF repair, both lower (p < 0.005) than in normal controls (2.42 (0.68) ml O(2)/min(2)/kg). The lower slope of oxygen uptake was correlated with a subnormal value for ventilatory anaerobic threshold, which averaged 78.0 (13.3)% of normal in TGA and 85.1 (10.6)% in TF. This was associated with a steeper slope (p = 0.001) of carbon dioxide output versus oxygen uptake above the ventilatory anaerobic threshold in TGA (1.26 (0.20)) and TF (1.20 (0. 18)) compared with the normal controls (1.05 (0.13)), and also a steeper slope of ventilation versus carbon dioxide in TGA (47.0 (15. 4)) and TF (41.5 (13.7)) than in the controls (30.3 (8.5)). CONCLUSIONS: Calculation of the steepness of the slope of oxygen uptake versus exercise intensity is a valid measurement of oxygen flow to the exercising tissues, which may be limited in congenital heart disease.

Adolescent↗
PubMedDate not supplied

Exercise performance and training in cardiac patients with atrial fibrillation.

PURPOSE: Exercise training in cardiac patients with chronic atrial fibrillation (AF) has received little attention in the literature. Therefore, this study compared exercise performance and the effect of an exercise training program over a period of 3 months in patients with and without AF. METHODS: Data in patients with AF (n = 19) were compared with a control group of patients in sinus rhythm (n = 44), drawn from a database of 2,116 patients. Patients performed a maximal exercise test on the bicycle until exhaustion before and after an ambulatory exercise training program where exercise training was offered 3 times a week for 3 months. RESULTS: Before training, peak oxygen uptake (VO2) was significantly lower in patients with AF compared with the control group (1271 +/- 368 versus 1496 +/- 414 mL/min, P < 0.05). Exercise training significantly increased peak VO2 in both groups (+31%, P < 0.001 in AF and +25%, P < 0.001 in the control group). The gain in peak VO2 did not significantly differ between both groups. A significant decrease in resting heart rate was achieved in both groups after exercise training. AF was also a significant and independent determinant of peak VO2 in the total database, but not of the change in peak VO2. CONCLUSIONS: Exercise training significantly improves exercise performance in cardiac patients with AF. AF affects exercise performance but does not impair the beneficial effects of training. Patients with chronic AF should therefore not be dissuaded from participating in exercise training after a cardiac event.

Aged↗