Johan Defoor

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.

Effect of bisoprolol and atenolol on endurance exercise capacity in healthy men

Objectives To compare the effects of a highly β1-selective adrenoceptor antagonist bisoprolol with those of atenolol and placebo on endurance exercise capacity in young, healthy male volunteers. Design Twelve subjects randomly received oral placebo, atenolol (100 mg/day) or bisoprolol (10 mg/day) for 3 weeks, following a double-blind cross-over design. Methods At the end of each period, the subects performed an endurance exercise test on the bicycle ergometer at 70% of maximal aerobic power. Cardiac output was measured by means of an automated CO2-rebreathing method. Venous blood was sampled before, during and after exercise. Results Exercise duration was not significantly different between the two drugs tested. Total exercise duration was significantly reduced by bisoprolol (−19.4 ± 6.7%, P < 0.01) (mean ± SEM) and by atenolol (−29.8 ± 6.6%, P < 0.001), compared with placebo. Atenolol and bisoprolol were equally effective in lowering resting plasma renin activity, heart rate and systolic blood pressure. Resting and exercise stroke volume were significantly increased by both drugs, so that cardiac output was not significantly affected. Both drugs induced significant decreases in plasma-free fatty acid concentrations during recovery and blunted the exercise-induced increase. There were no significant relationships between the reduction of exercise duration and the haemodynamic changes or the degree of impairment of the exercise-induced increase in free fatty acid release resulting from β-blockade. Conclusions It is concluded that both drugs affect endurance exercise capacity in young, normotensive men, with a tendency to a smaller reduction during bisoprolol treatment. Haemodynamic variables are unlikely to be involved in the reduction of endurance exercise capacity. The role of the reduced availability of plasma free fatty acids remains unclear.

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.

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 O2/min2/kg in the patients with TGA and 1.68 (0.75) ml O2/min2/kg after TF repair, both lower (p < 0.005) than in normal controls (2.42 (0.68) ml O2/min2/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.

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.

The CAREGENE study: ACE gene I/D polymorphism and effect of physical training on aerobic power in coronary artery disease

In coronary artery disease (CAD) the individual variation in aerobic power and the response to physical training are largely unexplained.1 The gene coding for the angiotensin converting enzyme (ACE) is expressed in several types of somatic cells, including vascular cells, heart, lung, and muscles.2 Intron 16 contains a polymorphism characterised by the presence (insertion (I)) or absence (deletion (D)) of a 287 bp Alu repeat sequence,3 which has been associated with endurance related phenotypes and the response to training.4 The objective of the present study was to investigate the role of ACE I/D polymorphism on aerobic power and its response to physical training in patients with CAD enrolled in the CAREGENE (cardiac rehabilitation and genetics of exercise performance) study. Biologically unrelated white patients with CAD (mean (SE) age 56 (0.3) years) who had achieved evident exhaustion during graded cycle ergometer testing before and after three months of physical training (three sessions weekly) from 1990 through 2001 (n  =  1095) were eligible for inclusion. The methods for graded exercise testing and training have been …

Effect of creatine supplementation as a potential adjuvant therapy to exercise training in cardiac patients: a randomized controlled trial:

Objective: To investigate the effect of oral creatine supplementation in conjunction with an exercise programme on physical fitness in patients with coronary artery disease or chronic heart failure. Design: Single centre double-blind randomized placebo controlled trial. Setting: Cardiac rehabilitation centre. Subjects and intervention: 70 (4 women) cardiac patients (age 57.5 (8.4) years) were randomized to a placebo (n = 37) or creatine (n = 33) treatment for three months. Combined aerobic endurance and resistance training (three sessions/ week) was performed during supplementation. Main Measures: Aerobic power was determined during graded bicycle testing, knee extensor peak isometric and isokinetic strength, endurance and recovery were assessed by an isokinetic dynamometer, and health related quality of life was evaluated with the SF-36 and MacNew Heart Disease questionnaires. In addition, blood samples were taken after an overnight fast and 24 hour urinary collection was performed. Results: At baseline there were no significant differences between both groups. We observed main time effects for aerobic power, muscle performance, health related quality of life, high density lipoprotein cholesterol and triglycerides (pre vs post; P<0.05 for all). However, changes after training were similar between placebo group and creatine group (P>0.05). Further, no detrimental effect on renal or liver function was observed nor were there any reports of side effects. Conclusion: Oral creatine supplementation in combination with exercise training does not exert any additional effect on the improvement in physical performance, health related quality of life, lipid profile in patients with coronary artery disease or chronic heart failure than exercise training alone.

Ventilatory response to exercise in patients after correction of cyanotic congenital heart disease: relation with clinical outcome after surgery

Patients with congenital heart disease can usually perform low intensity exercise as well as healthy peers, but often have difficulty in reaching maximal exercise intensity. However, formal exercise testing has repeatedly shown impaired values for cardiorespiratory exercise performance.1 A considerable number of patients may complain of exercise intolerance and dyspnoea at heavy intensities of exercise. The aim of this study was to assess the efficiency of the ventilatory response to exercise by means of breath by breath analysis of gas exchange. Special attention was paid to total ventilation and alveolar ventilation as the difference between these values reflects the physiological dead space ventilation (VD), and is used as an index of ventilatory efficiency during exercise. More specifically, we assessed how the ventilatory response during exercise was affected by the clinical result of surgery and whether this correlated with the functional status after surgery for congenital heart disease. To study whether an inefficient ventilatory response to exercise could be related to the effect of a sternotomy, the ventilatory response to exercise in the present group of patients was compared with a group of age matched patients who had also undergone sternotomy for surgical closure of a ventricular septal defect (VSD). One hundred and six patients were used for this analysis. At a routine outpatient visit, the patients were clinically assessed, and also underwent echocardiographic, electrocardiographic, and radiological examinations. Three patient …

The caregene study: muscle-specific creatine kinase gene and aerobic power in coronary artery disease

In 927 biologically unrelated Caucasian patients with coronary artery disease it was investigated whether the NcoI restriction fragment length polymorphism of the muscle-specific creatine kinase (CKMM) gene is associated with aerobic power and with the response to physical training. Physical training significantly (P<0.001) increased peak oxygen consumption in the GG, AG and AA NcoI genotypes. Covariate-adjusted peak oxygen consumption at baseline, after training and the response to training were not different across CKMM NcoI genotypes.

Influence of work rate on the determinants of oxygen deficit during short-term submaximal exercise: implications for clinical research*

Objective: The effect of increasing work rate was studied on the determinants of the oxygen deficit.