Differences in Perceived Barriers to Exercise between High and Low Intenders: Observations among Different Populations

Purpose.

The goal of this study was to describe the salient perceived barriers to exercise in three different groups and to examine the perceived barriers characterizing individuals with a high or a low intention to exercise in the context of the theory of planned behavior.

Design.

Cross-sectional studies relating perceived barriers and intention to exercise were utilized.

Subjects.

Three independent samples were used: general population (n=349), individuals who have suffered from coronary heart disease (n=162), and pregnant women (n=139).

Measures.

Firstly, standard elicitation procedures were applied to identify the particular perceived barriers characterizing each population. Then, three self-administered questionnaires, one per sample, were used to measure perceived barriers and intention to exercise.

Results.

MANOVA analyses contrasting high and low intenders indicated a significant difference in perceived barriers to exercise in two of the three samples: general population (F5,343=6.37, p<.001) and individuals suffering from coronary heart disease (F9,152=2.28, p<.05).

Conclusion.

The results indicate not only that each population has specific salient perceived barriers to exercise, but also that within each group high and low intenders differ on a number of these perceived barriers. Therefore, it is recommended that the study of perceived barriers to exercise in any population should be based upon a standardized method of measuring these barriers such as the method adopted in the present study.

Comparison of myocardial ischemia on the ergocycle versus the treadmill in patients with coronary heart disease

We previously observed an attenuation of exercise-induced myocardial ischemia on the ergocycle during a ramp protocol compared to the standard Bruce protocol treadmill test in patients with coronary heart disease. However, it was uncertain whether decreased ischemia on the ergocycle resulted from the warm-up effect of the more gradual ramp protocol or from the mode of exercise itself (cycling vs running). Sixteen stable patients, aged 64 +/- 5 years, with documented coronary heart disease (> or =70% coronary artery stenosis and/or reversible myocardial perfusion defects) performed 3 symptom-limited exercise tests: the standard Bruce protocol treadmill test and 2 individualized ramp protocols (treadmill and ergocycle). We measured the ischemic threshold (heart rate x systolic blood pressure product at 1-mm ST-segment depression) and oxygen consumption (VO(2)). The ischemic threshold was higher during cycling (ergocycle ramp, 24,009 +/- 5,769 beats/min x mm Hg) compared to running (Bruce treadmill, 20,429 +/- 3,508 beats/min x mm Hg; and ramp treadmill, 19,451 +/- 3,392 beats/min x mm Hg; p <0.001), independently of exercise intensity (VO(2)). The peak VO(2) did not significantly differ among all tests (p = 0.25) despite a greater peak rate-pressure product achieved with the ergocycle (29,378 +/- 6,291 beats/min x mm Hg) compared to either treadmill protocol (Bruce, 26,202 +/- 5,831 beats/min x mm Hg; ramp, 25,654 +/- 6,492 beats/min x mm Hg; p <0.001). In conclusion, the mode of exercise (ergocycle vs treadmill), rather than the type of protocol (ramp vs Bruce), is associated with an attenuation of electrocardiographic parameters of myocardial ischemia, independently of exercise intensity (VO(2)) and myocardial demand (rate-pressure product).

Modulation of arterial reactivity using amlodipine and atorvastatin measured by ultrasound examination (MARGAUX)

OBJECTIVE

To evaluate the effect of the calcium channel blocker amlodipine on endothelial function in normotensive patients with coronary disease taking concomitant atorvastatin therapy.

METHODS AND RESULTS

Atorvastatin was titrated (10-80 mg/day) to maintain LDL-C<2.5 mmol/L and patients were randomized to receive amlodipine (5-10mg/day, n=64) or placebo (n=70) for 12 months. Brachial artery flow-mediated vasodilation (FMD) was assessed using vascular ultrasound. Inflammatory markers were also measured. At 12 months there was a significant decrease in mean low-density lipoprotein cholesterol (LDL-C) (4.4-2.1 mmol/L, P<0.0001), high-sensitivity C-reactive protein (hsCRP) (3.8-2.3mg/L, P<0.0001) and soluble vascular cell adhesion molecule-1 (sVCAM-1) (710-665 ng/mL, P<0.0001) for all patients, compared with baseline. Amlodipine was associated with a mean blood pressure reduction of 8/3 mm Hg (P<0.0001) whereas patients on placebo had no significant change. In the atorvastatin-placebo group, mean FMD increased (7.3-9.5%, P<0.05) with no change in nitroglycerin-mediated dilation. No further benefit on FMD or inflammatory markers was observed with the addition of amlodipine.

CONCLUSIONS

Intensive reduction of LDL-C with atorvastatin improves endothelium-dependent vasodilation and reduces markers of inflammation in patients with coronary disease. Amlodipine was not associated with a significant additional benefit on these variables.

Impact of diabetes, chronic heart failure, congenital heart disease and chronic obstructive pulmonary disease on acute and chronic exercise responses

Several chronic diseases are known to negatively affect the ability of an individual to perform exercise. However, the altered exercise capacity observed in these patients is not solely associated with the heart and lungs dysfunction. Exercise has also been shown to play an important role in the management of several pathologies encountered in the fields of cardiology and pneumology. Studies conducted in our institution regarding the influence of diabetes, chronic heart failure, congenital heart disease and chronic pulmonary obstructive disease on the acute and chronic exercise responses, along with the beneficial effects of exercise training in these populations, are reviewed.

Can prolonged exercise-induced myocardial ischaemia be innocuous?

AIMS

To evaluate the innocuousness of intense and prolonged exercise training above the threshold for myocardial ischaemia (1 mm ST-segment depression).

METHODS AND RESULTS

Twenty-two patients with ischaemic heart disease (IHD) were randomized to exercise training either at a target intensity that induced myocardial ischaemia (ischaemic group) or that adhered to current guidelines (control group). Training was progressively increased to 60 min under continuous electrocardiographic (ECG) monitoring. Cardiac troponin T (cTnT) was measured at various intervals. Ambulatory ECG monitoring was performed before and after 6 weeks of training and left ventricular function was evaluated in the ischaemic group after at least 6 weeks of training. The ischaemic group had myocardial ischaemia during the first 20, 40, and 60 min exercise sessions for 12.3 +/- 6.8, 29.0 +/- 12.9, and 49.8 +/- 2.2 min, respectively, with ST-segment depression ranging from 1.0 to 2.1 mm. No patient in either group demonstrated significant arrhythmias or increased cTnT. The ischaemic group had preserved left ventricular function.

CONCLUSION

In patients with IHD, prolonged and repeated ischaemic training sessions up to 60 min can be well tolerated without evidence of myocardial injury, significant arrhythmias, or left ventricular dysfunction.

Is Prolonged and Repeated Exercise-Induced Myocardial Ischemic Training Deleterious?

Background: In patients with ischemic heart disease (IHD), the current guidelines on exercise prescription recommend that exercise training intensity be 10 beats/min below the heart rate at which there is >1 mm ST-segment depression (ischemic threshold). However, it is not well established that exercise training above the ischemic threshold is harmful. Methods: Twenty-two patients with angiographically documented IHD (>70% stenosis) were randomized to exercise training either at a target intensity that induced myocardial ischemia (ischemic group) or that adhered to current guidelines (control group). Training was progressively increased to 60 min under continuous ECG monitoring. Cardiac troponin T (cTnT) was measured at regular intervals. Ambulatory ECG monitoring was performed before and after 6 wkof training and left ventricular function was evaluated by echocardiography in the ischemic group after at least 6 wk of training. Results: The ischemic training sessions were very well tolerated. The ischemic group had myocardial ischemia during the first 20, 40, and 60 min exercise sessions for 12.3 ± 6.8 min, 29.0 ± 12.9 min and 49.8 ± 2.2 min, respectively, with ST-segment depression ranging from 1.0 to 2.1 mm. The estimated myocardial work (as expressed by RPP) during the training session was also higher in the ischemic than in the control group for the first 20 min (17 354 ± 6 528 vs 13 355 ± 2 936 beats/min • mmHg, respectively; P=0.08), 40 min (16 329 ± 5 407 vs 12 452 ± 2 330 beats/min • mmHg, respectively; P=0.04), and 60 min training sessions (18 750 ± 5 698 vs 13 352 ± 2 947 beats/min • mmHg, respectively; P=0.02) No patient in either group demonstrated significant arrhythmias nor increased cTnT. The measured cTnT stayed below the detectable values of the essay (>0.01μg/l) for all patients at all times. Left ventricular function remained unchanged in the ischemic group. Conclusion: In patients with IHD, prolonged and repeated ischemic training sessions up to 60 min can be well tolerated without evidence of myocardial injury, significant arrhythmias or left ventricular dysfunction. Thus exercising at or above the ischemic threshold does not appear deleterious under this kind of supervision.

Impact of Beta-Blockade on Exercise Capacity in Subjects with Type 2 Diabetes

Background: Beta-blockers are prescribed to subjects with type 2 diabetes with coronary disease to reduce all-cause mortality. However, this medication reduces exercise capacity in non diabetic individuals. The purpose of this study was to evaluate the impact of beta-blockade on exercise capacity in diabetic subjects free of coronary disease. Methods: Ten sedentary men with type 2 diabetes participated in this study. Subjects were treated with oral hypoglycemic agents and/or diet. Exercise capacity was evaluated using an incremental protocol performed on a cycle ergometer. Subjects were evaluated without (WBB group) and following the use of a beta-blocker (Atenolol 100 mg, id) for 5 consecutive days (BB group). Results: Per study design, subjects were their own control. The BB situation was characterized by a lower resting heart rate (HR) (54±4 vs 74±12 bpm; P < 0.001) and a trend toward a lower resting systolic blood pressure (SBP) (123±11 vs 131±14 mmHg; P=0.1) compared to the WBB evaluation. Even with comparable peak workload achieved (193±27 vs 200±22 watts), there was a 13 % reduction in relative and absolute values of peak oxygen uptake (25.8±3.4 vs 29.7±4.1 ml·kg-1·min-1; P < 0.05 and 2.5±0.5 vs 2.9±0.6 L·min-1 respectively; P < 0.001), a 35 % reduction in peak HR (110±9 vs 169±14 bpm; P < 0.001) and a 21 % reduction in peak SBP (167±24 vs 211±20 mmHg; P < 0.001) in the BB compared to the WBB situation. Also, the BB situation showed a lower peak minute-ventilation (97±15 vs 120±24 L/min; P < 0.05) compared with WBB. Conclusion: These results suggest that in subjects with type 2 diabetes free of coronary disease, the use of a beta-blockers impedes cardio-respiratory function at peak exercise beyond compensatory mechanisms leading to a decreased exercise capacity.

Attenuation of the Threshold for Myocardial Ischemia in Ramp vs Standard Bruce Protocol in Patients with Positive Exercise Stress Test and Angiographically Demonstrated Coronary Artery Narrowing?

Background: Gradual instead of abrupt increases in workload favour a more physiological response in terms of hemodynamic and gas exchange parameters. Therefore, we sought to determine whether myocardial ischemia is attenuated with a ramp compared to a standard Bruce exercise protocol in patients with coronary artery disease (CAD). Methods: We compared ischemic parameters on the Bruce protocol with an individualized ergocycle ramp protocol in 18 men with documented CAD (≥ 70% stenosis) and a reproducible ischemic ECG exercise test. These 2 symptom-limited tests were performed in random order 2 weeks apart. Oxygen consumption (VO2), ischemic threshold [systolic blood pressure x heart rate (RPP) at 1 mm ST-segment depression], and maximum ST-segment depression corresponding to the highest RPP common to the 2 tests (AdjSTmax) were determined. Results: While all subjects showed ischemia on the treadmill, 6/18 did not on the ergocycle. However, ischemic threshold was higher on the ramp than the Bruce protocol (23 420 ± 5 732 vs 20 018 ± 3 542 bpm•min-1•mmHg; P=0.007). Peak RPP was higher during the ramp than with the Bruce protocol (28 492 ± 6 450 vs 25 519 ± 6 067 bpm•min-1•mmHg, respectively; P=0.02), despite similar peak VO2 (25.59 ± 5.05 vs 26.39 ± 4.65 mlO2•kg-1•min-1, respectively; P=0.6). AdjSTmax was less on the ramp than the Bruce protocol (-1.2 ± 0.9 vs -1.9 ± 0.7 mm; P=0.003). Conclusion: Exercise-induced myocardial ischemia is markedly attenuated on the more gradually increasing workload of the individualized ramp ergocycle compared with the standard Bruce treadmill protocol. This effect is unexplained by energy expenditure (VO2) or myocardial work (RPP) and is consistent with a “warm-up” ischemic mechanism. The more gradually increasing workload of the ramp ergocycle protocol may have favoured a “warm-up” ischemic effect despite achieving higher RPP than the Bruce protocol treadmill suggesting it may be physiologically preferable for exercise prescription in patients with CAD.

Different thresholds of myocardial ischemia in ramp and standard bruce protocol exercise tests in patients with positive exercise stress tests and angiographically demonstrated coronary arterial narrowing

Gradual instead of abrupt increases in workload favor a more physiologic response in terms of hemodynamic and gas exchange parameters. Therefore, we investigated whether myocardial ischemia is attenuated with a ramp compared with a standard Bruce exercise protocol in patients with coronary artery disease. We compared electrocardiographic ischemic parameters on the standard Bruce protocol treadmill and the individualized ergocycle ramp protocol in 18 men with coronary artery disease and a reproducible ischemic electrocardiographic exercise test. Oxygen consumption (VO2), ischemic threshold (rate-pressure product [RPP]=systolic blood pressure x heart rate at 1-mm ST-segment depression), and maximum ST-segment depression corresponding to the highest RPP common to the 2 tests were determined. Ischemic threshold was higher with the ramp than with the Bruce protocol (23,420+/-5,732 vs 20,018+/-3,542 beats.min/mm Hg, p=0.007). Peak RPP was higher during the ramp than during the Bruce protocol (28,492+/-6,450 vs 25,519+/-6,067 beats.min/mm Hg, respectively, p=0.02) despite similar peak VO2 (25.59+/-5.05 vs 26.39+/-4.65 mlO2.kg-1.min-1, respectively, p=0.6). Maximum ST-segment depression corresponding to the highest RPP common to the 2 tests was less with the ramp than with the Bruce protocol (-1.2+/-0.9 vs -1.9+/-0.7 mm, p=0.003). In conclusion, exercise-induced myocardial ischemia is markedly attenuated on the more gradually increasing workload of the individualized ramp ergocycle compared with the standard Bruce treadmill protocol. This effect is unexplained by energy expenditure (VO2) or myocardial work (RPP) and is consistent with a "warm-up" ischemic mechanism.

Influence of glycemic control on pulmonary function and heart rate in response to exercise in subjects with type 2 diabetes mellitus

Conflicting results exist regarding the impact of glycemic control on peak oxygen uptake (VO2peak) in subjects with type 2 diabetes mellitus. The influence of glycemic control on submaximal oxygen uptake (VO2) in these subjects is unknown. The aim of this study was to evaluate the impact of fasting blood glucose (FBG) (short-term glycemic control) and glycated hemoglobin (HbA1c) (long-term glycemic control) on submaximal VO2 and VO2peak during exercise in subjects with type 2 diabetes mellitus without cardiovascular disease. FBG and HbA1c levels and exercise tolerance in 30 sedentary men with type 2 diabetes mellitus treated with oral hypoglycemic agents and/or diet were evaluated. VO2, carbon dioxide production (VCO2), heart rate, pulmonary ventilation (VE), and the respiratory exchange ratio (RER) were measured throughout the exercise protocol. Subjects were separated into 2 groups of the same age, weight, and body mass index according to median FBG and HbA1c levels (6.5 mmol/L and 6.1%, respectively). Per protocol design, there was a significant difference in FBG and HbA1c levels (P < .001), but not for age, weight, or body mass index. There was no significant difference in peak exercise parameters between the 2 groups according to median FBG or median HbA1c levels. However, the subjects with elevated HbA1c level had lower submaximal V e throughout the exercise protocol (P < .03), and the subjects with elevated FBG concentration had a blunted heart rate pattern during submaximal exercise (P < .03). Although relatively small abnormalities in the control of glycemia do not affect VO2peak in subjects with type 2 diabetes mellitus without cardiovascular disease, they may influence pulmonary function and the chronotropic response during submaximal exercise in these subjects.

Elevated peak exercise systolic blood pressure is not associated with reduced exercise capacity in subjects with Type 2 diabetes

Subjects with Type 2 diabetes without cardiovascular disease have a reduced exercise capacity compared with nondiabetic subjects. However, the mechanisms responsible for this phenomenon are unknown. The purpose of this study was to evaluate the impact of exercise systolic blood pressure (SBP) response on diverse exercise tolerance parameters in Type 2 diabetic subjects. Twenty-eight sedentary men with Type 2 diabetes were recruited for this study. Subjects were treated with oral hypoglycemic agents and/or diet. Evaluation of glycemic control and peak exercise capacity were performed for each subject. The subjects were divided into two groups according to the median value of peak SBP (210 mmHg) measured in each subject. We observed a 13, 13, and 16% reduction in the relative peak oxygen uptake (V̇o2 peak), absolute V̇o2 peak, and peak work rate in the low- compared with the high-peak SBP group [26.95 (SD 5.35) vs. 30.96 (SD 3.61) ml·kg−1·min−1, 2.5 (SD 0.4) vs. 2.8 (SD 0.6) l/min, and 169 (SD 34) vs. 202 (SD 32) W; all P < 0.05]. After adjusting for age, relative V̇o2 peak was still significantly different ( P < 0.05). There were similar peak respiratory exchange ratio (RER) [1.20 (SD 0.08) vs. 1.16 (SD 0.07); P = 0.24] and peak heart rate [160 (SD 20) vs. 169 (SD 15) beats/min; P = 0.18] between the low- compared with the high-SBP group. No difference in glycemic control was observed between the two groups. The results reported in this study suggest that in subjects with Type 2 diabetes without cardiovascular disease, an elevated exercise SBP is not associated with reduced exercise capacity and its modulation is probably not related to glycemic control.

Exercise capacity and impact of exercise training in patients after a Fontan procedure: a review

After a successful Fontan procedure, children and adolescents should improve their exercise capacity. However, several studies have shown that these children have a reduced maximal oxygen consumption compared with healthy children. The lower exercise performance in these patients was mainly explained by a reduced cardiorespiratory functional capacity. However, it has recently been reported that the lower exercise performance may also be related to altered skeletal muscle function. Moreover, exercise training had a beneficial impact on several parameters related to exercise tolerance in these patients. The main studies supporting these observations are reviewed, with a focus on the physiological adaptation and limitation of the exercise performance as well as the benefits of exercise training in patients after a Fontan procedure.

Skeletal muscle endurance and muscle metabolism in patients with chronic heart failure

BACKGROUND

Alterations in skeletal muscle function are known to contribute to exercise intolerance in patients with chronic heart failure (CHF).

OBJECTIVES

To evaluate whether muscle isometric endurance can be objectively measured and whether it is related to skeletal muscle metabolism in CHF.

METHODS

Isometric endurance of the vastus lateralis, measured as time to fatigue (T(F)), was evaluated in 25 patients with CHF (55+/-8 years of age [mean +/- SD]) and 18 healthy subjects (HS) (62+/-6 years of age [mean +/- SD]). Median frequency of surface electromyography was obtained from spectral analysis using a fast Fourier transformation. Citrate synthase (CS), 3-hydroxyacyl-CoA dehydrogenase (HADH), hexokinase (HK) and phosphofructokinase (PFK) activities were determined from the right vastus lateralis muscle.

RESULTS

T(F) was lower in CHF patients than in HS (49+/-4 s and 80+/-7 s, respectively; P<0.01). Muscle fatigue was present at the end of the endurance test in both groups (median frequency breakpoint at mid-exercise for both groups [P<0.05]). CS (P<0.01) and HK (P<0.01) activities were lower in CHF patients than in HS, but PFK activity was higher (P<0.05). T(F) correlated significantly with CS (r=0.50), HADH (r=0.42), PFK (r=-0.47) and HK (r=0.41) activities and the PFK/CS ratio (r=-0.39) when both groups were considered, and with HADH (r=0.47) and PFK (r=-0.57) activities for the CHF group alone (all P<0.05).

CONCLUSIONS

These results suggest that isometric endurance of the vastus lateralis muscle is reduced in patients with CHF and that it is related to a reduced muscle oxidative capacity.

Assessment of muscle fatigue during exercise in chronic obstructive pulmonary disease

Contractile fatigue is associated with exercise intolerance in patients with chronic obstructive pulmonary disease (COPD). Contractile fatigue may be assessed by quantifying the decline in strength after a fatiguing protocol but this may pose practical problems. The purpose of this study was to investigate the relationship between the decline in quadriceps strength, quadriceps electrical activity, perception of leg fatigue, and arterial lactate level in patients with COPD during constant work-rate cycling exercise. The decline in quadriceps strength was significantly associated with the decrease in electromyographic median frequency (r = 0.606), leg fatigue perception (r = 0.453), and arterial lactate level (r = 0.384). Using the receiver-operating-characteristic curve, it was found that a 4% decline in electromyographic median frequency had a 94% sensitivity and a 75% specificity to predict contractile fatigue. We conclude that contractile fatigue commonly occurs during cycling exercise in COPD. The electromyographic median frequency appears to be a valuable indirect marker to predict contractile leg fatigue.

[French-Canadian validation of the MOS Social Support Survey]

BACKGROUND

The MOS Social Support Survey was developed for patients who participated in the Medical Outcomes Study (MOS), a two-year study on persons who suffered from chronic illness. There are a number of advantages to using the MOS Social Support Survey, especially with those persons who suffer from chronic illness: it is easy to understand, is relatively short, is multidimensional, can be completed by the patient without assistance and has good psychometric properties.

OBJECTIVE

The goal of this study was to establish a French-Canadian version of the MOS Social Support Survey and to verify its psychometric properties following the cross-cultural translation and validation procedures proposed by Vallerand.

METHODS

A first draft of the MOS Social Support Survey was achieved by following the back-to-back translation technique. Next, a committee of four bilingual people reviewed and evaluated the preliminary versions of the questionnaire (English and French) to establish a French experimental version. A pre-test was done with 10 francophone persons. The Haccoun method was used to evaluate the construct validity and test-retest reliability, as well as the internal consistency of the questionnaire. The test-retest was performed with 20 students from the School of Languages from Laval University, Sainte-Foy, Quebec. The present research was approved by the ethics committee of the institution.

RESULTS

The results showed acceptable internal consistency and good reliability. The psychometric properties were found to be acceptable and comparable with those obtained by Sherbourne and Stewart with the English version.

CONCLUSION

The French-Canadian version of the MOS Social Support Survey should be useful in evaluating social support among patients to allow medical staff to plan rehabilitation programs that would include the necessary consultations and interventions needed to establish a better quality of life for the patient.

Usefulness of measuring net atrioventricular compliance by Doppler echocardiography in patients with mitral stenosis

Twenty-six patients with severe pure mitral stenosis underwent Doppler echocardiographic examination and cardiac catheterization within the same day before the realization of mitral valve balloon valvuloplasty. Net atrioventricular compliance estimated by Doppler echocardiography from the ratio of mitral valve effective orifice area and E-wave downslope was a major independent determinant of left atrial and pulmonary arterial pressures measured by catheterization.

Impact of exercise training on muscle function and ergoreflex in Fontan patients: a pilot study

BACKGROUND

Several studies have demonstrated persistent reduced exercise capacity in Fontan patients even after surgical intervention. The purpose of this study was to evaluate if the skeletal muscle function of these patients is abnormal, if it correlates with exercise tolerance and if it can be improved by exercise training.

METHODS

We evaluated the functional capacity of seven patients who underwent Fontan procedure (age:16+/-5 years, mean+/-SD) and seven healthy children (19+/-7 years) paired for age, sex, height and weight. Evaluation included pulmonary evaluation, neuromuscular function and exercise tolerance. Secondly, an 8-week exercise training program was performed by five of these patients.

RESULTS

The ergoreflex contribution to absolute diastolic blood pressure was higher (12.5+/-4.8 vs. 5.6+/-4.2 mmHg; p=0.04) in Fontan patients vs. healthy subjects whereas a trend was encountered regarding the ergoreflex contribution to absolute systolic blood pressure (9.0+/-7.0 vs. 0.4+/-9.0 mmHg; p=0.09). Furthermore, time to fatigue of the non-dominant forearm muscles was shorter in Fontan patients vs. healthy subjects (431+/-290 vs. 847+/-347 s; p=0.03). Following exercise training, there was a significant reduction of the ergoreflex contribution to absolute values of systolic blood pressure (9.8+/-0.9 vs. 0.3+/-2.7 mmHg; p<0.05). There was an association between muscle strength and VO2 peak in Fontan patients (upper limb: r=0.895; p<0.01; lower limb: r=0.838; p<0.05, respectively).

CONCLUSIONS

Skeletal muscle function in Fontan patients is abnormal which may have an impact in the reduced exercise tolerance encountered in these patients. Exercise training may have beneficial impacts on the skeletal muscle function in this population.

Post-exercise heart rate recovery and mortality in chronic obstructive pulmonary disease

Abnormal heart rate recovery (HRR) after exercise, a marker of cardiac autonomic dysfunction, is associated with poor prognosis in various populations. As chronic obstructive pulmonary disease (COPD) is associated with cardiac autonomic dysfunction, we tested the hypothesis that patients with COPD have a lower HRR than healthy people, and evaluated whether a delay in HRR is associated with an increased risk of mortality in COPD. The records of 147 COPD patients were reviewed (65.1+/-9.1 years, mean+/-sd, 42 women/105 men, forced expiratory volume in 1s (FEV1): 42+/-15% predicted) and compared to 25 healthy subjects (61.6+/-4.5 years, 5 women/20 men, FEV1: 100+/-14% predicted) during recovery after an exercise test. Heart rate was measured at peak exercise and at 1-min recovery, the difference between the two being defined as HRR (11+/-9 beats in COPD patients vs. 20+/-9 beats in healthy subjects, P < 0.0001). During a mean follow-up of 43.1+/-22.0 months, 32 patients died. Abnormal HRR (14 beats) was a strong predictor of mortality in COPD patients (adjusted hazard ratio: 5.12, 95% CI [1.54-17.00]). In conclusion, COPD patients have a lower HRR than healthy subjects, and have a worse prognosis when presenting abnormal HRR.

Long-term Effects of Cardiac Rehabilitation and the Paradigms of Cardiac Rehabilitation

BACKGROUND

The benefits of exercise training for postmyocardial infarction and postcoronary artery bypass surgery patients are well established, but little is known about the effects of rehabilitation in the months or years following the program. The purpose of this study was to assess exercise capacity, blood lipids, and physical activity patterns 2 years after completing a concentrated residential rehabilitation program in Switzerland.

METHODS

Seventy-eight patients (86% males, mean age = 56 +/- 10, mean ejection fraction = 64% +/- 12%) were referred to a residential rehabilitation program after a myocardial infarction or coronary artery bypass surgery between January 2001 and June 2001. Patients lived at the center for 1 month, during which time they underwent educational sessions, consumed a low-fat diet, and exercised 2 hours daily. Two years after completing the program, patients returned to the hospital and underwent a maximal exercise test, an assessment of recent and adulthood physical activity patterns, and evaluation of blood lipids.

RESULTS

During the 2-year follow-up period, there were 5 deaths, and 70 of the remaining 73 patients returned for repeat testing. Mean exercise capacity increased 27% during the rehabilitation program (P < .01). Gains in exercise capacity during rehabilitation were maintained after the follow-up period; mean exercise capacity after 2 years was 34% higher compared with that at baseline (P < .01). At the 2-year evaluation, patients were expending a mean of 3127 +/- 1689 kcals/wk during recreational activities compared with 977 +/- 842 kcals/wk during adulthood prior to their cardiac event (P < .001). Between the completion of rehabilitation and the 2-year follow-up, total cholesterol, total cholesterol/high-density lipoprotein ratio, and triglycerides increased significantly.

CONCLUSIONS

Two years after a cardiac event and participation in a concentrated residential rehabilitation program, patients maintained their exercise capacity and engaged in physical activities that exceed the levels recommended by guidelines for cardiovascular health. These observations suggest that a relatively intensive rehabilitation program provided a catalyst to maintain physical activity patterns and exercise tolerance in the 2 years following a cardiac event.

Contractile fatigue, muscle morphometry, and blood lactate in chronic obstructive pulmonary disease

We hypothesized that patients with chronic obstructive pulmonary disease developing contractile fatigue of the quadriceps during cycle exercise may have characteristic metabolic and muscle features that could increase their susceptibility to fatigue, thus differentiating them from those who do not develop fatigue. We examined, in 32 patients, the fiber-type proportion, enzymatic activities, and capillary density in the vastus lateralis and the arterial blood lactate level during constant work-rate cycling exercise. Contractile fatigue was defined as a postexercise fall in quadriceps twitch force greater than 15% of resting values. Twenty-two patients developed contractile fatigue after exercise. No significant differences were found between fatiguers and non-fatiguers for the endurance time, fiber-type proportion, and oxidative enzyme activities. The lactate dehydrogenase activity was significantly higher (p < 0.05) and muscle capillarization significantly reduced in fatiguers (p < 0.05). Compared with non-fatiguers, the arterial lactate level during exercise was significantly higher in fatiguers (p < 0.001). A significant relationship was found between the fall in quadriceps twitch force and lactate dehydrogenase activity, capillary/fiber ratio, and blood lactate level. We conclude that changes in muscle enzymatic profile and capillarization with a greater reliance on glycolytic metabolism during exercise are associated with contractile fatigue in patients with chronic obstructive pulmonary disease.

Reaching recommended lipid and blood pressure targets with amlodipine/atorvastatin combination in patients with coronary heart disease

The effects of combined atorvastatin and amlodipine on blood pressure (BP) and low-density lipoprotein (LDL) cholesterol levels were investigated in 134 patients with documented coronary heart disease treated for 1 year. BP at baseline was 128 +/- 15/79 +/- 9 mm Hg and was controlled by the treating physician; no calcium channel blockers were allowed. Baseline means for plasma cholesterol were 6.4 +/- 1.1 mmol/L (147 +/- 39 mg/dl), triglycerides 2.0 +/- 0.9 mmol/L (177 +/- 88 mg/dl), LDL cholesterol 4.4 +/- 1.0 mmol/L (170 +/- 39 mg/dl), and high-density lipoprotein cholesterol 1.2 +/- 0.3 mmol/L (46 +/- 12 mg/dl). Patients were all given atorvastatin 10 mg, then increased to 80 mg if the LDL cholesterol was <2.5 mmol/L (100 mg/dl). At 3 months, patients were randomized to amlodipine 10 mg or placebo. Plasma LDL cholesterol was decreased by 50%, and the LDL cholesterol target of <2.5 mmol/L was achieved in 81% of the patients. BP targets were achieved in 69% of the atorvastatin + placebo group, versus 96% in the atorvastatin + amlodipine group (p = 0.0002). With use of combination atorvastatin + amlodipine at doses ranging from 10 to 80 mg and 5 to 10 mg, respectively, recommended therapeutic goals were reached in most select subjects with coronary artery disease who were concomitantly receiving aspirin and antihypertensive therapy.

Peripheral muscle endurance and the oxidative profile of the quadriceps in patients with COPD

BACKGROUND

Based on previously reported changes in muscle metabolism that could increase susceptibility to fatigue, we speculated that patients with chronic obstructive pulmonary disease (COPD) have reduced quadriceps endurance and that this will be correlated with the proportion of type I muscle fibres and with the activity of oxidative enzymes.

METHODS

The endurance of the quadriceps was evaluated during an isometric contraction in 29 patients with COPD (mean (SE) age 65 (1) years; forced expiratory volume in 1 second 37 (3)% predicted) and 18 healthy subjects of similar age. The electrical activity of the quadriceps was recorded during muscle contraction as an objective index of fatigue. The time at which the isometric contraction at 60% of maximal voluntary capacity could no longer be sustained was used to define time to fatigue (Tf). Needle biopsies of the quadriceps were performed in 16 subjects in both groups to evaluate possible relationships between Tf and markers of muscle oxidative metabolism (type I fibre proportion and citrate synthase activity).

RESULTS

Tf was lower in patients with COPD than in controls (42 (3) v 80 (7) seconds; mean difference 38 seconds (95% CI 25 to 50), p<0.001). Subjects in both groups had evidence of electrical muscle fatigue at the end of the endurance test. In both groups significant correlations were found between Tf and the proportion of type I fibres and citrate synthase activity.

CONCLUSION

Isometric endurance of the quadriceps muscle is reduced in patients with COPD and the muscle oxidative profile is significantly correlated with muscle endurance.

Positive pleiotropic effects of HMG-CoA reductase inhibitor on vitiligo

Background

HMG-CoA reductase inhibitors (statins) are commonly used in medicine to control blood lipid disorder. Large clinical trials have demonstrated that statins greatly reduces cardiovascular-related morbidity and mortality in patients with and without coronary artery disease. Also, the use of HMG-CoA reductase inhibitors has been reported to have immunosuppressive effects.

Case presentation

We describe an unusual case of regression of vitiligo in a patient treated with high dose simvastatin. The relation between simvastatin and regression of vitiligo in this case report may be related to the autoimmune pathophysiology of the disease.

Conclusion

This unexpected beneficial impact provides another scientific credence to the hypothesis that immune mechanisms play a role in the development of vitiligo and that the use of statins as immuno-modulator could be of use not only for treatment relative to organ transplant but in other pathologies such as vitiligo.

Effect of atorvastatin on exercise-induced myocardial ischemia in patients with stable angina pectoris

To investigate whether marked and sustained lipid-lowering in subjects with stable angina pectoris and dyslipidemia reduces exercise-induced myocardial ischemia, 17 subjects were treated with dose-adjusted atorvastatin over 1 year and underwent serial evaluation of exercise electrocardiographic ischemic parameters, serum biomarkers, and brachial artery endothelial function. Endothelial function improved progressively and C-reactive protein, P-selectin, and tissue plasminogen activator inhibitor levels decreased, but there was no decrease in exercise electrocardiographic ischemia.

Contractile leg fatigue after cycle exercise: a factor limiting exercise in patients with chronic obstructive pulmonary disease

We evaluated whether contractile fatigue of the quadriceps occurs after cycling exercise in patients with chronic obstructive pulmonary disease (COPD) and whether it could contribute to exercise limitation. Eighteen COPD patients performed two constant work-rate cycling exercises up to exhaustion. These tests were preceded by nebulization of placebo or 500 microg of ipratropium bromide. Muscle fatigue was defined as a postexercise reduction in quadriceps twitch force of more than 15% of the resting value. There was an increase in endurance time postipratropium compared with placebo nebulization (440 +/- 244 seconds vs. 322 +/- 188 seconds, p = 0.06). Nine patients developed contractile fatigue after placebo exercise. In these patients, ipratropium did not increase the endurance time (394 +/- 220 seconds with placebo vs. 400 +/- 119 seconds with ipratropium) despite an 11% improvement in FEV1. In the nine patients who did not fatigue after placebo exercise, endurance time increased from 249 +/- 124 seconds with placebo to 479 +/- 298 seconds with ipratropium (p < 0.05). There was a significant correlation between the improvement in endurance time with ipratropium and quadriceps twitch force at 10 minutes after placebo exercise (r = 0.59, p = 0.01). The occurrence of contractile fatigue during exercise may explain why bronchodilation fails to improve exercise tolerance in some COPD patients.

What induces the warm-up ischemia/angina phenomenon: exercise or myocardial ischemia?

BACKGROUND

The relation of the warm-up ischemia phenomenon to the presence and intensity of initial myocardial ischemia is unclear. We sought to determine whether the warm-up ischemia phenomenon requires initial myocardial ischemia or can be induced by exercise without ischemia and whether there is a relation between the intensity of initial ischemia and the attenuation of ischemia on reexercise.

METHODS AND RESULTS

Twelve subjects with exertional myocardial ischemia performed 2 exercise ECG tests (1 and 2) at a +/-10-minute interval on 3 occasions (A, B, C) 1 month apart. A1 and A2 were symptom-limited. B1 was kept as long as A1, but its intensity was held under the ischemic threshold (heart ratexsystolic pressure at 1-mm ST depression [STD]) noted at A1. B2 was symptom-limited. C1 was also kept as long as A1 but with an intensity adjusted to maintain one-half maximum STD of A1. C2 was symptom-limited. Exercise duration of A2, B2, and C2 increased similarly compared with A1 (P=0.009). However, the ischemic threshold (x10-3) increased at A2 (23.5+/-6.0) compared with A1 (20.3+/-4.8; P<0.0001) but not at B2 (19.8+/-5.0) or C2 (21.5+/-5.8). Similarly, maximum STD adjusted to the highest heart rate-systolic pressure product common to A1, A2, B2, and C2 decreased at A2 (1.4+/-0.7 mm) compared with A1 (2.5+/-0.9 mm; P<0.0001) but not at B2 (2.7+/-0.9 mm) or C2 (2.3+/-0.9 mm).

CONCLUSIONS

Exercises under the ischemic threshold and of intermediate ischemic intensity increase short-term exercise capacity, but myocardial ischemia of more than moderate intensity is needed to induce the warm-up ischemia phenomenon.

Midthigh muscle cross-sectional area is a better predictor of mortality than body mass index in patients with chronic obstructive pulmonary disease

This study was undertaken to test the hypothesis that a reduction in midthigh muscle cross-sectional area obtained by CT scan (MTCSA(CT)) is a better predictor of mortality in chronic obstructive pulmonary disease (COPD) than low body mass index (BMI). We also wished to evaluate whether anthropometric measurements could be used to estimate MTCSA(CT). One hundred forty-two patients with COPD (age = 65 +/- 9 years, mean +/- SD, 26 F, BMI = 26 +/- 6 kg/m(2), FEV(1) = 42 +/- 16% predicted) were recruited from September 1995 to April 2000 with a mean follow-up of 41 +/- 18 months. The primary end-point was all-cause mortality during the study period. A Cox proportional hazards regression model was used to predict mortality using the following independent variables: age, sex, daily use of corticosteroid, FEV(1), DL(CO), BMI, thigh circumference, MTCSA(CT), peak exercise workrate, Pa(O2), and Pa(CO2). Only MTCSA(CT) and FEV(1) were found to be significant predictors of mortality (p = 0.0008 and p = 0.01, respectively). A second analysis was also performed with FEV(1) and MTCSA(CT) dichotomized. Patients were divided into four subgroups based on FEV(1) (< or >or= 50% predicted) and MTCSA(CT) (< or >or= 70 cm(2)). Compared with patients with an FEV(1) >or= 50% predicted and a MTCSA(CT) >or= 70 cm(2), those with an FEV(1) < 50% predicted and a MTCSA(CT) >or= 70 cm(2) had a mortality odds ratio of 3.37 (95% confidence interval, 0.41-28.00), whereas patients with an FEV(1) < 50% predicted and a MTCSA(CT) < 70 cm(2) had a mortality odds ratio of 13.16 (95% confidence interval, 1.74-99.20). MTCSA(CT) could not be estimated with sufficient accuracy from anthropometric measurements. In summary, we found in this cohort of patients with COPD that (1) MTCSA(CT) was a better predictor of mortality than BMI, and (2) MTCSA had a strong impact on mortality in patients with an FEV(1) < 50% predicted. These findings suggest that the assessment of body composition may be useful in the clinical evaluation of these patients.

[Peripheral muscle dysfunction in chronic obstructive pulmonary disease]

Patients with chronic obstructive pulmonary disease (COPD) often develop systemic complications of their disease. Peripheral muscle dysfunction is one such complication and is characterised by atrophy, weakness, and low oxidative capacity. These muscle changes influence exercise tolerance and quality of life independent of the impairment in lung function. In the following article, the evidence for peripheral muscle dysfunction in patients with COPD and the possible clinical implications of this problem will be discussed. Lastly, the available therapeutic options to improve peripheral muscle function in COPD will be reviewed.

Lipofuscin accumulation in the vastus lateralis muscle in patients with chronic obstructive pulmonary disease

Exercise-induced oxidative stress has been reported in patients with chronic obstructive pulmonary disease (COPD) and may play a role in muscle fatigue. It is speculated that oxidative stress during exercise originates from the contracting muscles but this has not been documented. The accumulation of lipofuscin, a marker of cellular oxidative damage, was evaluated in the vastus lateralis muscle in 17 patients with COPD and 10 healthy subjects of similar age. Each subject performed a stepwise exercise test up to maximal capacity during which oxygen uptake (VO(2)) was measured. Resting and peak exercise blood gases were also obtained. Two indices of lipofuscin accumulation were used: lipofuscin inclusions/fiber ratio (LI/F) and lipofuscin inclusions/fiber cross-sectional area ratio (LI/CSA). These ratios were also determined for each specific fiber-type. LI/F (P < 0.01) and LI/CSA (P < 0.01) were greater in COPD compared to healthy subjects. LI/F and LI/CSA for all fiber types were also greater in COPD (P < 0.001). In both groups, LI/F (P < 0.001) and LI/CSA (P < 0.01) were higher in type I than in type II fibers. LI/F and LI/CSA did not correlate significantly with resting PaO(2) and SaO(2), peak VO(2), and DeltaPaO(2) and DeltaSaO(2) during exercise (P > 0.05). Increased lipofuscin accumulation, a marker of oxidative damage, was found in the vastus lateralis muscle in patients with COPD compared to healthy subjects. Oxidative damage of muscle tissue may thus be involved in skeletal muscle dysfunction and wasting in COPD.

Effects of oxygen on lower limb blood flow and O2 uptake during exercise in COPD

PURPOSE

To quantify the effects of acute oxygen supplementation on lower limb blood flow (QLEG), O2 delivery (QO2LEG), and O2 uptake (VO2LEG) during exercise and to determine whether the metabolic capacity of the lower limb is exhausted at peak exercise during room air breathing in patients with COPD.

METHODS

Oxygen (FIO2 = 0.75) and air were randomly administered to 14 patients with COPD (FEV1: 35 +/- 2% pred, mean +/- SEM) during two symptom-limited incremental cycle exercise tests. Before exercise, a cannula was installed in a radial artery and a thermodilution catheter inserted in the right femoral vein. At each exercise step, five-breath averages of respiratory rate, tidal volume, and ventilation (VE), dyspnea and leg fatigue scores, arterial and venous blood gases, and QLEG were obtained. From these measurements, VO2LEG was calculated.

RESULTS

Peak exercise capacity increased from 46 +/- 3 W in room air to 59 +/- 5 W when supplemental oxygen was used (P < 0.001). QLEG, QO2LEG, and VO2LEG were greater at peak exercise with O2 than with air (P < 0.05). During submaximal exercise, dyspnea score and VE were significantly reduced with O2 (P < 0.05), whereas QLEG, VO2LEG, and leg fatigue were similar under both experimental conditions. The improvement in peak exercise work rate correlated with the increase in peak QO2LEG (r = 0.66, P < 0.01), peak VO2LEG (r = 0.53, P < 0.05), and reduction in dyspnea at iso-exercise intensity (r = 0.56, P < 0.05).

CONCLUSION

The improvement in peak exercise capacity with oxygen supplementation could be explained by the reduction in dyspnea at submaximal exercise and the increases in QO2LEG and VO2LEG, which enabled the exercising muscles to perform more external work. These data indicate that the metabolic capacity of the lower limb muscles was not exhausted at peak exercise during room air breathing in these patients with COPD.

Randomized trial of a noninvasive strategy to reduce hospital stay for patients with low-risk myocardial infarction

OBJECTIVES

This study evaluated the feasibility, pertinence and psychosocial repercussions of a noninvasive reduced hospital stay strategy (three days) for low-risk patients with acute myocardial infarction using simple clinical criteria and predischarge 24-h ambulatory ST-segment ischemic monitoring.

BACKGROUND

Previous studies evaluating shorter stays for uncomplicated myocardial infarction have been limited by retrospective or nonrandomized design and overdependence on invasive cardiac procedures.

METHODS

One-hundred twenty consecutive patients admitted with an acute myocardial infarction fulfilling low-risk criteria were randomized 2:1 to a short hospital stay (80 patients) or standard stay (40 patients). Short-stay patients with no ischemia on ST-segment monitoring were discharged on day 3, returning for exercise testing a week later. All analyses were on an intention-to-treat basis.

RESULTS

Forty-one percent of all screened patients with acute myocardial infarction would have been medically eligible for the short-stay strategy. Seventeen patients (21%) were not discharged early because of ischemia on ST-monitoring or angina. Median initial hospital stay was halved from 6.9 days in the standard stay to 3.5 days in the short-stay group. At six months, median total days hospitalized were 7.5 in the standard stay and 3.6 in the short-stay group (p < 0.0001). Adverse events and readmissions were low and not significantly different, and there were 25% fewer invasive cardiac procedures in the short-stay group. Psychosocial outcomes, risk factor changes and exercise test results were similar in the two groups.

CONCLUSIONS

This reduced hospital stay strategy for low-risk patients with acute myocardial infarction is feasible and worthwhile, resulting in a substantial and sustained reduction in days hospitalized. It is without unfavorable psychosocial consequences, appears safe and does not increase the number of invasive cardiac procedures.

Limitation of lower limb VO(2) during cycling exercise in COPD patients

Patients with chronic obstructive pulmonary disease (COPD) usually stop exercise before reaching physiological limits in terms of O(2) delivery and extraction. A plateau in lower limb O(2) uptake (VO(2)) and blood flow occurs despite progression of the imposed workload during cycling in some patients with COPD, suggesting that maximal capacity to transport O(2) had been reached and that it had been extracted in the peripheral exercising muscles. This study addresses this observation. Symptom-limited incremental cycle exercise was performed by 14 men [62 +/- 11 (SD) yr] with severe COPD (forced expiratory volume in 1 s = 35 +/- 7% of predicted value). Leg blood flow was measured at each exercise step with a thermodilution catheter inserted in the femoral vein. This value was multiplied by two to account for both working legs (Q(LEGS)). Arterial and femoral venous blood was sampled at each exercise step to measure blood gases. Leg O(2) consumption (VO(2LEGS)) was calculated according to the Fick equation. Total body VO(2) (VO(2TOT)) was measured from expired gas analysis, and tidal volume (VT) and minute ventilation (VE) were derived from the flow signal. In eight patients, VO(2LEGS) kept increasing in parallel with VO(2TOT) as external work rate was increasing. In six subjects, a plateau in VO(2LEGS) and Q(LEGS) occurred during exercise (increment of <3% between 2 consecutive increasing workloads) despite the increase in workload and VO(2TOT) [corresponding mean was 110 +/- 38 ml (11 +/- 4%)]. These six patients also exhibited a plateau in O(2) extraction during exercise. Peak exercise work rate was higher in the eight patients without a plateau than in the six with a plateau (51 +/- 10 vs. 40 +/- 13 W, P = 0.043). VT, VE, and dyspnea were significantly greater at submaximal exercise in patients of the plateau group compared with those of the nonplateau group. These results show that, in some patients with COPD, blood flow directed to peripheral muscles and O(2) extraction during exercise may be limited. We speculate that redistribution of cardiac output and O(2) from the lower limb exercising muscles to the ventilatory muscles is a possible mechanism.

Peripheral muscle dysfunction in chronic obstructive pulmonary disease

Peripheral muscle dysfunction is a common systemic complication of moderate to severe COPD and may contribute to disability, handicap, and premature mortality. In contrast to the lung impairment, which is largely irreversible, peripheral muscle dysfunction is potentially remediable with exercise training, nutritional intervention, oxygen, and anabolic drugs. Therapeutic success is often incomplete, however, and a better understanding of the mechanisms involved in the development of peripheral muscle dysfunction in COPD is needed to help develop innovative and more effective therapeutic strategies.

Influence of sympatho-vagal balance on airway responsiveness in athletes

The increased prevalence of airway hyperresponsiveness (AHR) observed among athletes suggests that high-level training may contribute to the development of AHR. We investigated the possible influence of the sympatho-vagal balance on this phenomenon in 40 athletes and 10 sedentary controls. Each subject filled out a respiratory questionnaire, had a methacholine challenge, and measurements were made of their baseline plasma catecholamines [epinephrine (E), norepinephrine (NE) and dopamine (DA)] as a reflection of sympathetic tone, and their heart rate variability (SDNN: standard deviation of all normal-to-normal intervals) as an indicator of parasympathetic tone. The athletes had a 45% prevalence of AHR (defined as PC20 < 16 mg/ml, where PC20 is the concentration of methacholine inducing a 20% fall in the forced expiratory volume in 1 s, FEV1) with a mean PC20 of 21.2 mg/ml compared with 10% prevalence (mean PC20: 74.4 mg/ml) in sedentary subjects (P < 0.01). Plasma catecholamine values were not significantly different between the two groups (all P > 0.05), but the estimated parasympathetic tone was higher in athletes (P = 0.01). When data from all subjects were analyzed together, plasma E and NE correlated with PC20 (r = 0.39, P = 0.005 and r = 0.29, P < 0.005) but DA and SDNN did not (both P > 0.05). However, the ratios E/SDNN, NE/SDNN and DA/SDNN showed significant correlations with PC20 (r = 0.42, P < 0.01; r = 0.33, P < 0.005 and r = 0.31, P < 0.05, respectively) This study suggests that the sympatho-vagal balance may contribute to the increased AHR in the population studied but this influence alone cannot explain the higher prevalence of AHR in athletes.

Oxidative enzyme activities of the vastus lateralis muscle and the functional status in patients with COPD

BACKGROUND

Enzymatic and histochemical abnormalities of the peripheral muscle may play a role in exercise intolerance in patients with chronic obstructive pulmonary disease (COPD). A study was undertaken to measure the mitochondrial enzyme activity of the vastus lateralis muscle in patients with COPD and to evaluate the relationship between enzyme activities and functional status.

METHODS

Fifty seven patients with COPD of mean (SD) age 66 (7) years with forced expiratory volume in one second (FEV(1)) 39 (15)% predicted and peak oxygen uptake (VO(2)) of 14 (4) ml/min/kg and 15 normal subjects of similar age were included in the study. Each subject performed a stepwise exercise test up to maximal capacity during which five-breath averages of VO(2) were measured. Muscle specimens were obtained by percutaneous needle biopsy of the vastus lateralis muscle and the activity of two mitochondrial enzymes (citrate synthase (CS) and 3-hydroxyacyl CoA dehydrogenase (HADH)) was measured. The functional status of the patients was classified according to peak VO(2).

RESULTS

CS and HADH activities were markedly reduced in patients with COPD compared with normal subjects (22.3 (2.7) versus 29.5 (7.3) micromol/min/g muscle (p<0.0001) and 5. 1 (2.0) versus 6.7 (1.9) micromol/min/g muscle (p<0.005), respectively). The activity of CS decreased progressively with the deterioration in the functional status while that of HADH was not related to functional status. Using a stepwise regression analysis, percentage predicted functional residual capacity (FRC), the activity of CS, oxygen desaturation during exercise, age, and inspiratory capacity (% pred) were found to be significant determinants of peak VO(2). The regression model explained 59% of the variance in peak VO(2) (p<0.0001).

CONCLUSIONS

The oxidative capacity of the vastus lateralis muscle is reduced in patients with moderate to severe COPD compared with normal subjects of similar age. In these individuals the activity of CS correlated significantly with peak exercise capacity and independently of lung function impairment.

Significant interaction between the nonprescription antihistamine diphenhydramine and the CYP2D6 substrate metoprolol in healthy men with high or low CYP2D6 activity

The prototype "classic" over-the-counter antihistamine diphenhydramine was shown to interact with the polymorphic P450 enzyme CYP2D6. This project was undertaken to investigate (1) whether diphenhydramine inhibits the biotransformation of the clinically relevant CYP2D6 substrate metoprolol in vitro and (2) whether this in vitro interaction results in a clinically significant pharmacokinetic and pharmacodynamic drug interaction in vivo. In vitro incubations were carried out with microsomes obtained from lymphoblastic cells transfected with CYP2D6 complementary deoxyribonucleic acid to determine the type and extent of inhibition. We then randomized 16 subjects with genetically determined high (extensive metabolizers) or low (poor metabolizers) CYP2D6 activity to receive metoprolol (100 mg) in the presence of steady-state concentrations of diphenhydramine or placebo. In vitro, diphenhydramine was a potent competitive inhibitor of metoprolol alpha-hydroxylation, exhibiting an inhibitory constant of 2 micromol/L and increasing the Michaelis-Menten constant of metoprolol sixfold. In vivo, diphenhydramine decreased metoprolol oral and nonrenal clearances twofold and metoprolol-->alpha-hydroxymetoprolol partial metabolic clearance 2.5-fold in extensive metabolizers (all P < .05) but not in poor metabolizers (P > .2). Although the hemodynamic response to metoprolol was unaltered by diphenhydramine in poor metabolizers (P > .05), metoprolol-related effects on heart rate, systolic blood pressure, and Doppler-derived aortic blood flow peak velocity were more pronounced and lasted significantly longer in extensive metabolizers receiving diphenhydramine compared with poor metabolizers and extensive metabolizers receiving placebo. We conclude that diphenhydramine inhibits the metabolism of metoprolol in extensive metabolizers, thereby prolonging the negative chronotropic and inotropic effects of the drug. Clinically relevant drug interactions may occur between diphenhydramine and many CYP2D6 substrates, particularly those with a narrow therapeutic index.

Airway hyperresponsiveness in elite athletes

It has been suggested that high-level training could contribute to the development of airway hyperresponsiveness (AHR), but the comparative effects of different sports on airway function remains to be determined. We evaluated 150 nonsmoking volunteers 18 to 55 yr of age; 100 athletes divided into four subgroups of 25 subjects each according to the predominant estimated hydrocaloric characteristic of ambient air inhaled during training: dry air (DA), cold air (CA), humid air (HA) and a mixture of dry and humid air (MA), and 50 sedentary subjects. Each subject had a respiratory questionnaire, a methacholine challenge, allergy skin-prick tests, and heart rate variability recording for evaluation of parasympathetic tone. The athletes had a 49% prevalence of AHR (PC(20) < 16 mg/ml), with a mean PC(20) of 16.9 mg/ml, compared with 28% (PC(20): 35.4) in sedentary subjects (p = 0.009). The prevalence (%) of AHR and mean PC(20) (mg/ml) varied as followed in the four subgroups of athletes: DA: 32% and 30.9; CA: 52% and 15.8; HA: 76% and 7.3; and MA: 32% and 21.5 (p = 0.002). The estimated parasympathetic tone was higher in athletes (p < 0.001), but this parameter showed only a weak correlation with PC(20) (r = -0.17, p = 0.04). This study has shown a significantly higher prevalence of AHR in athletes than in the control group because of the higher prevalence in the CA and HA groups. Parasympathetic activity may act as modulator of airway responsiveness, but the increased prevalence of AHR in our athlete population may be related to the type and possibly the content of inhaled air during training.

Impact of left ventricular diastolic dysfunction on maximal treadmill performance in normotensive subjects with well-controlled type 2 diabetes mellitus

Patients with type 2 diabetes often have impaired exercise capacity compared with nondiabetic subjects. Left ventricular (LV) diastolic dysfunction has been shown to limit exercise performance in nondiabetic subjects. Men with well-controlled type 2 diabetes were divided into 2 groups: normal LV diastolic function (group 1, n = 9) or LV diastolic dysfunction (group 2, n = 10) based on standard echocardiographic criteria using pulmonary veins and transmitral flow recordings. They were matched for age and had no evidence of systemic hypertension, macroalbuminuria, coronary artery disease, congestive heart failure, clinical diabetic complications, and thyroid disease. Good metabolic control was demonstrated by glycated hemoglobin levels of 6.7+/-1.6% and 6.6+/-2.5% (means +/- SD) in patients with LV diastolic dysfunction and in controls, respectively. Each subject performed a symptom-limited modified Bruce protocol treadmill exercise test. Maximal treadmill performance was higher in subjects with normal diastolic function compared with subjects with LV diastolic dysfunction when expressed in time (803+/-29 vs. 662+/-44 seconds, respectively, p<0.02) or in METs (11.4+/-1.2 vs. 9.5+/-1.9 METs, respectively, p<0.02). Moreover, there was a correlation between E/A ratio and exercise duration (r = 0.64, p = 0.004) or E/A ratio and METs (r = 0.658, p = 0.003). There were no significant differences in maximal heart rate, maximal systolic and diastolic blood pressure, or maximal rate-pressure product attained during the exercise test. In conclusion, this study demonstrated that LV diastolic dysfunction influences maximal treadmill performance and could explain lower maximal performance observed in patients with type 2 diabetes.

Hemodynamic and physical performance during maximal exercise in patients with an aortic bioprosthetic valve: comparison of stentless versus stented bioprostheses

OBJECTIVES

The objective of this study was to compare stentless bioprostheses with stented bioprostheses with regard to their hemodynamic behavior during exercise.

BACKGROUND

Stentless aortic bioprostheses have better hemodynamic performances at rest than stented bioprostheses, but very few comparisons were performed during exercise.

METHODS

Thirty-eight patients with normally functioning stentless (n = 19) or stented (n = 19) bioprostheses were submitted to a maximal ramp upright bicycle exercise test. Valve effective orifice area and mean transvalvular pressure gradient at rest and during peak exercise were successfully measured using Doppler echocardiography in 30 of the 38 patients.

RESULTS

At peak exercise, the mean gradient increased significantly less in stentless than in stented bioprostheses (+5 +/- 3 vs. +12 +/- 8 mm Hg; p = 0.002) despite similar increases in mean flow rates (+137 +/- 58 vs. +125 +/- 65 ml/s; p = 0.58); valve area also increased but with no significant difference between groups. Despite this hemodynamic difference, exercise capacity was not significantly different, but left ventricular (LV) mass and function were closer to normal in stentless bioprostheses. Overall, there was a strong inverse relation between the mean gradient during peak exercise and the indexed valve area at rest (r = 0.90).

CONCLUSIONS

Hemodynamics during exercise are better in stentless than stented bioprostheses due to the larger resting indexed valve area of stentless bioprostheses. This is associated with beneficial effects with regard to LV mass and function. The relation found between the resting indexed valve area and the gradient during exercise can be used to project the hemodynamic behavior of these bioprostheses at the time of operation. It should thus be useful to select the optimal prosthesis given the patient's body surface area and level of physical activity.