Acute alterations of oxygen uptake and symptom-limited exercise time in patients with mitral stenosis after balloon valvuloplasty

Mitral stenosis

Mitral stenosis is a common disease that causes substantial morbidity worldwide. The disease is most prevalent in developing countries, but is increasingly being identified in an atypical form in developed countries. All treatments that increase valve area improve morbidity. Mortality improves with surgery; the benefit of percutaneous balloon valvuloplasty to mortality might be similar to that of surgery but needs further study. Percutaneous balloon valvuloplasty is the treatment of choice for patients in whom treatment is indicated, except for those with suboptimum valve morphology, and even these patients are sometimes treated with this procedure if surgery is not feasible or if surgical risk is prohibitive. We review the pathology, diagnosis, and treatment options for patients with mitral stenosis.

Does balloon mitral valvuloplasty improve cardiac function? A mechanistic investigation into impact on exercise capacity

Procedural technical success of balloon mitral valvuloplasty (BMV) is indicated by an increase in valve area and a reduction in transvalvar gradient, but there are conflicting results regarding whether these indicators correlate with subsequent improvements in exercise capacity. We conducted a study to explore the effects of valvuloplasty on cardiac function to gain insight into the mechanisms responsible for the impact on exercise ability. Sixteen patients with mitral stenosis participated in the study and the five who did not proceed to valvuloplasty served as the control group. All patients performed maximal cardiopulmonary exercise tests before and 6 weeks after valvuloplasty (without valvuloplasty in controls). Central haemodynamics including cardiac output were measured non-invasively at rest and peak exercise. At baseline, the cardiopulmonary exercise test results were similar in the two groups. Following valvuloplasty, cardiac output did not alter at rest, but increased significantly at peak exercise (8.7+/-1.7 to 10.5+/-2.1 l min(-1), P<0.01), as did peak cardiac power output (1.88+/-0.55 to 2.28+/-0.74, P<0.05) and cardiac reserve (1.07+/-0.33 to 1.45+/-0.55 watts, P<0.05). Aerobic exercise capacity improved (13.9+/-4.2 to 16.4+/-4.3 ml kg(-1) min(-1), P<0.01) as did exercise duration (354+/-270 to 500+/-266 s, P<0.01). There were no significant changes in the controls. There was a significant correlation between the changes in peak VO(2) and changes in cardiac reserve (r=0.62, P<0.01) but not with changes in resting haemodynamics. These changes did not correlate with changes in peri-procedural mitral valve haemodynamics, despite increases in mitral valve area from 1.05+/-0.16 to 1.74+/-0.4 cm(2) (P<0.0001), accompanied by falls in the transvalvar gradient and pulmonary artery pressure (12.4+/-4.7 to 4.5+/-3 mmHg, and 26.8+/-8.4 to 17.4+/-5.2 mmHg, respectively, all P<0.0001). In conclusion, we found that successful mitral valvuloplasty in our patient cohort led to improved cardiac and physical functional capacity but not resting haemodynamics. Neither indicators of technical success nor resting haemodynamics were very reliable in predicting functional improvement.

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.

Lung water, hemodynamics and dyspnea before and after valvuloplasty in mitral stenosis

The investigation was to elucidate the role of the reduction of extravascular pulmonary fluid in the immediate symptomatic improvement and its impact on hemodynamics in patients with mitral stenosis treated by percutaneous transluminal valvuloplasty.

METHODS

In a prospective study of 12 patients with severe mitral stenosis extravascular pulmonary fluid volume was determined by a combined dye and thermodilution technique (COLD Z-021(TM) Version 5.x, Pulsion((R))) before and after valvuloplasty. Cardiac output, left atrial pressures, atrial V-waves, diastolic transmitral gradients and their respiratory changes were measured. Dyspnea was assessed by validated questionnaires.

RESULTS

Symptomatic improvement correlated (r=0. 808) with a decrease of extravascular lung water, but not with either an increase or a decrease of cardiac output or left atrial filling pressures. The decrease of the lung water index may be predicted from the lung water index before valvuloplasty, the final left atrial mean pressure and the cardiac index prior to intervention. The change of the mean difference between inspiratory and expiratory mitral gradient demonstrated a significant inverse correlation with the change of mean left atrial filling pressures (r=-0.778) and with extravascular lung water after valvuloplasty (r=-0.871).

CONCLUSION

There is a complex relationship between left atrial filling pressures, extravascular lung water, respiratory changes of gradients, and dyspnea that need further investigation.

Evaluation of a new treadmill exercise protocol

STUDY OBJECTIVES

To confirm that a newly drafted treadmill exercise protocol designed on a theoretical basis to span a range of 0 to 200 W with approximately 25-W increments by alteration of either speed or grade from one stage to the next should correspond to a standard bicycle protocol consisting of 25-W steps.

DESIGN

Randomized, crossover study to compare both exercise test modes.

STUDY PARTICIPANTS

Twenty-one consecutive healthy volunteers.

INTERVENTIONS

Subjects underwent both exercise tests until either exhaustion or completion of the respective protocol, and cardiopulmonary exercise parameters were assessed during either of them. For comparison, correlation coefficients (r) were calculated.

RESULTS

Exercise tolerance time was 9% higher on the treadmill (p<0.05). Ten subjects completed the bicycle program, whereas 18 subjects did so on the treadmill. With both protocols, there were comparably linear increases in heart rate (r=0.885), oxygen uptake (r=0.925), oxygen uptake per body weight (r=0.944), carbon dioxide output (r=0.937), and minute ventilation (r=0.914). For the 2-min stage duration, a plateau in oxygen uptake was achieved with neither protocol. The ventilatory equivalent for oxygen, which is not linear, showed its minimum at comparable workloads, at the point of surpassing the anaerobic threshold. Correlation of oxygen pulse was fair (r=0.896).

CONCLUSIONS

There was an excellent correlation of the parameters with respect to both measured values at identical workloads and slopes of both protocols, thus enabling comparability of treadmill and bicycle ergometry. Due to its practical handling, the new protocol may facilitate acceptance, especially when used for elderly or disabled patients.

Reproducibility of cardiopulmonary exercise parameters in patients with valvular heart disease

STUDY OBJECTIVES

To determine the degree of reproducibility of exercise parameters in patients with chronic heart failure. Parameters such as treadmill walking time (TWT), oxygen uptake (Vo2), heart rate, oxygen pulse, minute ventilation (VE) ventilatory equivalents for oxygen uptake (VE/Vo2) and carbon dioxide output (Vco2), and respiratory quotient at both anaerobic threshold (AT) and peak exercise (PE) each were assessed.

DESIGN

Using the Naughton-Weber protocol, two repeated cardiopulmonary treadmill exercise tests were performed after detailed instructions prior to the first test and on strict adherence to standardized investigational conditions, viz, at the same time of day and at the same ambient temperature, receiving constant medication, and while in a 12-h fasting state.

PATIENTS

The studies were carried out in 17 patients with chronic heart failure due to valvular heart disease considered candidates for intervention because of symptoms. According to Weber's classification of functional capacity, 10 patients were in class A (Vo2 max > 20 mL O2/min/kg), 5 patients were in class B (16 to 20 mL O2/min/kg), and the remaining 2 were in class C (10 to 16 mL O2/min/kg).

MEASUREMENTS

Parameters assessed were TWT, Vo2, heart rate, oxygen pulse, VE and ventilatory equivalents for oxygen (VE/Vo2) and carbon dioxide (VE/Vco2) both at AT and at PE. To reflect reproducibility, correlation coefficients (r) were calculated.

RESULTS

An excellent reproducibility was found for TWT (r = 0.963, p < 0.0001), Vo2 at AT in percent of predicted Vo2max (r = 0.984, p < 0.0001), Vo2 at PE (r = 0.996, p < 0.0001), heart rate at AT (r = 0.943, p < 0.0001) and at PE (r = 0.928, p < 0.0001), oxygen pulse at AT (r = 0.980, p < 0.001) and at PE (r = 0.991, p < 0.0001), VE at AT (r = 0.949, p < 0.0001) and at PE (r = 0.912, p < 0.0001) as well as VE/Vo2 at AT (r = 0.942, p < 0.0001) and at PE (r = 0.781, p < 0.0002) and VE/Vco2 at AT (r = 0.995, p < 0.0001) and at PE (r = 0.943, p < 0.0001), respectively.

CONCLUSIONS

On adherence to standardized conditions, an excellent reproducibility existed for TWT, Vo2 (reflecting cardiac output), ventilation, and heart rate as well as derived parameters, rendering cardiopulmonary exercise testing a reliable means of quantification of heart failure as a prerequisite for enabling diagnostic or therapeutic decisions.