Effect of balloon mitral valvuloplasty on exercise capacity, ventilation and skeletal muscle oxygenation

J receptor activity in idiopathic pulmonary hypertension and its expected change in the presence of pulmonary bed vasodilators

Juxtapulmonary receptors (J) lying in the lung parenchyma are stimulated naturally by any condition that produces interstitial oedema, transient increases in interstitial volume and pressure or raised pulmonary capillary pressure. There is no information available about the level of their stimulation in patients with idiopathic pulmonary hypertension (IPH) who have high levels of pulmonary artery systolic pressures. The aim of the present study therefore was to find the level of these receptors activity in these patients at their prevailing pulmonary artery systolic pressures. This was done by the established method of determining the dose of i.v. lobeline that gives rise to threshold levels of sensations in the upper chest areas and accelerates respiration. In IPH patients it was found to be as high as 31.6 ± 5.6 μg/kg i.e., twice as much as that known for healthy individuals which is 15 μg/kg. This shows an enhanced stimulation of J receptors in IPH patients. Expectedly when pulmonary artery systolic pressure falls with pulmonary bed vasodilator medication given to IPH patients, a reduction in the natural stimulus of J receptors would also occur leading to a fall in their activity and hence that of the quantum of their reflexes of respiratory acceleration and inhibition of exercise. This finding provides the first insight of a neural mechanism that could be influenced to produce its effects when pulmonary artery systolic pressure falls by pulmonary vasodilator medication.

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.

Interventional therapies for heart failure in the elderly

The aging of a population replete with risk factors for heart failure (HF) (coronary heart disease, diabetes, and hypertension) coupled with a declining age-adjusted mortality rate for coronary artery and hypertensive heart diseases has created, and will continue to create, a literal explosion in the prevalence of HF in the United States. Despite advances in maximal medical therapy, however, most patients who have symptomatic HF can expect functional impairment, interludes of worsening symptomatology, and a shortened lifespan. This article updates the use of interventional therapies for the treatment of elderly patients who have HF caused by coronary artery disease, valvular heart disease, congenital heart disease, myocardial disease, and renal vascular disease.

Interventional therapies for heart failure in the elderly

The aging of a population replete with risk factors for heart failure(HF) (coronary heart disease, diabetes, and hypertension) coupled with a declining age-adjusted mortality rate for coronary artery and hypertensive heart diseases has created, and will continue to create, a literal explosion in the prevalence of HF in the United States. Despite advances in maximal medical therapy, however, most patients who have symptomatic HF can expect functional impairment, interludes of worsening symptomatology, and a shortened lifespan. This article updates the use of interventional therapies for the treatment of elderly patients who have HF caused by coronary artery disease, valvular heart disease, congenital heart disease, myocardial disease, and renal vascular disease.

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.

Skeletal muscle abnormalities in chronic heart failure patients: relation to exercise capacity and therapeutic implications

Recent studies suggest that changes in the periphery, like those occurring in the skeletal muscles of patients with chronic heart failure, might play an important role in the origin of symptoms and exercise intolerance in this condition. Biochemical and histologic changes in the skeletal muscles of chronic heart failure patients relate with the degree of exercise intolerance better than hemodynamics parameters. A reduction in skeletal muscle mass represents another important determinant of exercise intolerance in chronic heart failure patients. The relationship between skeletal muscle changes and exercise intolerance suggests the possibility of modifying the peripheral changes in order to improve functional capacity in chronic heart failure patients. Recent studies have shown that the administration of angiotensin-converting enzyme inhibitors and angiotensin II receptor blockers can improve the properties of the skeletal muscles. Similarly, exercise training allows improvement in peak oxygen consumption, which parallels important biochemical and histologic changes in the skeletal muscles.

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.

Interventional therapy in heart failure management

The incidence and prevalence of congestive heart failure are rapidly increasing because of the progressive decrease in age-adjusted mortality rates for coronary artery disease and hypertensive heart disease, together with the progressive aging of the US population. Despite great advances in maximal medical therapy, most patients with symptomatic congestive heart failure can expect functional impairment, interludes of worsening symptomatology, and a shortened life span. Thus, it is appropriate to ask whether the interventional revolution that is under way for the management of ischemic cardiovascular disease can be applied with benefit to the management of congestive heart failure. The use of interventional therapies for the treatment of elderly patients with congestive heart failure caused by coronary artery disease, valvular heart disease, or renal vascular disease is addressed.

Determinants of delayed improvement in exercise capacity after percutaneous transvenous mitral commissurotomy

BACKGROUND

Percutaneous transvenous mitral commissurotomy (PTMC) results in short-term hemodynamic and symptomatic improvements. We have previously shown that the immediate symptomatic relief is related to the improvement in excessive exercise ventilation. The exercise capacity, however, does not improve in the short term but does improve gradually over several months. The pathophysiologic basis for the delayed improvement in exercise capacity has not been fully evaluated.

METHODS

To elucidate the determinants of improvement in exercise capacity late after PTMC, maximal ergometer exercise with respiratory gas analysis and exercise hemodynamic measurements were performed in 22 patients with symptomatic mitral stenosis before, immediately after, and 7 months after PTMC.

RESULTS

Mitral valve area increased from 0.9 +/- 0.2 cm(2) to 1.7 +/- 0.4 cm(2) after PTMC (P <.01). Significant improvements were observed in symptoms, cardiac output at peak exercise (6.6 +/- 1.5 L/min vs 8.6 +/- 1.9 L/min, P <.01), and mean pulmonary artery pressure at peak exercise (54.1 +/- 15.6 mm Hg vs 42.3 +/- 9.5 mm Hg, P <.01) immediately after PTMC. Excessive exercise ventilation, as assessed by the slope of the regression line between expired minute ventilation and carbon dioxide output (VE-VCo(2)), decreased significantly from 38.2 +/- 8.2 to 33.3 +/- 4.9 (P <.01). There were no significant changes in peak oxygen uptake (from 17.5 +/- 3.2 mL/kg per minute to 17.9 +/- 3.6 mL/kg per minute) immediately after PTMC. At 7 months, improved mitral valve area, symptoms, cardiac output at peak exercise, mean pulmonary artery pressure at peak exercise, and VE-VCo(2) were unchanged compared with values immediate after PTMC. Significant improvement was observed in peak oxygen uptake (19.7 +/- 3.0 mL/kg per minute [P <.01 compared with pre-PTMC or immediate post-PTMC values]). The increase in exercise cardiac output or the decrease in pulmonary artery pressure was not correlated with the late improvement in peak oxygen uptake. The short- or long-term improvements in VE-VCo(2), however, were significantly correlated with the late improvement in peak oxygen uptake.

CONCLUSIONS

Our results suggest that ventilatory improvement, not increased exercise cardiac output, contributed at least in part to the late improvement in exercise capacity after PTMC.

Immediate and delayed effects of successful percutaneous transvenous mitral commissurotomy on global right ventricular function in patients with isolated mitral stenosis

Global right ventricular function of the pressure-overloaded right ventricle in patients with mitral stenosis and pulmonary hypertension after successful percutaneous transvenous mitral commissurotomy (PTMC) has not been well-defined. With the use of a recently developed Doppler method for estimating right ventricular function in human beings, we studied 25 consecutive patients with isolated rheumatic mitral stenosis before, immediately after (mean, 40+/-12 h) and at a mean follow-up of 11.5 months after PTMC. Immediately after percutaneous mitral commissurotomy, there was a significant increase in mitral valve area (P = 0.000017) along with a decrease in mean pulmonary pressure (P = 0.001). The index was not affected immediately after successful PTMC (0.70+/-0.25 vs., 0.58+/-0.18; P = 0.06); however, at follow-up of about one year, the index showed a significant decrease (0.697+/-0.28 vs. 0.380+/-0.13; P = 0.0008, n = 24). The change in the index was characterised by a significant prolongation of the right ventricular ejection time, with a decrease in the isovolumic intervals. The Doppler index of combined right ventricular function was significantly correlated to the mean pulmonary artery pressure (r = 0.695, P<0.001) and systolic pulmonary artery pressure (r = 0.60, P = 0.007) before PTMC and also immediately after the procedure; however, at follow-up, the index had no correlation with the Doppler estimated pulmonary artery systolic pressure (r = 0.07). Despite a larger mitral valve area following PTMC, right ventricular isovolumic indices remain abnormal on mid-term follow-up, although global function tends to normalise in two-thirds of the patients.

Effect of percutaneous transvenous mitral commissurotomy on postexercise breathlessness as determined by ventilation during recovery from constant workload exercise

We evaluated the effect of percutaneous transvenous mitral commissurotomy (PTMC) on ventilatory variables and dyspnea during recovery from a 6-minute submaximal constant workload exercise, and showed that the decrease in postexercise ventilation after PTMC was closely related to improvement in postexercise dyspnea after PTMC. Ventilation during recovery from submaximal constant workload exercise is related to postexercise breathlessness and can be used to assess the effectiveness of therapeutic interventions.

Skeletal muscle deoxygenation during exercise assessed by near-infrared spectroscopy and its relation to expired gas analysis parameters

The present study was performed to determine the relation between oxygenated hemoglobin (oxy-Hb) changes in working muscles and ventilatory parameters. Six active normal subjects, 21 sedentary normal subjects and 16 patients with heart failure performed an incremental exercise with expired gas analysis. Deoxygenation of the vastus lateralis muscle was monitored for oxy-Hb changes using near-infrared spectroscopy. Near the anaerobic threshold (AT), oxy-Hb started to decrease, forming the first inflection point (P1). Near the respiratory compensation point (RCP), the second inflection point (P2) was observed. Oxygen uptake at the AT, RCP, P1 and P2 decreased in magnitude first in the active normal subjects, then in sedentary normal subjects and finally in the heart failure patients. High correlation was demonstrated between AT and P1 (r=0.8, p<0.0005) and between RCP and P2 (r=0.9, p<0.0005). In 12 sedentary normal subjects who underwent repeat exercise, reproducibility was confirmed for both P1 and P2. Constant work rate exercises were performed in 5 sedentary normal subjects, and in all of them the oxy-Hb remained unchanged below the AT work rate, whereas oxy-Hb decreased above the AT work rate. Exercise capacity, with respect to both working muscle deoxygenation and ventilation, could be evaluated in detail by the concomitant use of near-infrared spectroscopy and expired gas analysis.

Growth hormone: a new therapy for heart failure?

There is now little doubt that growth hormone (GH) and insulin-like growth factor-1 (IGF-1) play a role in cardiac development and in cardiovascular physiology in adult life. Congenital lack of GH is associated with defective cardiac growth, ventricular wall thinning, and impaired systolic function. These abnormalities limit exercise capacity and contribute to the poor quality of life in patients with GH deficiency. In addition, studies with in vitro muscle preparations have shown that IGF-1 affects myocardial contractility by a direct mechanism. These findings suggested that GH would benefit patients affected by heart failure. Indeed, GH and/or IGF-1 have proven beneficial in various models of experimental heart failure. Tested in patients with classes II-IV heart failure, they improved cardiac performance and clinical status. These effects were associated with improved myocardial energetics and de-activation of the neurohormonal system. Because of the uncontrolled nature of the studies and the small number of cases examined, conclusions as to the effectiveness of GH and IGF-1 must await the results from larger trials.

Pulmonary manifestations of chronic heart failure

These findings underscore the importance of understanding the complex interactions of multiple-organ systems in a chronic systemic disease state like congestive heart failure. The exaggerated ventilatory response in patients with heart failure is clearly multifactorial and it remains difficult to decipher whether this response results from or contributes to the sensation of dyspnea. Pulmonary dysfunction including ventilation-perfusion mismatching, decreased lung compliance, restriction, airway obstruction, decreased diffusion capacity, and decreases in respiratory muscle strength and endurance contribute to an inefficient breathing pattern and increased work of breathing. This is further compounded by the limited ability of the failing heart to meet the metabolic demands of the respiratory muscles, leading to under-perfusion and ischemia. This imbalance contributes to perceived dyspnea and exercise limitations. Understanding these physiologic cardiopulmonary interactions may lead to therapeutic modalities, such as respiratory muscle training, aimed at disrupting this intertwined cycle of events and improving functional capacity in patients with heart failure.

Valve Resistance in Mitral Stenosis: Its Determinants and its Role in the Evaluation of the Disease

To evaluate the value and the determinants of valve resistance in mitral stenosis, 95 patients with pure mitral stenosis were examined by Doppler echocardiography during their clinical follow-up, measuring cavity dimensions, left ventricular function, mitral area (by planimetry and pressure half time), mean transmitral pressure gradient, aortic flow, and pulmonary artery systolic pressure. The mitral resistance was calculated as mean transmitral pressure gradient/aortic flow ratio. To graduate the severity of the morphological abnormalities in valvular structure, we used a point score system with evaluation of leaflet and subvalvular thickness, calcification, and valvular mobility. The functional class was determined according to NYHA classification. In this study, both mitral area (r = -0.79, P < 0.001 and r(p) = -0.60, P < 0.001) and mitral score (r = 0.68, P < 0.001 and r(p) = 0.25, P = 0.013) were independent determinants of mitral resistance. In multivariate analysis, mitral resistance and female gender were selected by multiple linear regression analysis as determinants of pulmonary artery systolic pressure, and mitral area and pulmonary artery systolic pressure were selected by logistic linear regression analysis as determinants of NYHA functional class. In patients with moderate or severe mitral stenosis, the estimated probability for III and IV NYHA functional class considering mitral area 1 cm(2) or below went from 51.1-86.4% when mitral resistance below or above 130 dynes.sec.cm(-5), respectively, was considered together. Thus, mitral valve resistance should be used as a complement to the mitral area method in assessment of mitral stenosis, adding the effects of the reduction in mitral area and the damage in mitral valve apparatus.

Skeletal muscle function and its relation to exercise tolerance in chronic heart failure

OBJECTIVES

This study sought to define the relation between muscle function and bulk in chronic heart failure (HF) and to explore the association between muscle function and bulk and exercise capacity.

BACKGROUND

Skeletal muscle abnormalities have been postulated as determinants of exercise capacity in chronic HF. Previously, muscle function in chronic HF has been evaluated in relatively small numbers of patients and with variable results, with little account being taken of the effects of muscle wasting.

METHODS

One hundred male patients with chronic HF and 31 healthy male control subjects were studied. They were matched for age (59.0 +/- 1.0 vs. 58.7 +/- 1.7 years [mean +/- SEM]) and body mass index (26.6 +/- 0.4 vs. 26.3 +/- 0.7 kg/m2). We assessed maximal treadmill oxygen consumption (VO2), quadriceps maximal isometric strength, fatigue (20-min protocol, expressed in baseline maximal strength) and computed tomographic cross-sectional area (CSA) at midthigh.

RESULTS

Peak VO2 was lower in patients (18.0 +/- 0.6 vs. 33.3 +/- 1.4 ml/min per kg, p < 0.0001), although both groups achieved a similar respiratory exchange ratio at peak exercise (1.15 +/- 0.01 vs. 1.19 +/- 0.03, p = 0.13). Quadriceps (582 vs. 652 cm2, p < 0.05) and total leg muscle CSA (1,153 vs. 1,304 cm2, p < 0.005) were lower in patients with chronic HF. Patients were weaker than control subjects (357 +/- 12 vs. 434 +/- 18 N, p < 0.005) and also exhibited greater fatigue at 20 min (79.1% vs. 92.1% of baseline value, p < 0.0001). After correcting strength for quadriceps CSA, significant differences persisted (5.9 +/- 0.2 vs. 7.0 +/- 0.3 N/cm2, p < 0.005), indicating reduced strength per unit muscle. In patients, but not control subjects, muscle CSA significantly correlated with peak absolute VO2 (R = 0.66, p < 0.0001) and is an independent predictor of peak absolute VO2.

CONCLUSIONS

Patients with chronic HF have reduced quadriceps maximal isometric strength. This weakness occurs as a result of both quantitative and qualitative abnormalities of the muscle. With increasing exercise limitation there is increasing muscle weakness. This progressive weakness occurs predominantly as a result of loss of quadriceps bulk. In patients, this muscular atrophy becomes a major determinant of exercise capacity.

Effect of inadequate cardiac output reserve on exercise tolerance in patients with moderate mitral stenosis

Twenty-nine patients with moderate mitral stenosis and 29 age-matched normal controls underwent symptom-limited upright bicycle exercise testing with simultaneous hemodynamic monitoring. Exercise tolerance in the mitral stenosis group was found to be limited by inadequate cardiac output reserve and not by resting mitral valve area or exercise pulmonary capillary wedge pressure.

Acute unloading of the work of breathing extends exercise duration in patients with heart failure

OBJECTIVES

This study investigated whether maximal exercise performance can be improved by acutely decreasing the work of breathing in these patients.

BACKGROUND

Exertional dyspnea is a frequent limiting symptom in patients with heart failure. It may result from increased work of breathing.

METHODS

Fifteen patients with heart failure and nine age-matched normal subjects underwent two maximal exercise tests. Subjects exercised twice in randomized, single-blind manner using room air (RA) and a 79% helium/21% oxygen mixture (He). Respiratory gas analysis, Borg scale recordings of perceived dyspnea and near infrared spectroscopy of an accessory respiratory muscle were obtained during exercise.

RESULTS

In normal subjects there was no significant difference in peak oxygen uptake (Vo2) ([mean +/- SD] RA 38 +/- 8 vs. He 35 +/- 7 ml/kg per min), exercise duration (RA 724 +/- 163 vs. He 762 +/- 123 s) or peak minute ventilation (RA 97 +/- 27 vs. He 97 +/- 28 liters/min, all p = NS). Only three of nine control subjects thought that exercise with the He mixture was subjectively easier. In contrast, patients with heart failure exercised an average of 146 s longer with the He mixture (RA 868 +/- 293 vs. He 1,014 +/- 338, p < 0.01). Peak Vo2 (RA 19 +/- 4 vs. He 18 +/- 5 ml/kg per min) and peak minute ventilation (RA 53 +/- 12 vs. He 53 +/- 15 liters/min) were unchanged (both p = NS). The respiratory quotient at peak exercise was lower with the He mixture (RA 1.05 +/- 0.08 vs. He 0.98 +/- 0.06, p < 0.05). Thirteen of the 15 patients thought that exercise with the He mixture was subjectively easier (p < 0.02 vs. control group).

CONCLUSIONS

In patients with heart failure, pulmonary factors, including respiratory muscle work and airflow turbulence, contribute to limiting exercise performance. Therapeutic interventions aimed at attenuating work of breathing may be beneficial.

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.

31P nuclear magnetic resonance evidence of skeletal muscle metabolic abnormalities in mitral stenosis

We used in vivo 31P nuclear magnetic resonance spectroscopy to follow phosphorylated metabolites of dominant forearm flexor muscles during exercise in patients with mitral stenosis. The results showed that skeletal muscle metabolism during exercise is abnormal.

The sensation of dyspnea during exercise is not determined by the work of breathing in patients with heart failure

OBJECTIVES

The present study sought to investigate whether the work of breathing was reduced after heart transplantation. Accordingly, the tension time index of the diaphragm was measured in patients with heart failure and in transplant recipients.

BACKGROUND

Patients with heart failure are frequently limited by exertional dyspnea that may be due to the increased work of breathing. After heart transplantation, exertional dyspnea is markedly diminished. Whether work of breathing is reduced in posttransplant recipients is unknown.

METHODS

Nine patients with heart failure, six normal subjects and six heart transplant recipients were studied. Transdiaphragmatic pressure was measured throughout exercise. Accessory respiratory muscle oxygenation was assessed using near-infrared spectroscopy. Peak oxygen consumption, time in inspiration, time per breath and maximal inspiratory and expiratory pressures were measured in all subjects.

RESULTS

The tension time index remained markedly abnormal after heart transplantation both at rest ([mean +/- SD] normal group 0.01 +/- 0.006, heart failure group 0.026 +/- 0.018, transplant group 0.058 +/- 0.015, p < 0.004) and at peak exercise (normal group 0.03 +/- 0.02, heart failure group 0.10 +/- 0.03, transplant group 0.10 +/- 0.04, p < 0.0001). Accessory respiratory muscle deoxygenation was present only in patients with heart failure (near-infrared absorbency changes [arbitrary units]: normal group -3 +/- 6, heart failure group 28 +/- 5, transplant group -3.5 +/- 4.4, p < 0.0001).

CONCLUSIONS

Although heart transplantation alleviates dyspnea in patients with heart failure, the work of breathing as assessed by the tension time index of the diaphragm is not decreased. Amelioration of exertional dyspnea is achieved by other mechanisms, such as improved respiratory muscle perfusion.

Delayed improvement in skeletal muscle metabolism and exercise capacity in patients with mitral stenosis following immediate hemodynamic amelioration by percutaneous transvenous mitral commissurotomy

The abrupt improvement in hemodynamics after successful percutaneous transvenous mitral commissurotomy (PTMC) does not immediately enhance exercise capacity. Improved exercise capacity several months after PTMC has been reported. We hypothesized that the delayed improvement in exercise capacity is due partly to the slow improvement in the metabolism of skeletal muscle. This study examined the short- and long-term effects of PTMC on exercise capacity and skeletal muscle metabolism in patients with mitral stenosis. Treadmill exercise testing with respiratory gas analysis was performed in 11 patients with symptomatic mitral stenosis before and 3, 30, and 90 days after successful PTMC. On the same schedule, forearm metabolism of high-energy phosphates was measured by magnetic resonance spectroscopy during and after handgrip exercise. Ten healthy volunteers were examined. PTMC resulted in an immediate symptomatic improvement. However, exercise capacity and skeletal muscle metabolism remained unchanged 3 days after PTMC. At 30 days after PTMC, there were significant improvements in peak oxygen consumption (p <0.05), intracellular pH at end-exercise (p <0.05), and time constant for phosphocreatine recovery (mean +/- SD 88.9 +/- 11.3 vs 106.3 +/- 11.7 seconds, p <0.01) compared with these baseline values. These improvements remained even at 90 days after PTMC. Exercise capacity improved with some time delay after immediate hemodynamic amelioration by PTMC. Long-term improvement in exercise capacity depends partly on the slowly progressing improvement in skeletal muscle metabolism after long-standing mitral stenosis.

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

STUDY OBJECTIVES

To determine the acute influence of improvement in orifice area in mitral stenosis by percutaneous transluminal valvuloplasty (PTVP) on cardiopulmonary exercise capacity, treadmill walking time (TWT), oxygen uptake parameters at maximum exercise as well as at highest comparable workloads and parameters of breathing work were assessed pre- and post-PTVP.

PATIENTS AND INTERVENTIONS

PTVP was carried out in 16 patients who had moderately severe mitral stenosis, bringing about an average increase in mitral valve orifice area from 1.0 +/- 0.1 cm2 to 2.2 +/- 0.5 cm2 (p < 0.0005). Based on standardized conditions, the patients (six in functional class A, five in class B, and five in class C according to Weber's classification) underwent symptom-limited treadmill cardiopulmonary exercise testing before as well as 2 days after PTVP. In addition, subgroup analysis (eight patients in sinus rhythm, eight patients in atrial fibrillation) was performed to determine a potential influence of the underlying cardiac rhythm on cardiopulmonary exercise parameters. To rule out a PTVP-independent training effect, a control group of ten patients with mitral stenosis underwent the same kind of cardiopulmonary exercise testing on 2 consecutive days.

MEASUREMENTS AND RESULTS

After-PTVP, TWT augmented by 19% (p < 0.0005) in all patients. Maximum oxygen uptake in percent of predicted maximal values at peak exercise and at anaerobic threshold was enhanced by 10% (p < 0.005). Ventilation at highest comparable workload was diminished by 10% (p < 0.025), whereas oxygen uptake and oxygen pulse at highest comparable workload did not differ, reflecting both unaltered cardiac output at comparable workloads and a more economic ventilation, respectively. Furthermore, PTVP-mediated alterations of TWT, but not of oxygen uptake at peak exercise were more pronounced in patients in sinus rhythm than in those in atrial fibrillation, reflecting more effective economization of cardiac work and ventilation in the former subgroup. Except for a statistically significant increase of TWT of 5%, no clinically relevant differences between both exercise tests were found with respect to oxygen uptake in the control group.

CONCLUSIONS

Impaired cardiopulmonary fitness in patients with moderately severe mitral stenosis is improved substantially by PTVP immediately after the intervention, mainly the result of acute reduction of pulmonary congestion and subsequent decrease in dead space to tidal volume ratio. Adherence to standardized conditions is considered crucial for comparability of cardiopulmonary data.

Percutaneous transvenous mitral commissurotomy immediately restores quick response of VO2 to mild exercise despite insignificant increases in peak VO2

Percutaneous transvenous mitral commissurotomy (PTMC) increases peak oxygen uptake (VO2) chronically, but not acutely, despite early symptomatic improvements. Analysis of transient VO2 responses to submaximal exercise (an exercise regimen more comparable to the patients' daily activities than that provided by maximal exercise testing), may be sensitive in detecting the acute hemodynamic benefits of PTMC. Since no methods are available to accurately estimate the transient response of VO2, we developed a new technique, using random exercise. In 15 patients who underwent successful PTMC, we repeated the conventional maximal exercise test and the random exercise test before and within a few days after PTMC. For the random exercise test, we intermittently imposed upright bicycle exercise at 50 W, according to a random binary sequence, while measuring breath-by-breath VO2. After determining the transfer function relating workload to VO2, we computed the high resolution VO2 response to a hypothetical step increase in exercise. Despite improvements in resting hemodynamics and New York Heart Association (NYHA) Class, peak VO2 improved insignificantly (952 +/- 271 vs 1,029 +/- 342 ml/min, P = 0.063) shortly after successful PTMC. In contrast, the amplitude of the VO2 step response increased significantly in the early-to-mid portion (28-76s; P < 0.01-0.05). The remaining portion was unchanged. Consequently, the time constant shortened from 64 +/- 26 to 48 +/- 22s (P < 0.05). The maximal Borg scale value during random exercise decreased significantly (13.1 +/- 1.8 vs 11.4 +/- 1.1; P < 0.01). We conclude that the VO2 step response, using the random exercise test, is more sensitive than peak VO2 in detecting the functional improvement that is coupled with the hemodynamic improvement immediately after PTMC.

Exercise capacity and skeletal muscle structure and function before and after balloon mitral valvuloplasty

This study evaluated the effects of balloon mitral valvuloplasty (BMV) on exercise capacity and skeletal muscle structure and function in 10 subjects with mitral stenosis (mean age +/- SD 33 +/- 5.5). Measurements were obtained before, and 2 weeks and 4 months after BMV to provide baseline data, to examine the effects of improved hemodynamics, and to examine the effects of resumption of normal physical activity, respectively. Valvuloplasty caused an increase in mitral valve area (0.89 +/- 0.04 to 1.75 +/- 0.07 cm2; mean +/- SE), and an increase in resting cardiac output (3.8 +/- 0.18 to 4.6 +/- 0.19 L/min, p < 0.05). At early follow-up after 2 weeks, subjects did more work (31% increase, p < 0.01) and had greater maximal oxygen consumption (11% increase, p < 0.01). However, measurements reflecting skeletal muscle histology, biochemistry, and function were unaltered at this stage. Four months after BMV, subjects had a further increase in exercise capacity compared with both baseline (58% increase, p < 0.01) and early follow-up (20% increase, p < 0.05). There were associated late increases compared with baseline in quadriceps cross-sectional area (66 +/- 5.8 vs 61 +/- 5.5 cm2, p < 0.05) and torque production (125 +/- 14 vs 118 +/- 16 Nm, p < 0.05). The percentage of slow twitch type I fibers increased compared with baseline (41 +/- 2.0% vs 33 +/- 3.1%, p < 0.05), as did the size of type II fibers (5.9 +/- 0.49 vs 4.9 +/- 0.57 microns2 x 10(3), p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of atrial fibrillation on exercise capacity in mitral stenosis

To determine the preoperative and postoperative effect of atrial fibrillation (AF) on exercise capacity in mitral stenosis, 12 digitalized patients in AF (7 women and 5 men, age 52 +/- 6.1 years) and 10 in sinus rhythm (5 women and 5 men, age 46 +/- 5 years) underwent maximal cardiopulmonary exercise testing according to Weber's protocol and Doppler echocardiographic examination before and at 3 and 6 months after mitral valve replacement. The ratio of right ventricular acceleration to ejection time was used as an estimate of mean pulmonary artery pressure. Preoperative exercise duration (6.8 +/- 1 vs 8 +/- 2 minutes), peak oxygen consumption (9.7 +/- 3 vs 12.3 +/- 3 ml/kg/min), and right ventricular acceleration to ejection time ratio (0.34 +/- 0.07 vs 0.34 +/- 0.08) were not significantly different between patients with AF and those in sinus rhythm. Postoperative improvement in these parameters was lower in patients with AF than in those in sinus rhythm: exercise duration at 3 months, 7.5 +/- 2 vs 11.9 +/- 2 minutes (p < 0.001); at 6 months, 9 +/- 2 vs 12 +/- 2 minutes (p < 0.001); peak oxygen consumption at 3 months, 10.8 +/- 3 vs 17.5 +/- 3 ml/kg/min (p < 0.001); and at 6 months, 11.9 +/- 3 vs 17.8 +/- 3 ml/kg/min (p < 0.001); right ventricular acceleration to ejection time ratio at 3 months, 0.35 +/- 0.08 vs 0.42 +/- 0.05 (p < 0.05); and at 6 months, 0.38 +/- 0.05 vs 0.44 +/- 0.05 (p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Pulmonary factors limiting exercise capacity in patients with heart failure

Patients with heart failure are frequently limited by exertional dyspnea. The mechanisms underlying dyspnea in these patients remain unclear. In this review, the pathologic changes that occur in the lung as a consequence of chronic pulmonary venous hypertension, pulmonary function test abnormalities, and potential mechanisms for dyspnea including airflow obstruction and/or respiratory muscle dysfunction are discussed.

Comparison of results of percutaneous balloon valvuloplasty in patients with mild and moderate mitral stenosis to those with severe mitral stenosis. The North American Inoue Balloon Investigators

Most reported studies of percutaneous balloon valvuloplasty in adults with acquired mitral stenosis have used patients with severely stenosed valves. The risks and benefits of valvuloplasty were examined in a multicenter registry of patients to determine whether balloon valvuloplasty can effectively dilate less severely obstructed valves, and to clarify the role of this procedure in symptomatic patients with mild and moderate mitral stenosis. The study groups were derived from the North American Inoue Balloon Valvuloplasty Registry. Full hemodynamic data were available in 264 patients; 45 (17%) with mild or moderate mitral stenosis (mitral valve area > or = 1.3 cm2) were compared with the remaining 219 with severe mitral stenosis (valve area < 1.3 cm2). Percutaneous balloon valvuloplasty was performed using the anterograde transseptal technique with an Inoue balloon. The mean age of patients with mild and moderate mitral stenosis was 53 +/- 13 years, and all were symptomatic with a mean New York Heart Association functional class of 2.9 +/- 0.7. Balloon valvuloplasty resulted in an increase in calculated mitral valve area from 1.4 +/- 0.1 to 2.3 +/- 0.7 cm2 (p < 0.05), and a final valve area > or = 1.9 cm2 was achieved in 37 patients (82%). There were no procedural deaths, but complications included right atrial perforation, transient ischemic attack and emergency surgery for severe mitral regurgitation. One-year follow-up evaluation revealed symptomatic improvement in most patients (mean New York Heart Association class 1.4 +/- 0.6; p < 0.0001). However, 2 patients needed repeat valvuloplasty for restenosis, and 5 had mitral valve replacements.(ABSTRACT TRUNCATED AT 250 WORDS)