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

Investigation of Skeletal Muscle Indices Affecting Anaerobic Thresholds after Acute Myocardial Infarction

OBJECTIVE

To investigate skeletal muscle indices influencing the anaerobic threshold (AT) measured by cardiopulmonary exercise testing (CPX).

METHODS

This study included 125 consecutive men (median age: 66.0 years) diagnosed with acute myocardial infarction who underwent CPX before discharge. Participants were categorized into two groups based on their AT: the AT-lowering and AT-maintaining groups, comprising those with AT <11 and ≥11 ml/min/kg, respectively. Skeletal muscle indices that influenced AT, strengths of such influences, and respective cutoff values were investigated using multiple logistic regression analysis, decision-tree analysis, and the random-forest method. Skeletal muscle indices included grip strength, knee extension strength, lower-limb skeletal muscle index, phase angle (PhA), lower-limb PhA, arm circumference (AC), and calf circumference.

RESULTS

Lower-limb PhA, AC, age, and body mass index (BMI) influenced AT (model X2 test: p <0.05; Hosmer-Lemeshow test: p = 0.98). Among the skeletal muscle indices, Gini impurity reduction was the highest in the lower-limb PhA. The cutoff values for AT were ≥4.0° for BMI <24 kg/m2 and ≥6.4° for BMI ≥24 kg/m2.

CONCLUSION

Lower-limb PhA was the most influential skeletal muscle index affecting AT. PhA measured using body composition analyzers is useful to identify exercise-limiting factors and determine the effectiveness of exercise because it can be easily performed shortly.

Effects of cardiac rehabilitation on physical function and exercise capacity in elderly cardiovascular patients with frailty

BACKGROUND

The effects of cardiac rehabilitation (CR) on long-term prognosis of cardiovascular disease (CVD) are well known. However, the effect of CR on frail CVD patients has not been fully addressed.

METHODS

This study consisted of 89 CVD patients with their age ≥65 years old (68 males, 75 ± 6 years), who participated in the outpatient CR program for 3 months. All the patients underwent cardiopulmonary exercise testing and the physical frailty was assessed using the Japanese Version of the Cardiovascular Health Study Standard before and after CR. Based on the assessment of frailty before CR, the patients were divided into the following two groups: frailty group (n = 23) and non-frailty group (n = 66: robust in 10 and pre-frail in 56 patients).

RESULTS

In the frailty group, 20 patients (87%) improved from frail status after CR, and usual walking speed, maximal grip strength, and lower extremity strength were significantly improved (1.06±0.20 vs. 1.20±0.18 m/sec, p<0.001; 21.7 ± 5.5 vs. 23.6 ± 6.3 kg, p<0.01; 0.37±0.09 vs. 0.43±0.11 kgf/kg, p = 0.001, respectively), but peak VO₂ did not change after CR (15.9 ± 3.1 vs. 16.2 ± 3.8 ml/min/kg, NS). In the non-frailty group, all these parameters were significantly improved after CR (1.24±0.19 vs. 1.29±0.23 m/sec, p<0.05, 28.7 ± 7.0 vs. 30.2 ± 7.3 kg, p<0.001, 0.50±0.18 vs. 0.54±0.13 kgf/kg, p<0.05, 17.7 ± 4.7 vs 18.5 ± 4.2 ml/min/kg, p<0.01, respectively).

CONCLUSION

Short-term CR could obtain the improvement of the physical function, providing the prerequisite step for possibly following improvement of exercise capacity in elderly CVD patients with frailty. It may be inferred that longer duration of CR would be needed to obtain the improvement of exercise capacity in these patients, being the future consideration to be determined.

Abnormalities of Skeletal Muscle, Adipocyte Tissue, and Lipid Metabolism in Heart Failure: Practical Therapeutic Targets

Chronic diseases, including heart failure (HF), are often accompanied with skeletal muscle abnormalities in both quality and quantity, which are the major cause of impairment of the activities of daily living and quality of life. We have shown that skeletal muscle abnormalities are a hallmark of HF, in which metabolic pathways involving phosphocreatine and fatty acids are largely affected. Not only in HF, but the dysfunction of fatty acid metabolism may also occur in many chronic diseases, such as arteriosclerosis, as well as through insufficient physical exercise. Decreased fatty acid catabolism affects adenosine triphosphate (ATP) production in mitochondria, via decreased activity of the tricarboxylic acid cycle; and may cause abnormal accumulation of adipose tissue accompanied with hyperoxidation and ectopic lipid deposition. Such impairments of lipid metabolism are in turn detrimental to skeletal muscle, which is hence a chicken-and-egg problem between skeletal muscle and HF. In this review, we first discuss skeletal muscle abnormalities in HF, including sarcopenia; particularly their association with lipid metabolism and adipose tissue. On the other hand, the precise mechanisms involved in metabolic reprogramming and dysfunction are beginning to be understood, and an imbalance of daily nutritional intake of individuals has been found to be a causative factor for the development and worsening of HF. Physical exercise has long been known to be beneficial for the prevention and even treatment of HF. Again, the molecular mechanisms by which exercise promotes skeletal muscle as well as cardiac muscle functions are being clarified by recent studies. We propose that it is now the time to develop more “natural” methods to prevent and treat HF, rather than merely relying on drugs and medical interventions. Further analysis of the basic design of and molecular mechanisms involved in the human body, particularly the inextricable association between physical exercise and the integrity and functional plasticity of skeletal and cardiac muscles is required.

Respiratory muscle strength in rheumatic mitral stenosis improves after balloon valvotomy

BACKGROUND

Dyspnea is a common symptom in a patient with valvular heart disease. The mechanism underlying this disease is still uncertain. Respiratory muscle weakness has been proposed to be one of the mechanisms underlying dyspnea in heart failure, but this has not been adequately studied in valvular heart disease.

METHODS

We prospectively studied 20 patients with rheumatic mitral valve stenosis who were candidates for percutaneous balloon mitral valvotomy. Respiratory muscle strength assessment by maximal static inspiratory mouth pressure and maximal static expiratory mouth pressure was done on all patients at baseline and at 1 week after the procedure. The severity of dyspnea in study participants was also studied by the 6-min walk test and visual analog scale.

RESULTS

Balloon valvotomy was followed by a significant improvement in the 6-min walking distance (from 219 +/- 30.15 to 237.55 +/- 32.25 m, P < 0.001), visual analog scale as a measure of dyspnea (from 60.95 +/- 12.16 to 44.4 +/- 13.71 mm, P < 0.001), inspiratory muscle strength (from 51.9 +/- 10.28 to 56.55 +/- 11.87 cmH2O, P < 0.001) and expiratory muscle strength (from 62.15 +/- 19.68 to 67.20 +/- 21.91 cmH2O, P < 0.001).

CONCLUSION

Improvement in dyspnea in mitral stenosis after balloon valvotomy is associated with significant improvement in respiratory muscle strength.

Daily exercise and bone marrow-derived CD34+/133+ cells after myocardial infarction treated by bare metal stent implantation

BACKGROUND

The aims of the present study were to explore the mobilization of bone marrow-derived CD34(+)/133(+) cells in patients with acute myocardial infarction (AMI) and bare metal stent implantation who participated in daily exercise training, and associations with exercise capacity and restenosis.

METHODS AND RESULTS

Participants comprised 23 Japanese men with AMI (Killip 1) who had been treated with a bare metal stent. All patients were advised to walk for 30-60 min/day, at least 4 times per week starting at 11 days after AMI, and were instructed to record the amount of time spent walking each day. At 10 days and then at 3 months after onset of AMI, symptom-limited cardiopulmonary exercise tests were performed and the number of CD34(+)/133(+) cells in the peripheral blood were measured by fluorescence-activated cell sorter analysis. At 3 months after AMI, the number of CD34(+)/133(+) cells and oxygen consumption at anaerobic threshold were higher in the high exercise group (ie, exercise duration >4 h/week) than the low exercise group (ie, exercise duration <2 h/week). At 3 months after AMI, the number of CD34(+)/133(+) cells significantly correlated with oxygen consumption at the anaerobic threshold (p=0.002).

CONCLUSION

Moderate daily exercise of >4 h/week increases exercise capacity and the number of circulating CD34(+)/133(+) cells at 3 months after AMI.

Mechanism of improvement in exercise capacity after the maze procedure combined with mitral valve surgery

OBJECTIVE

To clarify the mechanism of improvement in exercise capacity after the maze procedure.

DESIGN

Retrospective study.

SETTING

Tertiary referral centre.

PATIENTS

26 patients (mean (SD) age 57 (9) years) with atrial fibrillation (AF) and mitral valve disease were studied with echocardiography and cardiopulmonary exercise testing before and after the maze procedure combined with mitral valve surgery. Of these, eight had persistent AF and 18 had restored sinus rhythm (SR) by the surgery. Six patients (mean (SD) age 59 (12) years) with AF undergoing mitral valve surgery without the maze procedure who had cardiopulmonary exercise testing before and after the surgery formed the control group.

MAIN OUTCOME MEASURES

Echocardiographic parameters of atrial function were measured from transmitral flow recordings. Peak oxygen uptake (VO2) and the slope of the relation between VO2 and workload (ratio of DeltaVO2 to Delta work) were determined as indices of exercise capacity.

RESULTS

The degree of improvements in peak VO2 and the ratio of DeltaVO2 to Delta work after the mitral valve surgery was comparable between the maze and control group. It was also comparable between patients with and those without successfully restored SR after the maze procedure. The degree of the increase in peak VO2 correlated with the change in left atrial diameter (r = -0.40, p = 0.047) but atrial contraction did not correlate with the increase.

CONCLUSIONS

Improvement in exercise capacity may not be caused by restored SR and atrial contraction but may at least partly relate to the reduction of left atrial size and improvement of haemodynamic variables by the surgery.

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.

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.

Phospholamban deficiency does not compromise exercise capacity

Deficiency of phospholamban (PLB) results in enhancement of basal murine cardiac function and an attenuated response to beta-adrenergic stimulation. To determine whether the absence of PLB also reduces the reserve capacity of the murine cardiovascular system to respond to stress, we evaluated the heart rate (HR), blood pressure, and metabolic responses of PLB-deficient (PLB-/-) mice to graded treadmill exercise (GTE). PLB-/- mice were hypertensive at rest (125 +/- 19 vs. 109 +/- 16 mmHg, P < 0.05) but had normal tachycardic and hypotensive responses to isoproterenol. The HR response to GTE was normal; however, the hypertension in PLB-/- mice normalized at peak exercise. Their exercise capacities, as measured by duration of exercise and peak oxygen consumption (VO2), were normal. The oxygen pulse (VO2/HR) curve was also normal in PLB-/- mice, suggesting an ability to appropriately increase stroke volume and oxygen extraction during GTE, despite an inability to increase beta-adrenergically stimulated cardiac contractility. Thus deficiency of PLB, although resulting in diminished beta-adrenergic inotropic reserve, does not compromise cardiac performance during exercise.

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.