Echo derived variables predicting exercise tolerance in patients with dilated and poorly functioning left ventricle.
(1/1872)
OBJECTIVE: To determine whether resting echo derived measurements predict exercise tolerance and its interrelation with heart rate response and ventilation drive in patients with systolic left ventricular disease. DESIGN: Prospective echocardiographic examination followed by cardiopulmonary exercise testing. SETTING: A tertiary referral centre for cardiac diseases. SUBJECTS: 21 patients (11 with coronary artery disease, 10 with idiopathic dilated cardiomyopathy) with end diastolic dimension > 6.4 cm, shortening fraction < 25%, and in sinus rhythm. There were 11 age matched normal controls. RESULTS: In the patients, peak oxygen consumption (mVo2) correlated with right ventricular long axis excursion (r = 0.62); 65% of the variance in mVo2 was predictable using a multivariate model with right ventricular long axis excursion and peak lengthening rate, and peak mitral atrial filling velocity as independent variables. Aetiology was not an independent predictor, although the right ventricular long axis excursion (mean (SD)) was greater in patients with idiopathic dilated cardiomyopathy than in those with coronary artery disease (2.4 (0.5) cm v 1.6 (0.5) cm, p < 0.001). Peak heart rate correlated with duration of mitral regurgitation (r = -0.52) and the slope of ventilation against CO2 production correlated with M mode isovolumic relaxation time (r = 0.61). CONCLUSIONS: In patients with systolic left ventricular dysfunction, more than half the variance in exercise tolerance can be predicted by factors measured on echocardiography at rest, particularly right ventricular long axis excursion. (+info)
Cardiac metaiodobenzylguanidine uptake in patients with moderate chronic heart failure: relationship with peak oxygen uptake and prognosis.
(2/1872)
OBJECTIVES: This prospective study was undertaken to correlate early and late metaiodobenzylguanidine (MIBG) cardiac uptake with cardiac hemodynamics and exercise capacity in patients with heart failure and to compare their prognostic values with that of peak oxygen uptake (VO2). BACKGROUND: The cardiac fixation of MIBG reflects presynaptic uptake and is reduced in heart failure. Whether it is related to exercise capacity and has better prognostic value than peak VO2 is unknown. METHODS: Ninety-three patients with heart failure (ejection fraction <45%) were studied with planar MIBG imaging, cardiopulmonary exercise tests and hemodynamics (n = 44). Early (20 min) and late (4 h) MIBG acquisition, as well as their ratio (washout, WO) were determined. Prognostic value was assessed by survival curves (Kaplan-Meier method) and uni- and multivariate Cox analyses. RESULTS: Late cardiac MIBG uptake was reduced (131+/-20%, normal values 192+/-42%) and correlated with ejection fraction (r = 0.49), cardiac index (r = 0.40) and pulmonary wedge pressure (r = -0.35). There was a significant correlation between peak VO2 and MIBG uptake (r = 0.41, p < 0.0001). With a mean follow-up of 10+/-8 months, both late MIBG uptake (p = 0.04) and peak VO2 (p < 0.0001) were predictive of death or heart transplantation, but only peak VO2 emerged by multivariate analysis. Neither early MIBG uptake nor WO yielded significant insights beyond those provided by late MIBG uptake. CONCLUSIONS: Metaiodobenzylguanidine uptake has prognostic value in patients with wide ranges of heart failure, but peak VO2 remains the most powerful prognostic index. (+info)
Diagnostic utility of metabolic exercise testing in a patient with cardiovascular disease.
(3/1872)
Disproportionate exercise limitation in patients with cardiovascular disease is a common problem faced by clinical cardiologists and other physicians. Symptoms may be attributed to psychological factors or hypothetical pathophysiological mechanisms that are difficult to confirm clinically. This case report describes how the use of metabolic exercise testing in a 28 year old woman with morphologically and haemodynamically mild hypertrophic cardiomyopathy and severe exercise limitation led to the diagnosis of an alternative cause for the patient's symptoms, namely a primary disturbance of the mitochondrial respiratory chain probably caused by a nuclear encoded gene defect. (+info)
Effect of thoracotomy and lung resection on exercise capacity in patients with lung cancer.
(4/1872)
BACKGROUND: Resection is the treatment of choice for lung cancer, but may cause impaired cardiopulmonary function with an adverse effect on quality of life. Few studies have considered the effects of thoracotomy alone on lung function, and whether the operation itself can impair subsequent exercise capacity. METHODS: Patients being considered for lung resection (n = 106) underwent full static and dynamic pulmonary function testing which was repeated 3-6 months after surgery (n = 53). RESULTS: Thoracotomy alone (n = 13) produced a reduction in forced expiratory volume in one second (FEV1; mean (SE) 2.10 (0.16) versus 1.87 (0.15) l; p<0.05). Wedge resection (n = 13) produced a non-significant reduction in total lung capacity (TLC) only. Lobectomy (n = 14) reduced forced vital capacity (FVC), TLC, and carbon monoxide transfer factor but exercise capacity was unchanged. Only pneumonectomy (n = 13) reduced exercise capacity by 28% (PVO2 23.9 (1.5) versus 17.2 (1.7) ml/min/kg; difference (95% CI) 6.72 (3.15 to 10.28); p<0.01) and three patients changed from a cardiac limitation to exercise before pneumonectomy to pulmonary limitation afterwards. CONCLUSIONS: Neither thoracotomy alone nor limited lung resection has a significant effect on exercise capacity. Only pneumonectomy is associated with impaired exercise performance, and then perhaps not as much as might be expected. (+info)
Validity of a modified shuttle test in adult cystic fibrosis.
(5/1872)
BACKGROUND: The purpose of this study was to provide some evidence of the validity of a modified shuttle test (MST) by comparing performance on the MST with peak oxygen consumption (VO2peak) measured during a treadmill test in a group of adult patients with cystic fibrosis. METHOD: Twenty patients with stable cystic fibrosis performed a ramped maximal treadmill test (STEEP protocol) and the MST using a randomised balanced design. RESULTS: The relationship between the distance achieved on the MST and VO2peak was strong (r = 0.95, p<0.01) with 90% of the variance in VO2peak explained by the variance in MST distance. The relationship was represented by the regression equation (with 95% confidence intervals) VO2peak = 6.83 (2.85 to 10.80) + 0.028 (0.019 to 0.024) x MST distance. CONCLUSION: This study provides evidence of the construct validity of the MST as an objective measure of exercise capacity in adults with cystic fibrosis. (+info)
Effects of L-arginine on lower limb vasodilator reserve and exercise capacity in patients with chronic heart failure.
(6/1872)
OBJECTIVE: To determine whether the reactive hyperaemic response of the lower limb increases with improved exercise capacity after acute supplementation with L-arginine, the precursor of nitric oxide, in patients with chronic heart failure. METHODS: 19 patients with chronic heart failure were enrolled in the study. Rest calf blood flow and femoral occlusion induced calf blood flow changes were measured by venous occlusion plethysmography before and after intravenous infusion of 10% L-arginine solution (5 ml/kg for 30 minutes) or placebo. Postexercise calf blood flow was also measured after the experimental infusion. During both postinfusion periods, several exercise capacity indices were determined by a symptom limited cardiopulmonary exercise test using a bicycle ergometer. RESULTS: Baseline calf blood flow, systemic blood pressure, and heart rate showed no significant changes in either of the two experimental conditions. However, the occlusion induced blood flow response was significantly enhanced by L-arginine infusion (mean (SEM) peak flow, 19.6 (1.5) v 28.9 (3.1) ml/min/dl calf tissue; p < 0.01), but not by placebo (peak flow, 19.1 (1.4) v 20.9 (1.8) ml/min/dl calf tissue; NS). Calf blood flow response after exercise was also higher after L-arginine infusion than after placebo (peak flow, 4.8 (0.4) v 6.0 (0.8) ml/min/dl calf tissue; p < 0.05). L-arginine infusion had no significant effect compared with placebo on exercise capacity indices such as peak oxygen uptake (17.1 (1.0) v 15.8 (1.1) ml/min/kg; NS), anaerobic threshold (10.5 (0.6) v 10.4 (0.7) ml/min/kg; NS), and exercise time (296 (23) v 283 (22) s; NS). CONCLUSIONS: Acute supplementation with the nitric oxide precursor L-arginine increased lower limb reactive hyperaemia but did not lead to any significant improvement in exercise capacity in patients with chronic heart failure. (+info)
Ventricular dilatation in the absence of ACE inhibitors: influence of haemodynamic and neurohormonal variables following myocardial infarction.
(7/1872)
OBJECTIVE: To examine the relation between patterns of ventricular remodelling and haemodynamic and neurohormonal variables, at rest and during symptom limited exercise, in the year following acute myocardial infarction in patients not receiving angiotensin converting enzyme (ACE) inhibitors. DESIGN: A prospective observational study. PATIENTS: 65 patients recruited following hospital admission with a transmural anterior myocardial infarction. METHODS: Central haemodynamics and neurohormonal activation at rest and during symptom limited treadmill exercise were measured at baseline before hospital discharge, one month later, and at three monthly intervals thereafter. PATIENTS were classified according to individual patterns of change in left ventricular end diastolic volumes at rest, assessed at each visit using transthoracic echocardiography. RESULTS: In most patients (n = 43, 66%) ventricular volumes were unchanged or reduced. Mean (SEM) treadmill exercise capacity and peak exercise cardiac index increased at month 12 by 200 (24) seconds (p < 0.001 v baseline) and by 0.8 (0.4) l/min/m2 (p<0.05 v baseline), respectively, in this group. In patients with limited ventricular dilatation (n = 11, 17%) exercise capacity increased by 259 (52) seconds (p < 0.001 v baseline) and peak exercise cardiac index improved by 0.8 (0.7) l/min/m2 (NS). In the remaining 11 patients with progressive left ventricular dilatation, exercise capacity increased by 308 (53) seconds (p< 0. 001 v baseline) and peak exercise cardiac index similarly improved by 1.3 (0.7) l/min/m2 (NS). There were trends towards increased atrial natriuretic factor (ANF) secretion at rest and at peak exercise in this group. CONCLUSIONS: Ventricular dilatation after acute myocardial infarction is a heterogeneous process that is progressive in only a minority of patients. Compensatory mechanisms, including ANF release, appear capable of maintaining and improving exercise capacity in most patients for at least 12 months, even in those with a progressive increase in ventricular size. (+info)
Physiological basis of improvement after lung volume reduction surgery for severe emphysema: where are we?
(8/1872)
Lung volume reduction surgery has become an accepted therapeutic option to relieve the symptoms of selected patients with severe emphysema. In a majority of these patients, it causes objective as well as subjective functional improvement. A proper understanding of the physiological determinants underlying these beneficial effects appears very important in order to better select patients for the procedure that is currently largely carried out on an empirical basis. Lung volume reduction surgery has two distinct effects. Firstly, it causes an increased elastic recoil, which at least partially explains the enhanced maximal expiratory flow. Secondly, it is associated with a reduction of hyperinflation which allows for an increase in global inspiratory muscle strength and in diaphragmatic contribution to tidal volume as well as a decrease in the inspiratory elastic load imposed by the chest wall. Taken together, these effects result in a reduced work of breathing and in an enhanced maximal ventilation which both contribute to the increased exercise capacity and reduced dyspnoea after surgery. The improved lung recoil and the reduced hyperinflation after volume reduction surgery were the primary postulates upon which the usual selection criteria for the procedure were based. It is now likely that these are correct. Nevertheless, some patients do not benefit from lung volume reduction surgery and the current literature does not allow for a refinement of the selection process from a physiological point of view. The exact mechanisms underlying the improvement in lung recoil, lung mechanics, and respiratory muscle function remain incompletely understood. Moreover, the effects of lung volume reduction surgery on gas exchange and pulmonary haemodynamics still need to be more fully investigated. An analysis of the characteristics of patients who do not benefit from the procedure and the development of an animal model for lung volume reduction surgery would probably help address these important issues. (+info)