Combining low-intensity and maximal exercise test results improves prognostic prediction in chronic heart failure

OBJECTIVES: This study investigated the combination of maximal and low-intensity exercise testing in predicting prognosis in chronic heart failure (CHF), using one single exercise test (two-step protocol). BACKGROUND: Risk assessment based on any single factor has limited accuracy and reproducibility. METHODS: Treadmill exercise testing was performed in 202 consecutive CHF patients (174 male; mean age 52 +/- 11 years) using "breath-by-breath" gas exchange monitoring. Oxygen uptake (VO(2)) kinetics were defined as oxygen deficit (DeltaVO(2) x time [rest to steady state] - Sigma VO(2) [rest to steady state]) and mean response time (MRT = oxygen-deficit/DeltaVO(2)). Peak VO(2) (VO(2)max) was defined as the highest VO(2). Mean follow-up was 873 +/- 628 days. The primary end point was cardiac mortality and the need for urgent heart transplantation. RESULTS: Forty-four patients (22%) died and 15 (7%) were urgently transplanted. In both univariate and multivariate analyses, MRT >50 s was the most powerful predictor of the primary end point (hazard ratio [HR] 4.44), followed by predicted VO(2)max <50% (HR 3.50) and resting systolic blood pressure <105 mm Hg (HR 2.49, all p < 0.001). A majority (n = 130 [64%]) had one or none of these risk factors, with a one-year event rate of only 3%. Patients with two risk factors (n = 45 [22%]) were at medium risk (one-year event rate of 33%). Twenty-seven patients (13%) had all three risk factors, with a one-year event rate of 59%. The area under the curve, using the number of risk factors, was 0.86 +/- 0.04 for the primary end point at one year. These results were independent of medication, in particular, beta-blockade. CONCLUSIONS: A combination of low-intensity and maximal exercise test results improves assessment of prognosis in patients with CHF.     

Cardiopulmonary exercise test for evaluating cardiac reserve in chronic congestive heart failure]

To evaluate whether maximal oxygen consumption (VO2 max) measured by cardiopulmonary exercise test (CAR-PET) reflects cardiac reserve in patients with congestive heart failure (CHF), supine bicycle CAR-PET and exercise hemodynamic measurements were performed simultaneously in 12 patients with CHF of NYHA II-IV. With increasing workload, VO2 and cardiac output elevated gradually, then plateaued, demonstrating that patients with CHF could reach VO2max. According to VO2max, patients were divided into 4 classes: including 2 patients of class A (VO2max: 24.5 +/- 2.29 ml.min-1/kg, mean +/- s mean), 3 of B (17.6 +/- 1.37 ml.min-1/kg), 5 of C (13.6 +/- 0.66 ml.min-1/kg) and 2 of D (6.5 +/- 1.64 ml.min-1/kg). Maximal cardiac indices were 8.79 +/- 2.35 L.min-1/m2 in class A, 5.82 +/- 0.97 L.min-1/m2 in B, 3.53 +/- 0.95 L.min-1/m2 in C and 2.21 +/- 1.56 L.min-1/m2 in D. No significant correlation between supine resting hemodynamic parameters and VO2max/kg was found, suggesting that exercise tolerance could not be predicted by the measurement of resting cardiac performance. Furthermore, VO2max correlated poorly with NYHA classification in these patients. However, cardiac output correlated linearly with VO2 during exercise, suggesting that VO2 max/kg is a good predictor for cardiac reserve in CHF(CI = 0.6809 +/- 0.2748 VO2/kg, n = 40, r = 0.84, P < 0.0001; CO = 1.1618 +/- 7.9065 VO2, n = 40, r = 0.84, P < 0.0001). The results also showed that VO2max/kg did not correlate with the changes of pulmonary capillary wedge pressure (PCWP), indicating that exercise tolerance in CHF depends more on cardiac output than on ventilatory consequence of pulmonary congestion.(ABSTRACT TRUNCATED AT 250 WORDS)     

Arrhythmias during acute and chronic exercise in chronic heart failure

Exercise can induce or prevent arrhythmias depending upon several factors, related to patient’s clinical characteristics and to exercise modalità (type, intensità, frequency, duration). In the present paper, the author reviews the mechanisms of arrhythmias during acute and chronic exercise in heart failure, and focuses on the relationship between exercise training programs and arrhythmias in chronic heart failure.     

有氧运动治疗慢性心力衰竭

慢性心力衰竭是各种心脏疾病导致心功能不全的最终结局.近年来有氧运动疗法对慢性心力衰竭的治疗逐渐受到重视.慢性心力衰竭的治疗模式已由原来的药物治疗发展到药物-运动治疗模式[1,2].     

步行试验对老年慢性心力衰竭患者运动耐量的评估

目的探讨6 min步行试验(6MWT)对老年慢性心力衰竭(CHF)患者运动耐量的评价.方法将54例CHF患者随机分为常规治疗组(n=25)和卡维地洛组(n=29),治疗前后进行步行试验,监测肿瘤坏死因子(TNF-α)、白细胞介素6(IL-6)、去甲肾上腺素(NE)和左室射血分数(LVEF).结果心功能Ⅳ级患者较Ⅱ级患者步行距离明显下降(P<0.01),Ⅲ级与Ⅱ级、Ⅳ级与Ⅲ级患者之间步行距离的差异无显著性意义(P>0.05);卡维地洛组6 min步行距离治疗前后差异有显著性意义(P<0.01), 而常规治疗组差异无显著性意义(P>0.05),两组患者步行距离与TNF-α、IL-6、NE呈显著负相关(P<0.05),与LVEF呈正相关(P<0.05).结论6MWT具有简单、易行、安全、可靠的特点,可作为评估CHF患者运动耐量的临床工具,尤其适用于老年患者,同时可提供一定的判断CHF预后及治疗效果的信息.     

Predictors of exercise capacity in chronic heart failure

Abnormalities of skeletal muscle rather than of haemodynamicsmay be important determinants of exercise capacity in chronicheart failure. We investigated an array of indicators of centralhaemodynamics and peripheral muscle function to establish whichresting measurements predicted exercise performance. In 20 patients quadriceps strength, resting and peak leg bloodflow and leg muscle cross sectional area were measured. In 18patients average daytime blood pressure and pulse rate, haemodynamicvariables at rest and during exercise, and autonomic activitywere measured. There were correlations between peak oxygen consumptionand quadriceps strength (0.65; P=0.007), thigh muscle crosssectional area (r=0.63; P=0.004), and average daytime systolicblood pressure (r=0.66; P<0.01). There were no correlationswith indices of peripheral blood flow, measures of haemodynamicfunction, or autonomic function. Quadriceps strength was themost important individual correlate of exercise tolerance (r=0.73).With total muscle cross sectional area and left quadriceps strengthalso taken into consideration, 82% of the variation in peakoxygen consumption was explained. Of the haemodynamic variables,only average daytime systolic blood pressure predicted exerciseperformance. The resting variables that best predict exercise performancein chronic heart failure are measures of skeletal muscle functionand bulk, and average daytime systolic blood pressure. Thesefindings suggest that abnormalities in the periphery largelydetermine exercise performance in chronic heart failure, andthat the ability of the heart to generate an adequate bloodpressure response to daily activities is also predictive offunctional status.     

心力衰竭患者的运动康复

心力衰竭是多种心血管疾病终末期的共同转归,临床症状重,死亡率较高,给个人及社会造成重大负担.心脏康复可提供综合性干预治疗,其中运动锻炼部分日益受到重视.本文重点介绍运动锻炼产生效应的可能机制,并对其实施和评估作一综述.     

Assessment of exercise tolerance in chronic congestive heart failure

In patients with chronic heart failure, exercise capacity is poorly related to cardiac hemodynamics, and peripheral circulation is an important determinant of exercise tolerance. The ability of the muscle vasculature to dilate is markedly impaired, in part, because of exaggerated neurohumoral activity increasing vascular wall stiffness. For this reason, increasing cardiac output is not sufficient to increase exercise capacity if not accompanied by improving vascular reactivity. The poor reliability and reproducibility of exercise tolerance assessed by maximal exercise duration or maximal attained work load (particularly on a treadmill) has led to widespread measurement of respiratory gas during exercise. Peak oxygen consumption (peak VO2), even if it is symptom-limited, has been shown to be a very reproducible criterion of exercise tolerance; moreover, because VO2 is the product of cardiac output and arteriovenous oxygen difference, it also has a qualitative hemodynamic significance. Ventilatory threshold can be determined before maximal exercise; however, problems of determination limit the practical value of this criterion. Unfortunately, peak VO2 lacks sensitivity to detect minor improvement or impairment of symptoms during daily life, although these are significant to the patient. Submaximal exercises have been proposed for this purpose and are currently being evaluated.     

Work-rate affects cardiopulmonary exercise test results in heart failure

AIMS: Cardiopulmonary exercise test (CPET) is used to evaluate patients with chronic heart failure (HF) usually by means of a personalized ramp exercise protocol. Our aim was to evaluate if exercise duration or ramp rate influences the results. METHODS AND RESULTS: Ninety HF patients were studied (peak V (O(2)): >20 ml/min/kg, n=28, 15-20 ml/min/kg, n=39 and <15 ml/min/kg, n=23). Each patient did four CPET studies. The initial study was used to separate the subjects into three groups, according to their exercise capacity. In the remaining studies, work-rate was increased at three different rates designed to have the subjects reach peak exercise in 5, 10 and 15 min from the start of the ramp increase in work-rate, respectively. The order was randomized. The work-rate applied for the total population averaged 22.7+/-8.0, 11.6+/-3.7, 7.5+/-2.9 W/min with effective loaded exercise duration of 5 min and 16 s+/-29 s, 9 min and 43 s+/-49 s and 14 min and 32 s+/-1 min and 12 s for the 5-, 10- and 15-min tests, respectively. Peak V (O(2)) averaged 16.9+/-4.3*, 18.0+/-4.4 and 18.0+/-5.4 ml/min/kg for the 5-, 10- and 15-min tests, (*=p<0.001 vs. 10 min). The shortest test had the lowest peak heart rate and ventilation and highest peak work-rate. Peak V (O(2)) and heart rate were lowest in 5-min tests regardless of HF severity. The DeltaV (O(2))/Deltawork-rate was lowest in 5-min tests and highest in 15-min tests. At all ramp rates, DeltaV (O(2))/Deltawork-rate was lower for the subjects with the lower peak V (O(2)). The V (e)/V (CO(2)) slope and V (O(2)) at anaerobic threshold were not affected by the protocol for any grade of HF. CONCLUSIONS: In chronic HF, exercise protocol has a small effect on peak V (O(2)) and DeltaV (O(2))/Deltawork but does not affect V (O(2)) at anaerobic threshold and V (e)/V (CO(2)) slope.     

Excess ventilation during exercise and prognosis in chronic heart failure

Excess ventilation during exercise with accompanying dyspnea is characteristic of chronic heart failure (CHF), and these patients often exhibit increased Ve relative to the Vco(2) compared with normal subjects. This can be measured in several ways, including using such variables as the slope of Ve versus Vco(2), the lowest ratio of Ve/Vco(2), and the ratio of Ve/Vco(2) at the lactic acidosis threshold or peak exercise. There is now considerable evidence that the degree of excess ventilation during exercise in patients with CHF is a robust predictor of outcome and identifies higher-risk patients requiring aggressive treatment, including heart transplantation. The mechanism of excess ventilation in patients with CHF during exercise is not completely understood. It may be related to enhanced output of chemoreceptors or peripheral muscle ergoreceptors, increased dead space/Vt ratio due to increased contribution of high ventilation-perfusion lung regions or rapid shallow breathing caused by earlier onset of lactic acidosis, or likely resulting from a combination of these causes.     

Role of endothelin in the exercise intolerance of chronic heart failure

In conclusion, plasma levels of the endothelialderived vasoconstrictor endothelin-1 (but not those of other neurohormonal vasoconstrictor factors), measured during exercise correlated closely with objective variables of exercise capacity in patients with heart failure. These findings suggest that endothelin-1 may contribute to exercise intolerance in patients with heart failure, perhaps by limiting the ability of the peripheral vasculature to dilate during exercise.