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European Heart Journal (2001) 22, 627–628 doi:10.1053/euhj.2000.2457, available online at http://www.idealibrary.com on How do you measure exercise capacity in chronic heart failure? See page 684 for the article to which this Editorial refers In older editions of textbooks of cardiology, chronic heart failure is described as a condition best treated by rest, and even as a relative contraindication to exercise testing. In common with much else we have been taught about heart failure, such as the adverse consequences of beta adrenoceptor blockade, these injunctions turn out to be false. A series of papers has testified to the potential symptomatic gains to be had from a programme of exercise training[1]. Exercise testing, particularly with metabolic gas exchange measurements, is now part of the routine assessment of heart failure patients, and has become an important tool for risk stratification and selection of patients for cardiac transplantation. Whilst there is now general agreement on the benefits of exercise for heart failure, there is considerable difference of opinion over which is the most appropriate exercise test to use. The standard method is an incremental test with expiratory gas analysis to derive maximal oxygen consumption, V ~ O2 max, which represents a rather artificial physiological construct. It should be measured as a plateau of oxygen consumption, such that an additional load imposed does not result in a further increase in V ~ O2. In practice, such a plateau is rarely seen in heart failure patients, who are unable to sustain this sort of exercise, and the term peak V ~ O2 is preferred. It is, of course, a highly artificial kind of test, wholly unrepresentative of daily activities. Different exercise test protocols elicit different results: cycle exercise elicits a lower peak V ~ O2 than treadmill[2], as do rapidly incremental protocols relative to slower. Despite these weaknesses peak V ~ O2 remains a potent predictor of outcome[4,5]. Tests more representative of ‘real life’ have become more widespread. These can take the form of distance covered in a fixed time, such as the 6 min walk test, or time at a fixed workload. More indirect tests have used pedometers to measure activity in the home in heart failure[6]. Larsen et al.[7] have addressed the issue of the best way of trying to measure the effects of training on exercise capacity by comparing the effects of an exercise training programme on end-points derived from different exercise tests. Previous investigators have concentrated on peak V ~ O2 as the main exercise end-point for assessing the training response, and most studies have reported an improvement of around 20%. Larsen et al. used an intensive training protocol with no strength training component and found only a modest (and non-significant) increase in peak V ~ O2. This is slightly unexpected as work performed during the maximal exercise test increased as a result of training, which should necessitate an increase in V ~ O2. By contrast, distance covered during a 6 min walk increased. Interestingly, the total lactate output during matched endurance exercise tests fell following training. This finding is consistent with the idea that a major impact of training is on skeletal muscle. As muscle function improves, so there is less reliance on anaerobic metabolism to perform work. Which is the most appropriate exercise test will depend upon the context of testing (Table 1). A protocol used for assessing symptoms need not be the same as one used for measuring the impact of a new drug on exercise capacity. Exercise testing in heart failure has a number of uses: (1) diagnosis; (2) risk stratification; (3) pathophysiological investigation; (4) measuring treatment response. Maximal incremental tests will continue to be used, because of the important information they contain about prognosis, and because of the additional information they may contain about the presence of ischaemia or arrhythmia. For pathophysiological investigation, tests need to be designed for individual studies. Table 1 Relative value of different forms of exercise testing depending upon the reason for testing Maximal tests Endurance tests Diagnosis Prognostication Pathophysiology Treatment response +++ + +++ + ++ ++ + +++ 2001 The European Society of Cardiology 628 Editorials These kinds of tests may well be inappropriate for assessing treatment effect. The work of Larsen et al. emphasizes the importance of designing exercise studies targeted at appropriate end-points. From the perspective of the patients’ symptoms, changes in peak V ~ O2 are not important, but changes in lactate production may well be; submaximal exercise testing appears to be a more sensitive indicator of a training effect. A. L. CLARK J. G. F. CLELAND Castle Hill Hospital, Cottingham, Hull, U.K. References [1] Coats AJS, Adamopoulos S, Radaelli A et al. Controlled trial of physical training in chronic heart failure: exercise performance, hemodynamics, ventilation, and autonomic function. Circulation 1992; 85: 2119–31. Eur Heart J, Vol. 22, issue 8, April 2001 [2] Buchfuhrer MJ, Hansen JE, Robinson TE, Sue DY, Wasserman K, Whipp BJ. Optimizing the exercise protocol for cardiopulmonary assessment. J Appl Physiol 1983; 55: 1558–64. [3] Lipkin DP, Canepa-Anson R, Stephens MR, Poole-Wilson PA. Factors determining symptoms in heart failure: comparison of fast and slow exercise tests. Br Heart J 1986; 55: 439–45. [4] Parameshwar J, Keegan J, Sparrow J, Sutton GC, PooleWilson PA. Predictors of prognosis in severe chronic heart failure. Am Heart J 1992; 123: 421–6. [5] Cohn JN, Johnson GR, Shabetai R et al. Ejection fraction, peak exercise consumption, cardiothoracic ratio, ventricular arrhythmias, and plasma norepinephrine as determinants of prognosis in heart failure. Circulation 1993; 87 (Suppl VI): 5–16. [6] Walsh JT, Charlesworth A, Andrews R, Hawkins M, Cowley AJ. Relation of daily activity levels in patients with chronic heart failure to long-term prognosis. Am J Cardiol 1997; 79: 1364–9. [7] Larsen AI, Aarsland T, Kristiansen PT, Haugland A, Dickstein K. Assessing the effect of exercise training in men with heart failure; comparison of maximal, submaximal and endurance exercise protocols. Eur Heart J 2001; 22: 684–92.