Can anaerobic threshold be used as an end-point for therapeutic trials in heart failure?

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Abstract
‘Anaerobic threshold’ (AT), proposed as a non-invasive index of exercise tolerance, independent of patient motivation, is considered more reliable than exercise duration in assessing the effect of drug therapy in chronic heart failure (CHF). However, inter-observer variation in patients may be more difficult than in normal subjects. In a multicentre study, 85 patients from 10 centres performed a total of 331 bicycle maximal tests (ramp protocols, 10 watts. min−1) with respiratory gas analysis by different systems. A central committee reviewed all the tests. Percentages of AT determination ranged from 34% to 71% depending on the method used. Apart from the respiratory exchange ratio (RER=1) method, which yielded the lowest rate of determination. and the crossing point (when RER=1), which yielded the highest rate, 71%, other methods of determination, such as carbon dioxide (42%), minute ventilation (52%) or ventilatory equivalents plotted vs time (57%), did not dtffer in the rate of AT determination. Thus, even among trained physicians, AT determination was not reliable. The crossing point may nevertheless be a valuable index from a pragmatic standpoint, although it occurs after the actual AT Peak oxygen uptake should remain the main end-point in assessment of exercise capacity.

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