Historical background

Although it had long been known that evaluating a symptomatic patient during exertion might disclose evidence of coronary artery disease, before the advent of the Bruce treadmill test there was no safe, standardised and validated stress protocol that could be used to monitor cardiovascular haemodynamic changes in exercising patients. Master's two-step test,2 a submaximal exercise test for diagnosing ‘coronary insufficiency’ (in which ECGs were recorded during and after a patient repeatedly ascended and descended two steps) was often used, but it was too strenuous for some patients, inadequate for simultaneous assessment of cardiac and respiratory function during exercise and, measured by the energy expenditure per unit of weight, stressed the underweight patient considerably more than the overweight patient.1 Submaximal stress tests were the preferred stress technique; the concept of testing patients to their maximum exercise capacity was almost unthinkable, owing to the perceived risk of complications, a perception reinforced by reports of major complications even during submaximal stress testing.3

Nonetheless, Bruce recognised that many patients were not reliably or reproducibly stressed. Consequently, he tested initially a single-stage treadmill test in thousands of normal volunteers and subsequently, in cardiac patients, proving its feasibility, safety and reproducibility.4 This stress was only moderate for normal subjects and cardiac patients …