Safety Concerns regarding article: Reliability and Validity of a Self-paced Cardiopulmonary Exercise Test in Post-MI Patients. L. A. Jenkins, A. Mauger, J. Fisher, J. Hopker. Int J Sports Med 2017; 38: 300–306.
13 July 2017 (online)
We have serious concerns regarding the safety implications of the study by Jenkins et al. . The authors assert that “…the SPV [self-paced peak oxygen uptake test] may be a safe, valid and reliable measure of peak oxygen uptake (V˙O2peak) in both clinical and healthy populations”. However they focus mainly on reliability, with almost no consideration given to the safety implications of the SPV. We contend that the SPV would be unsafe for many cardiovascular (CV) patients and it is almost impossible to see how it could be translated into practice. The authors acknowledge that large, multi-centre trials of exercise of these maximal intensities are needed before the SPV can be claimed as safe for CV patients. For ethical reasons, it is very unlikely that such a trial would ever be conducted.
It is well accepted that the intensity of exercise exertion is commensurate with the level of increased risk of adverse cardiac events in at risk populations  . The authors reported that SPV produces substantially higher peak power, (V˙O2peak), heart rate and minute ventilation (level of breathlessness), compared to standard cardiopulmonary exercise tests (sCPET). We are alarmed that they are prepared to recommend SPV for CV patients where risks of adverse events are almost certainly higher than standard protocols . Whilst we acknowledge emerging evidence in support of high intensity exercise training for CV patients    , no studies recommend that patients exercise at intensities where ratings of perceived exertion (RPE) reach maximal value (i.e. 20 on the Borg 6–20 RPE Scale) , let alone be sustained at maximal effort at RPE 20 for two minutes at the end of the exercise test as required in the SPV. The authors’ own data indicate that peak workload for SPV is considerably greater than peak workloads from sCPET. Given that stress tests conducted by cardiologists are designed to provoke adverse signs or symptoms in individuals with undiagnosed CV conditions, it is implausible to claim that the maximal intensities (RPE=20) as required in the SPV would not result in adverse events even in carefully selected patients.
The study was unclear on specific exclusion criteria for patients in Study 2. Many post-MI patients with co-morbidities or clinical sequelae would not be able to complete the SPV without experiencing adverse signs or symptoms, or worse still, adverse events. These include post-MI patients with ongoing coronary artery disease (e.g., diffuse coronary artery disease or subclinical stenoses), heart failure at New York Heart Association II or lower functional class, left bundle branch block or other conduction defects, valvular disease, atrial fibrillation that is not adequately rate-controlled during exercise, exercise-induced ventricular or supraventricular tachyarrhythmias, or treatment-resistant hypertension, to name a few. Readers who work with patients with ischaemic cardiomyopathy (post-MI) in exercise settings know empirically that maximal exercise intensities for sCPET (i.e. lower than for SPV) occasionally (not rarely) trigger adverse signs or symptoms including myocardial ischaemia, exercise-induced arrhythmias, rate-dependent conduction defects, post-exercise vaso-vagal episodes and even syncope, increased pro-thrombogenic potential, and signs and symptoms of acute heart failure, to name a few. Further, it is well established that high and especially maximal intensity exercise significantly increases shear-induced platelet reactivity and the potential for intra-arterial thrombus formation  , which is potentially a disastrous outcome for post-MI patients and other CV patients.
It is suggested in the paper that some researchers have criticised the SPV methodology. We contend however that this is a misrepresentation of the previous commentary and that in fact previous criticisms have concerned limitations with experimental methodology for the specific purpose of comparing V˙O2peak values obtained through different protocols rather than criticisms of the SPV per se    . As the authors have indicated, the SPV has been shown to provide a valid measurement of VO2peak in the majority of studies which have compared the SPV to standard CPET protocols. Indeed, the concept of applying the principle of perceptually-regulated exercise testing in the form of the SPV has been described as paradigm shift for exercise testing , and as acknowledged by the authors, offers the advantage of known duration and autonomy of the participant to control the intensity in each RPE-regulated bout during the SPV. However, we strongly believe that the SPV in its current form, is not suited to cardiac populations or any clinical population in whom the risk of adverse events is increased by a sustained 2-min maximal effort at the end of the test.
In summary, translation of this research to practice is fraught with risk for application for post-MI patients. We question the application of such a dangerous protocol which on the available evidence is unnecessary, produces no particular benefit and carries risks and levels of discomfort which are unlikely to be understood by the average participant.
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