The association between peripheral arterial disease, treadmill exercise test parameters and long-term outcome

Peripheral arterial disease (PAD), a manifestation of systemic artheriosclerosis, is affecting millions of people with prevalences between 4 to 29%, and is expected to rise in the following decades [1, 2]. According to the guidelines, a resting ankle brachial index (ABI) < 0.90 is defined as PAD, which is related to a higher cardiovascular morbidity and mortality [3, 4]. Surprisingly, in contrast to patients with coronary arterial disease, the value of the exercise test in patients with PAD is still unclear and hardly investigated. Nevertheless, the exercise test may provide a large amount of important clinical data to identify patients with increased cardiovascular risks. Recent publications have also shown that resting ABI between 0.90-1.10, thus classified as 'normal' according to the guidelines, was associated with a higher mortality [5-7]. In today's clinical practice, the ABI measured at rest is still the most used method to diagnose PAD. However, more than 30% of the patients with resting ABI ≥ 0.90 demonstrated after a treadmill exercise test an ABI < 0.90 and were associated with a higher mortality rate [8]. These patients would have been missed according to the current definitions. Not only exercise ABI, but also other factors which may have an important role in the prognosis of PAD can be identified with exercise tests. For example, a hypertensive blood pressure response and a hypotensive blood pressure response at a treadmill exercise test, are associated with an almost two-fold increased risk of cardiovascular death [9, 10]. Also, walking distance impairment was strongly associated with mortality, cardiac death and quality of life [11, 12]. Combining treadmill variables, exercise ABI, walking distance and blood pressure response, with the current known risk factors, provides important additional prognostic information of cardiovascular morbidity and mortality. Furthermore, not only a decline in ABI, but also a decline in walking distance turned out to be a strong prognostic factor of long-term mortality as well [13]. This indicates that exercise tests could be used not only for risk stratification but also for identifying progressive disease.Exercise tests might also be used for early risk factor modification. For instance, early treatment of cardiovascular risk factors such as life style changes, exercise training and optimal medical treatment with statins and beta-blockers, for example, have shown to be effective in patients with PAD [2, 4, 14, 15]. However, it is unknown if, when and how patients, especially with mild and borderline impaired ABI values must be treated.In conclusion, treadmill exercise test parameters are important to identify patients with increased mortality risks, which would otherwise remain unrecognised and untreated, and to identify patients with progressive PAD. However, further research is needed to investigate which and when treatment is needed to lower cardiovascular risks in these patients.