Occult peripheral artery disease is common and limits the benefit achieved in cardiac rehabilitation

Cardiac rehabilitation (CR) has proven morbidity and mortality benefits in cardiovascular disease, which directly correlates with exercise performance achieved. Many patients in CR exercise at sub-optimal levels, without obvious limitations. Occult lower-extremity peripheral artery disease (PAD) may be a determinant of diminished exercise capacity and reduced benefit obtained from traditional CR. In this prospective study of 150 consecutive patients enrolled in Phase II CR, we describe the prevalence of PAD, the utility of externally validated screening questionnaires, and the observed impact on CR outcomes. Abnormal ankle-brachial indices (ABI) (< 0.9 and >1.4) were observed in 19% of those studied. The Edinburgh Claudication Questionnaire was insensitive for detecting PAD by low ABI in this population, and the Walking Impairment Questionnaire and a modified Gardner protocol demonstrated a lack of typical symptoms with low levels of activity. Importantly, at completion of traditional CR, exercise improvement measured in metabolic equivalents (METs) was worse in those with a low ABI compared to those with a normal ABI (+1.39 vs +2.41 METs, p = 0.002). In conclusion, PAD is common in patients in Phase II CR and often clinically occult. Screening based on standard questionnaires appears insensitive in this population, suggesting a need for a broad-based screening strategy with ABI measurements. In this study, undiagnosed PAD significantly attenuated improvements in exercise performance, which potentially has bearings on future clinical events.