Low hot pain threshold predicts shorter time to exercise-induced angina: results from the psychophysiological investigations of myocardial ischemi (PIMI) study

OBJECTIVES The purpose of this study was to test whether cutaneous thermal pain thresholds are related to anginal pain perception. BACKGROUND Few ischemic episodes are associated with angina; symptoms have been related to pain perception thresholds. METHODS total of 196 patients with documented coronary artery disease underwent bicycle exercise testing and thermal pain testing. The Marstock test of cutaneous sensory perception was administered at baseline after 30 min of rest on two days and after exercise and mental stress. Resting hot pain thresholds (HPTs) were averaged for the two baseline visits and divided into two groups: 1) average HPT <41°C, and 2) average HPT ≥41°C, to be clearly indicative of abnormal hypersensitivity to noxious heat. RESULTS Patients with HPT <41°C had significantly shorter time to angin onset on exercise testing than patients with HPT ≥41°C (p < 0.04, log-rank test). Heart rates, systolic blood pressure and rate–pressure product at peak exercise were not different for the two groups. Resting plasm beta-endorphin levels were significantly higher in the HPT <41°C group (5.9 ± 3.7 pmol/liter vs. 4.7 ± 2.8 pmol/liter, p = 0.02). Using Cox proportional hazards model, patients with HPT <41°C had an increased risk of angin (p = 0.03, rate ratio = 2.0). These differences persisted after adjustment for age, gender, depression, anxiety and history of diabetes or hypertension (p < 0.01). CONCLUSIONS Occurrence of angin and timing of angin onset on an exercise test are related to overall hot pain sensory perception. The mechanism of this relationship requires further study.