Low hot pain threshold predicts shorter time to exercise-induced angina: Results from the psychophysiological investigations of myocardial ischemia (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 A 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 degrees C, and 2) average HPT greater than or equal to 41 degrees C, to be clearly indicative of abnormal hypersensitivity to noxious heat. RESULTS Patients with HPT <41 degrees C had significantly shorter time to angina onset on exercise testing than patients with HPT <41 degrees 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 plasma beta-endorphin levels were significantly higher in the HPT <41 degrees C group (5.9 +/- 3.7 pmol/liter vs. 4.7 +/- 2.8 pmol/liter, p = 0.02). Using a Cox proportional hazards model, patients with HPT <41 degrees C had an increased risk of angina (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 angina and timing of angina onset on an exercise test are related to overall hot pirin sensory perception. The mechanism of this relationship requires further study. (C) 1999 by the American College of Cardiology.