SUMMARY Seventeen male patients with angina pectoris, and a history of increased severity of angina in the cold, performed submaximal bicycle exercise tests in a normal (20°C) and a cold environment (-10°C, 2-2 m/s wind velocity) wearing standardised clothing. Observations were made during and after serial short-term exercise periods each starting at 50 W, with continuous load increase of 10 to 30 W per minute, separated by 30-minute rest intervals.In the group as a whole, maximal work load decreased by 7 per cent during exposure to cold. Heart rate, systolic blood pressure, and rate-pressure product were significantly higher during submaximal exercise in the cold, but at maximal work load there was no difference in heart rate, rate-pressure product, or magnitude of ST segment depression. The decrease in maximal work load exceeded 5 per cent (mean 11%) in 10 patients, who were described as cold-susceptible, while the decrease averaged 1 per cent in the seven non-susceptible patients. The cold-induced reduction in maximal work load showed a significant correlation with the increase in heart rate, blood pressure, and rate-pressure product during submaximal exercise.After exercise, heart rate was significantly lower and blood pressure and rate-pressure product significantly higher in the cold than at normal temperature in all patients. In cold-susceptible patients, blood pressure was significantly higher at two and four minutes after exercise, and rate-pressure product at two minutes after exercise, than in non-susceptible patients, but in spite of this angina disappeared more quickly in cold-susceptible patients.In conclusion, subjective cold intolerance was objectively demonstrated in 10 out of 17 patients with angina pectoris, by exercise in a room at -10°C. Susceptibility to cold was explained by a higher heart rate and blood pressure during exercise in the cold room, than during exercise in the room at normal temperature.Patients with angina pectoris often experience a worsening of their symptoms in cold weather. The physiological explanation of this has been said to be the earlier appearance of myocardial oxygen deficit during exercise in the cold, which may be caused by increased work done by the heart (Epstein et al., 1969), by nervous reflexes to the heart causing coronary vasoconstriction (Freedberg er al., 1944;Mudge et al., 1976), by release of sympatheticoadrenal hormones (Wilkerson et al., 1974), or by cooling of the blood in the heart chambers and coronary arteries (Leon et al., 1970 low exercise tolerance are most affected, because of a relatively greater decrease in work performance. This conclusion was based on studies at rest, and there has been no study of the effects of cold on angina during exercise. We therefore studied the effects of exposure to cold on effort angina during standardised conditions, in order to see whether cold intolerance could be explained by changes which could be measured non-invasively.
SubjectsA questionnaire about the relation of their symptoms to cold was given to 50...