Effect of Low-Level Carbon Monoxide Exposure on Onset and Duration of Angina Pectoris

Abstract

This study was done to ascertain the cardiovascular effects of exposure to low levels of carbon monoxide (CO) on 10 adult men with stable angina pectoris. The patients breathed air, with 50 ppm CO or 100 ppm CO, for 4 hours on 5 successive days. After each exposure a standard treadmill-exercise ECG was recorded. The time of onset and duration of anginal pain were recorded. Mean carboxyhemoglobin (COHb) level after air was 1.3%, rising to 2.9% after 50 ppm CO and to 4.5% after 100 ppm CO. Mean duration of exercise before onset of pain was significantly shortened after both 50 and 100 ppm CO in comparison with air (P < 0.005). The duration of pain was significantly prolonged after 100 ppm compared with air (P < 0.01), but not after 50 ppm. Electrocardiograms recorded during and after exercise generally showed worsening of ST-segment changes, with earlier onset and longer duration of ST-segment depression. Low levels of CO can cause decreased exercise tolerance and worsening of myocardial ischemia in patients with angina pectoris.