Acute changes in cardiopulmonary blood volume during upright exercise stress testing in patients with coronary heart disease

The effect of exercise-induced myocardial ischemia on cardiopulmonary blood volume was evaluated in patients with coronary artery disease during upright exercise stress testing. Regional pulmonary and cardiac blood volumes were monitored with a multicrystal positron camera positioned over the chest during maximal exercise on a bicycle ergometer. Inhaled carbon monoxide (<10 ppm) labeled with cyclotron-produced carbon-11 (¹¹C) (half-life 20.3 minutes) was used to label the blood with ¹¹C-carboxyhemoglobin. Regional ¹¹C activity was measured over the heart and lungs during rest, exercise and recovery periods, and blood volume was calculated from regional ¹¹C activity compared with the specific activity of a reference venous blood specimen. For patients developing angina pectoris and electrocardiographic ST-segment depression (ischemic group, n = 9), blood volume increased 18.7 ± 6.3% (SEM) (p<0.01) over the upper lung fields and 15.4 ± 6.8% (p<0.05) over the lower lung fields at peak exercise. Conversely, for patients without angina or ST-segment depression at peak exercise (nonischemic group, n = 7), the regional pulmonary blood volume was unchanged over both upper and lower lung fields. The cardiac blood volume rose 6.1 ± 2.6% (p<0.05) for the former group of patients and declined 10.6 ± 5.7% (p < 0.05) for the latter group at peak exercise. Coronary arteriography revealed double- or triple-vessel coronary disease in all patients in the ischemic group and normal coronary arteries or single-vessel disease in the nonischemic group. These data indicate that an ischemic response to exercise stress testing is associated with a transient rise in pulmonary and cardiac blood volume, which may be due to ischemia-induced left ventricular dysfunction.