Brain natriuretic peptide (BNP) is primarily secreted from the cardiac ventricles. Circulating concentrations of BNP are known to be increased in established chronic heart failure and acute myocardial infarction and to correlate well with left ventricular dysfunction and prognosis. It may also act as an index of ischemic severity. This study was performed to evaluate the value of plasma BNP measurement during exercise test in patients with ischemic heart disease for an assessment of myocardial ischemia.

This study included a total of 63 cases who had suspected ischemic heart disease or suffered from myocardial infarction. The subjects underwent treadmill exercise with modified Bruce protocol. Tc-99m MIBI (methoxyisobutyl Isonitrile) SPECT image was obtained by one-day or two-day protocol with rest-stress sequence. They were divided into 3 groups by findings in exercise TC-99m MIBI SPECT; 16 cases with reversible perfusion defect into angina pectoris group, 12 cases with myocardial infarction and fixed perfusion defect into myocardial infarction group and 35 cases without perfusion defect into control group. Venous blood was obtained at rest and just after peak exercise. Plasma levels of BNP level were measured by radioimmunoassay.

BNP levels increased with exercise from 20.1 ± 28.2 to 33.2 ± 44.0 pg/ml in the control group, 33.9 ± 48.8 to 44.6 ± 49.2 pg/ml in the angina pectoris group and 86.6 ± 85.0 to 140.9 ± 116.2 pg/ml in the myocardial infarction group (p<0.01, respectively). BNP levels in the myocardial infarction group were significantly higher than those in the control and angina pectoris group both at rest and after peak exercise (p<0.01, respectively). The changes in BNP levels with exercise were also significantly higher in the myocardial infarction group compared with those in the control and angina pectoris group (p<0.01). The BNP levels at rest were correlated significantly with the extent of perfusion defect and METs (r=0.465, p<0.001; r=-0.283, p<0.05, respectively). The BNP level after peak exercise correlated closely with the extent of perfusion defect and left ventricular ejection fraction (r=0.481, p<0.001; r=-0.301, p<0.05, respectively). The changes in BNP level with exercise were correlated well with the extent of perfusion defect and the ischemic severity (r=0.352, p<0.01; r=0.272, p<0.05, respectively).

These findings suggest that the changes in BNP level during an exercise test could be used for an index of ischemic severity in patients with ischemic heart disease.