Changes in myocardial ischaemia during isosorbide dinitrate or indoramin therapy in patients with stable angina using relations between the ST segment and heart rate.

The effect of isosorbide dinitrate or indoramin on myocardial ischaemia was examined in patients with stable angina pectoris. In a prospective trial, randomization resulted in 8 and 9 patients, respectively, given isosorbide dinitrate in a dose of 30-90 mg daily, and indoramin in a dose of 75-225 mg daily; 2 of these patients were serially examined during the two types of therapy. Changes in myocardial ischaemia were assessed by exercise testing using 12 standard electrocardiographic leads and a bipolar lead CM5. Individual and group comparisons showed that isosorbide dinitrate resulted in an increase in ST segment depression, the maximal ST/heart rate slope and the ratio of net ST segment depression to increases in heart rate (at least P less than 0.01). In contrast, with indoramin therapy there were no significant changes in these indices. The results in these patients suggest that isosorbide dinitrate leads more consistently to increases in the severity of myocardial ischaemia than indoramin, although this effect on ischaemia is apparently less than the benefit of these agents on exercise performance.