USEFULNESS OF CHANGES IN EXERCISE TOLERANCE INDUCED BY NITROGLYCERIN IN IDENTIFYING PATIENTS WITH SYNDROME-X

Two exercise tests, one under basal conditions and one after sublingua l nitroglycerin (NTG), were performed in 39 patients with stable angin a pectoris-16 with critical coronary stenoses and 23 with normal coron ary arteries (syndrome X). Under basal conditions, times at ischemic t hreshold, at peak exercise, and at complete ECG recovery were similar in the two groups. Peak ST depression was significantly higher in pati ents with coronary artery disease (CAD). In a similar proportion of pa tients, ST-segment depression developed earlier or at a low heart rate . Patterns of heart rate, blood pressure, and rate-pressure product du ring exercise and recovery were also similar. After NTG an increase in the ischemic threshold was observed in a significantly higher proport ion of patients with CAD (93.8% vs 39.1%). Furthermore, a subgroup of patients with syndrome: X showed a worsening of exercise performance. This suggests that NTG does not directly affect small coronary vessels . Our results confirm that no relevant differences exist in exercise r esponses between patients with CAD and those with syndrome X under bas al conditions. NTG-induced changes in this response could be useful in identifying patients with normal coronary arteries. Moreover this tes t could be used as a guide to therapeutic approaches.