Cooling down unstable angina with high dosage of isosorbide dinitrate (ISDN) continuously infused.

The aim of this study was to explore the capability of isosorbide dinitrate (ISDN) infusion to quench the 'hot phase' of unstable angina, a real cardiological emergency. Fifteen patients consecutively admitted to CCU because of angina at rest, with at least 4 ischaemic attacks per day, resistant to the usual therapy with oral and/or topical nitrates and calcium-antagonists, were included in the study. During ischaemia the electrocardiogram showed ST-segment elevation in 7 patients, ST-segment depression in 4, an alternation of ST-segment elevation and depression in 3 and pseudonormalization of a basally negative T wave in 1 patient. History of exertional angina with variable degrees of effort was reported in 6 patients and 9 had an old myocardial infarction. Coronary arteriography performed in 10 patients showed a significant stenosis of 1, 2 and 3 vessels in 5, 2 and 3 patients, respectively. ISDN infusion was started at 1.0 mg h-1, and was increased stepwise when persistence of ischaemic episodes had to be faced. The mean dosage infused was 3.5 mg h-1 (range 1.00-12). The mean duration of intravenous therapy was 8.3 days (range 2-25). Eleven of the 15 patients (73%) showed an effective decrease in the number of ischaemic episodes during ISDN infusion, as assessed by regression and variance analysis. After discharge (mean follow-up 59 months, range 2-96), 7 patients were free from ischaemic attacks, 3 underwent coronary by-pass surgery, 2 complained of some attacks and 3 died (2 because of sudden death three years after this study). In conclusion, ISDN infusion--individually tailored for dosage and duration--can be effective in 'cooling down' the storm of ischaemic episodes in unstable angina. An effective intravenous therapy with nitrates can represent, in some patients, a temporal remedy on the way to elective coronary bypass surgery and/or towards elective PTCA. Furthermore, in a sizeable number of patients with unstable angina, this approach can attain a complete abolishment of the ischaemic attacks.