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Nitrate tolerance in patients with effort angina
G Zambaldi1, F Cellerini, G Ciriello
1Unità Coronarica, Ospedale Santa Maria Nuova, Firenze.
Minerva Cardioangiologica
|October 22, 1998
Summary
Nitrate tolerance can develop at the venous level but not the coronary level in chronic stable angina patients. Higher nitrate doses may preserve coronary effects despite venous tolerance.
Area of Science:
- Cardiology
- Pharmacology
- Medical Physiology
Background:
- Beneficial effects of nitrates in chronic stable angina may involve coronary circulation, not just venous return.
- Some patients exhibit increased rate-pressure product at ischemia (RPPI) after sublingual nitrates (SLN).
- Nitrate tolerance development varies between venous and coronary systems.
Purpose of the Study:
- Investigate nitrate tolerance in venous and coronary circulation.
- Compare the effects of two isosorbide-5-mononitrate (IS5MN) dosing schedules on nitrate tolerance.
Main Methods:
- Two groups of patients received IS5MN: Group 1 (20 bid) and Group 2 (40 bid) for 1 week.
- Tolerance assessed by evaluating the effect of SLN on left ventricle area (LVA) and RPPI.
- LVA reduction indexed venous return effects; RPPI increase indexed coronary flow reserve.
Main Results:
- Group 1 showed no significant changes in LVA or RPPI post-treatment, indicating no tolerance.
- Group 2 exhibited significant LVA reduction, indicating venous tolerance.
- Group 2 maintained RPPI increases above ischemic thresholds, suggesting preserved coronary effects.
Conclusions:
- Lower IS5MN doses (20 bid) prevent nitrate tolerance in both venous and coronary systems.
- Higher IS5MN doses (40 bid) lead to venous tolerance but preserve coronary effects in angina patients.
- Coronary effects of nitrates may be preserved even when venous tolerance develops.