What is the role of oral nitrates after a ST-Elevation Myocardial Infarction (STEMI)?

From the Guidelines

Oral nitrates should not be routinely administered to patients after a STEMI, but may be considered in specific cases with ongoing angina, heart failure, or hypertension. When prescribed, common oral nitrate options include isosorbide mononitrate (typically 30-60mg once daily) or isosorbide dinitrate (10-40mg three times daily) 1. The decision to administer nitrates should be based on individual patient needs and should not preclude therapy with other proven mortality-reducing interventions such as beta blockers 1.

Key Considerations

• Nitrates should be avoided in patients with right ventricular infarction, severe hypotension (systolic BP <90 mmHg), or in those taking phosphodiesterase-5 inhibitors like sildenafil 1.
• Nitrates work by dilating blood vessels, reducing preload and afterload, thereby decreasing myocardial oxygen demand 1.
• They also dilate coronary arteries, potentially improving blood flow to ischemic areas 1.
• Be aware that tolerance can develop with continuous nitrate therapy, so a nitrate-free interval (typically overnight) is often recommended for long-term use to maintain efficacy 1.

Administration and Monitoring

• If prescribed, start at a lower dose and titrate up as needed based on symptoms and blood pressure response 1.
• Patients who require intravenous nitroglycerin for >24 hours may require periodic increases in the infusion rate and use of nontolerance-producing regimens (eg, intermittent dosing) to maintain efficacy 1.
• Topical or oral nitrates are acceptable alternatives to intravenous nitroglycerin for patients who do not have refractory or recurrent ischemia 1.

From the Research

Oral Nitrates after STEMI

• The use of oral nitrates in patients with acute myocardial infarction, including STEMI, has been studied extensively 2, 3.
• Nitrates have been shown to be effective in reducing morbidity and mortality from acute myocardial infarction by limiting myocardial ischemia and necrosis 2.
• The preferred route of nitroglycerin administration is intravenous infusion, but oral nitrates can also be used 2.
• Oral nitrates, such as isosorbide-5-mononitrate, have been shown to be effective in reducing infarct size and morbidity and mortality in patients with acute myocardial infarction 3.

Mechanism of Action

• Nitrates work by dilating coronary arteries and reducing preload through venodilatation, which decreases oxygen demand and increases blood flow to the ischemic myocardium 4, 5.
• Nitrates also replenish the deficient endothelium-derived relaxing factor (EDRF), nitric oxide (NO), in patients with coronary heart disease and inhibit platelet aggregation 3.

Clinical Use

• Oral nitrates are commonly used in the treatment of angina pectoris, including stable and unstable angina, and in patients with acute myocardial infarction 5, 3.
• The use of oral nitrates in patients with vasospastic angina has been associated with increased risk of adverse cardiac events, particularly when used in immediate-release formulations or administered at times other than bedtime 6.
• However, the use of nitrates in combination with other therapies, such as angiotensin-converting enzyme (ACE) inhibitors, has been shown to reduce mortality risks in patients with acute myocardial infarction 3.