Do nitrates cause hypotension in inferior wall myocardial infarction (MI)?

From the Guidelines

Nitrates should be used with caution in patients with inferior wall myocardial infarction (MI) due to the risk of causing severe hypotension, as stated in the 2015 guidelines from the American Heart Association, American College of Cardiology, and American Society of Hypertension 1. In inferior wall MI, the right ventricle is often involved, making these patients particularly sensitive to preload reduction. Nitrates work by dilating veins, which decreases venous return to the heart (preload). In patients with right ventricular involvement, cardiac output is highly dependent on adequate preload, and reducing it with nitrates can lead to profound hypotension, potentially worsening the patient's condition. Some key points to consider when administering nitrates to patients with MI include:

• Carefully titrating the dose to avoid excessive hypotension
• Monitoring for signs of right ventricular involvement, such as hypotension and bradycardia
• Avoiding nitrates in patients with suspected right ventricular infarction or those who have received phosphodiesterase inhibitors for erectile dysfunction within the last 24 hours (48 hours for tadalafil) 1
• Considering alternative medications for pain control and afterload reduction, such as carefully titrated opioids for pain and ACE inhibitors for afterload reduction once the patient is hemodynamically stable. The most recent and highest quality study, published in 2015, found that nitrates should be used with caution in patients with inferior STEMI and are contraindicated if right ventricular infarction is present because of their effects on lowering preload 1.

From the FDA Drug Label

Severe hypotension and shock may occur with even small doses of nitroglycerin. Hypotension induced by nitroglycerin may be accompanied by paradoxical bradycardia and increased angina pectoris

Nitrates and Hypotension in Inferior Wall MI:

• Nitrates, such as nitroglycerin, can cause severe hypotension and shock, even with small doses.
• This effect may be accompanied by paradoxical bradycardia and increased angina pectoris.
• The use of nitrates should be done with caution, especially in patients who may be volume depleted or already hypotensive 2, 2.
• It is essential to carefully monitor patients and adjust the dosage accordingly to avoid hypotension.
• The specific context of inferior wall MI does not alter the fundamental risk of hypotension associated with nitrate use.

From the Research

Nitrates and Hypotension in Inferior Wall MI

• Nitrates can cause hypotension in patients with inferior wall myocardial infarction (MI), particularly in those with right ventricular (RV) involvement 3.
• The administration of nitrates can precipitate profound hypotension in up to 60% of patients with inferior wall MI 3.
• RV involvement is a significant predictor of hypotension after nitrate administration, with 15 out of 20 patients with marked hypotensive response to nitroglycerin having evidence of RV involvement 3.

Right Ventricular Involvement

• Right ventricular infarct (RVI) occurs in approximately one third of all patients who present with an inferior wall MI 4.
• RVI can lead to severe hypotension and cardiogenic shock, and its diagnosis is based on physical examination, electrocardiography, echocardiography, and coronary angiography 5.
• The presence of RV involvement is an independent prognostic factor that dramatically increases in-hospital mortality, due in part to a significantly higher risk of hemodynamically compromising arrhythmias 5.

Treatment and Prognosis

• Patients with inferior wall MI and RV involvement have a worse prognosis and increased number of in-hospital complications, including cardiogenic shock, ventricular fibrillation, and pulmonary edema 6.
• Older patients (>70 years) with RVI have a significantly higher mortality rate compared to younger patients 6.
• Nitrates should be avoided in patients with RVI, as they can exacerbate hypotension and worsen prognosis 5.