Is Isoket Drip (isosorbide dinitrate) safe to use for controlling chest pain in patients with inferior wall myocardial infarction (MI)?

Isoket Drip in Inferior Wall MI: Safety Considerations

Isoket Drip (isosorbide dinitrate) should be used with extreme caution, if at all, in patients with inferior wall myocardial infarction, particularly those with suspected right ventricular involvement, due to the high risk of profound hypotension. 1

Mechanism of Concern

Nitrates like Isoket (isosorbide dinitrate) work through several mechanisms:

• Dilate epicardial conductance arteries
• Increase collateral blood flow to ischemic myocardium
• Decrease left ventricular preload

However, in inferior wall MI:

• These patients are especially dependent on adequate right ventricular preload to maintain cardiac output
• Nitrate-induced venodilation can dramatically reduce preload
• This can lead to profound hypotension and worsening of myocardial ischemia 1

Clinical Approach to Nitrates in Inferior MI

Before Considering Nitrates

1. Perform a right-sided ECG to evaluate for right ventricular involvement
2. Assess baseline hemodynamic status (BP, HR)
3. Ensure IV access is established for potential fluid resuscitation

If Nitrates Are Deemed Necessary

• Use with extreme caution
• Start with very low doses
• Carefully titrate while monitoring hemodynamic response
• Begin with 5-10 μg/min (lower than standard starting dose)
• Increase by 5-10 μg/min every 5-10 minutes with careful monitoring 1

Monitoring During Administration

• Continuous blood pressure monitoring
• Heart rate monitoring
• Watch for signs of hypotension or bradycardia
• Monitor for clinical improvement or worsening

Management of Nitrate-Induced Hypotension

If hypotension occurs during Isoket administration:

• Immediately discontinue the drug
• Elevate the patient's legs
• Administer rapid fluid bolus
• Consider atropine if bradycardia is present 1

Alternative Approaches for Chest Pain in Inferior MI

Given the risks, consider alternative strategies for managing chest pain:

• Adequate opioid analgesia (morphine)
• Beta-blockers (if no contraindications)
• Early reperfusion therapy (primary PCI or thrombolytics)
• Oxygen supplementation

Special Considerations

1. Contraindications:

   • Avoid in patients taking PDE-5 inhibitors (sildenafil, tadalafil, vardenafil) within 24-48 hours 1, 2
   • Avoid in patients with systolic BP <90 mmHg or 30 mmHg below baseline 1

2. Recent Evidence: While some research suggests that nitrates may be safer in inferior STEMI than previously thought 3, the guidelines still recommend extreme caution, and the potential benefit may not outweigh the risk.

3. Potential Benefits: Despite risks, intravenous nitrates may have some benefits in selected patients:

   • May reduce infarct size when started early
   • May decrease susceptibility to ventricular fibrillation
   • Can improve outcomes in patients with pulmonary congestion 1

The decision to use Isoket in inferior MI must carefully balance the potential relief of ischemic pain against the substantial risk of hemodynamic compromise, with particular attention to identifying right ventricular involvement where the risk is highest.