Why Nitrates Are Contraindicated in Right Ventricular Infarction
Nitrates are contraindicated in right ventricular (RV) infarction because they reduce preload through venodilation, and patients with RV infarction are critically dependent on adequate RV filling pressures to maintain cardiac output—nitrate administration can precipitate profound hypotension and hemodynamic collapse. 1, 2
Pathophysiologic Mechanism
The right ventricle in RV infarction becomes acutely ischemic and dilates, resulting in reduced RV systolic pressure and output. 2 This compromised RV cannot generate adequate forward flow to fill the left ventricle, making the entire cardiac output dependent on maintaining high RV preload (filling pressures). 1
Nitrates work primarily through venodilation in the splanchnic and mesenteric circulations, which dramatically reduces venous return and preload to both ventricles. 1 While this preload reduction is beneficial in left ventricular failure or typical myocardial infarction, it is catastrophic in RV infarction where the already failing right ventricle requires maximal filling pressures to generate any meaningful output. 2
Clinical Context and Recognition
RV infarction typically occurs with inferior wall myocardial infarctions, most commonly from proximal right coronary artery occlusion before the RV branches. 2 The classic clinical triad includes:
- Hypotension
- Clear lung fields (absence of pulmonary congestion)
- Elevated jugular venous pressure 2
This presentation carries a mortality rate of 25-30% compared to only 6% in inferior MI without RV involvement. 2 A right-sided ECG should be performed to evaluate for RV infarction in any patient with inferior wall STEMI before administering nitrates. 1
Guideline Recommendations
The American Heart Association explicitly states that nitrates in all forms are contraindicated in patients with right ventricular infarction. 1 The ACC/AHA guidelines emphasize that these patients are "especially dependent on adequate RV preload to maintain cardiac output and can experience profound hypotension during nitrate administration." 1
Nitrates should be administered with extreme caution, if at all, to patients with inferior STEMI and suspected RV involvement. 1 The guidelines also contraindicate nitrates when systolic blood pressure is <90 mmHg or ≥30 mmHg below baseline. 1
Important Caveats
While recent meta-analysis of 1,113 patients suggested that sublingual nitroglycerin 400 μg may not significantly increase adverse events in combined inferior and RV infarction (relative risk 1.31,95% CI 0.81-2.12), 3 this evidence is of very low certainty and challenges but does not override the established ACC/AHA and ESC guideline contraindications. 3 The guideline recommendations remain the standard of care given the potential for life-threatening hemodynamic collapse. 1, 2
The most serious consequence is inadvertent systemic hypotension, which may trigger reflex tachycardia and paradoxically worsen myocardial ischemia. 1 If hypotension occurs after inadvertent nitrate administration, immediate treatment includes leg elevation, rapid IV normal saline administration, and atropine if needed. 1
Correct Management Approach
The treatment strategy for RV infarction prioritizes maintaining adequate RV preload through volume loading with IV normal saline as first-line therapy for hypotension. 2 Avoid both nitrates and diuretics, which reduce preload. 2 If cardiac output fails to increase after volume loading, consider inotropic support with dobutamine. 2 Pursue urgent reperfusion strategies including primary PCI, thrombolytics, or CABG. 2