Abstract

IntroductionThis is a report of a 56-year-old man who became hypoxic due to an acute right to left shunt after sustaining a myocardial infarction involving the right ventricle. This case provides the opportunity to review several key pathophysiologic concepts in the setting of acute right ventricular infarction. Although the development of an acute right to left shunt is a rare complication of myocardial infarction, it is important to recognize the diagnosis early in order to prevent life threatening or debilitating clinical sequelae that may result from tissue hypoxia and embolic events. Transesophageal echocardiography is the noninvasive study of choice to confirm the diagnosis. Treatment involves optimization of right ventricular function to minimize shunting. However, medical therapy may provide only temporary relief, and closure of the atrial septal defect should be considered if a clinically significant shunt persists.Case presentationA 56-year-old Caucasian man with severe aortic insufficiency presented to the emergency department for evaluation of substernal chest pain. An inferior myocardial infarction was diagnosed by the electrocardiogram and serologic markers. Cardiac catheterization revealed complete occlusion of the right coronary artery as well as a 50-75% stenosis of the left anterior descending artery. Angioplasty of the right coronary artery was performed, but immediate re-occlusion occurred. Subsequently, hypotension and severe hypoxemia developed and persisted despite intubation and mechanical ventilation with 100% oxygen. A significant right-to-left shunt through a patent foramen ovale was diagnosed by contrast transesophageal echocardiogram. Surgical intervention was required and included coronary artery bypass grafting, aortic valve replacement as well as closure of his atrial septal defect.ConclusionA right to left atrial shunt is a rare complication of inferior myocardial infarction with right ventricular infarction. The diagnosis should be considered in the presence of inferior myocardial infarction when hypoxemia persists despite administration of 100% oxygen. Early diagnosis and treatment are critical in order to reduce the risk of embolization and to prevent end-organ damage due to hypoxemia.

Highlights

  • This is a report of a 56-year-old man who became hypoxic due to an acute right to left shunt after sustaining a myocardial infarction involving the right ventricle

  • The development of an acute right to left shunt is a rare complication of myocardial infarction, it is important to recognize the diagnosis early in order to prevent life threatening or debilitating clinical sequelae that may result from tissue hypoxia and embolic events

  • A right to left atrial shunt is a rare complication of inferior myocardial infarction with right ventricular infarction

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Summary

Introduction

Patent foramen ovale (PFO) is an anatomic inter-atrial communication with the potential risk for a right-to-left shunt. The hemodynamic consequences of a RVMI include elevated right ventricular diastolic pressure and depressed cardiac output. The potential increase in right atrial pressure can lead to a right-to-left shunt through the patent foramen ovale causing systemic hypoxia. We present a case of acute inferior myocardial infarction complicated by refractory hypoxemia due to the development of an acute right to left inter-atrial shunt through a previously dormant patent foramen ovale. Transesophageal echocardiography with intravenous microbubbles demonstrated a significant right-to-left shunt through a patent foramen ovale (Figure 2a). The magnitude of an intracardiac shunt may be quantified by the Qp:Qs ratio, which is the pulmonary to systemic blood flow ratio This can be measured from echocardiographic data or from cardiac catheterization.

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