SESSION TYPE: Cardiovascular Cases
PRESENTED ON: Wednesday, October 24, 2012 at 11:15 AM - 12:30 PM
INTRODUCTION: Severe hypoxemia is commonly encountered by physicians. In the absence of significant parenchymal lung disease, the differential is limited and includes disorders such as pulmonary embolism, pulmonary vascular disease, and either intrapulmonary or intracardiac shunts. We describe a case of a patient with a history of porcine mitral valve replacement, who presented with severe hypoxemia with clear lung fields on chest imaging. She was found to have a large right to left shunt secondary to a right pulmonary artery to superior pulmonary vein fistula.
CASE PRESENTATION: A 71-year-old female with a history of coronary artery bypass grafting and porcine mitral valve replacement in 2001 for severe mitral stenosis, presented with dyspnea. Her examination was remarkable for severe hypoxia and bilateral lower extremity edema. Pertinent laboratory data was remarkable for the following: hemoglobin 14.7 g/dL, brain natriuretic peptide of 2,590 pg/ml, and a PaO2 of 38 mm Hg on 100% nonrebreather mask. A chest roentogram showed clear lung fields bilaterally. Evaluation with a contrast enhanced chest CT was negative for acute pulmonary embolism or parenchymal pathology. A transthoracic echocardiogram showed right ventricular and left atrial dilatation, a functional bioprosthetic mitral valve, and a positive bubble study after the third heart beat. A transesophageal echocardiogram confirmed the positive bubble study, and did not show an atrial or ventricular septal defect. Right heart catheterization showed a mean pulmonary arterial pressure of 20 mm Hg, a pulmonary capillary wedge pressure of 12 mm Hg, and a pulmonary vascular resistance of 1.3 woods units. No left to right shunt was detected. Re-evaluation of the previous chest CT by the interventional radiologist revealed the presence of a large right pulmonary artery to superior pulmonary vein fistula, which was thought to be related to her previous mitral valve surgery. She underwent placement of an Amplatzer duct occluder with subsequent improvement in both symptoms and oxygenation.
DISCUSSION: Pulmonary arteriovenous malformations (PAVMs) are vascular communications between pulmonary arteries and veins. While the majority of PAVMs are congenital in nature, they have also been associated with other medical conditions, such as liver cirrhosis, mitral stenosis, and congenital heart disease. To the best of our knowledge, this is the only case that describes the presence of a large pulmonary arteriovenous fistula that may be related to mitral valve replacement and coronary artery bypass grafting.
CONCLUSIONS: This case illustrates the importance of evaluating patients for underlying pulmonary vascular shunts in the setting of unexplained hypoxemia.
1) Gossage JR, Kanj G. Pulmonary Arteriovenous Malformations: A State of the Art Review. Am J Respir Crit Care Med 1998; 158: 643-661
DISCLOSURE: The following authors have nothing to disclose: Anthony Cucci, Rajat Gupta, Sandeep Kukreja, Khalil Diab
No Product/Research Disclosure InformationIndiana University, Indianapolis, IN