Progressive hypoxemia after lung resection surgery.

SESSION TITLE: Cardiovascular Case Report Posters IISESSION TYPE: Case Report PosterPRESENTED ON: Sunday, March 23, 2014 at 01:15 PM - 02:15 PMINTRODUCTION: We present a case of progressive hypoxemia with platypnea-orthodeoxia developing after lung resection surgery for lung cancer.

CASE PRESENTATION: The patient is a 68 year-old Caucasian male who presented with progressive dyspnea and hypoxemia after right lower lobe resection 6 weeks prior for stage IIIA NSCLC. His surgery was unremarkable and post-operative course included atrial fibrillation. He was discharged on room air. After discharge, he noted increasing shortness of breath and required oxygen. He was treated with several courses of antibiotics for infiltrates on imaging studies without improvement. CT pulmonary angiogram was negative for pulmonary embolism and cardiac echo showed only diastolic dysfunction. He was readmitted with significant hypoxemia and worsening symptoms with sitting up and improvement lying down.

DISCUSSION: Clinical course included progressive hypoxemia requiring 100% FiO2 and non-invasive positive pressure ventilation. LE duplex was negative for DVT. VQ scanning was low probability for pulmonary embolism. Chest CT scan showed resolution of prior infiltrates. Post-surgery pulmonary function tests suggested restrictive disease but he could not tolerate further testing. Given concern for platypnea-orthodeoxia, and a recent echo with no intracardiac shunt, he underwent ventilation/perfusion testing with shunt calculation. This showed 36.3% shunt outside the lung (normal less than 10%). He underwent transesophageal echocardiogram that revealed a large atrial septal defect by Doppler and agitated saline contrast. There was right-to-left shunting that worsened with movement from supine to 70 degrees position. He was diagnosed with platypnea-orthodeoxia syndrome related to worsening of his ASD post-lung resection surgery. He underwent cardiac catheterization and closure of his ASD with an Amplatzer Cribiform Occluder. He was clinically improved and on room air over several days.

CONCLUSIONS: Symptoms of hypoxemia with platypnea-orthodeoxia are concerning for shunt physiology. The differential diagnosis includes sources of intracardiac (ASD, PFO) and intrapulmonary shunting. He had a prior intracardiac shunt on an earlier echo but not on the post-operative study. He had no evidence of other cardiac causes such as pericardial effusion, constrictive pericarditis or aortic aneurysm. He had an interstitial lung disease by CT scan but this was unchanged radiographically. There was no evidence of other pulmonary causes such as COPD, thromboembolic disease or an intrapulmonary shunt (arteriovenous malformation). He had no history of liver disease with shunt from cirrhosis or history of kyphoscoliosis. Platypnea-orthodeoxia was first described in 1949 and major causes are intracardiac shunts and intrapulmonary shunts. The intracardiac shunts are right-to-left and most often include atrial septal defect, patent foramen ovale or fenestrated atrial aneurysm. Other causes include pericardial effusion, lobectomy, pneumonectomy or upper abdominal surgery. This occurs from preferential blood flow towards the atrial septum that is accentuated by altered intracardiac anatomy, compliances of the right and left heart, pulmonary vascular resistance and transient right to left pressure gradients associated with respiratory and positional changes. This is generally not associated with pulmonary hypertension and atrial right-to-left shunting has been reported despite normal right-sided pressures. A right-to-left shunt is more likely to appear after a right-sided lung resection with most patients having symptoms develop a month to several months afterwards. Noncardiac causes can include intrapulmonary shunting, such as thromboembolic disease and AVMs, or cirrhosis and kyphoscolisoss. The key to diagnosis is clinical suspicion of symptoms of dyspnea and hypoxemia, induced or worsened by an upright posture. In conclusion, interatrial shunting through a PFO or ASD is a rare but clinically significant condition after thoracic surgery. There are several underlying etiologies and can occur in the immediate postoperative period or can be more delayed.Reference #1: Interatrial Shunting After Major Thoracic Surgery: A Rare but Clinically Significant Event. Ann Thorac Surg 2012;93:1647-51Reference #2: Dyspnoea and hypoxaemia after lung surgery: the role of interatrial right-to-left shunt. Eur Respir J 2006; 28: 174-181Reference #3: Platypnoea-orthodeoxia syndrome. Heart 2000;83:221-223DISCLOSURE: The following authors have nothing to disclose: Nitin Bhatt, Ulysses MagalangNo Product/Research Disclosure Information.