Right-to-Left Shunts in Patients with Severe Hypoxemia: Transesophageal Contrast Echocardiography Study

Severe hypoxemi due to right-to-left (R-to-L) shunt has been well-documented in isolated case reports. Several mechanisms of R-to-L interatrial shunt in hypoxic patients have been identified. Although less-well recognized, R-to-L intrapulmonary shunts have also been demonstrated on contrast echocardiography in patients presenting with hypoxemia. Transesophageal contrast echocardiography (TEE) has been established as sensitive tool in the diagnosis of R-to-L interatrial or intrapulmonary shunts, however, the utility of TEE in the evaluation and outcome has not been studied. We reviewed medical records of 45 consecutive inpatients with hypoxemi as an indication for echocardiographic examination from 1989 to 1993 and assessed the clinical impact of TEE. All had chief complaint of dyspne and baseline hypoxemi (room air pO2 less than 76 mmHg). The etiology of hypoxemi could not be determined following history, physical examination, and initial evaluation. Transthoracic (TTE) and transesophageal echocardiography were performed for suspected R-to-L shunt. There were 26 males and 19 females. Mean age was 56 ± 13. In 5 patients, TTE suggested R-to-L interatrial shunt. TEE findings were as follow: 35 interatrial shunts, 7 intrapulmonary shunts, 4 pulmonary embolisms (PE), and 1 superior ven cava-to-pulmonary venous (SVC-to-PV) shunt. Of those, 15 patients had recommendations for significant therapeutic change following TEE; medical treatment for PE in 4, interatrial shunt repair in 9, 1 intrapulmonary shunt repair, and 1 SVC-PV surgical repair. All patients with R-to-L interatrial shunts were associated with processes known to cause right heart pressure overload. The three most common associations in patients with R-to-L interatrial shunt were pulmonary embolism (10), COPD (7), and pulmonary fibrosis (5). The 7 intrapulmonary shunts were noted with hepatic cirrhosis (3), pulmonary fibrosis (2), and primary pulmonary hypertension (2). All patients except one improved symptomatically during subsequent follow-ups. Conclusion: Clinically significant hypoxemi can result from echo contrast detectable R-to-L interatrial or intrapulmonary shunt. In severely hypoxic patients with R-to-L shunt, TEE is the most effective diagnostic modality.