Acute right-to-left inter-atrial shunt; an important cause of profound hypoxia

Abstract

Three patients presented to our intensive care unit over a 3-yr period with profound hypoxia resulting from acute right-to-left inter-atrial shunt (RLIAS). Patient 1 was a 67-yr-old male with an atrial septal defect who became hypoxic and developed the rare sign of platypnoea following elective repair of an abdominal aortic aneurysm (breathlessness made worse when upright and relieved by lying flat). Patient 2 was a 38-yr-old female who developed platypnoea and hypoxia secondary to a patent foramen ovale (PFO) and pericardial effusion. Patient 3 was a 46-yr-old male with a PFO who developed hypoxia without platypnoea because of multiple pulmonary emboli following right hemicolectomy. These case reports illustrate the need to consider RLIAS as a cause of hypoxia of sudden onset. Early use of bubble contrast echocardiography is indicated.

Acute right to left shunt—Combination of tricuspid valve endocarditis, Chiari network, and ostium secundum atrial septal defect

“…Chronic right to left intra-cardiac shunts occur when increased left to right blood flow leads to pulmonary vascular disease in turn elevating pulmonary arterial pressure causing shunt reversal (Eisenmenger syndrome) [1,2]. Eisenmenger syndrome most commonly occurs in ventricular septal defects and is rare in ASDs.…”

“…Acute right to left intra-cardiac shunts are an uncommon but important cause of refractory hypoxia. They require an inter-atrial defect coupled with an acute insult which may or may not result in raised right atrial pressure [1]. The oxygen content of systemic arterial blood falls in proportion to the volume of systemic venous blood mixing with pulmonary venous blood.…”

Hypoxemia-orthodeoxia related to patent foramen ovale without pulmonary hypertension

“…a secondary cardiac or pulmonary insult. 4 Orthodeoxia may be accompanied by the symptom of platypnea, the sensation of difficulty in breathing when erect that is relieved by recumbency (a condition termed the "platypnea-orthodeoxia syndrome"). 1,5,6 When present, the platypnea-orthodeoxia syndrome is usually caused by a PFO, intrapulmonary vascular shunt, or severe ventilation-perfusion mismatching and should be considered when hypoxemia is positional or more pronounced than expected on the basis of cardiac and pulmonary findings.…”

“…PFO, which occurs in approximately 25% to 30% of healthy subjects, is present in the majority of reported cases of acute right-to-left intra-atrial shunt. [4][5][6][7] Right-to-left interatrial shunt is a rare but important cause of profound hypoxemia. The platypnea-orthodeoxia syndrome resulting from a patent foramen is often triggered by an intercurrent event or condition, such as aortic dilatation, pulmonary embolism, pneumonectomy, or diaphragmatic paralysis.…”

“…[5][6][7][8][9][10][11][12] Intravenous injection of saline mixed with microbubbles of air greatly enhances the diagnosis yield of right-to-left shunts by TTE or TEE by permitting visualization of the shunt between atria. 4,9,12 The sensitivity of this technique may be augmented by having the patient cough or perform a Valsalva manoeuvre, thereby increasing intrathoracic pressure and right-to-left shunting. 5 This technique was performed in different positions, such as in the upright position.…”