Enhancement of hypoxemia by right-to-left atrial shunting in severe asthma

Abstract

We report two cases of severe hypoxemia due to right-to-left shunt in acute asthmatic patients. During acute asthma, the transmural right atrial pressure can be higher than left atrial pressure during inspiration and then induce a right-to-left shunt through inter-atrial communication leading to hypoxemia. Contrast echography as well as Doppler analysis can easily confirm the diagnosis.

Diagnostic Bedside Ultrasonography for Acute Respiratory Failure and Severe Hypoxemia in the Medical Intensive Care Unit: Basics and Comprehensive Approaches

“…81 The resulting RA flow pattern is referred to as a persistent embryonic RA flow pattern (Figure 20; Supplemental Video 19). 82 When the right atrium is further distorted mechanically, the Acute occlusion of pulmonary vascular bed: Thromboembolism 48 Bone marrow embolism 49 Red cell sickling Leukemic cell aggregates Air Other substances injected into systemic veins, that is, sclerosing agents, chemotherapeutic agents 50,51 Change in mediastinal anatomic constellation: Pneumonectomy or lobectomy, especially of the right lung 62 Pulmonary collapse therapy for pulmonary tuberculosis 63 Atelectasis Hemidiaphragm elevation 64 Kyphosis 65 Acute reduction of pulmonary vascular bed diameter: Increased intrathoracic pressure, that is, mechanical ventilation 52 Bronchospasm, that is, anaphylaxis, asthma/chronic obstructive pulmonary (disease COPD) exacerbation 53 Cardiac impingement of mediastinal structures: Thoracic aortic aneurysm, especially at the aortic root 66,67 Pulmonary vasoconstriction: Hypoxia 54 Acidosis Hypercapnia 55 Change in pericardial anatomic constellation: Pericardial effusion Drainage of pericardial effusion 68,69 Acutely decreased right ventricular systolic function: Right ventricular myocardial ischemia/infarction 56 Right ventricular dysfunction after pericardiocentesis 57 Medication-induced myocardial depression 58 Stress cardiomyopathy Septic cardiomyopathy…”

Transcatheter Closure of Right-to-Left Interatrial Shunts to Resolve Hypoxemia

“…A rise in the right atrial pressure above the left atrial pressure may precipitate RLIAS. This can result from obstruction of the pulmonary blood flow because of multiple causes, such as: pulmonary embolus, 2 increased transmural pressures in asthmatics, 3 following right ventricular infarction, 4 a coronary artery bypass graft, or as a result of an anatomical shift such as hemidiaphragmatic paresis 5 . Increased right‐sided pressures occur in positive pressure ventilation, 6 patients with tricuspid atresia with an obligatory right‐to‐left shunt at the atrial level, Ebstein's anomaly, pulmonary stenosis, and cardiac tamponade 7 .…”

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

“…Kartagener's syndrome will occur in about 20% of patients. 5 Thus, the incidence being approximately 1 in 50 000 births. Our patient did not have an echocardiogram and on clinical grounds was assumed to have a totally normal heart.…”

“…They are most commonly transposition of the great arteries, double outlet right ventricle, ventricular septal defect, single ventricle and pulmonary stenosis or artresia. 5 In patients with dextrocardia and situs ambiguus, polysplenia or asplenia may be present in association with complex multiple cardiac abnormalities. These include a combination of systemic and pulmonary venous abnormalities, defects in the ventricular and atrial septa and endocardial cushion defects.…”

“…6 The incidence of isolated levocardia (a left-sided heart) with situs inversus is about 0.6% per 10 000 births and more than 90% have serious heart disease. 5 Shunting of blood across a defect between the two sides of the heart is usually directed by the left-to-right pressure gradient. A large and persistent left-to-right shunt can increase pulmonary blood¯ow, which over months or years leads to microvascular changes, increased pulmonary vascular resistance and elevated pulmonary artery pressure.…”