In either instance, the apex of the heart will be poorly positioned, which should alert a clinician of the likelihood of atrial isomerism. It is estimated that 5–10% of isomeric patients have mesocardia, in which the heart is positioned at the center of the thorax, 25–50% have dextrocardia, in which the apex of the heart is pointed toward the right side of the thorax, and 50–70% have levocardia, in which the apex of the heart is pointed toward the left side of the thorax. Right atrial appendage isomerism
Right atrial appendage isomerism, also called right atrial isomerism, is a cardiac development defect in which the heart has bilateral right atria and atrial attachments in the muscle wall, as opposed to the normal right atrium and left atrium. In right atrial isomerism, the pulmonary blood oxygen tract is damaged due to right-left shunting of blood. In addition, the atrial septum which distinguishes the 2 atria is absent. These impairments, in addition to congestion in the pulmonary tract, allows deoxygenated blood to mix with oxygenated blood, contributing to cyanosis and possible respiratory distress. Poor systemic circulation also results due to improper positioning of the aorta. Left atrial appendage isomerism
Left atrial appendage isomerism, also called left atrial isomerism, is a cardiac development defect in which the heart has two bilateral left atria and atrial appendages in the muscle wall. Left atrial isomerism can have varied clinical manifestations, including a later onset of symptoms.
Vascular abnormalities:
Interrupted inferior vena cava,
Bilateral superior or inferior venae cavae
Intrahepatic interruption of the inferior vena cava with connection to the azygos or hemiazygos veins
Aberrant portal veins. Bronchial tree and lungs
Pathophysiology in the bronchial tree can be observed by radiography. Under normal development, the bronchial tree consists of two main bronchi that are anatomically different:

Hyparterial bronchus (below the pulmonary artery): supplies blood to the bi-lobed left lung
Eparterial bronchus (adjacent to the artery): supplies blood to the tri-lobed right lungIn situs ambiguus, there is a duplication of either the hyparterial or eparterial bronchus. These features are not associated with any significant clinical complications. Mechanisms leading to bronchial duplication are not thoroughly understood. In pulmonary valve stenosis, there is a reduction in blood flow to the lungs due to an obstruction of the heart at the pulmonic valve. This contributes to cyanosis and pulmonary hypertension. Diagnosis
For proper diagnosis of situs ambiguus, cardiac and non-cardiac features must be evaluated. Diagnostic criteria for atrial isomerism includes observation of symmetry of thoracic visceral organs upon echocardiogram, arrhythmia upon electrocardiogram, and chest x-ray for confirmation of the hearts location across the left-right axis. Additional radiographic and cross-sectional imaging may be obtained to evaluate both cardiac and non-cardiac manifestations of situs ambiguus. In addition, a series of gastrointestinal tests can be conducted for observation of intestinal malrotation, as well as a scan of the liver and spleen for biliary function.