Common Mixing

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These conditions lead to the mixing of deoxygenated and oxygenated blood in a chamber, which leads to progressive cyanosis. These conditions are rarer than septal defects.

Atrioventricular Septal Defect (AVSD)

This is a condition where there is a defect in the middle of the heart with a single 5-leaflet valve between the atria and ventricles

– It is due to poor fusion of the endocardial cushion with the atrial and ventricular septum

– This 5-leaflet valve stretches across the AV junction but tends to leak allowing the mixing of blood.

– It is associated with a diagnosis of Down’s syndrome

Symptoms:

– Cyanosis at birth

– Heart failure within days of birth –> dyspnea, poor growth, oedema, fatigue

– Will lead to pulmonary hypertension as blood backs up into lungs due to weakened left ventricle

Diagnosis:

– Echocardiogram (it can be detected antenatally with ultrasound)

Management:

Medical treatment of heart failure followed by surgery to correct defect

Tricuspid Atresia

This is where the tricuspid valve orifice fails to develop, and the right ventricle is hypoplastic.

– This means that the right ventricle is small and non-functional leaving only one effective ventricle

– It leads to common mixing of systemic and pulmonary venous return in the left atrium

– Because of a lack of connection, you must also have an atrial and ventricular septal defect to allow you to receive blood form the pulmonary vein and pump it into the pulmonary artery

Symptoms:

– Progressive cyanosis

– Murmur due to the VSD

– Will lead to heart failure and breathlessness

Diagnosis:

Echocardiogram

Management:

– Prostaglandin infusion to maintain ductus arteriosus

– Surgery to connect the SVC to the pulmonary artery

– Fontan procedure –> channels IVC flow straight into pulmonary artery (bypassing non-functional right side of the heart)

Ebstein’s Anomaly

This is a rare heart problem in which the tricuspid valve is not developed properly.

– It has a very low insertion point which leads to a large right atrium and small right ventricle. Therefore, it is called ‘atrialisation’ of the right ventricle

– It is associated with Wolff-Parkinson White syndrome and mothers taking lithium during 1st trimester of pregnancy

– Half f individuals also have a shunt between the left and right, such as an ASD or patent foramen ovale allowing deoxygenated blood from the large right atrium to enter the left side of the circulation

Symptoms:

– Cyanosis and Breathlessness

– Systolic murmur due to tricuspid regurgitation

– Can lead to congestive heart failure due to valve incompetence

– Wolff-Parkinson White syndrome or other arrhythmias

Diagnosis:

– Echocardiogram

Management:

– Anti-arrhythmic (+ surgery)

Persistent truncus arteriosus

In embryological development, the truncus arteriosus gives rise to the aorta and the pulmonary trunk

– Persistent truncus arteriosus is a condition which occurs due to failure of the truncus arteriosus to divide into the pulmonary trunk and aorta, allowing deoxygenated and oxygenated blood to mix.

– It occurs due to problems in the cardiac neural crest cells which are responsible for forming the aorticopulmonary septum dividing the two main blood vessels off

– 50% of these cases due to chromosome 22q11 deletion syndrome (DiGeorge syndrome)