Congenital Heart Disease part 2

ATRIOVENTRICULAR SEPTAL DEFECT

An atriventricular septal defect (Atrioventricular canal or endocardial cushion defect) is characterized by the presence of a common antrioventricular annulus, guarded by five leaflets. In the partial form, the anterior and posterior bridging leaflets are fused centrally, creating separate left and right sided orifices. In the complete atrioventricular septal defect the central fusion is not present and there is only one orifice. The partial atrioventricular septal defect (Primum atrio septal defect, partial atrioventricular canal) has a defect only at the atrial level. A complete atrioventricular defect (Complete atrioventricular canal) has a septal defect in the crux of the heart, extending into both the interatrial and interventricular septum. The atrioventricular node is positioned posterior and inferior to the coronary sinus. The bundle of His and the left bundle branch are displaced posteriorly. This accounts for an abnormal activation sequence of the ventricles.

Clinical presentation will mainly depend on the presence and size of the atrial septal defect and ventricle septal defect and competence of the left sided atrioventricular valve. Symptoms are not specific for an atrioventricular septal defect  and are caused bay intracardiac shunting (left-right, right-left, or bidirectional), pulmonary hypertension, atrioventricular  valve regurgitation, ventricular dysfunction or left ventricular outflow tract obstruction. Exercise intolerance, dyspnoea, arrhytmia and cyanosis may be present. Subaortic stenosis may be present or develop in time.

The history of unoperated complete atrioventricular septal defect is that of Eisenmenger syndrome unless the ventricle septal defect  is only small.

Unrepaired partial atrioventricular septal defect is not uncommon in adults. The presenting clinical symptoms are that of an left-right shunt at the atrial level and/or that of left-sided atrioventricular valve regurgitation. Patient may be still asymptomatic , but symptoms tend to increase with age. Most adults are symptomatic by 40 years of age.

PATENT DUCTUS ARTERIOSUS

Patent ductus arteriosus is the persistent communication between the proximal left pulmonary artery and decending aorta just distal to the left subclavian artery. It can be associated with a variety of congenital heart disease lesions. However, in the adult it is usually an isolated finding.

Patent ductus arteriosus originally result in left-right shunt and left ventricle volume overload. In moderate or large patent ductus arteriosus, pulmonary pressure is elevated. In patients who reach adulthood with a moderate patent ductus arteriosus, either left ventricle volume overload or ppulmonary arterial hypertention may be predominant (genetic predisposition). Adult patients with large patent ductus arteriosus have in general Eisenmenger physiology.

Presentations of adult patients with patent ductus arteriosus include:

• Small duct with no left ventricle volume overload (normal left ventricle) and normal pulmonary artery pressure (generally asymptomatic)
• Moderate patent ductus arteriosus with predominant left ventricle volume overload, large left ventricle with normal or reduced function (may present with left heart failure)
• Moderate patend ductus arteriosus with predominant pulmonary arterial hypertention, pressure overloaded right ventricle (may present with right heart failure)
• Large patent ductus arteriosus, Eisenmenger physiology with differential hypoxaemia and differential cyanosis (lower extrimities cyanotic, sometimes left arm too)