Makindo Medical Notes.com

Related Subjects: |Congenital Acyanotic Heart Disease |Congenital Cyanotic Heart Disease |Cardiac Embryology |Cyanosis - Central and Peripheral |Down's syndrome (Trisomy 21) |Tetralogy of Fallot |Patent Foramen Ovale (PFO) |Ventricular Septal defect (VSD) |Atrial Septal defect (ASD)

In an ASD the main murmur is not due to flow across the septal defect but due to increased right-sided flow with an ESM across the pulmonary valves. There is a low risk of endocarditis. Operate if Pulmonary/systemic flow > 1.5

About

• Hole allowing flow between the atria
• Shunting of blood from left atrium to the right atrium
• 10% of congenital heart disease (VSD commonest)
• Females and Downs' syndrome

Aetiology

• LA to RA shunt leads to an increase in pulmonary blood flow with ASD
• Shunt amount depends on size, compliance of LA/RA
• LA to RA shunting causes RA/RV dilation and eventual failure
• Pulmonary flow > systemic flow with pulmonary plethora

Structure - 4 types

• Ostium secundum (70%) defects - milder and more commonly seen in 80% involving the foramen ovale. Central fossa ovalis defects have mitral valve prolapse. ECG RBBB with RAD
• Ostium primum (15%) defects - more serious and can involve mitral and tricuspid valves causing what is called a partial atrioventricular septal defect (pAVSD). May be both MR and TR. ECG RBBB and LAD. 1st-degree heart block. Associated with Down's syndrome, Noonan's and Klinefelter's
• Sinus venosus (15%) ASD defect - involves upper atrial septum near SVC often with anomalous venous drainage of the right upper pulmonary vein into the right atrium
• Unroofed Coronary sinus (<1%) with a defect allowing shunting RA/LA

Clinical

• Often no symptoms and may not be picked up until late adulthood
• Chest infections and wheeze, Heart failure, Fixed split A2, AF
• ESM at upper LSE due to increased flow across the pulmonary valve
• May be a PSM with MR due to an Ostium Primum defect with pAVSD
• Flow across the defect is very low pressure and no murmur was heard

Investigations

• CXR: pulmonary plethora with enlarged RA and RV and pulmonary artery
• ECG ostium secundum - RBBB + RAD
• ECG ostium primum (pAVSD) RBBB + LAD + 1st degree AV block
• Echocardiography defines the anatomy and flow
• Right heart catheterisation to measure shunt and Pulmonary artery pressure
• Role for cardiac MRI in defining anatomy

Complications

• Pulmonary hypertension
• Cardiac arrhythmias e.g. Atrial fibrillation with risk of thromboembolism
• Low risk for endocarditis and so Antibiotic endocarditis prophylaxis is not needed
• Right heart failure
• Stroke and paradoxical embolism

Management

• Small uncomplicated ASDs may be monitored.
• Moderate to large ASDs can affect life expectancy
• Those with a flow ratio of 1.5 (Pulm flow):1(systemic flow) or greater should be closed surgically or by catheter. In the absence of complications operative mortality < 1%
• Prognosis excellent unless pulmonary hypertension (Eisenmenger's syndrome) has developed
• Ostium secundum can be closed with a simple occlusion device inserted by PCI
• Ostium Primum with pAVSD may need open heart corrective surgery