Cardiac Shunts and Heart Defects

Left to Right Shunts

• Abnormal connections cause blood to flow from the left (systemic) side to the right (pulmonary) side of the heart.
• This leads to increased blood flow in the pulmonary circulation.
• Qp (pulmonary flow) is greater than Qs (systemic flow) in these shunts.
• Examples of left-to-right shunts include Atrial Septal Defect (ASD) and Ventricular Septal Defect (VSD).

Right to Left Shunts

• Involve abnormal connections that cause blood to flow from the right (pulmonary) side to the left (systemic) side of the heart.
• This results in increased blood flow to the systemic circulation.
• Qp (pulmonary flow) is less than Qs (systemic flow) in these shunts.
• Eisenmenger syndrome is an example of a right-to-left shunt.

Incidence Rates of Congenital Heart Defects

• All infants with congenital heart disease develop heart failure within 6 months.
• 25% of babies with congenital heart disease have a critical heart defect.

Normal Cardiac Pressures

• Right Atrium (RA) pressure is approximately 5 mmHg.
• Right Ventricle (RV) pressure is around 25 mmHg.
• Left Atrium (LA) pressure is about 10 mmHg.
• Left Ventricle (LV) pressure is approximately 100 mmHg.

Cyanosis

• Defined as a blue discoloration due to a lack of oxygen.
• Central cyanosis affects the mouth, head, thorax, and mucous membranes.
• Peripheral cyanosis impacts the distal portions of the extremities, around the mouth, and nail beds, and can be a normal variant.

Atrial Septal Defect (ASD)

• ASD is a defect in the atrial septum.
• The secundum ASD is the most common type.
• A shunt moves blood from the left atrium to the right atrium.
• Pulmonary flow exceeds systemic flow (Qp > Qs)
• There is an increase in volume load on the right atrium and right ventricle, leading to dilation.
• Patients experience dyspnea, frequent respiratory infections, fatigue, and poor feeding.
• Patients are normally asymptomatic.
• A wide split S2 with a murmur over the left upper sternal border is audible.
• The EKG shows a right axis deviation, right ventricular hypertrophy, and RSr' in V1.
• An Echocardiogram is the best method of diagnosis.
• 80% will close by 1 year, can do catheter closure above 3 years old

Patent Foramen Ovale (PFO)

• PFO occurs when the foramen ovale does not close properly, specifically when the septum primum and septum secundum fail to fuse.
• 25% of adults have this condition
• It is often asymptomatic without significant atrial shunting, but can increase the risk of stroke.

Ventricular Septal Defect (VSD)

• VSD is a defect existing in the ventricular wall.
• Blood is shunted from the left ventricle to the right ventricle due to the higher pressure on the left side.
• Pulmonary flow exceeds systemic flow (Qp > Qs)
• The increased volume and pressure on the pulmonary circulation can cause dilation.
• Pulmonary congestion, tachypnea, and tachycardia manifest.
• Poor weight gain, fatigue with feeds, diaphoresis, and failure to thrive can occur
• A murmur is heard at the left sternal border. Small VSDs correlate to louder murmurs, while large VSDs are associated with quieter murmurs.
• Diagnose with an Echocardiogram to determine size, location, and velocity of flow.
• An EKG may show left ventricular hypertrophy, left atrial enlargement, and left axis deviation.
• A Chest X-Ray may show cardiomegaly and pulmonary edema, especially when there is a large VSD.
• Manage with diuretics and ACE inhibitors, optimized nutrition, and surgical repair
• Small defects can resolve without intervention
• VSD is the most common congenital heart defect.

Patent Ductus Arteriosus (PDA)

• The ductus arteriosus, used to bypass pulmonary circulation in the fetus, fails to close.
• This is caused by the failure of closure of Ductus Arteriosus
• Patients exhibit a wide pulse pressure, pulmonary edema, and poor feeding/weight gain.
• Echocardiogram is used to assess size, direction, and velocity
• EKG shows a left axis dev.
• Diuretics and ACE inhibitors are used to manage moderate-to-large PDAs.
• NSAIDS stop prostaglandin production to close PDA

Coarctation of the Aorta

• Narrowing of the aortic arch happens when the PDA closes.
• This results in mild to critical obstruction and impacts the blood flow from the LV to the systemic circulation.
• Patients present with irritability, poor feeding, dyspnea, pallor, shock, and bowel ischemia
• Systemic hypertension, a murmur, decreased lower extremity pulses, and diminished LE compared to UE blood pressure
• In children, claudication with exertion and HTN are the keys
• EKG shows LVH
• Management includes starting prostaglandin and surgical repair
• The figure 3 sign will be viewable on a CXR.
• Diagnose Echo

Atrioventricular Septal Defect (AVSD)

• AVSD is an endocardial cushion defect affecting the atrial and ventricular walls.
• Mitral valve involvement is a key feature.
• This can lead to left-to-right shunting and heart failure.
• Surgical repair is the main treatment.
• AVSD is commonly seen in individuals with trisomy 21.

Tetralogy of Fallot (TOF)

• Presents as 4 malformations: Pulmonary Stenosis, RV Hypertrophy, Overriding Aorta, VSD
• Patients have hypercyanotic or "Tet" spells and squat.
• Harsh systolic murmur and Single S2 sounds on PE
• The EKG shows RVH and RBBB.
• Management aimed at increasing systemic pressure and decreasing right-to-left shunting.
• Provide 100% oxygen, minimize agitation
• Administer IV fluids, norepinephrine, or propranolol (slow HR).
• Prostaglandins
• Surgical repair needed at 4-6 months
• Most common cyanotic heart disease, 22q11, trisomy 21 chromosomal abnormality

Transposition of the Great Arteries (TGA)

• Characterized by abnormal origins of great arteries
• Infants exhibit profound cyanosis that doesn't respond to oxygen.
• Shows mixing, Coronary artery abnormalities
• Administer prostaglandin
• Surgical repair (Moss and Adams) 7-10 days of life

Eisenmenger Syndrome

• Results from an unrepaired congenital defect with a left-to-right shunt.
• Pulmonary artery hypertension reverses the shunt.
• Shunts can cause this: ASD, VSD, TGA with VSD, AVSD, PDA
• Hypoxia with cyanosis
• Administer 02
• Provide pulmonary vasodilator
• Prevent pulmonary artery thrombosis
• Lung transplant