March 1, 2016 - Left to Right Shunts Flashcards
Atrial Septal Defect (ASD)
A hole between the two atria.
There is not a big pressure difference between the two atria (the left has a mean pressure of 5 and the left has a mean pressure of 4). Because of this, there is left to right flow through the defect which can cause the right heart to enlarge over time.
On exam, the patient may have a RV heave, a widely split fixed second heart sound, an ejection systolic murmur near the pulmonary valve.
Symptoms are usually mild, and generally do not present until later in childhood and may include breathlessness with exercise.
Treated with surgical or device closure.
ASD Treatment
Surgical closure
Device closure
Ventricular Septal Defect (VSD)
A hole between the ventricles.
There is a much bigger pressure difference between the two ventricles in systole (but not diastole). Because of this, during systole, blood will shunt from the left ventricle into the right, BUT, because the right ventricle is contracting at the same time, it will be pumped into the pulmonary circulation and fill the left atrium, thereby dilation of the left atrium and soon after, the left ventricle. Eventually, the right side becomes enlarged too.
On exam, the apex is often displaced laterally, there may be a RV heave or an LV lift, thrills at the left lower sternal border, and a harsh pansystolic murmur.
Symptoms usually present at 4-6 weeks of life in large VSDs and may be associated with failure to thrive, feeding difficulties, cough, and fever.
Treatment is observation as most will close spontaneously and are not hemodynamically significant, but if they are, they require surgical closure.
VSD Treatment
Observation as many small hemodynamically insignificant VSDs will close on their own.
Hemodynamically significant VSDs require surgical repair and closure.
Patent Ductus Arteriosus (PDA)
When the ductus arteriosus does not close after birth.
Because of the big pressure difference between the aorta and the pulmonary artery, blood will flow from the aorta back into the pulmonary artery and to the lungs. This will continue during systole and during diastole. This will cause the left atrium to dilate and enlarge, as well as the left ventricle.
On exam, there may be bounding pulses, cardiac apex may be displaced laterally, there may be a thrill in the 2nd intercostal space, an there will be a continuous murmur in the 2nd intercostal space (P).
Often occurs in preterm babies with symptoms, and in children it often has mild sumptoms.
Treatment is surgical ligation or device closure.
PDA Treatment
Surgical ligation or device closure.
PDA is VERY common in premature infants, and may be closed with ibuprofen (inhibits prostaglandin synthesis).
Atroventricular Septal Defect (AVSD)
VSD and ASD with a common AV valve.
Most common in infants with Down Syndrome.
Left to right shunt at atrial and ventricular levels. RA and RV enlargement from atrial shunt, and LA and LV enlargement from ventricular shunt.
On exam, cardiac apex may be displaced leftward, RV heave or LV lift, normal S1 with a widely split S2. Systolic ejection murmur, and signs of pulmonary and systemic congestion.
Typically presents at 3-4 weeks of age with a failure to thrive, feeding difficulties, and recurrent respiratory tract infections.
Treatment is targetted surgical closure at 4-6 months of age when the infant is around 5kg.
AVSD Treatment
Surgery at around 6 months of age or when the infant is around 5kg.
Eisenmenger Syndrome
Prolonged left to right shunting results in increased pulmonary bloodflow and increased pulmonary artery pressure.
Pulmonary vascular bed reacts by remodelling, resulting in thickening of the media and intima and narrowing of the lumen of the arterioles which results in even FURTHER increased resistance through the pulmonary artery.
Eventually, the pulmonary artery pressure (and thus the RV pressure) exceeds systemic artery pressure and the flow through the defect reverses, producing a right to left shunt.
Primarily affects adolescents and adults with significant left to right shunts that are never repaired.
Symptoms of Eisenmenger Syndrome
Cyanosis
Shortness of breath/fatigue
Chest pain/palpitations
Headache/dizziness/syncope
Blurred vision
Clubbing
Eisenmenger Syndrome - Physical Exam
Cyanosis
Clubbing
RV heave
LOUD, palpable S2
Murmurs may be quiet or absent (not much flow)
Eisenmenger Syndrome Treatment
Supplemental oxygen
Pulmonary vasodilators to decrease pulmonary HTN
Heart-lung transplant may be considered
(Life expectancy severely reduced)
