Mixed (Cardiac) Heart Defects

Hey guys in this lesson we are going to be talking about mixed congenital heart defects.

So mixed congenital heart defects are usually pretty complex and they can present in a lot of different ways depending on how large the openings are or how severe the defect actually is. They are called mixed defects because survival depends on the ability of deoxygenated and oxygenated blood to mix. If it doesn’t mix then the blood circulated throughout the body will be even hypoxemic. The way blood mixes in these defects is through a PDA, an open Foramen Ovale or and ASD. Remember, the pda and foramen ovale are part of the fetal heart circulation so check out the OB less on fetal circulation if you want a refresher on this!

The first lesson we are going to look at is Transposition of the Great Arteries or ToGA as it is usually referred to. In this defect the aorta and pulmonary artery have swapped places. So, the aorta is leaving the right ventricle carrying deoxygenated blood through the body and the pulmonary artery is leaving the left ventricle, where that same blood is circulating through the heart over and over. So you have two separate systems circulated and never mixing and this is why you need an opening like a PDA to allow blood to mix if the patient is going to survive.

Most babies will experience cyanosis within hours of birth. But if there is a large PDA or VSD, presentation may be delayed and it may show up as respiratory and feeding difficulties within a month or so of birth.

Heart failure is very common and symptoms will worsen until it can be treated.

Truncus Arteriosus is a pretty uncommon defect and with it, the heart is missing the two distinct vessels that usually leave the heart, the pulmonary artery and the aorta. Instead it has one vessel that connects both the right and left ventricle. Symptoms usually present pretty quickly after birth and usually look like, cyanosis, tachypnea, poor feeding and activity intolerance.

Hypoplastic Left Heart is a diagnosis that includes a variety of defects, but the most significant is the hypoplastic left ventricle. It is small and unable to do the work needed. Other defects that can occur are a patent foramen ovale, VSD, PDA and coarctation of the aorta. If untreated, it is fatal within the first month of life.

Symptoms are cyanosis, tachypnea, dyspnea, poor feeding and signs of heart failure. If the PDA is allowed to close the patient will deteriorate quickly!

For therapeutic management the most important thing is to keep the PDA open so that blood can continue to mix. This is done by administering Prostaglandin E1 via IV infusion within the first 48 hours of life. If this is given, the patient will continue to have symptoms but they will have some oxygenated blood circulating. If the PDA closes, the patient will deteriorate quickly.

These defects often require multiple surgeries. For ToGA, they need an arterial switch and a lot of children with hypoplastic left heart end up needing a heart transplant.

Nursing care is all about decreasing cardiac workload and this is done primarily by encouraging rest and managing the child’s feeding. For more more details on the nursing care check out the Congenital Heart Defects Lesson.

Complications to be on the lookout for after heart surgery are infection, hemorrhage, stroke and pneumothorax.

You’re priority nursing concepts for a peds patient with a mixed congenital heart defect are oxygenation, perfusion and gas exchange.

Okay, lets go over your key points for this lesson. Mixed Congenital Heart defects are varied and complex. We talked about ToGA, Truncus Arteriosus and Hypoplastic Left Heart. The common factor for all of these is that they need blood to mix in order to survive. Blood mixes through an ASD, VSD, PDA or open foramen ovale.

These defects all present pretty quickly with cyanosis and eventually heart failure. Symptoms will worsen quickly as the heart is overworked and the patient will deteriorate rapidly if the PDA or other openings close.

Prostaglandin E1 is given within the first 48 hours of birth to keep the PDA open.

And these defects usually require major surgery. These surgeries are not curative. Their goal is to optimize blood flow for the patient. They will need monitoring throughout life.

That’s it for our lesson on mixed cardiac defects. Make sure you check out all the resources attached to this lesson. Now, go out and be your best self today. Happy Nursing!