CASE 2

Group B

Baby Fiona Goodchild was born on May 3, 2004. It was noted that she had a low birth weight of 2600g. Normally, the average weight of a newborn is approximately 2800g. After a physical examination, the baby was reported to have a continuous systolic murmur. Ultrasound revealed a problem with a structure in the heart. In the hopes that the structure would naturally correct itself, the physician allowed the parents to take Baby Fiona home with a scheduled two week return visit.

During the two week follow-up appointment at the cardiac clinic, Fiona’s mother reported that Fiona had been rather breathless when feeding. She also noticed that Fiona’s skin looked blue in color much of the time. On examination, the baby still had a systolic murmur and now had a diastolic murmur. Another ultrasound showed that the structure had not corrected itself. Baby Fiona was then admitted into the hospital for further testing.

What Is the Function

of the Heart ?

• Pumps blood throughout the entire body

• Beats approximately 72 beats per minute supplying cells of the body with nutrients they need to survive

Heart

• When looking at an image, the right and left are defined as the right and left of the patient.

• This means right and left are reversed when looking at an image.

• In this image of the heart, “right” is to the left of the image and “left” is to the right of the image.

LEFTRIGHT

The Heart Contains Four Compartments:

2 Atrial and

2 Ventricular Compartments

Atrial Compartments of the Heart

The atria of the heart are receiving chambers. The right atrium receives blood from the body via the superior and inferior vena cava and the left atrium receives blood from the lungs via the pulmonary veins.

Right Atrium

PectinateMuscle

AtrialCompartments

The atrial chambers contain pectinate muscles within the walls of the chamber. Blood passes from the atria to the ventricles through a one-way opening called the atrioventricular valve.

Ventricular Compartments of the Heart

The ventricles are the discharging chambers. The right ventricle pumps blood away from the heart to the lungs via the pulmonary arteries and the left ventricle pumps blood away from the heart to the body through the aorta.

The ventricular chambers contain trabeculae carneae muscle. Ventricular chambers are more muscular and larger in size because they must pump blood away from the heart into a system under higher pressure, the pulmonary arteries or aorta. The left ventricle is the most muscular since it functions to pump blood to the entire body via the aorta.

RightVentricle

VentricularCompartments

Trabeculae Carneae Muscle

As blood fills the atria, the pressure rises and forces the blood into the ventricles through the one-way atrioventricular valve. The period of ventricular filling is called diastole in the cardiac cycle. When a physician listens with a stethoscope, the ventricle filling with blood sounds like a “lub”. When the ventricles fill, an electrical impulse signals them to contract to push the blood into the pulmonary artery (right ventricle) or into the aorta (left ventricle). This period of ventricular contraction is called systole in the cardiac cycle. When a physician listens with a stethoscope, the ventricle squeezing blood out of the heard sounds like a “dub”.

To listen to heart sounds that determine healthy heart function, a physician places a stethoscope on the chest wall during an examination.The physician locates the intercostal spaces, or spaces between the ribs, where certain structures pertaining to heart function can be heard.This image of the anterior chest wall demonstrates stethoscope placements:

1= At the 2nd intercostal space, to the right of the midline, one can hear the blood in the aorta as it leaves the heart.

2= At the 2nd intercostal space, to the left of the midline, one can hear the blood in the pulmonary trunk as it leaves the heart.

3=At the 3rd through 5th intercostal spaces, just to the left of the midline, one listens for proper function of the right ventricle.

4=At the 5th intercostal space, far left of the midline, one listens for proper function of the left ventricle.

If one imagines the heart in place under the thoracic wall, the same stethoscope placements viewed in the previous slide can be correlated with blood flow through anatomically important structures of the heart.

1= Blood flow into the aorta can be heard.

2= Blood flow into the pulmonary trunk can be heard.

3= Blood flow between the right atrium and right ventricle, through the tricuspid valve, can be heard.4= Blood flow between the left atrium and left ventricle, through the mitral valve, can be heard.

How Does Blood Flow in the Fetal Heart Differ from Blood Flow in the Heart After

Birth?

VS.

Normally deoxygenated blood enters the right atrium, passes to the right ventricle and then to the lungs through the pulmonary artery to become oxygenated. The left atrium then receives the oxygenated blood. After passing through the left atrium, blood travels to the left ventricle and then to the aorta, and finally out to the body. However, in the fetus, blood in the heart is shunted away from the lungs.

Why do you think this happens?

To the Body

RightAtrium

RightVentricle

PulmonaryArtery

Aorta

LeftAtrium

LeftVentricle

Blood flow within the fetal heart is very similar to blood flow in the heart after birth. However, within the fetal circulation there are two shunts that direct blood flow away from the lungs. Blood must bypass the lungs because prior to birth the fetal lungs are not fully developed. These shunts are known as the foramen ovale and the ductus arteriosus. The foramen ovale is an opening located in the right atrium. This opening allows blood to be shunted from the right atrium directly to the left atrium and away from the fetal lungs. The ductus arteriosus is a vascular connection found directly between the pulmonary artery and the aorta. Blood is shunted from the pulmonary artery directly into the aorta and again away from the fetal lungs. The fetus is connected by the umbilical cord to the placenta of the mother. Oxygen and carbon dioxide exchange takes place at the placenta along with the elimination of waste products.

Ductus Arteriosus

ForamenOvale

Typically, the foramen ovale and ductus arteriosus close following birth, thus altering the circulatory system. Blood begins to move from the right atrium to the left atrium and then to the lungs for the exchange of oxygen and carbon dioxide and the newborn begins to breath on its own. However, in some cases either of the two shunts may not close leading to health complications. The foramen ovale is initially closed by a flap. The pressure in the left atrium prevents the flap from opening. Eventually the flap seals closed so that the foramen ovale opening in the fetus becomes the fossa ovale depression in heart after birth.

If the flap forms incompletely or does not completely seal close, then deoxygenated blood can pass from the right atrium to the left atrium. A patient with an open or patent foramen ovale will have a heart murmur. Unfortunately, this heart murmur maybe undetectable and the patient will exhibit no other obvious symptoms.

If the ductus arteriosus remains open after birth andfails to close it is referred to as a patent ductus arteriosus. The term “patent” means open. Complications associated with patent ductus arteriosus are poor growth and eating, easy tiring, and a rapid heart rate. It is also common to notice that the infant is blue in color especially whilefeeding due to a lack of oxygen.

Patent Ductus Arteriosus

Knowing Baby Fiona’s symptoms at the 2-week examination, which shunt do you think did not properly close?

An ultrasound confirmed that Baby Fiona had a large patent ductus arteriosus. The doctors sent her home for the first two weeks to see if the ductus arteriosis would close on its own. The ultrasound on the second week visit revealed that the ductus arteriosus had only closed slightly.

Upon admission into the hospital, Baby Fiona was given prostaglandin inhibitors, such as ibuprofen, which promote closure of the ductus arterious. Unfortunately, this form of treatment was unsuccessful and the the ductus arteriosus remained open. At 14 months, Baby Fiona underwent surgery to have the ductus ligated. Her development thereafter was normal, and she is now a healthy toddler.