Patient Education
Interventional Cardiology

If blood flow appears compromised in the patient's vascular system, the USC Cardiovascular Medicine Interventional specialists step in. To closely investigate narrowing or obstructed arteries, a Catheterization is generally performed. A long catheter wire is introduced into the patient's vasculature through a minor incision in the groin or arm. From there it can be advanced to vascular beds supplying the kidneys, lungs, brain and heart. Along the way, a dye is often used to provide contrast and examine the flow of blood. Through this technique, USC Interventionists are able to carefully examine the patient's vasculature and determine the location and extent of vascular narrowings and blockages.

When a narrowing, or Stenosis, is detected in the coronary arteries - which supply the heart muscle with oxygen - the USC Interventional Cardiologists are able to diagnose and remedy the blockage with various tools. A Stent, attached to the end of a catheter, may be advanced through the vasculature to the location of the stenosis. Once in place, the stent is deployed, providing a permanent scaffolding restoring the caliber of the stenosed section. This is often sufficient to restore normal blood flow across the diseased section of the vessel. Alternatively, a Drug Eluting Stent may be used, which slowly releases a drug to prevent inflammation and scarring around the stent. Each type of stent has its advantages and disadvantages and should be discussed with your USC Intervenionalist.

Atrial Septal Defect

An atrial septal defect (ASD) is a congenital defect (present at birth) which occurs when the atrial septum, the dividing wall between the two upper chambers of the heart known as the right and left atria, does not close completely. Atrial septal defects occur in 4 - 10 % of all children born with congenital heart disease.

An atrial septal defect allows oxygen-rich blood to pass from the left atrium, through the opening in the septum, and then mix with oxygen-poor blood in the right atrium. When there is a large defect between the atria, a large amount of oxygen-rich (red) blood leaks from the heart's left side back to the right side. This blood is then pumped back to the lungs, despite already having been refreshed with oxygen. This is inefficient, because already-oxygenated blood displaces blood that needs oxygen.

There are three major types of atrial septal defects:

• Ostium Secundum Atrial Septal Defect
  Ostium Secundum is the most common atrial septal defect. It is caused when a part of the atrial septum fails to close completely while the heart is developing. This causes an opening to develop between the atria.
  
  
• Ostium Primum Atrial Septal Defect
  Ostium Primum is located in the lower portion of the atrial septum and is the second most common type of ASD. This defect is part of the atrioventricular (AV) canals, and is often found at a split in the leaflet of the mitral valve known as a mitral valve cleft.
  
  
• Sinus Venosus Atrial Septal Defect
  A Sinus Venous defect os the lest common of ASD defects. It occurs at the superior vena cava and right atrium juncture. In this defect, one or more of the pulmonary veins enter the right atrium instead of correctly entering the left atrium.

How does an ASD affect the body?

Atrial septal defects result in blood flowing from the left atrium to the right atrium, causing the right ventricle and lungs to work harder to handle the flow. Usually, children with ASD's lead normal, healthy lives. However, the right ventricle may get largerand the pressure in the main arteries of the lungs can increase over time. It is also common for abnormal heart rhythms to occur as a long-term consequence of this defect. All of these conditions can lead to a decrease in exercise tolerance, and if left untreated, ASD is known to shorten average life expectancy. 

Occasionally, blood will flow from the right atrium to the left atrium, resulting in an increased risk of a stroke from the debris that is normally filtered out by the lungs.

An ASD can cause lung problems if not repaired. A small opening in the atrial septum allows a small amount of blood to pass through from the left atrium to the right atrium. A large opening allows more blood to pass through and mix with the normal blood flow in the right side of the heart. When blood passes through the ASD from the left atrium to the right atrium, a larger volume of blood than normal must be handled by the right side of the heart. Extra blood then passes through the pulmonary artery into the lungs, causing higher pressure than normal in the blood vessels in the lungs.The larger the volume of blood that goes to the lungs, the higher the pressure.

The lungs are able to cope with this extra pressure for a while, depending on how high the pressure is. However, over time, the blood vessels in the lungs become diseased by the extra pressure.

Many people exhibit no symptoms. However, if the ASD is large, permitting a large amount of blood to pass through to the right side of the heart, the right atrium, right ventricle, and lungs will become overworked, and symptoms may be noted. The following are the most common symptoms of atrial septal defect.  Symptoms may include: 

• fatigue
• sweating
• rapid breathing
• shortness of breath
• poor growth in children

The symptoms of an atrial septal defect may resemble other medical conditions or heart problems.

For these reasons, the current standard of care is to close atrial septal defects to reduce the shunt to a level which allows the right heart size and blood flow into the lungs to return to normal.  

What are the treatment options for an ASD?

There are several options available depending upon the size of the defect and effect on the patients quality of life.

Some individuals may need to take medications to help the heart work better, since the right side is under strain from the extra blood passing through the ASD. Medications that may be prescribed include the following:  digoxin (a medication that helps strengthen the heart muscle, enabling it to pump more efficiently) and/or diuretics (the body's water balance can be affected when the heart is not working as well as it could). These medications help the kidneys remove excess fluid from the body.

One option for repair if medical therapy fails is a septal repair implant can be placed via an ASD catheter based procedure. A cardiac-catheterization involves slowly moving a catheter (a long, thin, flexible tube) into the heart. The catheter is inserted into a large vein through a small incision usually made in the inner thigh and then is advanced to and into the heart.   This procedure is done in the cardiac cath lab.  The third option is having the defect closed with stitches or a special patch during an open heart procedure.

Patent Foramen Ovale (PFO)

The foramen ovale is a small opening located on the atrial septum that is used during fetal circulation to speed up the travel of oxygenated blood through the heart. When in the womb, a baby does not use its own lungs to oxygenate blood; it relies on the mother to provide oxygen rich blood from the placenta through the umbilical cord. Normally the foramen ovale closes at birth when increased blood pressure on the left side of the heart forces the opening to close.

If the atrial septum does not close properly, it is called a patent foramen ovale. This type of defect generally works like a flap valve, only opening during certain conditions when there is more pressure inside the chest. This increased pressure occurs when people strain while having a bowel movement, cough, or sneeze.

How does a PFO affect the body?

If the pressure is sufficient, blood may travel from the right atrium to the left atrium. If there is a clot or particles in the blood traveling in the right side of the heart, it can cross the PFO, enter the left atrium, and travel out of the heart to the brain (causing a stroke) or into a coronary artery (causing a heart attack).

A stroke occurs when circulation to a part of the brain is blocked. The resultant lack of oxygen can cause problems that range from death to permanent or temporary affects on muscle control and body function.

A PFO does not cause a stroke, but its presence may be a pathway for a stroke to occur by allowing blood to flow from the venous system to the arterial system without going through the lungs first. One of the important functions of the lungs, in addition to oxygen exchange, is to filter debris from the venous blood returning to the heart. If this debris goes to the arterial circulation, it can lodge in an artery serving the brain, heart, or other major organ causing an arterial embolization. When it lodges in the brain, a stroke occurs. If the effects of the stroke last less than 24 hours, the stroke is called a Transient Ischemic Attack (TIA). If the symptoms persist longer than 24 hours, it is termed a stroke.