Hole in the Heart: PFO, ASD and VSD

Congenital heart defects are structural abnormalities in the heart that are present from birth. They affect about 1% of live births. The most common defects involve communication between the left and right sides of the heart or a ‘hole in the heart’ which allows the mixing of arterial or oxygenated blood with venous or deoxygenated blood. The most common is the ventricular septal defect (VSD) with communication between the left and right ventricles. Other types are atrial septal defect (ASD) and patent foramen ovale (PFO) which both lead to a communication between the left and right atria. While an ASD arises due to an anatomical defect, a PFO is a normal variant that is usually asymptomatic.

There are genetic and developmental abnormalities noted to be underlying the incidence of heart defects. A family history increases the risk of these defects in children.

Ventricular Septal Defect

This is the second most common congenital heart defect, after the bicuspid aortic valve. There is a hole or defect present in the septum dividing the left and right ventricles of the heart. A VSD may be associated with other heart defects or maybe the only lesion. Some VSDs may be very small and close spontaneously in childhood whereas others may be very large and present early in life with rapid progression of symptoms.

Atrial Septal Defect

There are three types of ASDs which vary depending on the site on the septum between the left and right atria and the mechanism of formation

• Sinus venosus ASD: this occurs higher up in the septum
• Ostium Primum ASD: This occurs lower in the septum. This type occurs frequently in individuals with Down’s syndrome
• Ostium Secundum: This is the most common type and occurs in the middle of the septum. Individuals with ASD are generally asymptomatic till later in their life. After the 3rd to 4th decade, they may develop shortness of breath, palpitations and can progress to develop severe complications.

Patent Foramen Ovale

Prior to birth, there exists communication between the left and right atria known as the foramen Ovale. This is guarded by a flap and is necessary for normal circulation in the fetus. After birth, it closes spontaneously. Failure to close completely leads to PFO. A PFO is considered to be a normal variant and does not cause any symptoms.

It is important to note, however, that a PFO can allow a clot forming in the body, to move from the right to the left side of the heart and reach the brain to cause a stroke.

Diagnosis of Septal Defects

As these conditions are generally asymptomatic in the early stages, the diagnosis is usually suspected when an abnormal heart sound or a murmur is heard during a routine physical exam. Family history aids in making the diagnosis. The following are additional tests used to confirm the diagnosis:

• Echocardiogram: This test uses ultrasound waves to obtain a real-time image of the beating heart. It can directly visualize abnormal blood flow through an ASD or VSD.
• Echocardiogram bubble study: This test is used to diagnose an ASD where normal saline is inserted into the circulation after agitation. Bubbles of the saline can be visualized crossing the ASD.
• Cardiac catheterization: This test involves inserting a wire through a vein or an artery to reach the heart. It can help measure the pressure in the heart chambers and the vessels in the lung.
• Electrocardiogram (ECG): This test records the electrical activity of the heart and can show any rhythm abnormalities.
• Chest X-ray: This may show enlargement of the heart and the blood vessel leading to the lung.

Treatment of Septal Defects

Not all defects require treatment. Minor defects can be monitored using Echo. Treatment when indicated, with surgery or minimally invasive procedures is beneficial in preventing complications. Once complications set in and the vessels in the lungs are affected, there is no definitive treatment. The general treatment options include:

• Surgical closure of the defect: This involves open-heart surgery with the closure of the defect using a pericardial patch or prosthetic material.
• Transcatheter device closure: this is minimally invasive and allows the insertion of a wire containing a closure device through an artery.
• Medical therapy: drugs are used to control symptoms of shortness of breath and palpitations.

Complications of Septal Defects

• Eisenmenger Syndrome: If severe defects are left untreated, they can progress to a condition known as Eisenmenger syndrome. This occurs when the constant movement from the left to the right side of the heart increases the pressure in the pulmonary circulation of the blood vessels in the lungs leading to pulmonary hypertension. These increased pressures overload the right side of the heart and reverse the flow of blood from right to left. Once Eisenmenger syndrome develops, there is no benefit of treatment with surgery and the individual has a poor prognosis with a high rate of death.
• Infective endocarditis: This is an infective growth on the cardiac tissue with systemic infection. The ASD or VSD allows for the settling and growth of organisms.
• Arrhythmias: These are abnormal rhythms of the heart which lead to rapid heart rate or palpitations. These arise due to changes in the heart structure secondary to abnormal blood flow through the heart.

Prognosis of Septal Defects

The overall prognosis in individuals with septal defects is good in minor cases and in those who undergo corrective procedures. Severe defects when untreated can lead to complications and death.