Congenital Cardiac Anomaly: Understanding Patent Foramen Ovale and the Heart’s Structure

QUESTION

A 14-month-old girl is brought to the emergency department. When the child woke from her afternoon nap, the mother noted that she did not use her left arm and had difficulty standing without falling. The staff attaches the child to a cardiorespiratory monitor and a pulse oximeter to monitor the oxygen saturation of the hemoglobin. Although all vital signs are normal, the child is listless and barely responds to the staff’s interventions. An emergency computed tomographic (CT) scan is ordered, and the child is noted to have suffered a small stroke. The child is transferred to the pediatric intensive care unit for close monitoring. By the next morning, the child has begun to use her left arm; although a little wobbly, she keeps pulling herself up to stand while in the crib. A neurologist examines the little girl and orders some laboratory tests and an echocardiogram. Once the tests are complete, the neurologist meets with the mother and explains that the child has a congenital cardiac anomaly, patent foramen ovale.

1. Discuss the four chambers of the heart.

2. Describe a patent foramen ovale. Where is the valvular opening located?

3. Discuss the opening that has no effect on the normal electrical impulses in the heart.

4. Describe the usual pacemaker of the heart and its location.

ANSWER

Congenital Cardiac Anomaly: Understanding Patent Foramen Ovale and the Heart’s Structure

Introduction

Congenital cardiac anomalies can have significant implications for a child’s health and well-being. In the case of a 14-month-old girl presenting with stroke-like symptoms, further examination reveals a congenital heart defect called patent foramen ovale (PFO). To better understand this condition, it is important to explore the structure of the heart, the characteristics of PFO, and the heart’s electrical conduction system.

 The Four Chambers of the Heart

The heart is composed of four chambers, each with a specific role in the circulatory system:

Right Atrium: The right atrium receives deoxygenated blood returning from the body through the superior and inferior vena cava.

Right Ventricle: The right ventricle receives blood from the right atrium and pumps it to the lungs for oxygenation via the pulmonary artery.

Left Atrium: The left atrium receives oxygenated blood returning from the lungs through the pulmonary veins.

Left Ventricle: The left ventricle receives blood from the left atrium and is responsible for pumping oxygenated blood to the rest of the body through the aorta.

Patent Foramen Ovale (PFO)

A patent foramen ovale is a congenital heart defect characterized by the persistence of a hole between the atria, known as the foramen ovale. During fetal development, the foramen ovale allows blood to bypass the non-functional lungs and flow from the right atrium to the left atrium. Normally, the foramen ovale closes shortly after birth, ensuring separation of oxygenated and deoxygenated blood. However, in cases of PFO, the foramen ovale fails to close completely, resulting in a persistent opening between the atria.

The valvular opening of a PFO is located in the interatrial septum, the wall that separates the right and left atria of the heart.

Opening with No Effect on Normal Electrical Impulses

The opening of the patent foramen ovale has no direct impact on the heart’s normal electrical impulses. It primarily affects the blood flow between the atria. In a healthy heart, the electrical conduction system, consisting of specialized cells, controls the timing and coordination of the heart’s contractions. The impulses typically follow a specific pathway, including the sinoatrial (SA) node, atrioventricular (AV) node, bundle of His, and Purkinje fibers, ensuring proper contraction and rhythm.

Usual Pacemaker of the Heart and Its Location

The sinoatrial (SA) node, located in the right atrium near the junction with the superior vena cava, serves as the heart’s primary pacemaker. The SA node initiates the electrical impulses that regulate the heart’s rhythm. From the SA node, electrical signals spread across both atria, causing them to contract. The impulses then travel to the AV node, which acts as a relay station, transmitting the signals to the ventricles, resulting in their contraction and subsequent blood circulation.

Conclusion

Understanding the structure of the heart, including the four chambers and the normal electrical conduction system, is crucial for comprehending cardiac anomalies such as patent foramen ovale (PFO). In the case of PFO, the foramen ovale fails to close after birth, leading to an abnormal opening between the atria. This condition affects blood flow but does not directly influence the heart’s electrical impulses. The primary pacemaker of the heart is the sinoatrial (SA) node, located in the right atrium, which initiates the electrical signals that coordinate the heart’s contractions.