Patent Ductus Arteriosus Imaging: A Definitive Guide

Creator: Dr. Narmatha. A
Published: 2023-04-26T17:40:44

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Patent ductus arteriosus (PDA) is an abnormal heart condition that is more common in premature babies. This article describes PDA imaging.

Written by

Dr. Narmatha. A

Medically reviewed by

Dr. Yash Kathuria

April 26, 2023

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Contents

What Are the Causes of Patent Ductus Arteriosus?
What Is the Basic Embryology of Patent Ductus Arteriosus?
What Are the Different Types of Patent Ductus Arteriosus?
What Are the Imaging Techniques Used in the Diagnosis of Patent Ductus Arteriosus?
What Are the Complications of Patent Ductus Arteriosus?

Introduction:

Patent ductus arteriosus is a congenital heart condition that is characterized by failure in the closure of the fetal ductus arteriosus that serves as a communication between the pulmonary artery and descending thoracic aorta distal to the left subclavian artery. The ductus arteriosus is a fetal artery that connects the aorta and the pulmonary artery and thus skips the blood flow to the lungs before birth. Normally, a baby is born with a ductus arteriosus, but once after birth, it narrows and closes within a few days. Sometimes ductus arteriosus fails to close after birth and forms abnormal communication with the pulmonary artery. In large PDA, the extra blood pumped into the pulmonary artery makes the heart and lungs work harder, and the lungs become congested.

What Are the Causes of Patent Ductus Arteriosus?

Genetic disorders.
Family history.
German measles during pregnancy.
Neonatal respiratory distress syndrome (a breathing disorder that occurs when the baby's lung is not fully developed).

What Is the Basic Embryology of Patent Ductus Arteriosus?

Normally, the left side of the heart pumps blood to the body, and the right side pumps blood only to the lungs. The primary function of ductus arteriosus is to deliver unoxygenated blood to descending thoracic aorta from the superior vena cava and also to the maternal blood vessels through the umbilical artery and placenta and thus bypassing blood flow to the lungs.
The diameter of the ductus arteriosus is similar to that of descending thoracic aorta, but there is variation in its length.
The patency of ductus arteriosus is maintained by the high concentration of circulating or local prostaglandin, partial pressure of oxygen inside the ductus arteriosus, and high concentration of nitric oxide within the ductus arteriosus.
Once after birth, due to abrupt changes such as increased pulmonary venous return from increased partial pressure of oxygen, increased prostaglandin metabolism, and placental removal (contraction of muscles of ductus arteriosus) result in the closure of ductus arteriosus.
Usually, this physiological process of occlusion of ductus arteriosus occurs within 48 hours, and if it fails, it results in the formation of patent ductus arteriosus.

What Are the Different Types of Patent Ductus Arteriosus?

Based on their size, patent ductus arteriosus is classified into the following types:

Silent PDA - Less than 1.5 mm in diameter without an audible murmur of PDA.
Very Small PDA - Less than 1.5 mm in diameter with a murmur.
Small PDA - 1.5 to 3 mm in diameter with a murmur.
Moderate PDA - 3 to 5 mm in diameter with a murmur.
Large PDA - More than 5 mm in diameter with a murmur.

Based on the Krichenko classification system, PDA is classified as:

Type A - Conical.
Type B - Window.
Type C - Tubular.
Type D - Complex.
Type E - Elongated.

What Are the Imaging Techniques Used in the Diagnosis of Patent Ductus Arteriosus?

1) Chest Radiograph:

In a chest radiograph, PDA appears as a large heart with heart failure, pulmonary plethora, or pulmonary hypertension.
Sometimes aortopulmonary filling might be seen.
In patients with shunt, the left ventricle and left atrium are enlarged, and ascending aorta and aortic arch are dilated.
In lateral chest radiographs, calcified PDA is visible, which is more often seen in elderly patients.
The non-calcified PDA sometimes cannot be distinguished from adjacent vascular structures.

2) Electrocardiogram:

Electrocardiogram (ECG) can demonstrate atrial fibrillation or sinus tachycardia, left atrial enlargement and left ventricular hypertrophy in moderate or large patent ductus arteriosus.
In small PDA, electrocardiogram reports are normal.
In large PDA, biventricular hypertrophy and right atrial enlargement are often seen.

3) Echocardiogram:

The echocardiogram is a valuable imaging modality used to determine the types of PDA based on their size as silent, very small, small, moderate, or large. An echocardiogram can detect the associated cardiac abnormalities in addition to the PDA.
In a small PDA, though the size of the heart chambers is normal, mild left ventricular or left atrial enlargement is seen.
The M-mode echocardiogram is helpful in measuring the size of the heart chamber and determining the left ventricular systolic function.
In moderate or large PDA, the left ventricle and left atrium are enlarged.
Color doppler is an effective tool used to localize and detect the presence of PDA and is often used to determine the degree of ductal shunting. It can detect even a very small PDA.
In patients with high pulmonary vascular resistance and patent ductus arteriosus, with a right to left flow or low velocity, color doppler cannot diagnose the ductus arteriosus even though it is larger in size.
Transthoracic echocardiography is used as a guiding tool in the treatment of PDA in very low birth weight infants. It has lesser complications when compared to the aortograms through the femoral artery, which is used as a guiding tool.

4) Angiography:

Contrast angiography has no role in diagnosing PDA, but it is required before and during surgical interventions for PDA.
Angiography can determine the associated congenital heart diseases and exclude differential diagnosis such as aortopulmonary window and artery fistula.
Angiography is used to classify the PDA based on their shape as conical, window, tubular and elongated.

What Are the Complications of Patent Ductus Arteriosus?

Congestive heart failure (a cardiac condition in which the heart fails to pump blood effectively).
Endarteritis (swelling of the arterial wall).
Aneurysm (dilatation) of ductus arteriosus.
Recurrent laryngeal nerve paralysis (injury to the recurrent laryngeal nerve results in voice hoarseness).
Rupture of the dilated (due to aneurysm) pulmonary artery.
Acute aortic dissection (tear in the inner layer of the aorta).

Conclusion:

The echocardiogram is the standard choice of imaging tool used to detect and characterize patent ductus arteriosus (PDA). Doppler echocardiogram is a reliable and highly sensitive method used to detect PDA in patients even in normal clinical conditions. PDA is visible in CT angiography with the help of intravenous contrast materials and ionizing radiation. Echocardiography-directed Indomethacin treatment helps minimize the drug dose required during the closure of PDA. Patent ductus arteriosus is reported to be one in 2000 births and is more common in females than in males (2:1 ratio).

Frequently Asked Questions

1. Which Viewpoint Offers the Best Way to See Patent Ductus Arteriosus (PDA)?

The best viewpoint to visualize patent ductus arteriosus is typically the lateral view in radiography. This angle provides a clear and comprehensive image of the ductus arteriosus, aiding in accurate diagnosis and assessment of the condition.

2. How Is the X-ray Appearance of Patent Ductus Arteriosus Described?

The X-ray appearance of patent ductus arteriosus is described as a "notching" or "bump" on the descending aorta due to increased blood flow. This characteristic finding helps in identifying and evaluating the presence of PDA in radiographic images.

3. What Is the Preferred Test for Evaluating Patent Ductus Arteriosus?

The preferred test for evaluating patent ductus arteriosus is echocardiography. This non-invasive imaging technique allows for real-time visualization of the heart and blood flow, providing detailed information about the size and characteristics of the ductus arteriosus. Echocardiography is widely utilized in diagnosing and assessing PDA, offering valuable insights for effective management.

4. How Long Does It Usually Take for Patent Ductus Arteriosus to Close Up on Its Own?

The closure time of patent ductus arteriosus can vary, but it typically takes a few days to several weeks. In some cases, the ductus arteriosus may close on its own during the first few days of life, while in others, it might persist for a longer duration. The exact timeframe can depend on factors such as the size of the ductus and the overall health of the individual.

5. Where Is the Most Reliable Spot to Detect the Presence of Patent Ductus Arteriosus?

The most reliable spot to detect the presence of patent ductus arteriosus is often the second intercostal space at the left sternal border. This location corresponds to the auscultatory area where a continuous machine-like murmur, known as the PDA murmur, is commonly heard during a physical examination.

6. In PDA, Which Part of the Heart Shows Enlargement?

In patent ductus arteriosus (PDA), the left atrium and ventricle often show enlargement. This cardiac enlargement occurs due to the increased volume of blood flowing back into the left side of the heart from the aorta through the persistently open ductus arteriosus. Detection of this enlargement is a crucial diagnostic clue in assessing the impact of PDA on cardiac anatomy.

7. What Part of the Heart Is Affected When There Is Patent Ductus Arteriosus?

When there is patent ductus arteriosus, the pulmonary artery is the part of the heart that is primarily affected. This occurs because the persistent opening of the ductus arteriosus allows oxygenated blood from the aorta to flow back into the pulmonary artery, leading to increased blood volume and pressure in the pulmonary circulation. This can result in pulmonary congestion and contribute to the characteristic features associated with PDA.

8. Which Specific Area in the Cardiovascular System Is Influenced by Patent Ductus Arteriosus?

The cardiovascular system area influenced by patent ductus arteriosus is the connection between the pulmonary artery and the aorta. Specifically, the ductus arteriosus, a fetal blood vessel that normally closes shortly after birth, remains open, causing abnormal blood flow between these two major blood vessels. This abnormality affects the systemic and pulmonary circulation, leading to potential complications if left untreated.

9. In a Patent Ductus Arteriosus, How Does the Blood Flow?

In patent ductus arteriosus (PDA), blood flows abnormally from the aorta to the pulmonary artery. Normally, the ductus arteriosus closes shortly after birth, but in PDA, this passage remains open. As a result, oxygenated blood from the aorta returns to the lungs, creating a continuous flow and potentially causing an increased workload on the heart and other associated complications.

10. What Purpose Does the Patent Ductus Arteriosus Serve?

The patent ductus arteriosus serves a crucial purpose during fetal development by allowing blood to bypass the non-functional fetal lungs. However, after birth, it should ideally be close to redirect blood flow. When the ductus arteriosus remains open, it can lead to abnormal blood circulation, potentially causing strain on the heart and other complications in the postnatal period.

11. What Size Is Considered Clinically Significant for PDA?

A clinically significant size for patent ductus arteriosus (PDA) is generally considered when the diameter is above 1.5 to 2 millimeters. The size is a key factor in determining the severity of the condition and guides treatment decisions. Larger PDAs are more likely to cause significant shunting of blood between the aorta and pulmonary artery, potentially leading to complications and requiring intervention.

12. How Is Patent Ductus Arteriosus Categorized Based on Its Size?

Patent ductus arteriosus (PDA) is categorized based on its size, with small, moderate, and large classifications. The size of the PDA is determined by factors such as the diameter of the ductus arteriosus and the volume of blood flowing through it. This categorization helps healthcare professionals assess the severity of the condition and plan appropriate interventions or monitoring strategies.

13. What Imaging Feature Indicates the Remaining Part of Ductus Arteriosus?

The remaining part of the ductus arteriosus is indicated by an imaging feature known as a "persistence vessel" in imaging studies. This finding suggests that the ductus arteriosus, which normally closes after birth, has not fully closed, and a portion of it remains patent. Identification of this imaging feature is important in assessing the status of the ductus arteriosus and its potential impact on cardiovascular function.

14. Which Diagnostic Method Is Seen as the Best for Identifying PDA?

Echocardiography is considered the best diagnostic method for identifying patent ductus arteriosus (PDA). This imaging technique uses sound waves to create real-time images of the heart, allowing healthcare professionals to visualize the structure and blood flow in the cardiovascular system. Echocardiography provides detailed information about the size, location, and characteristics of the patent ductus arteriosus, aiding in accurate diagnosis and treatment planning.

15. What Is the Key Characteristics of Patent Ductus Arteriosus?

The key characteristic of patent ductus arteriosus (PDA) is the presence of a continuous, machine-like murmur heard upon auscultation. This murmur results from the abnormal flow of blood between the aorta and pulmonary artery due to the persistent opening of the ductus arteriosus.

Sources

Dr. Yash Kathuria

Family Physician

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