Fetal congenital arrhythmia is an irregular beating of the heart of a fetus, caused by a congenital disability or an inherited genetic condition. Most are brief, fleeting occurrences of slow or fast heartbeat or irregular heart rhythm. Less common but more fatal are those that cause low cardiac output, foetal hydrops and death. The heart could be beating too fast (tachycardia) or too slow (bradycardia).
Types of Fetal Arrhythmia
These are the most common arrhythmias in the fetus. Routine auscultation during a prenatal check-up is usually all it takes to detect and diagnose them. Isolated extrasystole arrhythmias are typically supraventricular but, on occasion, they can be junctional or ventricular.
Supraventricular Tachycardia (SVT) is a serious arrhythmia that can be detected prenatally. It is an unusually very fast heartbeat caused by faulty electrical activity in the upper region of the heart. The most common occurrence of an SVT is when an electric signal re-enters the atrium from the ventricle. This causes a repeated electric stimulation in the heart, faster than and independent of the normal sinus rhythm. Fetus with SVT is at risk for hydrops and cardiac arrest.
This arrhythmia is not very common and is sometimes misdiagnosed as SVT. Ventricular tachycardia, also known as V-tach or VT, is a fast lethal heartbeat caused by disturbed electrical impulses in the heart ventricles. VT is known to cause ventricular fibrillation and cardiac arrest, especially when misdiagnosed and mistreated.
Atrial Flutter and Fibrillation
These are uncommon origins of SVT in the fetus. Atrial flutter comes from a circular motion of electrical impulses in the atrium. The prognosis associated with atrial flutter has always been poor, given that it also puts the foetus at risk for hydrops and heart failure.
Bradyarrhythmia is usually caused by blocked premature contraction, sinus bradycardia or AV block.
Complete Heart Block
Complete heart block is quite rare, a probability of 1 in 20,000. It is associated with some form of congenital heart disease half the time. If the block is the result of abnormal anatomy, like a heart defect, the baby tends to develop hydrops and dies, either in the womb or shortly after birth. The prognosis is more optimistic if the anatomy is normal.
Long QT Syndrome
Scientific studies have linked long QT to a percentage of deaths caused by sudden infant death syndrome. The prolonged Q-T interval usually causes sinus bradycardia and, in rare cases, intermittent tachycardia.
The arrhythmia may not exist at the beginning of the pregnancy but can develop as the foetus comes to term. This condition is often first diagnosed when a doctor listens to the heartbeat of the foetus and detects the irregularity. If the doctor suspects an arrhythmia, further testing, including cardiac monitoring tests like a foetal echocardiogram.
An echocardiogram, also known as a cardiac echo or an echo, is a test that creates a sonogram, or ultrasound image of the heart. This image is used to identify any structural and functional abnormalities. A foetal echo is usually performed in the second trimester.
If necessary, a foetal ECG or foetal magnetocardiography is performed. An ECG (Electrocardiogram) is a recording of a heart’s electrical activity over , allowing doctors to read the pattern of the heart as it beats. Magnetocardiography is used to measure the magnetic fields produced by the heart’s electrical currents using tremendously complex equipment like the Superconducting Quantum Interference Device (SQUID). Unfortunately, these techniques are not available to every medical centre and the few that do have the means of performing ECGs and magnetocardiography mainly use them for research.
Doppler and M-Mode echocardiography can help in the study of the rate and timing of atrial and ventricular movements in the heart. Doppler echocardiography uses the Doppler effect to create images of the heart. The echocardiogram images the heart with sound waves in a high frequency and Doppler technology determines the speed and direction of the blood flowing in the heart. M-mode echocardiography is used to illustrate changes in the dimensions of a heart’s chambers, the collapse of a chamber and interventricular dependence due to respiratory variation. They provide no information as to the electrical activity taking place in the heart but, given the right experience, they can be used to identify arrhythmias in the foetus’s heart correctly.
Monitoring the Arrhythmia
Given the delicate condition of the foetus and the danger posed by any congenital arrhythmia, monitoring the unborn baby’s heart is critical. Any change in the baby’s condition could be fatal, so, knowing when to act and acting as quickly as possible are invaluable resources.
A Holter monitor can be used to detect foetal arrhythmia, especially if it occurs daily. But, some arrhythmias have atypical patterns that require specialised techniques and equipment to detect. A 24-hour or 48-hour Holter monitor may not be sufficient for those.
Remote cardiac monitoring can also be used to keep an eye on a foetus with congenital arrhythmia and their mothers. It involves a doctor reviewing the information provided by the patient’s rhythm management device on a daily basis any time.. This way, the patient doesn’t have to be present for the doctor or her medical team to review the foetus’s heart activity.
In some cases, the doctor will make use of an ECG monitoring service to track the foetus’s condition. An ECG monitoring service records the electrical activity of a patient’s heart and reports the results to the doctor. Those enrolled in the service usually experience heart conditions such as atrial flutter and fibrillation, syncope, palpitations and other heart rhythm anomalies.
Sathya Kumar is the Founder & CEO of Cardiac Rhythm .Cardiac Rhythm’s biosensor is an unobtrusive, easy to use the device for the patient’s long-term Holter monitoring, cardiac ECG monitoring and real-time mobile cardiac telemetry monitoring. The innovative, portable biosensor remotely monitors the health of patients and provides physicians with deeper clinical-grade data insights