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Fetal Heart Failure: Causes, Doppler Findings and Diagnosis

Posted on by Prof. Dr. İbrahim Cansaran TANIDIR

Fetal cardiac failure is a condition in which the fetal heart cannot pump enough blood to meet the metabolic demands of the tissues and is critically important in terms of perinatal morbidity and mortality. In the diagnostic process, Doppler ultrasonography parameters play a decisive role together with clinical findings.

In fetal cardiac failure, umbilical artery Doppler findings are important in demonstrating increased placental resistance and circulatory burden. Increased pulsatility index and loss of end-diastolic flow suggest that the fetus is under hemodynamic stress and require close obstetric monitoring.

Middle cerebral artery Doppler parameters are used to evaluate fetal compensation mechanisms. Cerebral vasodilation, defined as the brain-sparing effect, is observed with a decrease in the pulsatility index and indicates redistribution of the central circulation in progressive cardiac failure.

Ductus venosus and tricuspid valve Doppler examination provide detailed information about cardiac filling pressures and ventricular functions. Detection of reversed flow in the a-wave of the ductus venosus or tricuspid regurgitation has prognostic value in terms of advanced-stage heart failure and the development of fetal hydrops.

What Is the Normal Circulation Like Before Fetal Cardiac Failure in Babies in the Womb?

In life after birth, the circulatory system in the human body works as two separate consecutive loops. The heart sends deoxygenated blood to the lungs for oxygenation and pumps oxygenated blood coming from the lungs to the body. However, the world of a baby in the womb operates according to completely different rules. During this period, the baby’s lungs are not yet filled with air, remain completely collapsed, and have no function such as providing oxygen. The baby’s source of oxygen and nutrients is the placenta, a tremendous bridge between the mother and the baby. Since the lungs are out of function, the baby’s circulatory system must have a much different, parallel structure compared to ours.

There are very special shortcuts that keep this parallel system functioning and allow blood to bypass the lungs and directly reach vital organs. Thanks to these shortcuts, the clean and oxygen-rich blood coming from the mother is delivered to the baby’s brain and heart as quickly as possible. If fatigue or failure begins in the heart, the perfect balance in these extraordinary shortcuts begins to deteriorate. The vital transition points that ensure healthy circulation are as follows:

  • Ductus venosus
  • Foramen ovale
  • Ductus arteriosus

The blood coming from the mother through the umbilical cord first reaches the baby’s liver. However, most of this blood is directed straight to the heart without spending time in the liver. The blood reaching the heart passes through the opening between the right and left chambers and is distributed throughout the body. In a baby in the womb, the right side of the heart works much harder than the left side and carries most of the circulatory burden alone.

How Does Fetal Cardiac Failure Occur?

The heart muscle of an adult or a newborn baby is quite flexible. When filled with excess blood, it can stretch like a soft balloon to accommodate this load. However, the fetal heart muscle is structurally much stiffer and has a very limited ability to stretch. This rigid structure seriously limits the amount of blood the heart can receive. If the amount of blood returning to the baby’s heart suddenly increases or if resistance rises in the vessels into which the heart pumps blood, this stiff heart muscle has an incredibly difficult time adapting.

When the heart is strained and cannot adequately empty the blood inside it, pressure begins to build up in the vessels behind the heart. We can compare this to a clogged sink; when water cannot drain, it begins to accumulate in the pipes and sink basin. Likewise, when the heart cannot function properly, blood accumulates backward. This accumulation leads to congestion in the fetal veins and eventually fluid collection in body cavities. The main factors that initiate this exhausting process and increase the heart’s workload to an unbearable level are as follows:

  • Severe anemia
  • Inflammation of the heart muscle
  • Twin-to-twin transfusion
  • Rhythm disorders

Some of these causes arise directly from abnormalities in the heart itself, while many others are conditions developing outside the heart that indirectly exhaust it. For example, when severe anemia develops in the fetus, the heart tries to pump blood much faster and stronger than normal in order to deliver enough oxygen to body tissues. This excessive effort eventually leads to exhaustion of the heart muscle.

How Is Doppler Echocardiography Used in the Diagnosis of Fetal Cardiac Failure?

Evaluating the heart of a baby in the womb is much more complicated than examining a patient in the outside world. Imaging methods involving radiation, such as X-rays or tomography, cannot be used for the baby. At this point, Doppler ultrasonography, which utilizes the miracle of sound waves, comes into play. The working principle of this system is very similar to radar devices used for speed control on roads or the change in the siren sound of an ambulance rapidly passing by us.

The ultrasound probe sends sound waves at frequencies too high for the human ear to hear into the womb. These sound waves hit the red blood cells rapidly flowing in the baby’s vessels and are reflected back. Depending on the direction and speed of movement of the blood cells, the frequency of the reflected sound waves changes. The computer system instantly detects this change and converts it into colors, graphs, and numbers that we can understand.

The greatest advantage of this system is that it instantly displays how well the heart valves close, in which direction the blood flows through the vessels, and most importantly, whether there is any leakage in the heart. Thanks to color mapping, we observe the dance of red and blue colors on the screen. Some factors affecting imaging quality are as follows:

  • Body structure of the expectant mother
  • Position of the baby in the womb
  • Amount of amniotic fluid
  • Technology of the ultrasound device used

In order for this evaluation to be accurate, the measurement angle must be adjusted very precisely. Sending sound waves as parallel as possible to the blood flow allows the device to calculate speed completely and accurately. If the angle is adjusted incorrectly, erroneous data about heart performance may be obtained.

How Is the Pumping Power of the Heart Measured with a Doppler Device in Cases of Fetal Cardiac Failure?

The fundamental and most vital duty of the heart is to continuously pump blood to every cell of the body. This contraction and ejection phase of the heart is called systole. To determine whether the pumping power of a baby’s heart in the womb is adequate, certain critical mathematical and geometric calculations are performed using Doppler technology. Simply looking at how much the heart shrinks or how narrow its diameter becomes is not enough to understand the true pumping power.

For this reason, we calculate the total amount of blood pumped by the heart in one minute and the net volume of blood ejected into the vessels with each heartbeat. During these calculations, the width of the valves through which blood exits the heart and the speed of blood passing through that area are combined to produce a mathematical result. The main areas measured to evaluate the heart’s pumping performance are as follows:

  • Left ventricle
  • Right ventricle
  • Aorta
  • Pulmonary vessel

When the fetal heart wants to increase the amount of blood it pumps during any stressful moment, it cannot significantly increase the volume of blood ejected with each beat. Instead, the only thing it can do is increase the heart rate, namely the pulse. While an adult heart can contract more forcefully with each beat and send more blood, the fetus’s stiff heart muscle does not have this flexibility. Therefore, a marked slowing or excessive acceleration in fetal heartbeats immediately reduces the total amount of blood pumped by the heart and paves the way to heart failure.

Why Is the Relaxation Capacity of the Heart Important During the Process of Fetal Cardiac Failure?

Many people think of heart failure only as the inability of the heart to contract strongly enough. However, in babies in the womb, the problem usually begins in the relaxation phase of the heart long before the contraction strength deteriorates. In order for the heart to fill with blood, it must completely relax after each contraction and open like a sponge. This relaxation phase is called diastole. We previously mentioned that the fetal heart muscle is naturally stiff. This stiffness is the main factor preventing the heart from relaxing easily and comfortably receiving blood.

When the heart cannot relax, blood trying to pass from the upper chambers to the lower chambers begins to encounter difficulty. When the speed and shape of this blood passage are measured with the Doppler device, two different waveforms are observed. The first wave represents blood filling due to the heart muscle relaxing on its own, while the second wave shows the moment when the upper chambers contract and force the remaining blood into the lower chamber. Warning findings indicating a relaxation problem are as follows:

  • Weak first filling wave
  • Very strong second forcing wave
  • High pressure between chambers

As the failure worsens and the heart muscle becomes stiffer and more exhausted, the pressure inside the lower chamber increases so much that blood coming from the upper chamber encounters major resistance entering inside. The flow becomes completely disrupted and turns into a single rigid wave. This is the clearest evidence that the heart can no longer receive blood and that blood has started backing up toward the baby’s liver and other organs.

What Does MPI, One of the Doppler Parameters, Say About Fetal Cardiac Failure?

Evaluating only the contraction or only the relaxation of the heart may sometimes make it difficult to see all the pieces of the puzzle. To understand how far the disease has progressed, a common score showing the overall performance of the heart is needed. This special measurement called the Myocardial Performance Index calculates the time intervals between the contraction and relaxation phases of the heart and provides a global report card of cardiac health.

This calculation is based on a very interesting logic. Just before pumping blood, the heart briefly closes all its valves and prepares by increasing the pressure inside. Likewise, after ejecting blood, it again keeps its valves closed for a short period before starting to receive blood in order to prepare for relaxation. If the heart is damaged or the baby is deprived of oxygen, these preparation and recovery times become prolonged while the actual pumping duration shortens.

The ratio of these time intervals gives us a very clear number. If the resulting value rises above a certain limit, it indicates that the heart is giving an alarm and is under serious stress. The calculation of this index plays a critical role especially in understanding the severity of the following conditions:

  • Preeclampsia
  • Fetal growth restriction
  • Severe fetal anemia

The best aspect of this measurement is that it is not affected by the baby’s heart rate. Whether the baby is active or the pulse is fast or slow, this index reveals the true fatigue level of the heart without masking it and gives doctors the opportunity to intervene in time.

What Are the Doppler Findings in the Veins as Fetal Cardiac Failure Progresses?

The structures that announce the heart failure picture in the earliest and loudest way are the veins carrying blood to the heart. The veins in an adult’s legs contain one-way valves that prevent blood from flowing backward. However, there are no such protective valves in the venous system of a baby in the womb. Therefore, even the slightest pressure accumulating on the right side of the heart is transmitted directly backward toward the organs without encountering any barrier.

The place where we observe this most clearly with Doppler is the shortcut vessel where blood coming from the umbilical cord bypasses the liver and rapidly reaches the heart. In a normal and healthy baby, blood in this vessel continuously and uninterruptedly flows toward the heart. However, when heart failure begins and the inside of the heart becomes excessively filled with pressure, the heart can no longer accept more blood and pushes the incoming blood backward. On the Doppler screen, we begin to see reverse flows suddenly striking backward among the forward-moving red-colored waves. The main vessels examined are as follows:

  • Ductus venosus
  • Umbilical vein
  • Inferior vena cava

If the condition worsens further and the heart failure process accelerates, this backward pressure becomes so severe that it reaches the umbilical vein, the main bridge between the baby and the placenta. Under normal conditions, the umbilical cord vein should flow silently like a smooth river without pulsation. However, it begins to pulsate like an artery together with the heartbeat. When this pulsation is observed, it is understood that fluid accumulation has begun in the baby’s body and the condition has reached an extremely critical point.

What Do Brain Protection and Arterial Doppler Data Show During Fetal Cardiac Failure?

Babies in the womb develop extraordinary defense mechanisms against the dangers they encounter. When heart failure begins or oxygen reaching the baby decreases, the baby activates an emergency plan. In order not to waste the limited amount of blood and oxygen in the body, it constricts the vessels going to the kidneys, intestines, and skin, thereby reducing blood flow to these regions. The saved blood is redirected to the organs most essential for survival, namely the brain and heart. This is medically called the brain-sparing effect.

When we examine the vessels in the baby’s brain with the Doppler device, we can directly observe this extraordinary mechanism. Brain vessels, which normally have high resistance, dilate and reduce vascular resistance in order to attract more blood. At the same time, resistance increases in the arteries of the umbilical cord. The body has mobilized all its energy and resources to protect the brain. The arteries evaluated are as follows:

  • Middle cerebral artery
  • Umbilical artery
  • Aortic isthmus

However, this heroic defense mechanism cannot continue forever. As heart failure worsens and the process becomes prolonged, the brain vessels dilate to their maximum limit and their capacity becomes exhausted. The mechanism controlling blood pressure to the brain collapses. At this point, even the direction of blood flow in the aorta begins to change. Blood that should normally flow toward the body starts flowing backward toward the vessels desperately trying to nourish the brain. This condition represents an extremely critical stage threatening the baby’s neurological development after birth.

Which Criteria Are Included in the CVPS Score Determining the Severity of Fetal Cardiac Failure?

In order for doctors working in different cities or hospitals to speak a common language about the condition of the same baby and clearly monitor the course of the disease, a standard scoring system is needed. Like a school report card, the Cardiovascular Profile Score, which scores the condition of the baby’s heart and vascular system out of 10, summarizes all these complex ultrasound data in an understandable form.

This scoring system examines the baby’s circulatory system from five different perspectives. Points are assigned to each section according to the severity of the baby’s condition. If everything is normal in that section, full points are given; if there is mild deterioration, points are deducted; if there is severe danger, no points are given for that section. The scoring criteria are as follows:

  • Fluid accumulation in the body
  • Heart size
  • Heart function
  • Arterial flow
  • Venous flow

If a baby receives a full score, it means the circulatory system is functioning perfectly. However, when the score begins to fall below 7, alarm bells start ringing. If the score is 5 or below, the condition is extremely urgent and the heart is close to complete failure. This scoring not only identifies the disease but also serves as the most important guide in determining when the next examination should be performed and how the timing of delivery should be planned.

How Do Rhythm Disorders Affect the Picture of Fetal Cardiac Failure?

How regularly the heart functions is just as vital as how strong it is. Rhythm disorders in fetal heartbeats are among the most common causes of heart failure and at the same time among the causes most successfully treatable with medications while the baby is still in the womb. A heartbeat that is much slower or much faster than normal fundamentally disrupts the dynamics of blood pumping.

If there is excessive acceleration in the heart and the pulse exceeds 200 beats per minute, the heart muscle cannot find enough time to refill with blood after contracting. The heart beats so rapidly that it contracts almost empty and only trembles. Since blood cannot be effectively ejected, it accumulates in the body and causes fluid retention. Types of tachycardia are as follows:

  • Supraventricular tachycardia
  • Atrial flutter
  • Atrial fibrillation

In the opposite situation, when the heart rate drops below 60 beats per minute, events develop differently. The heart beats so slowly that it tries to compensate by filling and ejecting the maximum amount of blood possible with each contraction. However, the stiff fetal heart muscle has a limit of endurance. After a while, the muscle becomes exhausted from overstretching, its structure deteriorates, and it once again falls into the vortex of heart failure by becoming unable to contract sufficiently. Both conditions can be immediately detected with the Doppler device and attempts are made to control them by transferring medications given to the mother to the baby.

How Is the Timing of Delivery Planned According to Doppler Criteria When Fetal Cardiac Failure Is Detected?

Once the diagnosis of heart failure is confirmed, the most difficult decision-making phase begins for medical professionals. On one hand, the baby needs to remain in the womb to continue development, especially lung development; on the other hand, there is the necessity to deliver the baby and begin treatment before the exhausted and failing heart is exposed to more stress. This is like walking on a double-edged sword. This difficult decision is not left to the shoulders of a single physician; instead, a large and experienced council comes together.

When deciding on delivery timing, Doppler findings determine the red lines. If blood in the veins has started strongly flowing backward, blood flow to the brain has become disrupted, and generalized edema has begun in the body, it is understood that the intrauterine environment is no longer safe for the baby. In light of these findings, an emergency delivery plan is made despite the risks of premature birth. The specialists making the delivery decision are as follows:

  • Perinatologists
  • Pediatric cardiologists
  • Neonatologists
  • Obstetricians and gynecologists

Through the collaboration of these teams, the neonatal intensive care unit is prepared before delivery. The moment the birth occurs, special medications preventing closure of the baby’s vessels are administered intravenously within seconds. If there is a structural problem in the heart, pediatric cardiac surgery teams remain ready in the operating room. Thanks to Doppler echocardiography, we find our way in the dark, see the invisible, and touch the lives of unborn babies, helping them step into a healthy future.

Güncellenme Tarihi: 13.10.2026

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