Symptoms include difficulty breathing (dyspnea) and bluish discoloration on skin and lips (cyanosis). A newborn baby will show signs of heart failure such as edema, fatigue, wheezing, sweating and irregular heartbeat.

If there is a defect in the septum, it is possible for blood to travel from the left side of the heart to the right side of the heart, or the other way around. Since the right side of the heart contains venous blood with a low oxygen content, and the left side of the heart contains arterial blood with a high oxygen content, it is beneficial to prevent any communication between the two sides of the heart and prevent the blood from the two sides of the heart from mixing with each other.

At birth, the ductus arteriosus is still open, and there is higher than normal resistance to blood flow in the lungs. This allows for adequate oxygenation via mixing between the atria and a normal appearance at birth. When the ductus begins to close and pulmonary vascular resistance decreases, blood flow through the ductus is restricted and flow to the lungs is increased, reducing oxygen delivery to the systemic circulation. This results in cyanosis and respiratory distress which can progress to cardiogenic shock. The first symptoms are cyanosis that does not respond to oxygen administration or poor feeding. Peripheral pulses may be weak and extremities cool to the touch.

HLHS often co-occurs with low birth weight and premature birth.

In neonates with a small atrial septal defect, termed "restrictive", there is inadequate mixing of oxygenated and deoxygenated blood. These neonates quickly decompensate and develop acidosis and cyanosis.

On EKG, right axis deviation and right ventricular hypertrophy are common, but not indicative of HLHS. Chest x-ray may show a large heart (cardiomegaly) or increased pulmonary vasculature. Neonates with HLHS do not typically have a heart murmur, but in some cases, a pulmonary flow murmur or tricuspid regurgitation murmur may be audible.

Co-occurring tricuspid regurgitation or right ventricular dysfunction can cause hepatomegaly to develop.

Major symptoms of Lutembacher's syndrome as a result of ASD and MS can range from heart failure to pulmonary congestion.

- Right ventricular overload and Right-sided heart failure: Both are caused by a large ASD and MS (moderate to severe).

- Palpitations: This is caused by blood flowing from left atrium to the right atrium causing a higher left atrial pressure and leading to mitral stenosis. Both atria will be dilated (stretched or open)leading to future atrial arrhythmias or atrial fibrillation (Riaz).

- Pulmonary congestion: When blood or fluid pools within the lungs; this is usually a symptom of mitral stenosis and a small ASD.

- Loud mitral S1 and wide fixed split of pulmonary S2: The loud sound of the mitral S1 and the wide fixed split of pulmonary S2 is a symptoms of mitral stenosis. The sounds often are caused by a reduced pressure gradient in the mitral area that was caused from decompression of the left atrium from the ASD and a displacement (moving from normal position) of the left ventricular lower portion of the heart to the a large right ventricle. The second heart sound (S2) split is caused by the increase right heart blood flow through the ASD causing a late closing of the pulmonary component of the S2 as well as decreased left ventricular and aortic blood flow.

- III/IV mid diastolic murmur, early systolic murmur: This heart murmur is caused by an increase blood flow through the tricuspid valve due to ASD; it is heard best in the left lower sternal area or the bottom of the heart (apex).

Ventricular septal defect is usually symptomless at birth. It usually manifests a few weeks after birth.

VSD is an acyanotic congenital heart defect, aka a left-to-right shunt, so there are no signs of cyanosis in the early stage. However, uncorrected VSD can increase pulmonary resistance leading to the reversal of the shunt and corresponding cyanosis.

- Pansystolic (Holosystolic) murmur along lower left sternal border (depending upon the size of the defect) +/- palpable thrill (palpable turbulence of blood flow). Heart sounds are normal. Larger VSDs may cause a parasternal heave, a displaced apex beat (the palpable heartbeat moves laterally over time, as the heart enlarges). An infant with a large VSD will fail to thrive and become sweaty and tachypnoeic (breathe faster) with feeds.

The restrictive VSDs (smaller defects) are associated with a louder murmur and more palpable thrill (grade IV murmur). Larger defects may eventually be associated with pulmonary hypertension due to the increased blood flow. Over time this may lead to an Eisenmenger's syndrome the original VSD operating with a left-to-right shunt, now becomes a right-to-left shunt because of the increased pressures in the pulmonary vascular bed.

Common symptoms include a grayish-blue (cyanosis) coloration to the skin, lips, fingernails and other parts of the body. Other pronounced symptoms can be rapid/difficulty breathing, poor feeding, cold hands or feet, or being inactive and drowsy. "In a baby with hypoplastic left heart syndrome, if the natural connections between the heart's left and right sides (foramen oval and ductus arteriosus) are allowed to close, he or she may go into shock." Signs of shock can include cool or clammy skin, a weak or rapid pulse, and dilated pupils.

A defect in the ostium primum is occasionally classified as an atrial septal defect, but it is more commonly classified as an atrioventricular septal defect

An enlargement of the aorta may occur; an increased risk of abnormality is seen in babies of women taking lithium during the first trimester of pregnancy (though some have questioned this) and in those with Wolff-Parkinson-White syndrome.

Most individuals with an uncorrected secundum ASD do not have significant symptoms through early adulthood. More than 70% develop symptoms by about 40 years of age. Symptoms are typically decreased exercise tolerance, easy fatigability, palpitations, and syncope.

Complications of an uncorrected secundum ASD include pulmonary hypertension, right-sided heart failure, atrial fibrillation or flutter, stroke, and Eisenmenger's syndrome.

While pulmonary hypertension is unusual before 20 years of age, it is seen in 50% of individuals above the age of 40. Progression to Eisenmenger's syndrome occurs in 5 to 10% of individuals late in the disease process.

Left to right shunting heart defects include:

- Ventricular septal defect (VSD) (30% of all congenital heart defects)

- Atrial septal defect (ASD)

- Atrioventricular septal defect (AVSD)

- Patent ductus arteriosus (PDA)

- Previously, Patent ductus arteriosus (PDA) was listed as acyanotic but in actuality it can be cyanotic due to pulmonary hypertension resulting from the high pressure aorta pumping blood into the pulmonary trunk, which then results in damage to the lungs which can then result in pulmonary hypertension as well as shunting of blood back to the right ventricle. This consequently results in less oxygenation of blood due to alveolar damage as well as oxygenated blood shunting back to the right side of the heart, not allowing the oxygenated blood to pass through the pulmonary vein and back to the left atrium.

- (Edit - this is called Eisenmenger's syndrome and can occur with Atrial septal defect and ventricular septal defect as well (actually more common in ASD and VSD) therefore PDA can still be listed as acyanotic as, acutely, it is)

Others:

- levo-Transposition of the great arteries (l-TGA)

Acyanotic heart defects without shunting include:

- Pulmonary stenosis (a narrowing of the pulmonary valve)

- Aortic stenosis

- Coarctation of the aorta

The ostium secundum atrial septal defect is the most common type of atrial septal defect, and comprises 6–10% of all congenital heart diseases.

The secundum atrial septal defect usually arises from an enlarged foramen ovale, inadequate growth of the septum secundum, or excessive absorption of the septum primum. About 10 to 20% of individuals with ostium secundum ASDs also have mitral valve prolapse.

An ostium secundum ASD accompanied by an acquired mitral valve stenosis is called Lutembacher's syndrome.

While Ebstein's anomaly is defined as the congenital displacement of the tricuspid valve towards the apex of the right ventricle, it is often associated with other abnormalities.

Symptoms are caused by vascular compression of the airway, esophagus or both. Presentation is often within the first month (neonatal period) and usually within the first 6 months of life. Starting at birth an inspiratory and expiratory stridor (high pitch noise from turbulent airflow in trachea) may be present often in combination with an expiratory wheeze. The severity of the stridor may depend on the patient’s body position. It can be worse when the baby is lying on his back rather than its side. Sometimes the stridor can be relieved by extending the neck (lifting the chin up). Parents may notice that the baby’s cry is hoarse and the breathing noisy. Frequently a persistent cough is present. When the airway obstruction is significant there may be episodes of severe cyanosis (“blue baby”) that can lead to unconsciousness. Recurrent respiratory infections are common and secondary pulmonary secretions can further increase the airway obstruction.

Secondary to compression of the esophagus babies often feed poorly. They may have difficulties in swallowing liquids with choking or regurgitating and increased respiratory obstruction during feeding. Older patients might refuse to take solid food, although most infants with severe symptoms nowadays are operated upon before they are offered solid food.

Occasionally patients with double aortic arches present late (during later childhood or adulthood). Symptoms may mimic asthma.

Due to the low oxygen saturation of the blood, cyanosis will appear in areas: around the mouth and lips, fingertips, and toes; these areas are furthest from the heart, and since the circulated blood is not fully oxygenated to begin with, very little oxygen reaches the peripheral arteries. A d-TGA baby will exhibit indrawing beneath the ribcage and "comfortable tachypnea" (rapid breathing); this is likely a homeostatic reflex of the autonomic nervous system in response to hypoxic hypoxia. The infant will be easily fatigued and may experience weakness, particularly during feeding or playing; this interruption to feeding combined with hypoxia can cause failure to thrive. If d-TGA is not diagnosed and corrected early on, the infant may eventually experience syncopic episodes and develop clubbing of the fingers and toes.

As Lutembacher's syndrome is known for ASD and MS, most of the symptoms experienced will be associated with ASD and MS. For most people, they will remain asymptomatic (experience no symptoms) but when symptoms are shown, they are due mainly to ASD and will vary depending on the size of the hole in the atria. If the patient has a large ASD, pulmonary congestion (blood or fluid buildup in the lungs) will happen later but if the patient has a small ASD, symptoms will appear early in the disorder. In general, unless the ASD and mitral stenosis causing Lutembacher's syndrome is severe, symptoms may not appear until the second and third decade of the patient's life. As many of the symptoms are asymptomic and may not appear until later in life, the duration or frequency of the symptoms varies. For symptoms such as palipitations, ventricular overload, heart failure, and pulmonary congenstion, these symptoms may be sudden and not that frequent as they are very severe symptoms. For symptoms such as loud mitral S1, pulmonary S2, mid-diastolic murmur, fatigue, reduced exercise tolerance, weight gain, ankle edema, and right upper quadrant pain, and ascities, these symptoms may be less frequent and severe; their duration may be only a few seconds, minutes, or even months.

In right atrial isomerism, both atria of the heart are morphological right atria leading to associated abnormalities in the pulmonary venous system. In addition, individuals with right atrial isomerism develop asplenia, a midline liver, malrotation of the small intestine and the presence of two morphologic right lungs. Individuals with left atrial isomerism, by comparison, have two morphologic left atria, polysplenia, intestinal malrotation and two morphologic left lungs.

The majority of cases present at the time of birth or within a few days or weeks. Presenting signs and symptoms of the congenital heart defect may include cyanosis, breathlessness, lethargy and poor feeding.

On ECG superior axis deviation is generally found in primum ASD, but an RSR pattern (M pattern) in V1 is characteristic. Fixed splitting of the second heart sound occurs because of equal filling of the left and right atria during all phases of the respiratory cycle.

Patients with Atrial Septal Defects may have Atrial Fibrillation, Atrial Tachycardia, or Atrial Flutter, but these arrythmias are not usually seen until patients grow older. Features also seen on the EKG include Right Atrial Enlargement, PR prolongation and advanced AV block. When you suspect a patient has an ASD based on the findings of an incomplete Right Bundle Branch Block with a rSr' or rSR' the next thing you should do is examine the frontal plane QRS. The frontal plane QRS is the most helpful clue to help you differentiate Secundum ASD from Primum ASD. In Primum defects left axis deviation is seen in most patients with an axis of > -30 degrees and very few patients have right axis deviation. In contrast Secundum defects have an axis between 0 degrees and 180 degrees with most cases to the right of 100 degrees.

In the ECG above, you can see an example of the rSR' pattern in V1 with a R' greater than S with T wave inversion which is commonly seen in volume overload Right Ventricular Hypertrophy.

Children with tetralogy of Fallot may develop "tet spells". These are acute hypoxia spells, characterized by shortness of breath, cyanosis, agitation, and loss of consciousness. This may be initiated by any event leading to decreased oxygen saturation or that causes decreased systemic vascular resistance, leading to increased venous return, which in turn leads to increased shunting through the ventricular septal defect.

Tet spells are characterized by a sudden, marked increase in cyanosis followed by syncope, and may result in hypoxic brain injury and death.

Older children will often squat during a tet spell. This increases systemic vascular resistance and allows for a temporary reversal of the shunt. It increases pressure on the left side of the heart, decreasing the right to left shunt thus decreasing the amount of deoxygenated blood entering the systemic circulation.

Simple l-TGA does not immediately produce any visually identifiable symptoms, but since each ventricle is intended to handle different blood pressures, the right ventricle may eventually hypertrophy due to increased pressure and produce symptoms such as dyspnea or fatigue.

Complex l-TGA may produce immediate or more quickly-developed symptoms, depending on the nature, degree and number of accompanying defect(s). If a right-to-left or bidirectional shunt is present, the list of symptoms may include mild cyanosis.

There are numerous types, differentiated by the extent of the defect. These types are:

- Type I: simple defects leading to communication between the ascending aorta and pulmonic trunk

- Type II: defects that extend to the origin of the right pulmonary artery

- Type III: anomalous origin of the right pulmonary artery from the ascending aorta

It is also classified as simple or complex. Simple defects are those that do not require surgical repair, occur with no other defects, or those that require minor stright-forward repair (ductus arteriosus, atrial septal defect). Complex defects are those that occur with other anatomical anomalies or require non-standard repair.

A sinus venosus atrial septal defect is a type of atrial septal defect primarily associated with the sinus venosus.

They represent 5% of atrial septal defects.

They can occur near the superior vena cava or inferior vena cava, but the former are more common.

They can be associated with anomalous pulmonary venous connection.

Abdominal organs, including the liver, stomach, intestinal tract, and spleen may be randomly arranged throughout the left-right axis of the body. Distribution of these organs largely dictates treatment, clinical outcomes, and further evaluation.

The liver is typically symmetrical across the left-right axis in patients with situs ambiguous, which is abnormal. A majority of left atrial isomeric patients have defects throughout the biliary tree, which is responsible for bile production, even when the gall bladder is functional and morphologically normal. This biliary atresia can lead to acute problems such as nutrient malabsorption, pale stools, dark urine, and abdominal swelling. If this condition continues without proper treatment, cirrhosis and liver failure become a major concern. Biliary atresia is not usually observed in patients with right atrial isomerism.

Random positioning of the stomach is often one of the first signals of situs ambiguous upon examination. Malrotation of the entire intestinal tract, or improper folding and bulging of the stomach and intestines, results in bowel obstruction. This impairment leads to vomiting, abdominal distention, mucus and blood in the stool. Patients may also experience abdominal pain. Intestinal malrotation is more commonly identified in patients with right atrial isomerism than in those with left atrial isomerism.

Isomeric patients often experience disruptions to splenic development during embryogenesis, resulting in an overall lack a spleen (asplenia) or development of many spleens (polysplenia). Asplenia is most often observed in patients with right atrial isomerism. Polysplenia results in 90% of patients with left atrial isomerism. Although they have many spleens, each is usually ineffective resulting in functional asplenia. Rarely, left atrial isomeric patients have a single, normal, functional spleen. Patients lacking a functional spleen are in danger of sepsis and must be monitored.

Tetralogy of Fallot results in low oxygenation of blood due to the mixing of oxygenated and deoxygenated blood in the left ventricle via the ventricular septal defect (VSD) and preferential flow of the mixed blood from both ventricles through the aorta because of the obstruction to flow through the pulmonary valve. This is known as a right-to-left shunt. The primary symptom is low blood oxygen saturation with or without cyanosis from birth or developing in the first year of life. If the baby is not cyanotic then it is sometimes referred to as a "pink tet". Other symptoms include a heart murmur which may range from almost imperceptible to very loud, difficulty in feeding, failure to gain weight, retarded growth and physical development, dyspnea on exertion, clubbing of the fingers and toes, and polycythemia. The baby may turn blue with breast feeding or crying.

Persistent truncus arteriosus (or Patent truncus arteriosus or Common arterial trunk), is a rare form of congenital heart disease that presents at birth. In this condition, the embryological structure known as the truncus arteriosus fails to properly divide into the pulmonary trunk and aorta. This results in one arterial trunk arising from the heart and providing mixed blood to the coronary arteries, pulmonary arteries, and systemic circulation.

Hypoplastic right heart syndrome is a congenital heart defect in which the right atrium and right ventricle are underdeveloped. This defect causes inadequate blood flow to the lungs and thus, a blue or cyanotic infant.[3]