The diagnosis is made by transthoracic or transesophageal echocardiography, angiography, and more recently by CT angiography or MR Angiography.

Surgical correction should be considered in the presence of significant left to right shunting (Qp:Qs ≥ 2:1) and pulmonary hypertension. This involves creation of an inter-atrial baffle to redirect the pulmonary venous return into the left atrium. Alternatively, the anomalous vein can be re-implanted directly into the left atrium.

Patients who are diagnosed with AAOCA at or before age 30 years are eligible for this study. They should have otherwise normal heart or only minor defects such as Atrial septal defect, Ventricular septal defect, Patent ductus arteriosus, bicuspid aortic valve, mild pulmonary stenosis etc.

Patients who have other major heart problems that require operations are currently not included in this Cohort study. Any other problems with coronary arteries are also not included.

It can be diagnosed with CT scan, angiography, transesophageal echocardiography, or cardiac MRI. Unfortunately, less invasive and expensive testing, such as transthoracic echocardiography and CT scanning are generally less sensitive.

l-TGA can sometimes be diagnosed in utero with an ultrasound after 18 weeks gestation. However, many cases of simple l-TGA are "accidentally" diagnosed in adulthood, during diagnosis or treatment of other conditions.

For proper diagnosis of situs ambiguous, cardiac and non-cardiac features must be evaluated. Diagnostic criteria for atrial isomerism includes observation of symmetry of thoracic visceral organs upon echocardiogram, arrhythmia upon electrocardiogram, and chest x-ray for confirmation of the heart's location across the left-right axis. In addition, a series of gastrointestinal tests can be conducted for observation of intestinal malrotation, as well as a scan of the liver and spleen for biliary function.

The Registry has been enrolling new patients from participating institutions that are member of the Congenital Heart Surgeons' Society. Hospitals from across North America continue to join the study group and enroll patients. Over 140 patients with AAOCA have been enrolled by June 2011, making it the largest cohort ever assembled of this anomaly.

d-TGA can sometimes be diagnosed in utero with an ultrasound after 18 weeks gestation. However, if it is not diagnosed in utero, cyanosis of the newborn (blue baby) should immediately indicate that there is a problem with the cardiovascular system. Normally, the lungs are examined first, then the heart is examined if there are no apparent problems with the lungs. These examinations are typically performed using ultrasound, known as an echocardiogram when performed on the heart. Chest x-rays and electrocardiograms (EKG) may also be used in reaching or confirming a diagnosis; however, an x-ray may appear normal immediately following birth. If d-TGA is accompanied by both a VSD and pulmonary stenosis, a systolic murmur will be present.

On the rare occasion (when there is a large VSD with no significant left ventricular outflow tract obstruction), initial symptoms may go unnoticed, resulting in the infant being discharged without treatment in the event of a hospital or birthing center birth, or a delay in bringing the infant for diagnosis in the event of a home birth. On these occasions, a layperson is likely not to recognize symptoms until the infant is experiencing moderate to serious congestive heart failure (CHF) as a result of the heart working harder in a attempt to increase oxygen flow to the body; this overworking of the heart muscle eventually leads to hypertrophy and may result in cardiac arrest if left untreated.

Although its cause is poorly understood, situs ambiguous has been linked to family history of malformations and maternal cocaine use, suggesting both genetic and environmental factors play a role. Several genes in the TGF-beta pathway, which controls left-right patterning of viseral organs across the body axis, have been indicated in sporadic and familial cases of atrial isomerism.

There does not appear to be a screening method for prevention of heterotaxy syndrome. However, genetic testing in family members that display atrial isomerism or other cardiac malformations may help to discern risk for additional family members, especially in X-linked causes of heterotaxy syndrome.

ARVD is an autosomal dominant trait with reduced penetrance. Approximately 40–50% of ARVD patients have a mutation identified in one of several genes encoding components of the desmosome, which can help confirm a diagnosis of ARVD. Since ARVD is an autosomal dominant trait, children of an ARVD patient have a 50% chance of inheriting the disease causing mutation. Whenever a mutation is identified by genetic testing, family-specific genetic testing can be used to differentiate between relatives who are at-risk for the disease and those who are not. ARVD genetic testing is clinically available.

A chest x-ray will be given to determine the size of the heart and the blood vessels supplying blood to the lungs.

Hypoplastic right heart syndrome is less common than hypoplastic left heart syndrome which occurs in 4 out of every 10,000 births. [3].

This rare anomaly requires prenatal diagnosis since it needs immediate and emergency treatment. Pregnant women whose pregnancy is complicated with this anomaly should be referred to a level 3 hospital with pediatric cardiology and pediatric cardiothoracic surgical team.[3]

It can be associated with aortic stenosis.

A color flow and doppler imaging is used to help confirm the presence as well as evaluate the severity of ASD and MS.

With simple d-TGA, if the foramen ovale and ductus arteriosus are allowed to close naturally, the newborn will likely not survive long enough to receive corrective surgery. With complex d-TGA, the infant will fail to thrive and is unlikely to survive longer than a year if corrective surgery is not performed. In most cases, the patient's condition will deteriorate to the point of inoperability if the defect is not corrected in the first year.

While the foramen ovale and ductus arteriosus are open after birth, some mixing of red and blue blood occurs allowing a small amount of oxygen to be delivered to the body; if ASD, VSD, PFO, and/or PDA are present, this will allow a higher amount of the red and blue blood to be mixed, therefore delivering more oxygen to the body, but can complicate and lengthen the corrective surgery and/or be symptomatic.

Modern repair procedures within the ideal timeframe and without additional complications have a very high success rate.

Hypoplastic left heart syndrome can be diagnosed prenatally or after birth via echocardiography. Typical findings include a small left ventricle and aorta, abnormalities of the mitral and aortic valves, retrograde flow in the transverse arch of the aorta, and left-to-right flow between the atria. It is often recognized during the second trimester of pregnancy, between 18 and 24 weeks' gestation.

"Prenatal diagnosis (fetal ultrasound):"

Today the diagnosis of double aortic arch can be obtained in-utero in experienced centers. Scheduled repair soon after birth in symptomatic patients can relieve tracheal compression early and therefore potentially prevent the development of severe tracheomalacia.

"Chest X-ray:"

Plain chest x-rays of patients with double aortic arch may appear normal (often) or show a dominant right aortic arch or two aortic arches . There might be evidence of tracheal deviation and/or compression. Sometimes patients present with radiologic findings of pneumonia.

"Barium swallow (esophagraphy):"

Historically the esophagram used to be the gold standard for diagnosis of double aortic arch. In patients with double aortic arch the esophagus shows left- and right-sided indentations from the vascular compression. Due to the blood-pressure related movement of the aorta and the two arches, moving images of the barium-filled esophagus can demonstrate the typical pulsatile nature of the obstruction. The indentation from a dominant right arch is usually deeper and higher compared to the dent from the left arch.

"Bronchoscopy:"

Although bronchoscopy is not routinely done in patients with suspected or confirmed double aortic arch, it can visualize sites and severity of pulsatile tracheal compression.

"Echocardiography:"

In babies under the age of 12 months, echocardiography is considered to be sensitive and specific in making the diagnosis of double aortic arch when both arches are open. Non-perfused elements of other types of vascular rings (e.g. left arch with atretic (closed) end) or the ligamentum arteriosum might be difficult to visualize by echocardiography.

"Computed tomography (CT):"

Computed tomography after application of contrast media is usually diagnostically accurate. It shows the relationship of the arches to the trachea and bronchi.

"Magnetic resonance imaging (MRI):"

Magnetic resonance imaging provides excellent images of the trachea and surrounding vascular structures and has the advantage of not using radiation for imaging compared to Computed tomography.

"Cardiac catherization/aortography:"

Today patients with double aortic arch usually only undergo cardiac catherization to evaluate the hemodynamics and anatomy of associated congenital cardiac defects. Through a catheter in the ascending aorta contrast media is injected and the resulting aortography may be used to delineate the anatomy of the double aortic arch including sites of narrowing in the left aortic arch. Aortography can also be used to visualize the origin of all head and arm vessels originating from the two arches.

A "Partial anomalous pulmonary venous connection" (or "Partial anomalous pulmonary venous drainage" or "Partial anomalous pulmonary venous return") is a congenital defect where the left atrium is the point of return for the blood from some (but not all) of the pulmonary veins.

It is less severe than total anomalous pulmonary venous connection which is a life-threatening anomaly requiring emergent surgical correction, usually diagnosed in the first few days of life. Partial anomalous venous connection may be diagnosed at any time from birth to old age. The severity of symptoms, and thus the likelihood of diagnosis, varies significantly depending on the amount of blood flow through the anomalous connections. In less severe cases, with smaller amounts of blood flow, diagnosis may be delayed until adulthood, when it can be confused with other causes of pulmonary hypertension. There is also evidence that a significant number of mild cases are never diagnosed, or diagnosed incidentally. It is associated with other vascular anomalies, and some genetic syndromes such as Turner syndrome.

In regards to the diagnosis of pulmonary atresia the body requires oxygenated blood for survival. pulmonary atresia is not threatening to a developing fetus however, because the mother's placenta provides the needed oxygen since the baby's lungs are not yet functional. Once the baby is born its lungs must now provide the oxygen needed for survival, but with pulmonary atresia there is no opening on the pulmonary valve for blood to get to the lungs and become oxygenated. Due to this, the newborn baby is blue in color and pulmonary atresia can usually be diagnosed within hours or minutes after birth.

The diagnosis of pulmonary atresia can be done via the following exams/methods: an echocardiogram, chest x-ray, EKG and an exam to measure the amount of in the body.

With a series of operations or even a heart transplant, a newborn can be treated but not be cured. Young individuals who have undergone reconstructive surgery must refer to a cardiologist who is experienced in congenital heart diseases, "Children with HLHS are at an increased level for developing endocarditis." Kids that have been diagnosed with HRHS must limit the physical activity they participate in to their own endurance level.

Early diagnosis still remains a challenge in CTEPH, with a median time of 14 months between symptom onset and diagnosis in expert centres. A suspicion of PH is often raised by echocardiography, but an invasive right heart catheterisation is required to confirm it. Once PH is diagnosed, the presence of thromboembolic disease requires imaging. The recommended diagnostic algorithm stresses the importance of initial investigation using an echocardiogram and V/Q scan and confirmation with right heart catheter and pulmonary angiography (PA).

Both V/Q scanning and modern multidetector CT angiography (CTPA) may be accurate methods for the detection of CTEPH, with excellent diagnostic efficacy in expert hands (sensitivity, specificity, and accuracy of 100%, 93.7%, and 96.5% for V/Q and 96.1%, 95.2%, and 95.6% for CTPA). However, CTPA alone cannot exclude the disease, but may help identify pulmonary artery distension resulting in left main coronary artery compression, pulmonary parenchymal lesions (e.g. as complications from previous pulmonary infarctions), and bleeding from bronchial collateral arteries. Today, the gold standard imaging remains invasive pulmonary angiography (PAG) using native angiograms or a digital subtraction technique.

Congenital heart defects are now diagnosed with echocardiography, which is quick, involves no radiation, is very specific, and can be done prenatally.

Before more sophisticated techniques became available, chest x-ray was the definitive method of diagnosis. The abnormal "coeur-en-sabot" (boot-like) appearance of a heart with tetralogy of Fallot is classically visible via chest x-ray, although most infants with tetralogy may not show this finding. Absence of interstitial lung markings secondary to pulmonary oligaemia are another classic finding in tetralogy, as is the pulmonary bay sign.

Treatment is with neonatal surgical repair, with the objective of restoring a normal pattern of blood flow. The surgery is open heart, and the patient will be placed on cardiopulmonary bypass to allow the surgeon to work on a still heart. The heart is opened and the ventricular septal defect is closed with a patch. The pulmonary arteries are then detached from the common artery (truncus arteriosus) and connected to the right ventricle using a tube (a conduit or tunnel). The common artery, now separated from the pulmonary circulation, functions as the aorta with the truncal valve operating as the aortic valve. Most babies survive this surgical repair, but may require further surgery as they grow up. For example, the conduit does not grow with the child and may need to be replaced as the child grows. Furthermore, the truncal valve is often abnormal and may require future surgery to improve its function.

There have been cases where the condition has been diagnosed at birth and surgical intervention is an option. A number of these cases have survived well into adulthood.

Historically the prognosis for patients with untreated CTEPH was poor, with a 5-year survival of 40 mmHg at presentation. More contemporary data from the European CTEPH registry have demonstrated a 70% 3-year survival in patients with CTEPH who do not undergo the surgical procedure of pulmonary endarterectomy (PEA). Recent data from an international CTEPH registry demonstrate that mortality in CTEPH is associated with New York Heart Association (NYHA) functional class IV, increased right atrial pressure, and a history of cancer. Furthermore, comorbidities such as coronary disease, left heart failure, and chronic obstructive pulmonary disease (COPD) are risk factors for mortality.

Transvenous biopsy of the right ventricle can be highly specific for ARVD, but it has low sensitivity. False positives include other conditions with fatty infiltration of the ventricle, such as chronic alcohol abuse and Duchenne/Becker muscular dystrophy.

False negatives are common, however, because the disease progresses typically from the epicardium to the endocardium (with the biopsy sample coming from the endocardium), and the segmental nature of the disease. Also, due to the paper-thin right ventricular free wall that is common in this disease process, most biopsy samples are taken from the ventricular septum, which is commonly "not" involved in the disease process.

A biopsy sample that is consistent with ARVD would have > 3% fat, >40% fibrous tissue, and <45% myocytes.

A post mortem histological demonstration of full thickness substitution of the RV myocardium by fatty or fibro-fatty tissue is consistent with ARVD.

A doctor will listen to the heart with stethoscope. A "tumor plop" (a sound related to movement of the tumor), abnormal heart sounds, or a murmur similar to the mid-diastolic rumble of mitral stenosis may be heard. These sounds may change when the patient changes position.

Right atrial myxomas rarely produce symptoms until they have grown to be at least 13 cm (about 5 inches) wide.

Tests may include:

- Echocardiogram and Doppler study

- Chest x-ray

- CT scan of chest

- Heart MRI

- Left heart angiography

- Right heart angiography

- ECG—may show atrial fibrillation

Blood tests:

A FBC may show anemia and increased WBCs (white blood cells). The erythrocyte sedimentation rate (ESR) is usually increased.