A right to left shunt is a term describing the flow of deoxygenated blood from the right heart (previously from the inferior and superior vena cava) straight into the left heart, which predominantly occurs in the setting of several congenital heart diseases (CHDs) [1] [2] [3] [4]:

• Tetralogy of Fallot - One of the most important and most common CHDs (constituting 7-10% of all cases) causing a right to left shunt, Tetralogy of Fallot is comprised of a ventricular septal defect (VSD), pulmonary stenosis that obstructs the outflow of the right ventricle, consequent right ventricular hypertrophy and an overriding aorta [2] [4].
• Transposition of great vessels - Seen in 1 per 3,000-5,000 live birth, and more commonly in males, the transposition of great vessels is a CHD in which the discordant ventricular outflow occurs due to the aorta arising from the right ventricle and the pulmonary trunk arising from the left ventricle [3].
• Tricuspid atresia - Defined as total or near-total loss of the right atrioventricular connection, this rare CHD is also an important disorder that induces a right to left shunt [5].
• Persistent truncus arteriosus - A disorder characterized by a single vessel arising from the connected ventricular system of the heart [6].

All CHDs that induce a right to left shunt present with central cyanosis and the term cyanotic heart disease is sometimes used to describe these disorders [1] [4]. Signs and symptoms may appear very early, during the neonatal period in most cases, and cyanosis could be mild or severe and life-threatening, depending on the extent of hypoxemia [4] [7]. If the diagnosis is not made immediately, clubbing of the fingers and toes, polycythemia, paradoxical embolization and respiratory distress can ensue [3] [4] [5] [7].

• Hypoxemia

  […] and/or right-to-left shunting are two of several causes of hypoxemia in the absence of congenital heart disease. [ncbi.nlm.nih.gov]

• Cyanotic Congenital Heart Disease

  […] with Cyanotic Heart Diseases. [dovemed.com]

  Right to left cardiac shunt is hence referred as cyanotic congenital heart disease. Causes Of Right To Left Cardiac Shunt Right to left cardiac shunt is congenital heart malformation which is present since birth. [tandurust.com]

  Much rarer etiological causes include cavopulmonary surgical corrections of cyanotic congenital heart disease; gestational trophoblastic disease; and arteriovenous fistulae induced by trauma. [orpha.net]

  In newborns, the oxygen deprivation causes a bluish discoloration of the skin known as cyanosis and this is often referred to a cyanotic congenital heart disease. [healthhype.com]

• Platypnea

  Endovascular patent foramen ovale closure permitted the resolution of symptoms and disappearance of platypnea-orthodeoxia syndrome. [ncbi.nlm.nih.gov]

• Heart Disease

  We wish to report two cases of congenital cyanotic heart disease in whom coexisting thyrotoxicosis increased the right to left shunt. [ncbi.nlm.nih.gov]

  Several congenital heart diseases induce right to left shunting of blood, during which deoxygenated blood from the right heart gains entry straight into the left heart. [symptoma.com]

  […] with Cyanotic Heart Diseases. [dovemed.com]

  Left To Right Shunt Congenital Heart Disease Human heart is made up of four chambers; the two upper atrium and the two lower ventricles. [tandurust.com]

• Cyanosis

  In neonates, a properly performed physical examination immediately detects cyanosis, after which various diagnostic and imaging tests should be ordered. [symptoma.com]

  He suffered from exertional dyspnea and cyanosis (oxygen saturation: 85%) for years and he still did not accept any reintervention. [scopemed.org]

  A patient with Gaucher disease with the hepatopulmonary syndrome associated with severe cyanosis and hypoxemia was examined for intrapulmonary right-to-left shunt using Tc-99m MAA. [ncbi.nlm.nih.gov]

  As with any right-to-left shunt, there is decreased blood flow to the lungs, resulting in decreased oxygenation of blood and cyanosis. [en.wikipedia.org]

  Right-to-left shunt in the absence of elevated pulmonary vascular resistance is a rare condition which can also explain cyanosis and hypoxemia in the presence of an ASD [ 1, 2, 4 ]. [omicsonline.org]

• Systolic Murmur

  SAWING WOOD murmur- long, loud, harsh mid-systolic murmur followed by a shorter harsh diastolic murmur • ECG (vs TOF e PS)- tall monophasic R wave in lead V1 extends to adjacent precordial leads, in contrast to TOF with PS in which tall right precordial [slideshare.net]

  Auscultation Systolic ejection murmur over the left second ICS sternal border Widely split second heart sound (S 2 ) over the left second ICS ;, which is fi xed (does not change with respiration ), normal S 1 Soft mid- diastolic murmur over the lower [amboss.com]

  Upon auscultation of the heart sounds, there may be an ejection systolic murmur that is attributed to the pulmonic valve. [marmur.com]

• Heart Murmur

  Small ventricular septal defects, which did not close spontaneously in childhood, result in a distinctive heart murmur. Larger defects may cause shortness of breath and other problems caused by excessive pulmonary blood flow. [pted.org]

  Auscultation Systolic ejection murmur over the left second ICS sternal border Widely split second heart sound (S 2 ) over the left second ICS ;, which is fi xed (does not change with respiration ), normal S 1 Soft mid- diastolic murmur over the lower [amboss.com]

• Arm Weakness

  This patient developed acute onset of right arm weakness with facial droop and aphasia which improved after intravenous thrombolysis. [ncbi.nlm.nih.gov]

• Suggestibility

  We suggest that CPET is an appropriate noninvasive tool to begin and guide the evaluation of undiagnosed dyspnea. [ncbi.nlm.nih.gov]

• Neglect

  The possible causes for paradoxical embolism in young patients with cryptogenic stroke appear more variable than usually considered, and other causes than PFO should not be neglected. [ncbi.nlm.nih.gov]

Mortality rates of CHDs causing a right to left shunt are very high in the absence of an early diagnosis and appropriate treatment, and unfortunately, the diagnosis is missed in up to 25% of neonates [3] [7]. For this reason, a meticulous prenatal and postnatal workup is vital in recognizing CHDs of any type, especially those that can be of life-threatening. In neonates, a properly performed physical examination immediately detects cyanosis, after which various diagnostic and imaging tests should be ordered. One of the easiest tests that might be used in the clinical setting is the evaluation of pulse oximetry, a procedure that rapidly evaluates the percentage of oxygen in systemic circulation [7]. When a right to left shunt exists, profound hypoxemia is virtually always present, and pulse oximetry has been used as an effective neonatal screening method for tricuspid atresia, tetralogy of Fallot, and the transposition of the great vessels [7]. Plain radiography of the chest and electrocardiography (ECG) may be useful methods as well, and if clinical suspicion is raised, imaging studies in the form of echocardiography, are the gold standard in visualizing the shunt and confirming the underlying cause [2] [3] [5] [6]. Standard 2D, 3D, and color Doppler are all used to identify the anatomical anomaly and make the diagnosis. The benefit of ultrasonography is that it enables physicians to make a prenatal diagnosis, and tetralogy of Fallot can be diagnosed as early as 12 weeks [2] [5]. In addition, it enables adequate therapeutic preparation, thus significantly reducing the risk for complications.

• Mediastinal Mass

  Computed tomographic pulmonary angiogram showed a right-sided mediastinal mass adjacent to the right atrium. [ncbi.nlm.nih.gov]

• Pleural Adhesions

  This uncommon collateral pathway represents a rare form of acquired right-to-left shunt due to previous pleural adhesions with an increased risk of stroke due to right-to-left venous shunting, which requires lifelong anticoagulation. [ncbi.nlm.nih.gov]

[…] report describes a patients with PPH with atrial septal aneurysm and a severe right to left shunt through the patent foramen ovale who showed a dramatic decrease in the pulmonary artery systolic pressure and interatrial shunt disappeared after sildenafil treatment [ncbi.nlm.nih.gov]

In some the treatment may become essential as soon as the child is born, while some patients may need treatment few years later when the symptoms become apparent. Both medication and surgery are essential part of treatment. [tandurust.com]

treatment, prevention, prognosis, and additional useful information HERE. [dovemed.com]

Prognosis With appropriate management and interventions, prognosis is generally very good with many patients reaching their 9th and 10th decades of life. During pregnancy, however, there is a 1% maternal death rate. [orpha.net]

Abstract Introduction Cardiopulmonary complications are a major cause of morbidity and mortality in sickle cell disease (SCD) as shown by worse prognosis in patients who have experienced acute chest syndrome or who have an elevated tricuspid regurgitant [bloodjournal.org]

The prognosis for patients whose VSDs either closed spontaneously or through surgery before the development of pulmonary vascular disease is excellent, with no exercise restrictions and normal life expectancy. [pted.org]

• Neonatal presentation associated with poor prognosis – 20% die in 1 month, and less than 50% survive to 5 years – Cause: HF/Hypoxia Circulation. 2007.115.277-285 36. [slideshare.net]

and (5) stroke of undetermined etiology. [stroke.ahajournals.org]

These results could lead to more comprehensive evaluation for occult malignancy or a pulmonary arteriovenous malformation, both potentially treatable etiologies of ischemic stroke. [ncbi.nlm.nih.gov]

Distribution of etiologic groups did not differ from the overall population of 263 patients evaluated for precapillary PH in our department. Table 2 Etiologic groups of pulmonary hypertension [ 1 ]. [bmccardiovascdisord.biomedcentral.com]

Etiology The exact pathogenesis is still unknown. Although generally observed in the context of HHT, PAVMs may also be idiopathic. [orpha.net]

CONCLUSIONS: In addition to recently defined criteria, genetically determined inheritable traits and epidemiologic characteristics (male gender) should be taken into account when assessing PFO and related cerebrovascular risk profile. [ncbi.nlm.nih.gov]

Complications Heart failure in infancy Infective endocarditis Common cause of pulmonary hypertension and Eisenmenger syndrome in adolescents and adults References: [2] [3] [22] [23] [24] [25] Coarctation of the aorta Epidemiology Prevalence : 4/10,000 [amboss.com]

Summary Epidemiology Prevalence is estimated at around 1/ 2,600. There is a minor female predominance. [orpha.net]

[…] determined by transcranial Doppler (TCD) with injection of agitated air/saline/autologous blood contrast in 166 migraineurs (mean age: 56 years; 70% women) and 69 controls (mean age: 55 years; 65% women) from the Cerebral Abnormalities in Migraine: An Epidemiological [ahcmedia.com]

Epidemiology United States statistics Patent foramen ovale (PFO) is detected in 10-15% of the population by contrast transthoracic echocardiography. [emedicine.medscape.com]

A review of the literature on different pathophysiologic factors is presented and some therapeutic implications, specifically the adverse effect of PEEP in such situations, are discussed. [ncbi.nlm.nih.gov]

[…] previously unrecognized patent foramen ovale in a Novacor patient, the subsequent transient hypoxemia could be managed by avoiding PEEP of more than 3 mmHg, and mean airway pressure of more than 11 mmHg and by careful volume replacement in order to prevent [ncbi.nlm.nih.gov]

1. Sommer RJ, Hijazi ZM, Rhodes JF Jr. Pathophysiology of congenital heart disease in the adult: part I: Shunt lesions. Circulation. 2008;117(8):1090-1099.
2. Bailliard F, Anderson RH. Tetralogy of Fallot. Orphanet J Rare Dis. 2009;4:2.
3. Martins P, Castela E. Transposition of the great arteries. Orphanet J Rare Dis. 2008;3:27.
4. Aster, JC, Abbas, AK, Robbins, SL, Kumar, V. Robbins basic pathology. Ninth edition. Philadelphia, PA: Elsevier Saunders; 2013.
5. Berg C, Lachmann R, Kaiser C, et al. Prenatal diagnosis of tricuspid atresia: intrauterine course and outcome. Ultrasound Obstet Gynecol. 2010;35(2):183-190.
6. Ruan W, Loh YJ, Guo KWQ, Tan JL. Surgical correction of persistent truncus arteriosus on a 33-year-old male with unilateral pulmonary hypertension from migration of pulmonary artery band. J Cardiothorac Surg. 2016;11:39.
7. Engel MS, Kochilas LK. Pulse oximetry screening: a review of diagnosing critical congenital heart disease in newborns. Med Devices (Auckl). 2016;9:199-203.