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Right to Left Shunt

Right to Left Cardiac Shunt

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. As a result, a very early onset of cyanosis and severe hypoxemia is typical in a right to left shunt. Clinical criteria, followed by imaging studies, mainly echocardiography, are used to identify the cause of symptoms.

Presentation

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].

Entire Body System

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]
Intracardiac right to left shunt through a patent foramen ovale (PFO) may result in the development of hypoxemia after cardiac surgery.[ncbi.nlm.nih.gov]
Platypnea-orthodeoxia is a syndrome characterized by dyspnea and hypoxemia on adoption of an upright posture (i.e., orthodeoxia), and by the absence or reduction of symptoms and of hypoxemia in a supine position.[ncbi.nlm.nih.gov]
This phenomenon should be considered as a possible cause of hypoxemia in the presence of right ventricular infarction.[ncbi.nlm.nih.gov]
A balloon tip catheter was positioned in the left atrium and retracted against the atrial septum and the hypoxemia resolved.[ncbi.nlm.nih.gov]

Cyanotic Congenital Heart Disease

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

Gaucher Disease

Hepatomegaly is a common manifestation in Gaucher disease. In some patients with the disease, hepatic fibrosis and portal hypertension are observed.[ncbi.nlm.nih.gov]

Respiratoric

Platypnea

Endovascular patent foramen ovale closure permitted the resolution of symptoms and disappearance of platypnea-orthodeoxia syndrome.[ncbi.nlm.nih.gov]
This article describes a patient presenting with dyspnea and platypnea and whose only clinical finding was presence of patent foramen ovale with a right to left shunt, without pulmonary hypertension, characteristic of the rare Platypnea-Orthodeoxya Syndrome[ncbi.nlm.nih.gov]
Diagnosis of platypnea-orthodeoxia syndrome was demonstrated by O2 saturation and arterial blood gas analysis in the supine and upright positions.[ncbi.nlm.nih.gov]
A 61-year-old woman presented with platypnea and orthodeoxia after right pneumonectomy for lung cancer.[ncbi.nlm.nih.gov]
Clinically, right-to-left shunts are often related to platypnea-orthodeoxia.[ncbi.nlm.nih.gov]

Cardiovascular

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]
This report suggests that coronary artery disease can be one of the potential factors in inducing critical hemodynamic changes in aging patients with congenital heart disease, especially those who have a shunt between the right and left chambers.[ncbi.nlm.nih.gov]
[…] with Cyanotic Heart Diseases.[dovemed.com]

Cyanosis

In neonates, a properly performed physical examination immediately detects cyanosis, after which various diagnostic and imaging tests should be ordered.[symptoma.com]
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]
He suffered from exertional dyspnea and cyanosis (oxygen saturation: 85%) for years and he still did not accept any reintervention.[scopemed.org]
A 47-year-old woman diagnosed with arrhythmogenic right ventricular cardiomyopathy, was studied at our institution with palpitations, progressive dyspnoea and cyanosis over a 3-year period. Her haemoglobin saturation was 76.1%.[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]

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]

Systolic Murmur

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

Neurologic

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]

Workup

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.

X-Ray

Mediastinal Mass

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

Serum

Hyperviscosity

AIMS: Patients with Ebstein's anomaly of the tricuspid valve may have right-to-left shunt at atrial level resulting in hypoxaemia, high haematocrit and hyperviscosity syndrome.[ncbi.nlm.nih.gov]

Treatment

Interventional treatment of a cardiac RLS may offer a small benefit, but has to be weighed against possible complications and the problem of establishing causality.[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]
Treatment consisted of peripheral embolectomy, removal of the atrial mass, and closure of the atrial septum defect.[ncbi.nlm.nih.gov]
The treatment is surgical, but with very high mortality. We describe a case of type A aortic dissection complicated with shock and fistulization into the right atrium with the right-to-left shunt through a patent foramen ovale.[ncbi.nlm.nih.gov]
Surgical treatment of a right atrial myxoma with a right-to-left shunt and coronary artery disease was successfully performed in a 61-year-old man.[ncbi.nlm.nih.gov]

Prognosis

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

Etiology

In most cases, however, it is difficult to establish a firm etiological association and the debate about management is ongoing.[ncbi.nlm.nih.gov]
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]
The fact that the secondary RLS group had more atrial septal aneurysms and a larger balloon waist diameter would also suggest that incomplete balloon occlusion of large, floppy PFOs is a more likely source of RLS than an intrapulmonary etiology.[interventions.onlinejacc.org]
Etiology The exact pathogenesis is still unknown. Although generally observed in the context of HHT, PAVMs may also be idiopathic.[orpha.net]
Search for "ventilation-perfusion defect" to find other etiologies.[pathwaymedicine.org]

Epidemiology

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

Sex distribution

Age distribution

Pathophysiology

[…] patient presenting with dyspnea and platypnea and whose only clinical finding was presence of patent foramen ovale with a right to left shunt, without pulmonary hypertension, characteristic of the rare Platypnea-Orthodeoxya Syndrome, with very interesting pathophysiological[ncbi.nlm.nih.gov]
This case report illustrates how a step-by-step diagnostic procedure, based on pathophysiology, may lead to such unexpected findings.[ncbi.nlm.nih.gov]
To report a specific pathophysiology of hemidiaphragmatic paralysis that may result in severe hypoxemia. Case series. Intensive care unit in a cardiology hospital.[ncbi.nlm.nih.gov]
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]
In the absence of any possible pathophysiological mechanism, to explain the observed R-L shunt, we deduce that the particles of Tc-99m MAA might have passed through the precapillary pulmonary arteriovenous anastomoses and/or through dilated pulmonary[ncbi.nlm.nih.gov]

Prevention

Preoperative nebulized salbutamol and ipratroprium were given to prevent bronchospasm and adrenaline and noradrenaline were infused to maintain cardiac output and the balance between systemic and pulmonary vascular resistance.[ncbi.nlm.nih.gov]
[…] this study was to investigate the relationship between right-to-left shunt (RLS) and the clinical features of decompression sickness (DCS) in scuba divers and to determine the potential benefit for screening this anatomical predisposition in primary prevention[ncbi.nlm.nih.gov]
: An increasing number of patients are being evaluated for percutaneous patent foramen ovale (PFO) closure to prevent recurrent cerebrovascular events, but debate still exists on therapeutic indications and off-label closure device implantation.[ncbi.nlm.nih.gov]
[…] systemic oxygen saturation, with right atrial pressures remaining CONCLUSIONS: Percutaneous closure of atrial right-to-left shunt in selected patients with Ebstein's anomaly offers significant improvement, abolishing hypoxaemia and hyperviscosity and preventing[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]

References

Article

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.
Bailliard F, Anderson RH. Tetralogy of Fallot. Orphanet J Rare Dis. 2009;4:2.
Martins P, Castela E. Transposition of the great arteries. Orphanet J Rare Dis. 2008;3:27.
Aster, JC, Abbas, AK, Robbins, SL, Kumar, V. Robbins basic pathology. Ninth edition. Philadelphia, PA: Elsevier Saunders; 2013.
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.
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.
Engel MS, Kochilas LK. Pulse oximetry screening: a review of diagnosing critical congenital heart disease in newborns. Med Devices (Auckl). 2016;9:199-203.

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Last updated: 2019-07-11 21:17