Eisenmenger’s syndrome pathophysiology
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Abdelrahman Ibrahim Abushouk, MD[2]
Overview
Pathophysiology
Physiology
The normal physiology of [name of process] can be understood as follows:
Pathogenesis
- Eisenmenger's syndrome can develop in many types of congenital heart diseases.
- It has been found that among all the congenital heart defects, ventricular septal defect most frequently develops Eisenmenger's syndrome followed by atrial septal defect and patent ductus arteriosus[1].
- The progression of a heart defect to Eisenmenger's syndrome depends on:
- Size of left to right shunt
- Severity of pulmonary vascular disease.
- Type of defect (it develops more frequently in uncorrected ventricular septal defect compared to atrial septal defect)[2]
- The left-to-right shunting causes an increase in pulmonary vascular flow, which in turn leads to pulmonary artery hypertension.
- This leads to reversal of shunt and development of cyanosis.
- Further, the increased pressure causes damage to delicate capillaries, which then are replaced with scar tissue.
- The scar tissue does not contribute to oxygen transfer, therefore decreasing the useful volume of the pulmonary vasculature. The scar tissue also provides less flexibility than normal lung tissue, causing further increases in blood pressure.
- The reduction in oxygen transfer reduces oxygen saturation in the blood, leading to increased production of red blood cells in an attempt to bring the oxygen saturation up. The excess of red blood cells is called polycythemia.
- Desperate for enough circulating oxygen, the body begins to dump immature red cells into the blood stream. Immature red cells are not as efficient at carrying oxygen as mature red cells, and they are less flexible, less able to easily squeeze through tiny capillaries in the lungs, and so contribute to death of pulmonary capillary beds. The increase in red blood cells also causes hyperviscosity syndrome.
- A person with Eisenmenger's Syndrome is paradoxically subject to the possibility of both uncontrolled bleeding due to damaged capillaries and high pressure, and random clots due to hyperviscosity and stasis of blood.
- Eventually, due to increased resistance, pulmonary pressures may increase sufficiently to cause a reversal of blood flow, so blood begins to travel from the right side of the heart to the left side, and the body is supplied with deoxygenated blood, leading to cyanosis and resultant organ damage.
Genetics
- Eisenmenger's Syndrome is not currently identified as an inherited disorder.
- Specific genes that cause Eisenmenger's syndrome have not been identified so far.
Associated Conditions
Conditions associated with Eisenmenger's syndrome include:
- Causative congenital heart diseases.
- Tricuspid and pulmonary valve regurgitation
- Atherosclerosis
Gross Pathology
On gross pathology, Eisenmenger's syndrome may show the following[3]:
- Atrial or ventricular septal defect.
- Right ventricular hypertrophy
- Pulmonary trunk dilatation
- Atherosclerosis of pulmonary artery and its branches.
- Tricuspid regurgitation may be seen.
Microscopic Pathology
According to the histopathologic criteria of Heath and Edwards, there are six stages of pulmonary vascular disease (including Eisenmenger's syndrome)[4]:
- Stage I: Medial hypertrophy (reversible)
- Stage II: Cellular intimal hyperplasia in an abnormally muscular artery (reversible)
- Stage III: Lumen occlusion from intimal hyperplasia of fibroelastic tissue (partially reversible)
- Stage IV: Arteriolar dilatation and medial thinning (irreversible)
- Stage V: Plexiform lesion, which is an angiomatoid formation (terminal and irreversible)
- Stage VI: Fibrinoid/necrotizing arteritis (terminal and irreversible)
References
- ↑ Saha A, Balakrishnan KG, Jaiswal PK, Venkitachalam CG, Tharakan J, Titus T; et al. (1994). "Prognosis for patients with Eisenmenger syndrome of various aetiology". Int J Cardiol. 45 (3): 199–207. PMID 7960265.
- ↑ Granton JT, Rabinovitch M (2002). "Pulmonary arterial hypertension in congenital heart disease". Cardiol Clin. 20 (3): 441–57, vii. PMID 12371012.
- ↑ de Campos FPF, Benvenuti LA (2017). "Eisenmenger syndrome". Autops Case Rep. 7 (1): 5–7. doi:10.4322/acr.2017.006. PMC 5436914. PMID 28536680.
- ↑ HEATH D, EDWARDS JE (1958). "The pathology of hypertensive pulmonary vascular disease; a description of six grades of structural changes in the pulmonary arteries with special reference to congenital cardiac septal defects". Circulation. 18 (4 Part 1): 533–47. doi:10.1161/01.cir.18.4.533. PMID 13573570.