28. Eisenmenger Syndrome
Definition
Eisenmenger syndrome (ES) is the presence of a bidirectional or exclusively right-to-left cardiac shunt in conjunction with pulmonary hypertension and a patent heart defect.
Incidence
Congenital heart defects occur in approximately 1% of all live births. Out of this group, approximately 8% overall, and 11% of those with a left-to-right shunt, will eventually develop ES.
Etiology
ES is a rare disorder that affects both the respiratory and cardiac systems. This disorder is very insidious and sinister. Fulminate signs and symptoms of the disorder do not typically manifest until the third, fourth, or fifth decade of life.
The patient with ES has a congenital heart defect that has never been surgically repaired; for example, an atrial or ventricular septal defect. The blood shunted from the left side of the heart through the right side increases the stroke volume of the right side of the heart. The increased stroke volume produces shear forces within the pulmonary microvasculature. The shear forces combine with the increased stroke volume to produce irreversible damage to the walls of the pulmonary vessels. The damage to these vessel walls scars the vessels, making them less compliant.
Eventually the pulmonary vascular resistance (PVR) becomes equal to and finally exceeds the systemic vascular resistance (SVR). The shunt becomes bidirectional and eventually reverses to an exclusively right-to-left shunt, mixing deoxygenated blood with oxygenated blood, resulting in chronic hypoxemia.
Signs and Symptoms
• Angina
• Clubbing of digits
• Cyanosis
• Dyspnea on exertion
• Fatigue
• Hemoptysis
• Palpitations
• Polycythemia
• Syncope
Medical Management
The primary focus of current medical management of ES is on reducing the PVR and, by extension, the right-to-left shunting and cyanosis. Medications and treatments that have detrimental effects must be avoided. For example, calcium channel–blocking agents must be avoided; even though these medications produce reductions in the PVR, they also produce unacceptably greater reductions in the SVR, effectively exacerbating the right-to-left shunting.
Sildenafil and l-arginine are effective in decreasing or reducing the degree of pulmonary hypertension. l-Arginine is converted to nitric oxide (NO) in vivo, which activates guanylate cyclase. Guanylate cyclase increases the level of cyclic guanosine monophosphate (cGMP), which is instrumental in relaxing the smooth muscles of the pulmonary blood vessels. Sildenafil inhibits the degradation of cGMP, thus fostering greater cGMP availability. Sildenafil works synergistically with inhaled NO to enhance the effects of both in the NO-cGMP pathway. Combining sildenafil with l-arginine enhances the NO-cGMP pathway in an effort to effectively reduce the PVR.
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