Chad Cripe, M.D., gave the Frank Murphy Memorial Lecture for 2008 on the subject of the implications of congenital heart disease in adults (CHD). His major points for CHD are as follows:
Congenital heart diseases (CHD) may encompass a number of different structural lesions in the fetal circulation that persist after birth. Some may be life threatening, requiring immediate surgical correction. Others may go unnoticed until symptoms of advanced disease present themselves. A physiologic classification of CHD exists in order to allow grouping of similar lesions. These classifications include shunts, mixing lesions, obstructive lesions and regurgitant lesions.
Shunts are lesions that produce abnormal blood flow within the heart from left to right or right to left. In left to right shunts, such as ASD, VSD and PDA, some of the blood in the left side of the heart is directed to the right side of the heart without being delivered to the peripheral circulation. This creates an excess volume overload on the heart. In the case of right to left shunts, such as in Tetralogy of Fallot, Pulmonary Atresia and Eisenmenger complex, blood is diverted to the left heart without picking up much needed oxygen in the lungs. This creates problems of hypoxia for these patients.
Mixing lesions, such as transposition of the great arteries, tricuspid atresia and univentricular heart, represent the most complex type of CHD. As the term mixing lesion implies, there is often a mixing of oxygenated and deoxygenated blood occurring in these patients. The degree of mixing is often represented by the Qp:Qs ratio. Qp represents flow to the pulmonary system, whereas Qs represents flow to the systemic circulation. In healthy individuals the Qp:Qs ratio is approximately 1:1 (there exists a small amount of blood that is diverted back to the right heart from the pulmonary/bronchial circulation and cardiac thesbian vessels without being oxygenated). The degree of shunting is variable and may often change quickly depending on the patient’s clinical situation. Factors that increase or decrease pulmonary vascular resistance (PVR) will directly affect the Qp:Qs ratio. Patients often develop some degree of cyanosis. Changes in vascular resistance can also affect patients with shunting lesions. For example, in patients with Tetralogy of Fallot, an increase in systemic vascular resistance leads to increased pulmonary blood flow and improved oxygenation. In contrast, systemic vasodilation often leads to increased right to left shunt, hypoxia and cyanosis.
Obstructive lesions include pulmonic stenosis, aortic stenosis, coarctation of the aorta, mitral stenosis and hypoplastic left heart syndrome. In these situations the heart sees a pressure overload as a result of the obstruction. Signs of pressure overload may develop such as an increase in systolic and diastolic BP and and an increase in LV wall thickness.
Regurgitant lesions are rare in CHD, yet may be seen commonly in some adult settings. Ebstein’s anomaly is a congenital downward displacement of the tricuspid valve which occurs rarely in newborns. The tricuspid valve becomes regurgitant and signs of volume overload may occur, such as an increase in diastolic BP, wall thickness and radius of the ventricle.
Dr. Cripe has recently completed his training in Anesthesiology at the University of Pennsylvania