Congenital Heart Disease Student PDF

CONGENITAL HEART DISEASE Hillary Hammond DVM, MS, DACVIM (Cardiology)  LEARNING OBJEC TIVES List clinical findings suggestive of possible congenital heart disease When provided the description of a heart murmur in a young animal, determine whether it is lik...

CONGENITAL HEART DISEASE Hillary Hammond DVM, MS, DACVIM (Cardiology)  LEARNING OBJEC TIVES List clinical findings suggestive of possible congenital heart disease When provided the description of a heart murmur in a young animal, determine whether it is likely to be associated with structural heart disease Contrast the fetal and adult circulatory systems List the major cardiovascular changes that normally occur in the immediate post-natal period List the most common congenital heart diseases affecting each of the following: dogs, cats, horses, cattle, and camelids For each of the following, describe basic pathophysiology, expected clinical findings, and general treatment approach: Patent ductus arteriosus Ventricular septal defect Left and right ventricular outflow tract stenoses Tetralogy of Fallot  CONGENITAL HEART DISEASE DEFINITION PREVALENCE Defect in cardiac structure that is Dogs and cats present at birth 0.5 – 0.9% of dogs, 0.05% of cats examined May be inherited at referral hospitals May develop spontaneously 5 g/dL Patients are frequently polycythemic Most common: Tetralogy of Fallot, Eisenmenger’s syndrome (reversed PDA, reversed VSD) Left-sided circulation Right-sided circulation  EISENMENGER’S SYNDROME Reversal of a normally left-to-right shunting lesion due to increased right-sided pressures due to pulmonary hypertension When pulmonary vascular resistance > systemic vascular resistance, shunt reverses May complicate large PDA, VSD or ASD Most common example: reversed PDA  TETRALOGY OF FALLOT Most commonly diagnosed cyanotic heart disease Malformation of upper interventricular septum leads to FOUR abnormalities  TETRALOGY OF FALLOT Pulmonary Stenosis Over-riding aorta (dextroposition) Resists normal blood flow from right Accepts blood from BOTH right and ventricle to lungs left ventricles Stenosis severity influences degree of right-to-left shunt Large ventricular septal defect (VSD) Right ventricular hypertrophy High in the interventricular septum Purely secondary response Extends up to the aortic valve  TETRALOGY OF FALLOT: CLINIC AL FEATURES Asymptomatic to signs of severe exercise intolerance, syncope, seizures Physical examination Cyanosis present in 90% at rest, worsens with exercise Most have a murmur associated with pulmonary stenosis Left basilar systolic Pulses usually normal  TETRALOGY OF FALLOT: PROGNOSIS AND RECOMMENDATIONS SA Medical therapy Ao Intermittent phlebotomy, exercise restriction PA Long-term prognosis relatively poor May survive years with intermittent phlebotomy; many die at < 1 y old Surgical options are limited Definitive – requires cardiac bypass Palliation with systemic-to-pulmonary shunt Re-routes arterial blood through lungs Modified Blalock-Taussig shunt Subclavian artery-to-pulmonary artery conduit 83% survival with improved clinical signs and long-term survival  TAKE HOME POINTS Severity may range from trivial (well-tolerated) to life- threatening While CHD is the most common cause of heart disease in young animals, affected patients may not manifest clinical signs until adulthood Diagnosis of specific defects can be made by echocardiographic examination Prognosis is heavily dependent on type and severity of malformation, and availability of definitive or palliative treatment options In most cases, successful management requires: Prompt recognition by the family veterinarian Referral to a cardiologist for detailed evaluation