Pathophysiology Module 13

what is congenital heart disease

a defect in cardiac structure, present at birth, sufficiently severe to alter cardiac function

what is the incidence of CHD highly related to

chromosomal abnormalities, specifically Down’s syndrome

what are some etiologic agents of CHD

warfarin, trimethadione, chronic alcohol abuse, rubella infection

what percentage of genetic and environmental causes compromise all causes

10%

what are the 3 groups of classification of CHD in terms of structural abnormality

persistence of normal fetal blood channels into post-uterine life

genesis of some structure or failure of completion of its development

malformation or malposition of some structure

how do atrial septal defects form during embryogenesis

formation of a septum primum, which grows from the superior surface toward the endocardial cushions forming the AV canal

development of a hole (ostium secundum) in the upper part of the septum primum, before it fuses with the endocardial cushions

formation of another stiffer septum which grows downward over the ostium secondum but does not form a complete barrier, allowing blood to pass from right to left but not in the opposite direction

after birth the valve of the foreman ovale does not seal

what are the 3 types of ASDs

ostium secundum defect, ostium primum defect and sinus venosus defect

what is ostium secundum defect and what % does it account for all ASDs

a hole in the midpart of the septum caused by an excessively large ostium primum or failure of the septum secundum to extend over a normal ostium primum, 70%

what is ostium primum defect and what % does it account for all ASDs

incomplete formation of the septum primum, with the ostium primum persisting as a hole in the lower part of the septum, 20%

what is sinus venosus defect and what % does it account for all ASDs

anomalous drainage of the right pulmonary veins into the right atrium instead of the left, 10%

what are the consequences on the atrial and ventricular chambers during systole and diastole in ASD

left and right atrial pressures are nearly equal during ventricular systole

during diastole, blood passes through the septal defect into the right atrium and right ventricle

why is it difficult to diagnose ASD at birth

left and right ventricular walls are of equal thickness and compliance, so there is no left-to-right shunting of blood

what are the signs and symptoms of ASD

symptom free for years but after prolonged hyperperfusion of the lungs causes resistance to flow to increase, dyspnea, fatigue, exercise intolerance, frequent respiratory tract infections and orthopnea, right-sided heart failure

what are the factors that determine the clinical significance of ASD

relative compliance of the ventricle, relative pulmonary and systemic vascular resistance, size of the defect

what are the auscultatory findings for ASD

systolic ejection murmur, maybe a third heart sound, second heart sound is split,

which valves are incompetent in the ostium primum defect

mitral and tricuspid

what does CXR show in ASD

enlarged right side of the heart and prominent pulmonary vessels

what does echocardiogram show in ASD

enlarged right ventricle, shunt and direction of flow, turbulence of tricuspid and pulmonary valves

what does ECG show for ASD

incomplete RBBB, RAD, atrial arrhythmias

what is the treatment of choice for ASD

surgical repair unless there is high pulmonary vascular resistance and shunt reversal

what is the prognosis for ASD after surgical repair

generally good unless pulmonary vascular resistance is high

what percentage do VSDs account for heart defects in a newborn

20%

what are the hemodynamic changes in VSDs

blood is shunted from the left to the right ventricle during systole

what are the factors that determine the flow rate through the VSD

size and location of the defect, relative resistance of the pulmonary and systemic vascular resistance, contractility of the ventricular myocardium and presence of other defects

what are the auscultatory findings of VSDs

harsh holosystolic murmur, a third heart sound derives from rapid filling of the left ventricle through the mitral valve

why is VSD rarely seen as an adult

the large pressure gradient produces a prominent murmur and symptoms are noticed early in life

what does CXR show for VSDs

enlarged heart, prominent pulmonary vessels

what does ECG show for VSDs

may be normal but bilateral enlargement is seen 50% of the time

what does echocardiography show for VSDs besides the defect

cardiac enlargement and exaggerated motion of the left ventricle

what are the complications from VSDs

risk of infective endocarditis due to turbulent blood flow, risk of progressive pulmonary vascular sclerosis, arrhythmias and bilateral heart failure

what is the ductus arteriosus

a short vessel that allows fetal blood to pass from the pulmonary artery to the distal end of the aortic arch, bypassing the nonfunctional lungs

what happens to the ductus arteriosis after birth

narrows and flow ceases

what is patent ductus arteriosus

the ductus arteriosus remains open after birth and blood continues to pass from the systemic to the pulmonary circulation

what are the hemodynamic consequences of patent ductus arteriosus

chronic volume and pressure overload of the pulmonary vascular bed, development of infective endocarditis, pulmonary vascular sclerosis, pulmonary hypertension, CHF, left side is affected by volume overload

what are the predispositions to patent ductus arteriosus

rubella infection during pregnancy, premature birth and presence of other congenital heart defects

what are the auscultatory findings of PDA

continuous murmur

what are the long-term consequences of PDA

risk of infective endocarditis due to turbulent flow, prolonged pulmonary blood flow may cause pulmonary sclerosis and increased PVR

what is the preferred method of treatment for PDA

surgical closure

what is coarctation of the aorta

a congenital stenosis of the aorta, usually in the distal portion of the aortic arch, adjacent to the site of connection of the ductus arteriosus

what other disorders is coarctation of the aorta found in conjunction with

3x more likely in males, encountered more often in females with Turner’s syndrome, and in conjunction with other congenital heart defects

what are the differences in blood pressure in coarctation of the aorta

upstream hypertension and downstream hypotension

what are the two types of coarctation of the aorta

post-ductal coarctation and pre-ductal coarctation

what is post-ductal coarctation

stenosis is located distally to the opening of the ductus

what is pre-ductal coarctation

stenotic portion of the aorta lies proximal to the opening of the ductus

what is the clinical presentation of coarctation of the aorta

increased left ventricular afterload results in LVH, upper body is well developed and perfused due to receiving oxygenated blood while lower body is poorly developed due to receiving poorly oxygenated blood

what is seen on CXR in coarctation of the aorta

dilated, pulsating, intercostal vessels that have notched irregular borders due to the blood establishing a collateral circulation

what are the auscultatory findings in coarctation of the aorta

systolic murmur as blood jets through the aortic constriction and a more diffuse, continuous murmur as blood passes through the collateral vessels in the chest

what are the signs and symptoms of coarctation of the aorta

headaches, exertional dyspnea, leg fatigue, angina, CVA, cerebral aneurysms, hypertension, left-heart failure

what is the preferred treatment for coarctation of aorta

surgery during infancy

what is the prognosis for coarctation of aorta after surgery

generally good but surgical correction in an adult is more difficult and post-op complications are more seere

what is pulmonary stenosis

structural defects that increase resistance to blood flow from the right ventricle to the lungs

what are the hemodynamic consequences of pulmonary stenosis

obstructed outflow of the right ventricle, results in RVH and sometimes RAE

what is the auscultatory finding in pulmonary stenosis

systolic ejection murmur, second heart sound is split and the second heart sound is fainter

what is the amplitude and duration of the systolic murmur in pulmonary stenosis proportional to

the severity of the valve obstruction

what is the best way to diagnose pulmonary stenosis

right heart catheterization as the catheter passes through the pulmonary valve into the pulmonary artery and records the pressures

what is the treatment for mild pulmonary stenosis

prophylactic antibiotic therapy, surgery is unnecessary

what is the treatment for severe pulmonary stenosis

surgical repair but there is a risk of progressive valve injury and right heart failure

what are the 4 related anomalies in TOF

pulmonary stenosis, VSD, wide aorta that overrides the septal defect and RVH

what is the etiology of TOF

genetic - a single embryologic malformation as there is an unequal division of the outflow portion of the primitive ventricle by the conus septum and the VSD develops high in the septum

what is the clinical presentation of TOF

cyanosis at birth that becomes more severe with age, intolerance to exercise, small build with clubbed fingers, normal blood pressure

what are the 3 factors that determine the distribution of ventricular outflow between the pulmonary and systemic circulations

size of the VSD, severity of obstruction to right ventricular outflow and the status of the systemic vascular resistance

what is the underlying hemodynamic issue with TOF

right ventricular outflow obstruction is severe enough to limit flow through the pulmonary vascular bed, the pressure in the right ventricle rises and is equal to the left ventricle pressure, blood is forced through the VSD to the left and poorly oxygenated blood enters the systemic circulation

what are the auscultatory findings of TOF

pulmonary ejection murmur, collateral pathways to the lungs may produce a diffuse, continuous murmur, second heart sound is widely split and fixed

what does CXR show in TOF

RVH and reduction in size of the left heart, characteristic boot shape with the long axis pointing almost horizontally to the left

what does echocardiography show in TOF

the 4 components of the deficit

what does compensatory polycythemia involve

renal hypoxia provokes the release of erythropoietin, which stimulates RBC synthesis, hematocrit rises and increases blood viscosity, resulting in thrombosis and thromboemboli

what is the treatment for TOF

surgical correction, ideally in infancy

what is transposition of the great vessels

a cyanotic defect in which the aorta arises from the right ventricle and the pulmonary artery arises from the left ventricle

what is present in transposition of the great vessels to allow some exchange of blood after birth

ASD, VSD, PDA or patent foremen ovale

what happens at birth that results in rapid cyanosis in the newborn if they have transposition of the great vessels

the communicating pathways between the left and right sides of the heart close, isolating the pulmonary and systemic circulations, causing the infant to rapidly become cyanotic

what is the treatment for transposition of the great vessels

corrective surgery, mainly in older children or adults

how does transposition of the great vessels happen

malformation of the conus septum, which forms the left and right ventricular outflow tracts and of its continuation, the truncus septum, which divides the aorta from the pulmonary artery

what does CXR show in transposition of the great vessels

prominent pulmonary vessels and an enlarged right side due to chronic volume overload of the pulmonary vascular system

what does cardiac catheterization assess in transposition of the great vessels

the magnitude of the communicating shunt by measuring the oxygen step-up that occurs at the shunt site

what is Ebstein’s anomaly

a defect in the malformation of the tricuspid valve in which the right side of the AV valve ring is displaced toward the apex of the heart

what are the consequences on the right atrium and right ventricle due to Ebstein’s anomaly

right atrium is enlarged at the expense of the right ventricle, resulting in impaired ventricular filling, and the tricuspid valve is usually incompetent

what may also be present in Ebstein’s anomaly

ASD, blood shunts from right to left, systemic flow is enhanced, pulmonary flow is reduced, resulting in cyanosis

what are the common signs and symptoms of Ebstein’s anomaly

dyspnea and fatigue, but if there is no ASD present, then it may not be detected until adulthood

what is the auscultatory finding in Ebstein’s anomaly

systolic murmur of tricuspid insufficiency and a diastolic murmur of tricuspid insufficiency

what does CXR show in Ebstein’s anomaly

enlarged right atrium and enlarged left heart if the shunt represents a considerable proportion of the right atrial volume

what does echocardiography show in Ebstein’s anomaly

abnormal flow through the tricuspid valve and right-to-left shunting of blood through ASD

what does ECG show in Ebstein’s anomaly

p-pulmonale, long PR, RBBB, atrial arrhythmias

what is the prognosis of Ebstein’s anomaly

variable, fatal arrhythmias are not uncommon even in corrected defects and patients often succumb to right-heart failure