IUHS Student-2-Student USMLE Step 1 Recall

                                                Cardiovascular

                                     Embryological Heart Defects

Atrial Septal Defects (ASDs)

an ASD is an abnormal opening in the atrial septum that allows communication of blood between the left and right atria (not to be confused with a patent foramen ovale, present in up to one third of normal individuals, which generally does not permit flow unless right atrial pressures are elevated)...

ASD is the most common congenital cardiac anomaly that is usually asymptomatic until adulthood...

Ostium Septum Secundum accounts for approximately 90% of all ASDs, results from a defect in the fossa ovalis near the mid-septum...

Septum Primum - accounts for approxiamtely 5% of all ASDs, occurs adjacent to the AV valves and are usually associated with a cleft anterior mitral leaflet (lower part of septum)...

Sinus Venosus - accounts for approximately 5% of all ASDs, located near the entrance of the superior vena cava (near coronary sinus)...

Ventricular Septal Defects (VSDs)

incomplete closure of the ventricular septum, allowing free communication between right and left ventricles, is the most common congenital cardiac anomaly...

VSD is frequently associated with other structural defects, such as tetralolgy...

about 90% involve the region of the membranous septum (membranous VSD)...

the remainder lie below the pulmonary valve (infundibular VSD) or within the muscular septum...

swiss-cheese septum are multiple VSDs...

50% of small muscular VSDs close spontaneously...

right ventricular hypertrophy and pulmonary hypertension are present from birth...over time, irreversible pulmonary vascular disease develops in virtually all patients with large unoperated VSDs, leading to shunt reversal, cyanosis, and death...

Patent Ductus Arteriosus (PDA)

PDA is a persistence after birth of the normal communication between the pulmonary arterial system and the aorta of the fetus...

about 90% of PDAs occur as an isolated anomaly...

the remainder are most often associated with VSD, coarctation, or pulmonary or aortic stenosis...

PDAs most often do not produce functional difficulties at birth...its existance can generally be detectd by a continuous harsh murmur, described as machinery-like...b/c the shunt is left-to-right there is no cyanosis...

obstructive pulmonary vascular disease eventually ensues, however, with ultimate reversal of flow and its associated consequences...

PDA should be closed as early in life as possible...preservation of ductal patency (by administration of prostaglandin E) may assure great importance in the survival of infants with various forms of congenital heart disease with obstructed pulmonary or systemic blood flow, such as aortic valve atresia...

close PDA with Indomethacin...

machine-like diastolic and systolic murmur heard over the left sternoclavicular joint...there will be blood flow from the arch of the aorta into the pulmonary trunk through the defect...

Tetralogy of Fallot

the four features of the Fallot tetralogy are (1) VSD, (2) obstruction to the right ventricular outflow tract (subpulmonary stenosis), (3) an aorta that overrides the VSD, and (4) right ventricular hypertrophy...

all of the features result embryologically from anterosuperior displacement of the infundibular (aorticopulmonary) septum...

ASD and patent ductus arteriousus help the oxygen content in tetraology of fallot...

the heart is often enlarged and may be boot-shaped owing to marked right ventricular hypertrophy, particulary of the apical region...

VSD is usually large and approximates the diameter of the aortic orifice...

the aortic valve forms its superior border, thereby overriding the defect and both ventricular outflow is most often due to narrowing of the infundibulum (subpulmonary stenosis), but is often accompanied by pulmonary valvular stenosis...

if the subpulmonary stenosis is mild, the abnormality resembles an isolated VSD, and the shunt may be left-to-right, without cyanosis (so called pink tetralogy)...as the obstruction increases in severity, there is commensurately greater resistance to right ventricular outflow...as it approaches the level of systemic vascular resistance, right-to-left shunting predominates and, along with it, cyanosis (classic tetralogy)...

Transpostion of Great Arteries

transposition implies ventriculoarterial discordance, such that the aorta arises form the right ventricle, and the pulmonary artery emanates from the left ventricle...

the AV connections are normal (concordant), with right atrium joining right ventricle and left atrium emptying into the left ventricle...

embryologic defect in complete transposition is abnormal formation of the truncal and aortopulmonary septa...

the aorta arises from the right ventricle and lies anterior and to the right of the pulmonary artery; in contrast, in the normal heart, the aorta is posterior and to the right...

the result is separation of the systemic and pulmonary circulation, a condition incompatible with postnatal life, unless a shunt exists for adequate mixing of blood...ASD, VSD

there is a specific correlation between gestational diabetes and transposition of the great arteries...

Truncus Arteriosus

the persistant truncus arteriosus anomaly arises from a deveopmental failure of separation of the embryologic truncus arteriosus into the aorta and pulmonary artery...

the result is a single great artery that receives blood from  both ventricles, accompanied by an underlying VSD, and that gives rise to the systemic pulmonary, and coronary circulations...

b/c blood from the right and left ventricles mixes, there is early systemic cyanosis as well as increased pulmonary blood flow, with the danger of inoperable pulmonary hypertension...

Coarctation of Aorta

coarctation (narrowing, constriction) of aorta ranks high in frequency among the common structural anomalies...

males are affected twice as often as females, although females with Turner syndrome frequently have a coarctation...

Infantile Form - with tubular hypoplasia of the aortic arch proximal to a PDA that is often symptomatic in early childhood...

Adult Form - there is a discrete ridgelike infolding of the aorta, just opposite the closed ductus arteriosus (ligamentum arteriosum)

it is accompanied by a bicuspid aortic valve in 50% of cases and may also be associated with congenital aortic stenosis, ASD, VSD, mitral regurgitatioin, and Berry aneurysms of the circle of Willis...

coarctation with a PDA usually leads to manifestations early in life, and indeed it may cause signs and symptoms immediately after birth...

many infants with this anomaly do not survive the neonatal period without surgical intervention...

in such cases, the delivery of unsaturated blood through the ductus arteriousus produces cyanosis localized to the lower half of the body...

Coarctation without PDA most children are asymptomatic, and the disease may go unrecognized until well into adult life...

typically, there is hypertension in the upper extremities, but there are weak pulses and a lower blood pressure in the lower extremities, associated with manifestations of arterial insufficiency (claudication and coldness)...

in adults, there is the development of colateral circulation between the precoarctation arterial branches and the postcoarctation arteries through enlarged intercostal and internal mammary arteries and the radiographically visible erosions (notching) of the undersurfaces of the ribs...

murmures are often present througout systole, and sometimes a thrill may be present and there is cardiomegaly owing to left ventricular hypertrophy...