HEART DISEASE

CONGENITALHEART DISEASE (CHD)

Congenital heart diseases

• CHDs are abnormalities of the heart or great vessels that are present at birth.

• Most such disorders arise from faulty embryogenesis during gestational weeks 3 through 8, when major cardiovascular structures develop.

• Overall incidence 1% of live births

• INCREASED owing to increased diagnostic sensitivity via non invasive methods, e.g., ECHO, MRI, CT, etc.

Malformation

• Ventricular septal defect

Atrial septal defectPulmonary stenosisPatent ductus arteriosusTetralogy of FallotCoarctation of aortaAtrioventricular septal defectAortic stenosis

Transposition of great arteriesTruncus arteriosusTotal anomalous pulmonary venous connectionTricuspid atresia

Etiology

• Unknown causes in almost 90% of cases.

• Genetic factors (8%) are clearly involved, as evidenced by familial forms of congenital heart disease and by well-defined associations with certain chromosomal abnormalities (e.g., trisomies 13 (Patau, MR, AR), 15, 18 (Edward), and 21(Down, ASD) and Turner syndrome (Coarctation of aorta)

• Environmental factors (2%), such as congenital rubella infection.

GENETICS

• Trisomies 21, 13, 15, 18, XO• Mutations of genes which encode for transcription

factorsTBX5ASD,VSD• NKX2.5ASD

• Region of chromosome 22 important in heart development, 22q11.2 deletionconotruncus (craniofascial & cardiac abnormalities), 4th branchial arch (thyroid) and 3rd and 4th pharyngeal pouch derivative (thymus and parathyroid, Di George syndrome and hypocalcemia) defect

Environmental factors

• Congenital rubella (PDA)

• TERATOGENS (thalidomide, retinoid acid, alcohol

• Maternal disease: DM, HTN, smoking, alcohol

Type of CHD

• LR SHUNTS: all “D’s” in their names– NO cyanosis– Pulmonary hypertension– SIGNIFICANT pulmonary hypertension is

IRREVERSIBLE• RL SHUNTS: all “T’s” in their names

– CYANOSIS– VENOUS EMBOLI become SYSTEMIC

• OBSTRUCTIONS

Shunt

• A shunt is an abnormal communication between chambers or blood vessels.

• Left-to-right shunts increase pulmonary blood flow and are not associated with cyanosis.

• When there is a right-to-left shunt, a dusky blueness of the skin (cyanosis) results because the pulmonary circulation is bypassed and poorly oxygenated blood enters the systemic circulation.

LR• ASD

• VSD

• AVSD

• PDA

NON CYANOTIC

IRREVERSIBLE PULMONARY HYPERTENSION IS THE MOST FEARED CONSEQUENCE

Left-to-Right Shunts

• Prolonged left-to-right shunting has produced pulmonary hypertension sufficient to yield right-sided pressures that exceed those on the left and thus result in a reversal of blood flow through the shunt. Such reversal of flow and shunting of unoxygenated blood to the systemic circulation is called Eisenmenger syndrome.

• Therefore, Cyanosis is not an early feature of these defects, but it can occur late.

ASD

• Opening in the atrial septum permitting the shunting of blood between two atria

• Usually asymptomatic until adult hood

• Usually appear after 3rd decade of life

ASD-embryological insight

• The atrial septum begins as an ingrowth of the septum primum from the dorsal wall of the common atrial chamber toward the developing endocardial cushion; a gap, termed the ostium primum, initially separates the two.

• Continued growth and fusion of the septum with the endocardial cushion ultimately obliterates the ostium primum.

• However, a second opening, ostium secundum, now appears in the central area of the septum primum (allowing continued flow of oxygenated blood from the right to left atria, essential for fetal life).

• As the ostium secundum enlarges, the septum secundum makes its appearance adjacent to the septum primum. This septum secundum proliferates to form a crescent-shaped structure overlapping a space termed the foramen ovale

• The foramen ovale is closed on its left side by a flap of tissue derived from the primary septum; this flap acts as a one-way valve that allows right-to-left blood flow during intrauterine life.

• At the time of birth, there will closure of the foramen ovale.

Type of ASD

• Ostium secundum ASD (90%), which occurs when the septum secundum does not enlarge sufficiently to cover the ostium secundum.

• Ostium primum ASDs (5%); these occur if the septum primum and endocardial cushion fail to fuse and are often associated with abnormalities in other structures derived from the endocardial cushion (e.g., mitral and tricuspid valves).

• The sinus venosus ASDs (5%) are located near the entrance of the superior vena cava and have been associated with frameshift mutations in the NKX2.5 transcription factor.

Morphology

• Ostium secundum :Right atrial and ventricular dilation, right ventricular hypertrophy, and dilation of the pulmonary artery, reflecting the effects of a chronically increased volume load on the right side of the heart.

• Ostium primum : Abnormalities of the atrioventricular valves are usually present, typically in the form of a cleft in the anterior leaflet of the mitral valve or septal leaflet of the tricuspid valve.

• Sinus venosus ASDs: Anomalous drainage of the pulmonary veins into the right atrium or superior vena cava.

VSD

• Most common CHD defect at birth. The ventricular septum is normally formed by the fusion of an intraventricular muscular ridge that grows upward from the apex of the heart with a thinner membranous partition that grows downward from the endocardial cushion.

• Only 30% are isolated• Often with TETRALOGY of FALLOT• 90% involve the membranous septum• If muscular septum is involved, likely to have

multiple holes

Morphology

• The size and location of VSDs are variable, ranging from minute defects in the muscular or membranous portions of the septum to large defects involving virtually the entire septum.

• In defects associated with a significant left-to-right shunt, the right ventricle is hypertrophied and often dilated. The diameter of the pulmonary artery is increased because of the increased volume ejected by the right ventricle.

PDA• During intrauterine life, the ductus arteriosus permits blood flow

from the pulmonary artery to the aorta.

• In healthy term infants, the ductus is obliterated within 1 to 2 days after birth to form the ligamentum arteriosum.

• Ductal closure is often delayed in infants with hypoxia.

• PDAs account for about 7% of cases of congenital heart lesions.

• 90% of these are isolated defects. The remaining occur with other congenital defects, most commonly VSDs and coarctation of aorta.

Morphology• The DA arises from the left pulmonary artery and j

oins the aorta just distal to the origin of the left subclavian artery.

• In PDAs some of the oxygenated blood flowing out from the left ventricle is shunted back to the lungs. Because of the resultant volume overload, the proximal pulmonary arteries, left atrium, and ventricle can become dilated.

• With the development of pulmonary hypertension, right heart hypertrophy and dilation may develop.

Clinical Features

• PDAs: audible as harsh "machinery-like" murmurs. • Overload of pulmonary artery- Eisenmenger syndrome.• With reversal of shunt, unoxygenated blood is delivered

distal to subclavian artery (differential cyanosis)• Medical closure is by indomethacin• Preservation of ductal patency (by administering PG E)

may be critically important for infants with various forms of congenital heart disease wherein the PDA is the only means to provide systemic or pulmonary blood flow (e.g., aortic or pulmonic atresia).

• Ironically, then, the ductus can be either life threatening or lifesaving.

PDA• 90% isolated

• HARSH, machinery-like murmur

• LR, possibly RL as pulmonary hypertension approaches systemic pressure

• Closing the defect may be life saving

• Keeping it open may be life saving (Prostaglandin E). Why?

AVSD

• Associated with defective, inadequate AV valves

• Can be partial, or COMPLETE (ALL 4 CHAMBERS FREELY COMMUNICATE)

RL

• Tetralogy of Fallot

• Transposition of great arteries

• Truncus arteriosus

• Total anomalous pulmonary venous connection

• Tricuspid atresia

Clinical features

• Cyanosis present at or near the time of birth.• Clubbing of fingertips • Hypertrophic osteoarthropathy• Polycythemia (hypoxemia induced). • In addition, right-to-left shunts permit venous em

boli to bypass the lungs and directly enter the systemic circulation (paradoxical embolism)

• More chance to develop Bacterial endocarditis• septicemia and brain abscess

Tetralogy of Fallot

• The most common cause of cyanotic congenital heart disease.

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

• All of the features result from anterosuperior displacement of the infundibular septum, so that there is abnormal division into the pulmonary trunk and aortic root.

RL SHUNTS

• TETRALOGY of FALLOT most COMMON– 1) VSD, large– 2) OBSTRUCTION to RV flow– 3) Aorta OVERRIDES the VSD– 4) RVH– SURVIVAL DEPENDS on SEVERITY of

SUBPULMONIC STENOSIS– Can be a “PINK” tetralogy if pulmonic obstruction

is small– but the greater the obstruction, the greater is the

RL shunt

Morphology

• The heart is large and "boot shaped" as a result of RVH; the proximal aorta is typically larger than normal, with a diminished pulmonary trunk.

• • The left-sided cardiac chambers are normal sized. • The VSD lies in the vicinity of the membranous por

tion of the interventricular septum.

• The pulmonary outflow tract is narrowed.

• Additional abnormalities may present: PDA or ASD

Clinical Features (TOF)

• Marked subpulmonic stenosis causes cyanosis early in life.

• The lungs are protected from hemodynamic overload by the pulmonic stenosis, so that pulmonary hypertension does not develop.

• As with any cyanotic heart disease, patients develop polycythemia with hyperviscosity, and hypertrophic osteoarthropathy.

• The right-to-left shunting also increases the risk for infective endocarditis, systemic emboli, and brain abscesses.

Transposition of the Great Arteries (TGA)

• TGA is a discordant connection of the ventricles to their vascular outflow.

• The aorta arises from the right ventricle and the pulmonary artery arises from the left ventricle.

• The atrium-to-ventricle connections, however, are normal (concordant), with right atrium joining right ventricle and left atrium emptying into left ventricle.

• • The functional outcome is separation of the

systemic and pulmonary circulations.

Morphology (TGA)

• The fundamental lesion is the abnormal origin of the pulmonary trunk and aortic root.

• Incompatible with life unless VSD, ASD or PDA present

• Varying combinations of ASD, VSD, and PDA are seen in patients surviving beyond the neonatal period.

• Right ventricular hypertrophy becomes prominent because this chamber functions as the systemic ventricle.

• The left ventricle becomes somewhat atrophic, since it only has to support the low-resistance pulmonary circulation.

Clinical Features (TGA)

• Early cyanosis.

• Infusions of prostaglandin E2 and atrial septostomy are performed to create ASDs that enhance arterial oxygen saturation.

• Even with stable shunting, most uncorrected TGA patients still die within the first months of life.

TGA (TRANSPOSITION of GREAT ARTERIES)

• NEEDS a SHUNT for survival

– PDA or PFO (65%), “unstable” shunt

– VSD (35%), “stable” shunt

– RV>LV in thickness

– Fatal in first few months

– Surgical “switching”

TRUNCUS ARTERIOSIS

• Developmental failure of separation of embryogenic TA into aorta and pulmonary artery.

• Single great vessel receive blood from both ventricle.

TRUNCUS ARTERIOSIS

TRICUSPID ATRESIA

• Hypoplastic RV

• Needs a shunt, ASD, VSD, or PDA

• High mortality

Total Anomalous Pulmonary Venous Connection (TAPVC)

• PULMONARY VEINS do NOT go into LA, but into L. innominate v. or coronary sinus

• Needs a PFO or a VSD

• HYPOPLASTIC LA

Obstructive CHD

• Coarctation of aorta

• Pulmonary stenosis/atresia

• Aortic stenosis/atresia

COARCTATION of AORTA

• Aortic coarctation is common obstructive congenital heart disease.

• Males are affected twice as often as females, although females with Turner syndrome frequently have aortic coarctation.

• Two classic forms have been described : an "infantile (preductal)" form with hypoplasia of the aortic arch proximal to a PDA, and an "adult (postductal)" form in which there is a discrete ridgelike infolding of the aorta, just opposite the ligementum artreriosum.

Clinical features

• With PDA: differential cyanosis, CHF

• Adult form: May be asymptomatic, high BP in upper limb, weak pulse and lower BP in lower limb, notching of rib on X-ray

COARCTATION of AORTA

• M>F

• But XO’s frequently have it

• INFANTILE FORM (proximal to PDA) (SERIOUS)

• ADULT FORM (CLOSED DUCTUS)

• Bicuspid aortic valve 50% of the time

PULMONIC STENOSIS/ATRESIA

• If 100% atretic, hypoplastic RV with ASD

• Clinical severity ~ stenosis severity

AORTIC STENOSIS/ATRESIA

• VALVULAR– If severe, hypoplastic LVfatal

• SUB-valvular (subaortic)– Aortic wall THICK BELOW cusps

• SUPRA-valvular– Aortic wall THICK ABOVE cusps in

ascending aorta

SUMMARY

• CHD result in shunting of blood between the right and left circulation or cause outflow obstructions.

• Left-to-right shunts involve ASDs, VSDs, or a PDA. These lesions result in chronic right-sided pressure and volume overload that eventually causes pulmonary hypertension with reversal of flow and right-to-left shunts with cyanosis (Eisenmenger syndrome).

• Right-to-left shunts are caused by TOF or transposition of great vessels. These are cyanotic lesions from the outset and are associated with polycythemia, hypertrophic osteoarthropathy, and paradoxical emboli.

• Obstructive lesions include aortic coarctation; the clinical severity of the lesion depends the degree of stenosis and the patency of the ductus arteriosus.