SBM2 Cardiovascular System 9 PDF

SBM2 Cardiovascul ar System 9 JENNIFER RAYBURN, M.D. MTSU PHYSICIAN ASSISTANT STUDIES  Objectives 1. Criticize the developmental anatomy of the cardiovascular system in children 2. Illustrate the transitional circulation and closure of the fetal shunts 3. Apply the...

SBM2 Cardiovascul ar System 9 JENNIFER RAYBURN, M.D. MTSU PHYSICIAN ASSISTANT STUDIES  Objectives 1. Criticize the developmental anatomy of the cardiovascular system in children 2. Illustrate the transitional circulation and closure of the fetal shunts 3. Apply the principles of postnatal development of the cardiovascular system 4. Analyze the classification of congenital heart defects and associated conditions: A. Atrial Septal Defects B. Ventricular Septal Defects  Objectives II ▪ 4. Analyze the classification of congenital heart defects and associated conditions continued: C. Coarctation of the Aorta D. Patent Ductus Arteriosus E. Patent Foramen Ovale F. Tetralogy of Fallot G. Transposition of the Great Vessels ▪ 5. Differentiate the defects of increasing pulmonary blood flow and defects of decreasing pulmonary blood flow in congenital heart disease ▪ 6. Compare and contrast the obstructive defects to the mixing defects of congenital heart disease ▪ 7. Analyze the cardiovascular implications of Kawasaki disease, systemic hypertension, and obesity in children  Congenital Heart Disease ▪ Congenital heart conditions affect 8 of every 1000 births in the US ▪ 1.4 million adults and 1 million children in the United States are living withcongenital heart disease ▪ Formation of the CV system begins during the 3rd week of embryonic development ▪ A unique circulation then develops that allows the fetus to mature in the uterus, using the placenta as the primary organ of gas, nutrient, and waste exchange ▪ At birth, the fetal lungs inflate and become functional, making the placenta unnecessary and dramatically alters the circulation patterns that allow the neonate to adjust to life outside of the womb  Development of the Heart Tube ▪ In the middle of the third week of embryogenesis, mesodermal cells proliferate and form longitudinal cell clusters called angioblastic cords. These canalize and become paired endothelial heart tubes. ▪ Folding of the embryo gradually causes these two tubes to oppose one another and then fuse in the ventral midline forming a single endocardial tube by day 22 (the layers of the endocardial heart tube become endocardium and muscular tissue) ▪ The primitive heart begins to beat around day 22 or 23 causing blood to circulate by the beginning of the 4th week  Formation of the Heart Loop ▪ As the heart tube grows and elongates, it develops the first sign of primitive heart chambers: ▪ Truncus arteriosus ▪ Bulbus Cordis ▪ Primitive ventricle ▪ Primitive atrium ▪ Sinus venosus ▪ Heart tube bends on itself around day 23 forming a U- shaped loop. The result is placing the atrium and sinus venosus above and behind the truncus arteriosus, bulbus cordis, and ventricle ▪ The atrioventricular canal is the connection between the primitive atrium and ventricle (in time this will become the tricuspid valve and mitral valve)  Septation of the Atria Very Important to Know! ▪ Occurs between 4th and 6th weeks ▪ Primary atrial septum is known as the septum primum ▪ Ostium primum allows passage of blood between the forming atria. ▪ Ostium secundum allows passage of blood flow between atria once the ostium primum is closed ▪ Septum secundum more muscular membrane that forms after the closure of the ostium primum. Grows downward and overlaps the ostium secundum ▪ Foramen ovale: Oval shaped opening between the RA and LA that acts as a flaplike valve to allow only R to L flow  Septation of Ventricles and Ventricular Outflow Tracts ▪ At the end of the 4th week, the primitive ventricle begins to grow, leaving a median muscular ridge, the primitive interventricular septum. Dilation of the two developing ventricles also increases the height of the interventricular septum ▪ Interventricular foramen: opening that allows the RV and LV to communicate. Remains open until the end of the 7th week ▪ During the 5th week, mesenchymal cells proliferate and cause a pair of protrusions called bulbar ridges to fuse and cause a 180- degree spiraling process forming the aorticopulmonary septum. This septum divides the bulbus cordis and truncus arteriosus into pulmonary artery and aorta  Development of Cardiac Valves ▪ Semilunar valves begin to develop just before the completion of the aorticopulmonary septum ▪ After the endocardial cushions fuse to form the R and L AV canals, the surrounding tissue proliferates and develops outgrowths that eventually leads to mitral and tricuspid valve formation.  Fetal Circulation "Fetal Circulation" by Lisa McCabe, for OPENPediatrics - YouTube  Fetal Circulation Know This!!! ▪ Umbilical vein (oxygenated blood from placenta) Ductus ▪ venosus (shunt that bypasses the hepatic vasculature) *IVC ▪ (well oxygenated umbilical venous blood & low oxygen tension ▪ returning from the systemic veins of the fetus) RA through ▪ foramen ovale Blood mixes with poorly oxygenated blood ▪ returning to the LA from the fetal pulmonary veins some LV & ▪ pumped into the ascending aorta (9% coronary arteries; 62% ▪ carotid & subclavian veins/ upper body and brain; 29% into the ▪ descending aorta to the rest of the fetal body) & some into the RV ▪ (“workhorse of the heart”, provides 2/3 of the total CO) Pulmonary ▪ Artery lungs (12%) or ductus arteriosus into the descending aorta  Transitional Circulation ▪ Immediately following birth, newly functioning lungs replace the placenta as the organ for gas exchange, and three shunts that operated during gestation ultimately close. ▪ As the umbilical cord is clamped, the low- resistance placental flow is removed from the circulation resulting in an increase in systemic vascular resistance and pulmonary vascular resistance falls: ▪ 1. The mechanical inflation of the lungs after birth stretches the lung tissues, causing pulmonary artery expansion and wall thinning ▪ 2. Vasodilation of the pulmonary vasculature occurs in response to the rise in blood oxygen tension accompanying aeration in the lungs ▪ This continues from birth to several weeks until adult levels of pulmonary resistance are achieved.  Transitional Circulation https://www.youtube.com/watch?v=HVBu9HhTkD4 (great video about fetal & transitional circulation) ▪ When pulmonary vascular resistance falls and more blood travels to the lungs, venous return from the pulmonary veins to the LA increases causing LA volume and pressure to rise. The flap of the foramen ovale becomes positioned more midline against the septum secundum eliminating the previous flow between the atria. ▪ Failure of the valve to fuse to the septum secundum results in patent foramen ovale (PFO) ▪ With oxygenation now occurring in the newborn lungs, the ductus arteriosus becomes superfluous and closes. After birth, PGE1 levels decline as the oxygen tension rises and the ductus arteriosus constricts and closes. However, this is dependent on the gestational age of the fetus. Failure of constriction of the ductus arteriosus is called patent ductus arteriosus (PDA) ▪ Ductus venosus closes within 3-7 days of birth  Congenital Heart Defects ▪ Categorized as Cyanotic or Acyanotic ▪ Cyanosis refers to blue-purple discoloration of the skin and mucus membranes caused by elevated blood concentration of deoxygenated hemoglobin ▪ Cyanosis results from defects that allow poorly oxygenated blood from the R side of the heart to be shunted to the Left side, bypassing the lungs (Right to Left Shunts) ▪ Acyanotic lesions include intracardiac or vascular stenoses, valvular regurgitation, and defects that result in left to right shunting of blood. (Left to Right Shunts) ▪ Patients with congenital heart disease are susceptible to endocarditis (covered later in ClinMed)  Workup for Congenital Heart Defects ▪ Thorough medical history: feeding difficulties, color changes with feeding or crying, diaphoresis with feeds, changes in energy levels. Ask older children if they have any chest pain, palpitations, shortness of breath (with exertion), presyncope, or overt syncope. Birth history and complications, medications or drug exposures, maternal autoimmune disease, FH of congenital heart disease, cardiomyopathy, cardiac dysrhythmias, or sudden death ▪ Symptoms: Feeding difficulties and failure to thrive in newborn or sudden onset of chest pain, palpitations, and presyncope or overt syncope in older children ▪ PE: vitals, poor weight gain, BP discrepancies between upper and lower extremities, tachypnea, tachycardia and/or bradycardia, orthostatic VS, pallor or cyanosis, lung fields, cardiac exam for murmurs, PMI, heaves or lifts, abdomen for bruits, palpate peripheral pulses ▪ All newborns screened for this condition prior to discharge (pulse ox 10 mmHg or higher in R arm compared to R leg). ▪ Diminished or delayed lower extremity pulses (ex. Femoral or dorsalis pedis pulses) ▪ Systolic murmur: harsh systolic murmur along the left sternal border radiating to the back, left infrascapular region, or chest (best heard on the back between the scapulae near the aortic isthmus where coarctation usually occurs)  Coarctation of the Aorta ▪ Diagnosis: ▪ Echocardiography is the confirmatory test – shows narrowing of the aorta ▪ CXR: Shows posterior rib notching (due to increased intercostal artery collateral flow) and/or Figure 3 sign (narrowed indented aorta looks like the notch of 3) ▪ ECG: LVH ▪ Management: ▪ Repair: Corrective surgery or transcatheter –based intervention (balloon angioplasty with or without stent placement); preferable early childhood ▪ Prostaglandin E1 (Alprostadil): preoperatively in neonates to stabilize the condition – maintains a PDA, reduces symptoms & improves lower extremity blood flow by relaxing the tissue of the coarctation segment  Congenital Heart Disease/Cyanotic Tetralogy of Fallot Congenital Heart Disease: Tetralogy of Fallot, Animation - YouTube ▪ Single developmental defect: an abnormal anterior and cephalad displacement of the infundibular (outflow tract) portion of the interventricular septum ▪ 5 in 10,000 live births (most common cyanotic lesion) ▪ Four anomalies arise (KNOW THESE!!): ▪ 1. A large unrestrictive VSD caused by anterior malalignment of the interventricular septum ▪ 2. Subvalvular pulmonic stenosis because of obstruction from the displaced infundibular septum ▪ 3. Overriding aorta that receives blood from both ventricles ▪ 4. Right ventricular hypertrophy (obstruction) owing to the high-pressure load placed on the RV by pulmonic stenosis  Tetralogy of Fallot ▪ Symptoms: ▪ Infancy: Cyanosis is the most common presentation (blue baby syndrome), poor feeding, hemoptysis ▪ Older Children: exertional dyspnea, cyanosis that worsens with age. Tet Spells (paroxysms of cyanosis relieved with squatting which decreases right to left shunting, improving oxygenation ▪ PE: mild cyanosis of lips, mucous membranes,& digital clubbing. Chronic hypoxemia, RV heave, Harsh systolic ejection murmur at L mid to upper sternal border. Loud single S2 (pulmonic component hardly audible) ▪ Diagnosis: ECHO test of choice to establish the diagnosis (some diagnosed before birth) ▪ CXR: Boot shaped heart (upturned apex and concave main pulmonary artery) Blue Baby Syndrome ▪ ECG: RVH, RAE, RAD Tetralogy of Fallot Boot Shaped Heart  Tetralogy of Fallot Management ▪ 1. Neonates with severe RVOT obstruction may require IV prostaglandin therapy to maintain the ductus arteriosus patency, ductal stenting, or palliative shunt placement to maintain adequate pulmonary blood flow prior to surgical repair ▪ 2. Surgical repair is the definitive management. Usually performed in the first 12 months of life (ideally 3-6 mos). Includes patch closure of the VSD and enlargement of the RVOT to relieve pulmonary outflow obstruction. ▪ 3. Hypercyanotic or Tet Spells: knee-chest positioning in infants or squatting in older children to increase preload and systemic vascular resistance, supplemental oxygen, IV morphine, IV fluid bolus. If these measures fail, then IV Beta Blockers or IV phenylephrine is the next step. Palliative surgical procedure if medical therapy fails.  Congenital Heart Disease/Cyanotic Transposition of the Great Vessels/Arteries ▪ Each great artery inappropriately arises from the opposite ventricle ▪ Aorta originates from the RV and the pulmonary artery arises from the LV ▪ 40 in 100,000 live births ▪ Most common cause of cyanosis in the neonatal period ▪ Cause remains unknown (possibly abnormal spiral of the aorticopulmonary septum) ▪ Places two circuits in parallel rather than a series. Forces desaturated blood from the systemic venous system to pass through the RV and then return to the systemic circulation through the aorta without undergoing normal oxygenation in the lungs. Oxygenated pulmonary venous return passes through the LV and then back through the pulmonary artery to the lungs without imparting oxygen to the systemic circulation. Results in an extremely hypoxic, cyanotic neonate ▪ Lethal without intervention!! (medical emergency) ▪ Patient depends on shunts between the right and left circulations (PDA, ASD, VSD)  Transposition of the Great Arteries ▪ Clinical manifestations: ▪ Severe cyanosis and tachypnea within the first 30 days of life not affected by exertion or oxygen use ▪ Tachypnea : usually have a RR of >60 breaths per minute but often appear comfortable without retractions, grunting, or flaring ▪ Diaphoresis and poor feeding ▪ Physical Exam: ▪ Central cyanosis. Loud and single second heart sound (S2), murmurs usually not present  Transposition of the Great Arteries ▪ Diagnosis: ▪ Echocardiogram is the primary means of diagnosis ▪ CXR: “egg on a string” appearance – cardiomegaly and narrowed mediastinum ▪ Cardiac Cath: rarely used except in therapeutic treatment ▪ Management: ▪ Ensure adequate oxygenation such as with Prostaglandin E1 administration (maintain PDA) & possible balloon septostomy & corrective surgery (Arterial switch operation) once the patient is hemodynamically stable. ▪ Without treatment, 90% die within 1 year. 5-year survival rate with surgery >80%  Hypoplastic Left Heart Syndrome (HLHS)/Cyanotic ▪ Failure of the development of the mitral valve, aortic valve, or the aortic arch leading to a small ventricle unable to supply the normal systemic circulation requirements. ▪ If left untreated, HLHS is universally fatal (responsible for 25 to 40 percent of all neonatal cardiac deaths). ▪ HLHS is the most common form of functional single-ventricle heart disease, with a birth prevalence of approximately 2 to 3 cases per 10,000 live births in the United States; Male>Female ▪ Pathogenesis not well known ▪ With hypoplastic or atretic mitral and aortic valves, and a diminutive left ventricle (LV), the right ventricle (RV) must support both the pulmonary and systemic circulations. Survival is dependent on a patent ductus arteriosus (PDA) to ensure adequate systemic perfusion (from the RV to the aorta) and a nonrestrictive atrial septal defect (ASD) to ensure adequate mixing of oxygenated and deoxygenated blood. The relative distribution of RV output to the systemic and pulmonary circulations is dependent on the relative resistances of these parallel circuits.  Hypoplastic Left Heart Syndrome (HLHS)/Cyanotic ▪ Diagnosis: prenatal ultrasound & fetal echo, ecg, CXR ▪ PE: cyanosis (when PDA starts to constrict), tachypnea, no murmur, cool extremities, hepatomegaly and dysmorphic features ▪ Treatment: Continuous IV prostaglandin to maintain PDA and staged palliative surgical repair over cardiac transplant  Congenital Heart Disease/Acyanotic Congenital Aortic Stenosis (AS) ▪ Abnormal structural development of the valve leaflets ▪ 5 in 10,000 live births; males>females ▪ 20% have additional abnormality called coarctation of the aorta ▪ Usually have bicuspid valve (usually become progressively stenosed over the years as the leaflets fibrose and calcify & are a common cause of AS in adults) ▪ Valve is significantly narrowed leading to LV systolic pressure increase and leads to LV hypertrophy ▪ Symptoms: tachycardia, tachypnea, failure to thrive, poor feeding ▪ PE: crescendo-decrescendo systolic murmur at the base of the heart with radiation toward the neck ▪ Diagnosis: EKG, CXR, ECHO ▪ Treatment: Transcatheter balloon valvuloplasty if needed  Congenital Heart Disease/Acyanotic Pulmonic Valve Stenosis ▪ Obstruction to RV outflow may occur at the level of the pulmonic valve, within the body of the RV, or in the pulmonary artery. ▪ Valvular pulmonic stenosis is the most frequent form ▪ Almost always congenital & a disease of the young!! ▪ RV chamber hypertrophy; if severe can lead to R sided heart failure ▪ Symptoms: asymptomatic, murmur on exam, R sided heart failure symptoms ▪ PE: loud, late peaking crescendo-decrescendo systolic ejection murmur at left sternal border. Increases with inspiration ▪ Treatment: moderate or severe obstruction ill receive balloon valvuloplasty  Kawasaki Disease (Mucocutaneus Lymph Node Syndrome) ▪ Self-limited necrotizing vasculitis of medium & small sized arteries that affects many organs including the blood vessels and heart (coronary arteries) ▪ Not contagious ▪ Risk Factors: Disease of young children (3 mos-5 yrs); 80% 1.5cm (unilateral anterior cervical adenpathy ▪ *Often begins with a high and persistent fever that is nonresponsive to normal doses of ibuprofen or acetaminophen. Fever may rise for up to 2 weeks and is accompanied by irritability  Kawasaki Disease ▪ Labs: nonspecific, elevated WBC, platelets, transaminases, and acute phase reactants ▪ Complications: Coronary vessel arteritis, coronary artery aneurysm, MI, pericarditis, myocarditis. ▪ ECHO and ECG recommended to look for these complications ▪ Management: ▪ IV Immunoglobulin plus Aspirin. IVIG reduces coronary complications. One single dose of IVIG in the first ten days of the illness preferred. Aspirin is an anti- inflammatory and antiplatelet drug  Childhood Hypertension ▪ Can lead to early development of cardiovascular disease in adult life. ▪ Prevalence is 4.2% of pediatric population ▪ Modifiable risk factors: Dietary sodium intake, OSA, obesity, breastfeeding (lower BPs in childhood), white coat hypertension, tobacco exposure (active and passive exposure), childhood adversity, prenatal and neonatal factors (low birth weight, preeclampsia) ▪ Non-modifiable risk factors: Sex (boys>girls), race (non-Hispanic African Americans), FH (70-80% have FH)  Childhood Hypertension ▪ Primary Hypertension: no underlying cause identified ▪ Secondary hypertension: Renal disease (glomerulonephritis, CRF, scarring), endocrine (catecholamine excess, Corticosteroid excess) and renovascular disease (fibromuscular dysplasia); genetic disorders (PCKD, LIDDLE syndrome, CAH, etc); cardiac disease, drugs and toxins ▪ Initial Evaluation: Primary or secondary, identify risk factors, end-organ damage; CMP, UA, lipids, renal US ▪ Treatment: similar as for adults  Childhood Obesity and Cardiovascular Health ▪ Two cardiovascular risk factors of hypertension and dyslipidemia are components of metabolic syndrome that can predict risk of CV disease in adulthood ▪ The risk of hypertension is increased in children and adolescents that are overweight or obese and increases with the severity of obesity (4% with moderate obesity and 9% with severe obesity) ▪ Dyslipidemia occurs among children who are overweight or obese, particularly those with central fat distribution. Elevated serum LDL and TG and decreased HDL ▪ Obesity is also linked to alterations in cardiac structure and function similar to those seen in middle aged adults (increased LV mass, increased LV and LA diameter, greater epicardial fat; and systolic and diastolic dysfunction) ▪ Endothelial dysfunction, intima-media thickness, premature development of aortic and coronary arterial fatty streaks and fibrous plaques and increased arterial stiffness (markers for sub-clinical atherosclerosis) Questions????