Dr. S. Ismat BukhariMD Resident

Dr. Ziauddin hospital

Introduction

• Coarctation of the aorta accounts for 5-8% of all congenital heart defects.

• Coarctation of the aorta may occur as an isolated defect or in association with various other lesions, most commonly bicuspid aortic valve and ventricular septal defect (VSD).

Epidemiology

The prevalence of coarctation of the aorta appears to be lower (< 2%) in Asian countries than in European and North American countries.

• The prevalence of coarctation of the aorta in genetic abnormalities such as Turner syndrome (45,X), is as high as 15-20%.

• Familial patterns of inheritance of coarctation have been reported, as well as for other left heart obstructive lesions.

Mortality/Morbidity

Past autopsy studies suggest that the mortality rate in patients in whom coarctation of the aorta is not surgically repaired is 90% by age 50 years, with a mean age of 35 years.

In the current era, mortality is often determined by patient age, patient size, and associated major cardiovascular anomalies.

Associated problems that may contribute to death or morbidity include hypertension, intracranial hemorrhage, aortic rupture or dissection, endocarditis, and CHF.

Sex

• The male-to-female ratio is 2:1, although this ratio is not valid in abdominal coarctation of the aorta, in which this rare lesion predominantly affects females.

• The ratio of abdominal-to-thoracic coarctation is approximately 1:1000.

• The male preponderance observed in older patients is not seen in infants with coarctation of the aorta.

Age

• Generally, patients with coarctation of the aorta present early in life with CHF or later in life with hypertension.

• Studies continue to document that coarctation of the aorta is often missed in the first year of life, and the median age of referral to a pediatric cardiologist in one study was 5 years.

Histological defect

• Coarctation of the aorta results from marked ridge like thickening of the media of the aortic wall opposite the insertion of the patent ductus arteriosus or ligamentum arteriosum.

• This ridge or shelf becomes an obstruction when the patent ductus involutes and when ductal tissue in the wall of the aorta involutes.

• The diagnosis of coarctation of the aorta may be missed unless an index of suspicion is maintained, and diagnosis is often delayed until the patient develops congestive heart failure, which is common in infants, or hypertension, which is common in older children.

• In the past, coarctation of the aorta has been described as:– preductal (or infantile) type – postductal (or adult) type

• The classic coarctation of the aorta is located in the thoracic aorta distal to the origin of the left subclavian artery at about the level of the ductal structure.

• However, rarely, a coarcted segment is present in the lower thoracic or abdominal aorta.

• Dilatation of the descending aorta immediately distal to the coarctation segment (poststenotic dilatation) is usually present.

• Varying degrees of hypoplasia of the isthmus of the aorta (the portion of the aorta between the origin of the left subclavian artery and ductus arteriosus) are present in most patients with thoracic coarctation; this hypoplasia may be significant in symptomatic coarctation of the neonate and infant; in children and adults, the isthmus may have only mild narrowing.

• The transverse aortic arch (the arch between the origin of the right innominate artery and the left subclavian artery) is also hypoplastic in symptomatic neonates and infants.

• Collateral vessels that connect arteries from the upper part of the body to the vessels below the level of coarctation may be seen; these may be present as early as a few weeks to a few months of life.

• The most commonly associated clinically significant defects include patent ductus arteriosus, VSD, and aortic stenosis.

• Bicuspid aortic valve may be seen in nearly two thirds of infants with coarctation of the aorta, whereas only 30% of those who present in childhood have such an anomaly.

• Mitral valve anomalies, although less common than those of the aortic valve, are also associated with coarctation of the aorta.

• Sometimes, coarctation of the aorta is a complicating feature of a more complex cyanotic heart defect, such as:– Ttransposition of the great arteries– Taussig-Bing anomaly– Double-inlet left ventricle– Tricuspid atresia with transposition of the great arteries – Hypoplastic left heart syndrome.

• Some patients with coarctation of the aorta may have cerebral aneurysms, predisposing them to cerebrovascular accidents with severe hypertension later in life.

• Coarctation of the aorta is the most common cardiac defect associated with Turner syndrome.

Pathophysiology

• Coarctation of the aorta imposes significant afterload on the left ventricle (LV), which results in compensatory ventricular hypertrophy.

• As the ductus (aortic end) constricts, the left ventricular afterload rapidly increases, with a resultant increase in left ventricular pressures (systolic and diastolic).

• This causes elevation of the left atrial pressure, which may open the foramen ovale, causing left-to-right shunt and dilatation of the right atrium and right ventricle.

Development of collateral circulation

• LV afterload may also gradually increase, allowing children with less severe coarctation to develop arterial collateral vessels that partially bypass the aortic obstruction.

• These children may be asymptomatic until hypertension is detected or another complication develops.

Hypertension

• The mechanism for development of hypertension is not clearly understood; – mechanical obstruction – renin-angiotensin mediated humoral mechanisms

• Activation of the renin-angiotensin system results in vasoconstriction, cell hypertrophy, and the release of aldosterone.

• Unlike most cases of CHF, coarctation of the aorta is more complex because pre-coarctation and post-coarctation hemodynamics are quite different.

Clinical presentation

• The presence of associated defects and aortic arch anomalies, the extent of patency of the ductus arteriosus, the rapidity of the process of closure of the ductus arteriosus, and the level of pulmonary vascular resistance determine the timing of clinical presentation and the severity of symptoms.

Early presentation

• Young patients may present in the first few weeks of life with;– Poor feeding– Tachypnea– Lethargy– Progression to overt CHF– Shock.

• These patients may have appeared well prior to hospital discharge, and deterioration coincides with closure of the patent ductus arteriosus.

Physical findings in early presentation

• Tachypnea• Tachycardia• increased work of breathing • Shock• Blood pressue discrepancies between the upper and lower

extremities • reduced or absent lower extremity pulses to palpation

• However, when the infant is in severe heart failure, all pulses are diminished. • Upon treatment for heart failure, prominent brachial pulses with weak or

nonpalpable femoral arterial pulses may be discerned.

• In patients with an aberrant origin of the right subclavian artery from the aorta distal to the obstruction, such discrepancies in BP may not be present, although lower extremity pulses are diminished versus the carotid pulses.

Murmur

• The murmur associated with coarctation of the aorta may be nonspecific initially and is usually a systolic murmur in the left infraclavicular area and under the left scapula.

• Additional murmurs that result from the presence of associated abnormalities, such as VSD or aortic valve stenosis, may also be detected.

• An ejection click may signify the presence of a bicuspid aortic valve, whereas a gallop rhythm may indicate ventricular dysfunction.

Late presentation

• Patients often present after the neonatal period with hypertension or a murmur.

• These patients often have not developed overt CHF because of the presence of arterial collateral vessels.

• Diagnosis is often made after hypertension is noted as an incidental finding during evaluation of other problems.

• Other presenting symptoms may include; – Headaches– chest pain– Fatigue– life-threatening intracranial hemorrhage.

• True claudication is rare, although an occasional child may experience pain or weakness in the legs.

• Palpation of femoral pulses and measurement of blood pressure during routine examination is necessary to avoid a delay in the diagnosis.

Physical findings in Late presentation

• Hypertension• Murmur

• Occasionally, the left arm pressure is lower than the right arm pressure if the origin of the left subclavian artery is involved in the coarctation.

• Similarly, anomalous origin of the right subclavian artery (below the level of coarctation) may produce decreased or absent right brachial pulse.

• Careful simultaneous palpation of upper and lower extremity pulses may help confirm suspected coarctation.

• Blood pressure in both arms and one leg must be determined; a pressure difference of more than 20 mm Hg in favor of the arms may be considered evidence of coarctation of the aorta.

• ejection click is found on auscultation

• A thrill may be present in the suprasternal notch or on the precordium in the presence of significant aortic valve stenosis.

• In the rare case of abdominal coarctation, an abdominal bruit may be noted.

Laboratory investigations

• Laboratory studies in neonatal patients who present in shock include the following:– Septic workup includes blood, urine– cerebral spinal fluid (CSF) cultures.– Electrolyte levels, BUN, creatinine, and glucose concentration.

• Measure arterial blood gases and serum lactate levels.

• Laboratory studies in older patients who present with hypertension include urinalysis, electrolyte levels, BUN, creatinine, and glucose concentrations.

Imaging studies

• Chest radiography in patients with early onset of coarctation of the aorta may reveal cardiomegaly, pulmonary edema, and other signs of congestive heart failure.

• Radiography in patients with late onset of coarctation of the aorta may reveal cardiomegaly.

• An inverted "3" sign of the barium-filled esophagus or a "3" sign on a highly penetrated chest radiograph (frontal view) may be visualized. Rib notching secondary to collateral vessels may also be seen.

Echocardiography: • Echocardiography delineates intracardiac

anatomy and allows assessment of associated significant intracardiac anomalies.

MRI and CT:• Useful in older or postoperative patients to

assess residual arch obstruction, arch hypoplasia, or formation of aneurysms.

Electrocardiography :• in the neonate or infant with early onset of coarctation of the

aorta may reveal right ventricular rather than left ventricular (LV) hypertrophy.

• ECG findings in patients with late onset of coarctation of the aorta may be normal or may reveal LV hypertrophy and may show signs of LV ischemia or strain.

• Sometimes, LV hypertrophy may manifest as increased S waves in leads V5 and V6, the so-called posterobasal LV hypertrophy.

• In the neonatal period , the ECG may reflect RVH rather than LVH. This is because the right ventricle in-utero is the dominant ventricle, and through the PDA pumps blood to the descending aorta. Therefore, coarctation of the aorta may cause an increase in the afterload of the RV as it will cause narrowing of the aortic arch-descending aorta junction.

• This ECG, shows rsR' pattern in the right chest leads indicating RVH. In addition there are deep S waves in the left chest leads.

• Cardiac catheterization is a prerequisite for intervention in the form of either balloon angioplasty or stent implantation in native or recurrent coarctation.

• Selective aortic root or aortic arch angiography is necessary to clearly demonstrate the aortic narrowing.

• Aortography is useful in demonstrating the type of aortic coarctation (diffuse, long segment, aortic kinking [pseudocoarctation]); extent of collateral circulation; the size of ductus arteriosus, if patent; and the presence and degree of hypoplasia of transverse aortic arch and aortic isthmus, especially in neonates.

• LV angiography is particularly useful in neonates and infants who demonstrate ventricular septal defects (VSDs) and in evaluating LV function.

Treatment of early presentation

• Treatment in patients with congestive heart failure (CHF) includes the use of diuretics and inotropic drugs.

• Prostaglandin E1 (0.05-0.15 mcg/kg/min) is infused intravenously to open the ductus arteriosus.

• Ventilatory assistance is provided to patients with markedly increased work of breathing.

Treatment of late presentation

• Treatment of hypertensionPreoperative hypertension can be effectively treated using beta-blockers.

• The goal should be to reduce upper extremity hypertension, but remember that vigorous attempts to achieve normal upper extremity blood pressure (BP) may result in inadequate lower-body perfusion.

• Beta-blocker therapy prior to surgery may reduce the severity of postoperative hypertension, although most patients with preoperative hypertension require at least transient postoperative therapy.

• Evaluate associated abnormalities, such as aortic stenosis, subaortic stenosis, or mitral valve disease.

• Evaluate adequacy of collateral blood vessels to assess the safety of surgical intervention.

Surgical treatment

• At initial presentation, if cardiac failure or hypertension is the presenting problem, it should be addressed to stabilize the patient.

• Subsequently, the aortic obstruction should be relieved.

Pharmacotherapy

• The goals of pharmacotherapy are to reduce morbidity and to prevent complications of coarctation of the aorta (CoA).

• Prostaglandin • Inotropic agents• Cardiac glycosides• Diuretics • Beta blockers• Angiotensin converting enzyme inhibitor• Vasodilators

Prostaglandins

• Identical to the naturally occurring prostaglandin E1 (PGE1) and possesses various pharmacologic effects, including vasodilation and inhibition of platelet aggregation.

• Used as palliative therapy to temporarily maintain patency of the ductus arteriosus before surgery.

• Beneficial in infants with congenital defects that restrict pulmonary or systemic blood flow and in patients who depend on a PDA for adequate oxygenation and lower-body perfusion.

• Produces vasodilation and increases cardiac output. Each 1-mL ampule contains 500 mcg/ml

Inotropic agents• Used to stimulate alpha-receptor and beta-receptors in the heart

and vascular bed.

• Positive inotropic agents increase the force of contraction of the myocardium and are used to treat acute and chronic CHF.

• Some may also increase or decrease the heart rate (ie, positive or negative chronotropic agents), provide vasodilatation, or improve myocardial relaxation.

• These additional properties influence the choice of drug for specific circumstances.

Cardiac glycosides (digoxin)

• These medications improve ventricular systolic function by increasing the calcium supply available for myocyte contraction.

Diuretics

• Promote excretion of water and electrolytes by the kidneys.

• They are used to treat heart failure or hepatic, renal, or pulmonary disease when sodium and water retention have resulted in edema or ascites.

• Generally includes a loop diuretic that inhibits sodium chloride reabsorption in the ascending loop of Henle.

Beta blockers

• These agents inhibit chronotropic, inotropic, and vasodilatory responses to beta-adrenergic stimulation.

• Preoperative hypertension can be treated effectively with beta-blockers.

ACE inhibitors

• These agents reduce afterload and decrease myocardial remodeling that worsens chronic heart failure.

• May be added if hypertension persists despite beta-blocker therapy and no residual arch obstruction is noted.

Vasodilators

• Postoperative hypertension can be treated short-term with vasodilators, which reduce systemic vascular resistance, allowing more forward flow, thus improving cardiac output.

Follow up

• Focus postoperative recovery of patients • control of blood pressure (BP)• slow advancement of diet• manipulation of antihypertensive medications• progressive ambulation• pulmonary therapy to improve left lung atelectasis (common

after left thoracotomy)

Outpatient care• Focus early outpatient follow-up care on wound healing, resolution of lung atelectasis, and

adjustment of antihypertensive medications.

• Assess postoperative BP response to exercise prior to discontinuation of antihypertensive therapy.

• Many patients may be weaned from antihypertensive therapy over months or years following repair of coarctation.

• Other patients may require some form of ongoing antihypertensive therapy.

• Search for late complications of coarctation repair, including recurrent coarctation and aneurysm formation.

• Patients should receive antibiotic prophylaxis before undergoing any bacteremia-producing surgery or procedures, especially in view of reported incidence of bacterial endocarditis during follow-up.

Prevention of complications

• Fetal echocardiography is indicated during pregnancy in every woman who has previously borne a child with congenital heart disease (CHD), especially left heart obstructive lesions.

• Postnatally, early detection of coarctation of the aorta is important to avoid prolonged hypertension or other complications.

• Careful measurement of BPs and evaluation of lower extremity pulses in newborns and at subsequent healthy child examinations is imperative.

Complications • Coarctation of the aorta is a lifelong disease with complications that may

not be evident until many years following an initial and apparently successful repair.

• Recurrent coarctationRecurrence of coarctation is associated with patient size, age at surgery, and associated transverse arch or isthmic hypoplasia.

• Ductal tissue in the wall of the aorta may involute and contribute to recurrence, as might scarring at the repair site.

• Some surgeons believe that the use of interrupted sutures in the anterior portion of the anastomotic suture line improves aortic growth and reduces the risk of recurrence.

• Sometimes, the surgical repair site is unobstructed, yet obstruction develops at the transverse arch or isthmus because of the failure of these areas to grow proportionally to the rest of the arch.

Hypertension

• Related to alterations in the renin-angiotensin system and baroreceptors.

• As with other forms of uncontrolled hypertension, patients may be at risk for premature atherosclerosis, ventricular dysfunction, and rupture of cerebral aneurysms.

Cerebral aneurysms

• Berry aneurysms of the circle of Willis or other vessels are believed to occur in as many as 10% of patients with coarctation of the aorta and may be multiple.

• Aneurysm size tends to increase with age, as does the risk of rupture.

• Uncontrolled hypertension promotes the growth of the aneurysms and increases risk of rupture.

• Most patients are asymptomatic until rupture occurs, although some aneurysms may leak prior to rupture, resulting in warning symptoms of headache, photophobia, weakness, or other symptoms.

• Rupture of a cerebral aneurysm is associated with high mortality rates and should prompt repair of both the aneurysm and coarctation.

Paralysis

• Paraplegia can occur from spinal cord ischemia, resulting from a compromised blood supply to the anterior spinal artery.

• Risk of paralysis is increased with reduced arterial collateral vessels, prolonged aortic cross-clamping time, and intraoperative sacrifice of intercostal arteries, as well as other factors.

• Cardiomyopathy is usually present in infants with critical coarctation, especially if additional levels of left heart obstruction, such as aortic stenosis or subaortic stenosis, are present.

• Some patients may have changes of endocardial fibroelastosis that result in chronic dilated cardiomyopathy, requiring medical management or, in rare cases, cardiac transplantation.

• Hypertrophic cardiomyopathic changes also may occur, predisposing the patient to subendocardial ischemia, arrhythmias, or congestive heart failure (CHF) related to diastolic dysfunction.

Chlyothorax • Extensive dissection at surgery may result in disruption of the

thoracic duct, leading to chylothorax.

• Chylothorax is recognized when feedings are instituted postoperatively.

• Persistent chylous pleural effusions may necessitate long-term chest tube drainage.

• Some patients respond to dietary therapy with medium-chain triglyceride diet, fat restriction, and/or total parental nutrition. Patients with refractory chylothorax may require pleurodesis or thoracic duct ligation.

Post-coarctectomy syndrome

• Restoring pulsatile blood flow to the mesenteric arteries may result in mesenteric arteritis, in which the arteries become distended and may rupture.

• Reflex arteriolar vasoconstriction occurs as part of autoregulation of blood flow and can result in ischemia.

• Clinical manifestations may range from mild abdominal discomfort to an acute abdomen with severe abdominal distention, vomiting, ileus, and progression to intestinal wall hemorrhage or perforation.

• Thus, feedings are usually delayed for 48 hours after surgery, and nasogastric tube decompression is continued until feedings are begun slowly and advanced as tolerated.

• Patients with severe postcoarctectomy syndrome may require exploratory laparotomy for treatment of bowel necrosis or perforation.

• Careful monitoring and good control of BP in the postoperative period may reduce the risk of postcoarctectomy syndrome.

Valvular stenosis

• Valvar aortic stenosis, membranous subaortic stenosis, and mitral valve stenosis: These may develop during the follow-up period; if these are significant, transcatheter or surgical relief of the obstruction may become necessary.

Prognosis • Coarctation of the aorta is a lifelong disease with a guarded prognosis.

• Relief of obstruction, control of hypertension, follow-up monitoring for recurrent obstruction, and follow-up care of associated anomalies are imperative.

• Continue subacute bacterial endocarditis prophylaxis indefinitely, even in the absence of associated abnormalities.

• Patients without residual obstruction who are normotensive both at rest and with exercise should lead normally active lives without restriction. They should be able to obtain health and life insurance.

• Patients with persistent hypertension, untreated residual obstruction, or other complications have a variable prognosis related to the severity of these problems.

• Death appears to be secondary to recoarctation repair, aneurysms at site of coarctation repair or at a remote site, congestive heart failure, bacterial endocarditis, and hypertension.

• Attempts to define factors that affect long-term survival have been made; age at operation and degree and duration of hypertension prior to surgery appear to affect the long-term survival.