Congenital heart defects: Clinical practice

Congenital heart defects are usually divided into two categories based on the presence or absence of cyanosis, as well as by how it sounds on cardiac auscultation.

Acyanotic defects cause left to right shunting, and include four conditions: ventricular septal defect or VSD, atrial septal defect or ASD, patent ductus arteriosus or PDA, and coarctation.

Cyanotic defects present right to left shunting, and include five conditions: tetralogy, transposition, truncus arteriosus, total anomalous pulmonary venous return, and hypoplastic left heart syndrome.

Usually the diagnosis is then confirmed by echocardiography.

An ECG should be performed as part of the initial work-up.

Chest x-ray is important when there’s suspicion of heart failure, and, sometimes a CT or MRI are done if the diagnosis is inconclusive.

Rarely, cardiac catheterisation with angiography is used if the diagnosis remains uncertain after non-invasive studies.

Regarding infective endocarditis prophylaxis, it is recommended for high risk individuals: those with a cyanotic congenital heart disease that has not been fully repaired; a congenital heart defect that's been completely repaired with prosthetic material or a device for the first six months after the repair procedure; repaired anomalies with residual defects, such as persisting leaks or abnormal flow.

Most heart defects can also be detected prenatally by standard obstetric ultrasound examination. However, small ventricular septal defects or atrial septal defects, minor valve lesions, partial anomalous pulmonary venous connection, and coronary artery anomalies are often not detected prenatally.

The optimal gestational age for screening for structural fetal cardiac anomalies is 18 to 22 weeks of gestation, although in some cases it can be done as early as 10 weeks of gestation.

In the first two days of life, a pulse oximetry saturation less than 90% in the right hand or either foot requires urgent echocardiography.

If the saturation is 90% to 95% in either location or if there’s a saturation difference greater than 3% between the right hand and either foot, the test should be repeated hourly, and it’s positive three times, then echocardiography should be done.

In acyanotic defects, the high-pressured left-sided systemic blood gets shunted to the right-sided pulmonary circulation.

Because this extra blood is already oxygenated, there’s no issue of cyanosis, but it does add increase the pulmonary flow and that leads to pulmonary hypertension.

In some cases over a long period of time, the pulmonary hypertension gets so bad that the pulmonary pressure exceeds the systemic pressure causing reversal of blood flow from the right to the left side of the heart.

This reversal is called the Eisenmenger syndrome, and at that point the deoxygenated right-sided pulmonary blood gets shunted to the left-sided systemic circulation - leading to cyanosis.

In cyanotic defects, there’s a defect which allows deoxygenated systemic venous blood to bypass the lungs and return to the body - leading to cyanosis.

Ventricular septal defects are the most common pediatric heart defects.

A small defect leads to minimal left-to-right shunting across the ventricles, and is not associated with any increase in pulmonary vascular resistance or with any symptoms.

Larger defects can be heard on auscultation as a loud, harsh, or blowing holosystolic murmur, and are best heard over the lower left sternal border. There may also be a palpable thrill.

The pulmonic component of the second heart sound can also get louder as a result of pulmonary hypertension.

And because of the increased blood flow across the mitral valve, a mid-diastolic, low-pitched rumble at the apex might be heard too.

Larger VSDs can cause a parasternal heave and a displaced apex beat.

Over time, left heart failure might develop, leading to pitting peripheral edema, ascites, and liver enlargement.

In terms of imaging, transthoracic echocardiography is best at estimating the position and size of the VSD, and doppler echocardiography can assess the magnitude of the shunt.

It is usually the first and only test needed to diagnose a ventricular septal defect.

Next, a chest x-ray might show signs of cardiomegaly and increased pulmonary vasculature, and ECG might show left ventricle hypertrophy in those with large shunts.

Both x-ray and ECG are not diagnostic of a VSD, but can be part of the initial workup when other cardiac issues are suspected.

Treatment of small VDSs is usually not required, because they often close spontaneously during the first year of life.

Even if they don’t, small, asymptomatic VSDs typically don’t cause any problems.

When there’s a large VSD, and a history of endocarditis or left ventricle dysfunction, treatment consists of surgical or percutaneous closure of the VSD.

In cases of severe pulmonary hypertension and Eisenmenger's syndrome, closure of the VSD is not recommended, and instead pulmonary vasodilators such as bosentan or sildenafil can be used.

Next, atrial septal defects can occur in any portion of the atrial septum.

A small defect is less than 0.5 centimeters in diameter and is associated with no clinically significant shunting of blood, whereas a sizable defect is usually larger than 2 centimeters in diameter and can associate a large shunt and substantial hemodynamic consequences.

On auscultation, characteristic findings include a mid-systolic pulmonary flow or ejection murmur accompanied by a widened split second heart sound in all respiratory phases because the extra blood return during inspiration gets equalized between the left and right atria.

The widening of the split is due to prolonged emptying of the enlarged right ventricle which delays pulmonic closure.

An additional short, rumbling mid-diastolic murmur might be heard along the lower sternal border due to increased blood flow across the tricuspid valve.

Over time, the individual might present signs of heart failure.

In some cases, atrial enlargement leads to chest deformity with transverse depressions along the sixth and seventh costal cartilages which are known as Harrison grooves.

In terms of imaging, transthoracic echocardiography remains the preferred initial diagnostic modality in children, and transesophageal echocardiography in adults because it offers significantly more anatomic information compared with transthoracic echocardiography, especially when it comes to measuring the size and position of ASDs.

Next, a chest radiograph could be performed as well, as it might show heart enlargement and increased pulmonary vascular markings.

Additionally, ECG in those with large shunts can shows a slightly prolonged QRS complex with a characteristic rSr' or rsR' pattern in V1 due to right ventricular hypertrophy, right axis deviation, or p waves taller than 2.5 millimeters, suggesting right atrial enlargement.

Regarding treatment, small atrial septal defects frequently close spontaneous closure of the defect in the first year of life.

Defects that are greater than 1 cm often require surgical or percutaneous closure.

Next is patent ductus arteriosus, and that’s when the ductus arteriosus stays open after birth.

On auscultation, a continuous murmur with like machinery in quality, is best heard in the second left intercostal space. soon after onset of the first sound.

In those with a large left-to-right shunt, a low-pitched mitral mid-diastolic murmur may be audible at the apex as a result of the increased volume of blood flow across the mitral valve.

A systolic thrill, maximal in the second left interspace may radiate toward the left clavicle, down the left sternal border.

Over time a large PDA could can lead to congestive heart failure, impaired growth, and bounding peripheral arterial pulses and a wide pulse pressure due to runoff of blood into the pulmonary artery during diastole.

Regarding imaging, echocardiography is the first step towards diagnosis as it can visualize and measure the ductus, show left atrial and left ventricular enlargement in large defects, and masses the direction and volume of the shunt.

Additionally, Doppler examination usually shows systolic or diastolic retrograde turbulent flow in the pulmonary artery, and aortic retrograde flow in diastole.

Next, chest radiography can might prominent pulmonary artery with increased pulmonary vascular markings, and cardiac enlargement if the shunt is important.

And ECG in older infants and children may demonstrate left ventricular enlargement with a deep Q wave and tall R waves in leads II, III, Avf, V5, and V6.

Treatment of hemodynamically stable individuals consists of indomethacin, ibuprofen, and acetaminophen.

Acetaminophen, for example, is administered intravenously 15 milligrams per kilogram every 6 hours for 3 to 8 days.

If the PDA is hemodynamically significant despite pharmacologic therapy and results in increased respiratory support or renal impairment, they should be ligated surgically or occluded percutaneously.

However, once severe pulmonary vascular obstructive disease develops, ligation or closure is contraindicated.

And finally, coarctation is a narrowing of the aorta which mostly occurs below the origin of the left subclavian artery at the origin of the ductus arteriosus.

On auscultation, a short systolic murmur is often heard along the left sternal border at the 3rd and 4th intercostal spaces, which might also be transmitted to the left infrascapular area and occasionally to the neck.

A systolic ejection click may be heard if there is an associated bicuspid aortic valve.

On examination, the classic sign of coarctation is a disparity in pulsation and blood pressure in the arms and legs.

Normally, the femoral pulse occurs slightly before the radial pulse, but in coarctation a radial-femoral delay occurs when blood flow to the descending aorta is dependent on collaterals, so the femoral pulse is felt after the radial pulse.

Moreover, in healthy individuals, systolic blood pressure in the legs obtained by the cuff method is 10 to 20 millimetres of mercury higher than that in the arms, but in coarctation of the aorta, blood pressure in the legs is lower than that in the arms.

Over time, individuals might develop cyanosis, tachypnea, and signs of heart failure. Imaging-wise, the first step towards diagnosis is echocardiography, which can visualise the location of the coarctation alongside associated anomalies of the mitral and aortic valve.

Next, chest radiography can show cardiac enlargement and pulmonary congestion, mostly in those with severe coarctation.

Electrocardiography is usually normal in young children but reveals evidence of left ventricular hypertrophy in older individuals.

Treatment of mild cases is done with prostaglandin E1 infusion, which can open the ductus arteriosus but also seems to relax the tissue of the coarctation segment.

Definitive treatment is elimination of the narrowed segment either through surgery or via transcatheter techniques.

Surgery requires removal of the coarctation segment and direct anastomosis of the normal aorta.

The transcatheter technique utilizes balloon and stent angioplasty.

Ok so let's now discus cyanotic heart defects. First, tetralogy of Fallot has four components: pulmonary stenosis; a malalignment type of ventricular septal defect; dextroposition of the aorta so that it overrides the ventricular septum; and right ventricular hypertrophy.

On auscultation, there might be a systolic murmur that is usually loud, harsh, crescendo-decrescendo, and most intense at the left sternal border and usually preceded by a click.

The murmur is caused by turbulence through the right ventricular outflow tract and it tends to become louder and harsher as the severity of pulmonary stenosis increases.

In some cases, the P2 sounds might not be audible, and a systolic thrill may be felt along the left sternal border in the 3rd and 4th parasternal spaces.

Over time, individuals might have a left anterior hemithorax bulge due to right ventricular hypertrophy and signs of heart failure.

Often, cyanosis is not present at birth; but it occurs later in the 1st year of life.

Older children who have not undergone surgery may have dusky blue skin, gray sclerae with engorged blood vessels, and marked clubbing of the fingers and toes.

Moreover, they present dyspnea occurs on mild exertion like playing.

Characteristically, children assume a squatting position for the relief of dyspnea caused by physical effort.

Paroxysmal hypercyanotic attacks, also called hypoxic or blue spells, are a particular problem during the first two years of life. Individuals become hyperpneic and restless, cyanosis increases, gasping respirations ensue, and syncope may follow.

The spells occur mostly frequently in the morning or after crying, and can progress unconsciousness and, occasionally, to convulsions or hemiparesis.

Imaging-wise, the main study is two-dimensional echocardiography, which confirms the diagnosis, establishes the extent of aortic override of the septum, the location and degree of the right ventricular outflow tract obstruction, the size of the pulmonary valve annulus and main and proximal branch pulmonary arteries, and the side of the aortic arch.

Next, chest radiography might show a classic boot-shaped heart and an enlarged and right-sided aorta.

Electrocardiography might demonstrates right axis deviation and evidence of right ventricular hypertrophy with prominent R waves anteriorly and S waves posteriorly, upright T wave in V1, and a qR pattern in the right precordial leads.

The P wave is usually tall and peaked, suggesting right atrial enlargement.

And finally, pre-ductal and post-ductal or right arm and either leg pulse oximetry should be ordered if there is any suspicion of a congenital cardiac malformation.

Treatment of neonates with severe right ventricle outflow obstruction presenting with severe hypoxemia and cyanosis consists of prostaglandin therapy to maintain ductal patency and pulmonary flow before surgical repair.