Question 1

Which of the following methods is involved in the management of a PDA?

Accepted Answer

Medical management includes maintaining euvolemia and by optimizing the hemoglobin to ensure adequate oxygen delivery.In mechanically ventilated patients,increasing PEEP may serve to decrease the pulmonary blood flow by increasing PVR.In addition nonsteroidal anti-inflammatory agents such as indomethacin and ibuprofen are often used in the medical management of PDA.Indomethacin may be used prophylactically to prevent PDA and therapeutically to treat a symptomatic PDA.A dose of indomethacin (0.2 mg/kg/dose IV)given in the first 24 hours of life can be effective in preventing a PDA.Therapy later in life is usually given over a 48-hour period.Doses of 0.1 to 0.2 mg/kg/dose IV every 12 to 24 hours are effective.Side effects are uncommon but include oliguria,renal insufficiency,and dilutional hyponatremia.Ibuprofen may also be used,though a recent meta-analysis found that the use of ibuprofen was associated with increased incidence of chronic lung disease when compared to indomethacin.

Question 2

Which of the following statements describe truncus arteriosus?
I.The pulmonary artery arises from the left ventricle,and the aorta stems from the right ventricle.
II.If PVR increases relative to systemic vascular resistance (SVR),more blood flows to the lungs through the truncus,decreasing systemic cardiac output.
III.If SVR decreases relative to PVR,blood flow will be shunted from right to left,bypassing the lungs.
IV.A large VSD allows total mixing of blood from the two ventricles.

Accepted Answer

Truncus arteriosus refers to a rare defect where a single great artery arises from the ventricles of the heart,supplying the systemic,pulmonary,and coronary arteries (see Figure 24-18 in the textbook).A large VSD allows complete mixing of blood in the ventricles.The blood passes through a truncal valve before passing into the common truncus.The cardiac output and systemic oxygen saturations are determined by the balance between PVR and SVR.As PVR drops in the first several days of life,more blood flows to the lungs relative to the body,resulting in decreased systemic perfusion.If SVR decreases,blood will flow more to the body,leading to decreased pulmonary blood flow and hypoxemia.

Question 3

Which of the following physiologic mechanisms need to be in place to ensure adequate systemic perfusion in infants with HLHS?

Accepted Answer

Adequate systemic perfusion in these infants depends on the presence of a nonrestrictive atrial septal connection,adequate right ventricular function,a patent ductus arteriosus,and a balance between the pulmonary and systemic circulations.

Question 4

Which of the following medications is the most common preoperative treatment to minimize preductal constriction until surgical correction of coarctation of the aorta can be achieved?

Accepted Answer

Treatment of neonates with severe coarctation includes prostaglandin E₁ to restore patency of the ductus arteriosus.These patients may also have significant ventricular dysfunction,congestive heart failure,and acidosis,requiring inotropes,diuresis,and ventilatory support.

Question 5

Which of the following vessels return blood to the right ventricle?
I.Pulmonary vein
II.Inferior vena cava
III.Superior vena cava
IV.Coronary sinus

Accepted Answer

To understand the normal anatomy of the heart,one can trace the path of blood as it travels through the heart.This begins with deoxygenated venous blood that enters the right atrium (RA)from one of three sources.Venous blood from organs superior to the heart drains to the RA by way of the superior vena cava (SVC).Venous blood from organs inferior to the heart enters the RA via the inferior vena cava (IVC).Finally,venous blood from the heart itself drains into the RA by way of the coronary sinus.

Question 6

Which of the following blood flow patterns occurs in complete transposition of the great arteries?

Accepted Answer

In TGA the positions of the aorta and the pulmonary artery are reversed,with the aorta arising from the RV and the pulmonary artery arising from the LV (see Figure 24-17 in the textbook).The physiologic result is that the two circulations are in parallel rather than in series with each other.Deoxygenated systemic venous blood passes through the right heart and to the body without flowing through the lungs.Oxygenated pulmonary venous blood passes through the left heart and back to the lungs without flowing to the body.Survival depends on mixing at one or more points in the circulation.The potential sites for mixing of blood are ASDs,VSDs,or the PDA.

Question 7

Identify the congenital cardiac defect depicted in the following illustration:

Accepted Answer

The cardiac anomaly depicted in this question is hypoplastic left ventricular syndrome,which can be viewed in the textbook in Figure 24-8.

Question 8

Which of the following clinical pathophysiologic manifestations are consistent with a large ventricular septal defect (VSD)?
I.The majority of the blood flow is shunted from left right to right left.
II.Shunting typically occurs during ventricular diastole,which causes left atrial enlargement.
III.Chest radiography reveals an enlarged cardiac silhouette and increased pulmonary vascular markings,increasing pulmonary blood flow.
IV.Thickening and fibrosing of the pulmonary veins develop,decreasing pulmonary artery pressure.

Accepted Answer

The pathophysiology of VSDs involves left-to-right shunting,left ventricular volume overload,left atrial enlargement,and increased pulmonary blood flow.The size of the defect and the pulmonary vascular resistance determines the amount of shunting,which usually occurs during systole.Large defects may lead to large shunts,sometimes termed nonrestrictive VSDs,and may result in congestive heart failure and pulmonary hypertension.

Question 9

How should the therapist interpret a preductal-to-postductal PaO₂ difference of 8 mm Hg in a neonate?

Accepted Answer

Clinical signs of a PDA depend on the degree of left-to-right shunting but may include tachypnea and a continuous murmur.In addition to signs on exam,one can detect the presence of shunting by looking for a difference in oxygenation of preductal and postductal blood.A preductal blood gas should be obtained from the right radial or temporal artery,while a postductal gas may be obtained from the umbilical artery or from a peripheral artery in the lower extremity.A difference in PaO₂ > 15 mm Hg indicates significant shunting across the PDA.

Question 10

The therapist is treating a child with TOF who appears to be having a "tet" spell.What should the therapist suggest to treat this event?
I.Beta blockers
II.Knee-chest position to increase SVR
III.Morphine sulfate
IV.Oxygen

Accepted Answer

See Box 24-1 in the text (Treatment of "tet" spells).Knee-chest position increases systemic vascular resistance and promotes blood flow from the right ventricle to the pulmonary artery rather than the aorta.Morphine sulfate decreases irritability and may lead to pulmonary artery dilation,which will increase pulmonary blood flow.Oxygen improves oxygenation and decreases pulmonary vascular resistance.Beta blockers (propranolol)may relax RVOT spasms.Systemic vasoconstrictors (phenylephrine)increase systemic vascular resistance to promote pulmonary blood flow.Sodium bicarbonate,administered to treat acidosis,decreases PVR.

Question 11

Which of the following clinical manifestations is consistent with an atrial septal defect (ASD)?

Accepted Answer

The pathophysiology of an ASD involves left-to-right shunting,leading to right atrial enlargement,right ventricular volume overload,and increased pulmonary blood flow.Over time this may result in right ventricular hypertrophy,congestive heart failure,and pulmonary vascular disease.Infants with ASDs rarely are symptomatic and may remain so well into adulthood.Only 8% of children with ASDs develop symptoms before 2 years of age.Chest radiographs are typically normal,unless the child has congestive heart failure,which may result in cardiomegaly and prominent pulmonary vascular markings.

Question 12

Which of the following congenital cardiac anomalies is classified as conotruncal,associated with a "boot-shaped" appearance of the heart?

Accepted Answer

Chest radiography of patients with TOF classically reveals a "boot-shaped" appearance of the heart,which is a result of the narrow mediastinum and the effects of right ventricular outflow tract obstruction that leads to right ventricular hypertrophy.

Question 13

Why must supplemental oxygen be judiciously administered to patients with an atrioventricular canal defect?

Accepted Answer

Oxygen saturations in these children may be low (75% to 90%)due to venous admixing but are tolerated well by most patients.Supplemental oxygen may be given judiciously,given the potential for oxygen to induce pulmonary vascular dilation and increased pulmonary blood flow.

Question 14

What should the therapist select as target gas exchange parameters after surgical intervention for infants with hypoplastic left ventricular syndrome HLHS?

Accepted Answer

Goal gas exchange in these infants should follow the "rule of forties," which targets PaO₂ approximately 40 mm Hg and PaCO₂ 40 mm Hg.Any manipulation of the endotracheal tube in these patients should be conducted with caution.

Question 15

What factor is responsible for closure of the foramen ovale?

Accepted Answer

The increased fetal blood flow that results from the drop in PVR increases pulmonary venous blood return and,therefore,increases the left atrial pressure.At the same time,the RA pressure decreases when the umbilical cord is ligated and no longer provides placental blood flow to the IVC.The result of the higher LA pressures and the lower RA pressures is the closure of the foramen ovale.

Question 16

Identify the following congenital cardiac anomaly:

Accepted Answer

The cardiac anomaly depicted in this question is truncus arteriosus,which can be viewed in the textbook in Figure 24-16.

Question 17

Which of the following strategies can be used to increase PVR in infants with HLHS?

Accepted Answer

A number of interventions may be employed to balance the systemic and pulmonary circulations.As the PVR decreases,minimizing the amount of administered oxygen can decrease pulmonary vasodilation and pulmonary blood flow.Occasionally,subambient oxygen concentrations (FiO₂ < 0.21)are used to increase PVR.Target FIO₂s are usually in the 0.17 to 0.21 range in order to keep systemic oxygen saturations 70% to 80%.Hypercarbia can also be utilized to elevate PVR.

Question 18

For which of the following congenital cardiac defects may spontaneous closure of the ductus arteriosus be catastrophic?
I.Tetralogy of Fallot with pulmonary atresia
II.Atrial septal defect
III.Severe coarctation of the aorta
IV.Hypoplastic left heart syndrome

Accepted Answer

Shunting is potentially harmful,either due to prolonged cyanosis and decreased end organ oxygen delivery,or to increased PVR over time.However,shunting also has an important compensatory effect in patients with obstructed pulmonary or systemic blood flow.In these lesions,referred to as ductal-dependent lesions,the presence of a PDA provides lifesaving blood flow.Lesions with systemic outflow tract obstruction,such as critical coarctation of the aorta or hypoplastic left heart syndrome,rely on the PDA to provide systemic blood flow via a right-to-left shunt;these lesions have ductal-dependent systemic blood flow.With both right-to-left shunt (cyanotic cardiac defect)and left-to-right shunt (acyanotic cardiac defect),several lesions depend on a patent ductus arteriosus for adequate pulmonary and systemic blood flow.These anomalies are also called ductal-dependent lesions because spontaneous closure of the ductus arteriosus can prove catastrophic.Anomalies included in this group are severe coarctation of the aorta,hypoplastic left heart syndrome,and tetralogy of Fallot with pulmonary atresia.

Question 19

Which of the following clinical features characterize a critical aortic stenosis in a neonate?

Accepted Answer

The clinical presentation and natural history of aortic stenosis is determined by the time of presentation and the degree of stenosis.Neonates who present with critical aortic stenosis frequently present in cardiogenic shock with hypotension,poor perfusion,and metabolic acidosis.The chest radiograph frequently includes cardiomegaly and pulmonary edema.

Question 20

At birth,what factor causes dilation of the pulmonary vascular bed and a decrease in the pulmonary vascular resistance?

Accepted Answer

With inflation of the lungs and the beginning of their participation in gas exchange,PaO₂ increases and PaCO₂ decreases,both of which contribute to dilation of the pulmonary vasculature and a resultant reduction in pulmonary vascular resistance (PVR).This leads to reduced right ventricular pressures and increased pulmonary blood flow.

Quiz 24: Congenital Cardiac Defects