**5. Cardiac evaluation of newborn infant**

In the cardiac evaluation of the newborn infant, understanding the circulatory status at birth is very important. As the result of fetal circulation, newborn infants have right ventricular (RV) dominance associated with a thick RV wall, elevated pulmonary vascular resistance (PVR), and a thick medial layer of the pulmonary arterioles. The thick pulmonary artery smooth muscle gradually becomes thinner, and it resembles that of the adult by the time the baby is age 6 to 8 weeks. Most perinatal changes in hemodynamics are related to the thinning of the pulmonary vascular smooth muscle, resulting in a gradual fall in the PVR and a loss of RV dominance of the neonate. Premature infants in general have lessRV dominance than full-term infants, and the PVR is not as high in the full-term neonate, which adds variability to the process. Because of these unique aspects of the perinatal circulatory system, the basic tools in the initial cardiac evaluation discussed are less reliable and the findings may be different in the newborn infant. Therefore echo studies are commonly performed in the neonatal cardiac evaluation. Some important aspects of normal and abnormal findings in physical examination, electrocardiograpgy (ECG), and chest x-ray films of the neonate are briefly reviewed in this chapter.

#### **5.1 Physical examination**

	- a. Heart rate is generally faster ( usually over 100 beats/min, with normal ranges from 70 to 180 beats/min) than that of older children and adults.
	- b. A varying degree of acrocyanosis is the rule rather than the exception.
	- c. Mild arterial desaturation with arterial Po2 as low as 60 mmHg is not unusual in an otherwise normal neonate. This may be caused by an intrapulmonary shunt through an as yet unexpanded portion of the lungs or by a right-to-left arterial shunt through the patent foramen ovale (PFO).

Evaluation and Emergency Treatment of

discussed later in this chapter.

syndrome.

tricuspid atresia.

indicates relative LAD.

abnormal inferior forces for age

1. S waves in lead I 12 mm or greater

greater than 3 mm in any lead.

0.1 sec or greater as in the adult)

5. Upright T waves in V1 after 3 days of age.

may indicate RAD.

following are present:

progression.

in the newborn infant.

e. Atrial hypertrophy

in V1).

neonate.

a. P axis

b. QRS axis

Criticlly Ill Neonate with Cyanosis and Respiratory Distress 237

2. An abnormal ECG may be in the form of an abnormal P axis, abnormal QRS axis, hypertrophy of the ventricles or atria, vantricular conduction disturbances, or arrhythmias. Because of the wide ranges of normal values, many newborn infants with significant CHDs may show a normal ECG for their age. Arrhythmias in neonates are

1. A P axis in the right lower quadrant ( +90 to + 180 degrees) suggests atrial situs

2. A superor P axis suggests an ectopic atrial rhythm, as seen in polysplenia

1. A superiorly oriented QRS axis between 0 and -150 degrees ( left anterior hemiblock) suggests partial or complete ECD, including splenic syndromes, or

2. A QRS axis less than + 30 degrees is abnormal and indicates left axis deviation (LAD) in the neonate. The QRSetween + 30 and +60 degrees is unusual and

3. A QRS axis greater than +180 degrees (in the range of -150 to -180 degrees)

1. Left atrial hypertrophy (LAD) or relative LAD (less than +60 degrees) for the

2. An R/S progression in the precordial leads that resembles the adult R/S

3. QRS voltages demonstrating abnormal leftward and posterior forces or

d. Right ventricular hypertrophy (RVH) is difficult to diagnose because of the normal dominance of the RV at this age. However, the following are helpful clues to RVH

3. R waves in V1 greater than 25 mm or R waves in aVR greater than 8 mm.

6. Right axis deviation (RAD) with the QRS axis greater than + 180 degrees.

1. Right atrial hypertrophy (RAH) is present when the P wave amplitude is

2. Left atrial hypertrophy (LAH) iswhen the P wave duration is 0.08 sec or greater (usually with notched P waves in the limb leads and biphasic P waves

f. Ventricular conduction disturbances ( i.e , right bundle branch block (RBBB),left bundle branch block (LBBB), Wolff-Parkinson-Wite (WPW) syndrome, and intraventricular block)are present when the QRS duration is 0.07 sec or more ( not

2. Pure R waves with no S waves in V1 greater than 10 mm.

4. A qR pattern in V1 ( this is also seen in 10% of normal neonates).

c. Left ventricular hypertrophy (LVH) is suggested in the newborn infant when the

inversus, asplenia syndrome, or incorrectly placed ECG electrodes.

	- a. The pulmonary flow murmur of the newborn infant is more frequent and louder in premature than in full-term infants.
	- b. The likelihood of a patent ductus arteriosus (PDA) murmur is greater in premature infants.
	- c. The peripheral pulses normally appear bounding because of the lack of a normal amount of subcutaneous tissue.

The following abnormal physical findings cardiac pathology.


#### **5.2 Blood gases**

Normal 1-day-old infant may have P02 as low as 60 mmHg, but transcutaneous oxygen saturation is higher than 90%.

### **5.3 Electrocardiographraphy**

	- a. Sinus tachycardia with a rate as high as 180 beats/min.
	- b. A rightward QRS axis with a mean of +125 degrees and a maximum of +180 degrees.
	- c. Relatively small voltages for the QRS complex and the T wave.
	- d. RV dominance with tall R waves in the RPLs (V4R, V1, and V2).
	- e. Occasional q waves in V1(seen in about 10% of normal neonates)
	- f. Benign arrhythmias
	- a. P axis

the lower left sternal border (LLSB) rather than at the apex.

an ejection click (reflecting pulmonary hypertension) is audible.

group is the pulmonary flow murmur of the newborn infant.

The following abnormal physical findings cardiac pathology.

the arm require further evaluation for COA.

a. Sinus tachycardia with a rate as high as 180 beats/min.

c. Relatively small voltages for the QRS complex and the T wave. d. RV dominance with tall R waves in the RPLs (V4R, V1, and V2). e. Occasional q waves in V1(seen in about 10% of normal neonates)

normal infant.

3. Abnormal phycical findings

infants.

**5.2 Blood gases** 

follows:

saturation is higher than 90%.

**5.3 Electrocardiographraphy** 

degrees.

f. Benign arrhythmias

2. Additional important features of premature infants

premature than in full-term infants.

amount of subcutaneous tissue.

requires further evaluation.

d. There is relative hyperactivity of the RV, with the point of maximal impuls (PMI)at

e. The second heart sound (S2) may be single in the first days of life, and occasionally

f. An innocent heart murmur may be present. The most common one in this age

g. Peripheral pulses are easily palpable in all extremities, including the foot, in every

a. The pulmonary flow murmur of the newborn infant is more frequent and louder in

b. The likelihood of a patent ductus arteriosus (PDA) murmur is greater in premature

c. The peripheral pulses normally appear bounding because of the lack of a normal

a. Cyanosis, particularly when it does not improve with oxygen administration,

b. Decreased or absent peripheral pulses in the lower extremities suggest coarctation of aorta (COA). Generalized weak peripheral pulses suggest hypoplastic left heart syndrome (HLHS) or circulatory shock. Bounding peripheral pulses suggest an

c. Tachypnea of greater than 60 breaths/min with or without retraction is abnormal. d. Hepatomegaly may suggest a heart defect manifesting with congestive heart failure

e. A heart murmur may be a presenting sign of congenital heart disease (CHD). However, innocent murmurs are more common than pathologic murmurs. f. An irregular rhythm or abnormal heart rate may suggest cardiac arrhythmias. g. Blood pressure readings in the lower extremities 6 to 7 mm Hg lower than those in

Normal 1-day-old infant may have P02 as low as 60 mmHg, but transcutaneous oxygen

1. The normal ECG of a newborn infant is different from that of a child or an adult as

b. A rightward QRS axis with a mean of +125 degrees and a maximum of +180

aortic run-off lesion such as PDA or persistent truncus arterious.

(CHF). A midline liver suggests asplenia or polysplenia syndrome.

	- 1. A superiorly oriented QRS axis between 0 and -150 degrees ( left anterior hemiblock) suggests partial or complete ECD, including splenic syndromes, or tricuspid atresia.
	- 2. A QRS axis less than + 30 degrees is abnormal and indicates left axis deviation (LAD) in the neonate. The QRSetween + 30 and +60 degrees is unusual and indicates relative LAD.
	- 3. A QRS axis greater than +180 degrees (in the range of -150 to -180 degrees) may indicate RAD.
	- 1. Left atrial hypertrophy (LAD) or relative LAD (less than +60 degrees) for the neonate.
	- 2. An R/S progression in the precordial leads that resembles the adult R/S progression.
	- 3. QRS voltages demonstrating abnormal leftward and posterior forces or abnormal inferior forces for age
	- 1. S waves in lead I 12 mm or greater
	- 2. Pure R waves with no S waves in V1 greater than 10 mm.
	- 3. R waves in V1 greater than 25 mm or R waves in aVR greater than 8 mm.
	- 4. A qR pattern in V1 ( this is also seen in 10% of normal neonates).
	- 5. Upright T waves in V1 after 3 days of age.
	- 6. Right axis deviation (RAD) with the QRS axis greater than + 180 degrees.
	- 1. Right atrial hypertrophy (RAH) is present when the P wave amplitude is greater than 3 mm in any lead.
	- 2. Left atrial hypertrophy (LAH) iswhen the P wave duration is 0.08 sec or greater (usually with notched P waves in the limb leads and biphasic P waves in V1).

Evaluation and Emergency Treatment of

syndrome.

c. Dextrocardia or mesocardia

e. Pulmonary vascular markings

initially be associated with a murmur.

the newborn period are as follows:

shortly thereafter.

asphyxia.

Heart murmurs.

suggests asplenia or polysplenia syndrome.

severe pulmonary stenosis or atresia.

characteristic of pulmonary venous obstruction.

**6. Suggested approach to neonates with central cyanosis** 

Criticlly Ill Neonate with Cyanosis and Respiratory Distress 239

The presence of dextrocardia or mesocardia does not always indicate a serious heart defect. The segmental approach should be used for further evaluation. Four common situations seen in dextrocardia or mesocardia are situs inversus totalis with a normal heart, a rightward displacement of a normallyformed heart due to hypoplasia of the right lung, a complex cyanotic CHD, and asplenia or polysplenia

d. The situs of abdominal viscera: A left-sided liver with the heart in the right side of the chest is seen in situs inversus totalis with normal heart. The liver and the cardiac apex on the same side suggest a complex cyanotic CHD. A midline liver

1. Increased pulmonary vascular marking (PVM) in a cyanotic infant suggest TGA, persistent truncus arteriosus, or single ventricle. In an acyanotic infant, increased PVMs suggest VSD, PDA, or endocardial cushion defect (ECD). 2. Decreased PVMs suggest a critical cyanotic CHD with decreased pulmonary blood flow(PBF), such as pulmonary atresia, tricuspid atresia, mor TOF with

3. A ground-glass appearance or a reticulated pattern of the lung fields is

a. Although a significant heart murmur usually suggests a cardiac basis for the cyanosis, several of the more severe cardiac defects (transposition of the great vessels) may not

1. Innocent heart murmurs: More than 50% of full-term newborn infants ( and a higher percentage of premature infants) have an innocent systolic murmur at some time during the first week of life. Infants with innocent heart murmurs have normal ECG and chest x-ray findings. The four most common innocent murmurs in

a. Pulmonary flow murmur is most common. It is more often found in premature and small-for-gestational-age infants than in full-term infants. A soft systolic murmur ( grade 1 to 2/6), heard best at the upper left sternal border (ULSB),

b. Transient systolic murmur of PDA is soft ( grade 1 to 2/6), audible at the ULSB and in the left infraclavicular area on the first day. It usually disappears

c. Transient systolic murmur of tricuspid regurgitation is indistinguishable from that of VSD and is most common in infants who had fetal distress or neonatal

d. Vibratory systolic innocent murmur is a counterpart of Still's murmur in older

2. Pathologic heart murmurs: Most pathologic murmurs except atrial septal defect (ASD) are audible during the first month of life. The time of appearance of a

transmits well to bozh sides of the chest, axillae, and the back.

children. It is audible at the LLSB, apex, or midprecordium.

murmur depends on the nature of the defect.


#### **5.4 Chest roentgenography**

	- a. The cardiothoracic (CT) ratio of normal newborn infants may be greater than 0.5 because of inadequate inspiration and a large thymic shadow.
	- b. The thymic shadow may have any of several shapes, including a classic sail sign, or may have undulant or smooth borders, either unilateral or bilateral, on the upper mediastinum.
	- c. Cardiac silhouette is not always as well defined in neonates as in older children.
	- d. Evaluation of pulmonary vascular markings in the neonate poses a special problem. Although a reduced PBF is usually easier to detect ( and indicates serious cyanotic CHD), increased vascularity is not always apparent even when the pulmonary blood flow is large. The distinction between increased PBF and pulmonary venous congestion is often difficult.
	- a. Heart size

The CT ratio is of limited value, since that of normal neonates is usually greater than 0.5. Many serious CHDs that eventually result in cardiomegaly show a normal heart size in neonates. Unequivocal cardiomegaly may be due to CHD (such as ventricular septal defect (VSD), PDA, transposition of the great arteries (TGA), Ebstein anomaly, hypoplastic left heart syndrome (HLHS), and other), myocarditis or cardiomyopathy, pericardial effusion, metabolic disturbance (e.g., hypoglycemia, severe hypoxemia, and acidosis), and overhydration or overtransfusion.

In the newborn infant who is intubated and on a ventilator, the heart size is greatly influenced by the ventilator setting. For example, a premature infant with a large-shunt PDA may have a normal-sized heart on chest x-ray film if the ventilator settings are high, especially the positive end-expiratory pressure.

	- 1. A boot-shaped heart (coeur en sabot) is seen in tetralogy of Fallot (TOF) and in tricuspid atresia.
	- 2. An egg-shaped heart with narrow waist may be seen in TGA.
	- 3. A large, globular heart is seen in Ebstein anomaly.

c. Dextrocardia or mesocardia

238 Congenital Heart Disease – Selected Aspects

sometimes seen in otherwise normal neonates. 2. LBBB is extremely rare in the newborn infant.

diffuse myocardial diseases.

**5.4 Chest roentgenography**  1. Normal CXR findings

mediastinum.

a. Heart size

overtransfusion.

diagnosis.

tricuspid atresia.

1. RBBB may be associated with Ebstein anomaly and COA in the newborn. It is

3. Intraventricular block ( with a widening of the QRS complex throughout the QRS duration) is more significant than RBBB because it is often associated with significant metabolic abnormalities (e.g., hypoxia, acidosis, hyperkalemia) and

4. WPW syndrome may be an isolated finding or may be associated with CHDs

a. The cardiothoracic (CT) ratio of normal newborn infants may be greater than 0.5

b. The thymic shadow may have any of several shapes, including a classic sail sign, or may have undulant or smooth borders, either unilateral or bilateral, on the upper

c. Cardiac silhouette is not always as well defined in neonates as in older children. d. Evaluation of pulmonary vascular markings in the neonate poses a special problem. Although a reduced PBF is usually easier to detect ( and indicates serious cyanotic CHD), increased vascularity is not always apparent even when the pulmonary blood flow is large. The distinction between increased PBF and

2. Abnormal chest x-ray findings: A cardiac problem is suggested by an abnormal size, position, or silhouette of the heart, by an abnormal shape or position of the liver, and by

The CT ratio is of limited value, since that of normal neonates is usually greater than 0.5. Many serious CHDs that eventually result in cardiomegaly show a normal heart size in neonates. Unequivocal cardiomegaly may be due to CHD (such as ventricular septal defect (VSD), PDA, transposition of the great arteries (TGA), Ebstein anomaly, hypoplastic left heart syndrome (HLHS), and other), myocarditis or cardiomyopathy, pericardial effusion, metabolic disturbance (e.g., hypoglycemia, severe hypoxemia, and acidosis), and overhydration or

In the newborn infant who is intubated and on a ventilator, the heart size is greatly influenced by the ventilator setting. For example, a premature infant with a large-shunt PDA may have a normal-sized heart on chest x-ray film if the ventilator settings are

b. Abnormal cardiac silhouettes may be of considerable help in suggesting the correct

2. An egg-shaped heart with narrow waist may be seen in TGA.

3. A large, globular heart is seen in Ebstein anomaly.

1. A boot-shaped heart (coeur en sabot) is seen in tetralogy of Fallot (TOF) and in

such as Ebstein anomaly or L-TGA. It is a frequent cause of SVT.

because of inadequate inspiration and a large thymic shadow.

pulmonary venous congestion is often difficult.

high, especially the positive end-expiratory pressure.

increased or decreased pulmonary vascularity on CXR films.

	- 1. Increased pulmonary vascular marking (PVM) in a cyanotic infant suggest TGA, persistent truncus arteriosus, or single ventricle. In an acyanotic infant, increased PVMs suggest VSD, PDA, or endocardial cushion defect (ECD).
	- 2. Decreased PVMs suggest a critical cyanotic CHD with decreased pulmonary blood flow(PBF), such as pulmonary atresia, tricuspid atresia, mor TOF with severe pulmonary stenosis or atresia.
	- 3. A ground-glass appearance or a reticulated pattern of the lung fields is characteristic of pulmonary venous obstruction.
