The baby was born by normal spontaneous vaginal delivery without perinatal problem at a local obstetric clinic. During a routine neonatal check-up, heart murmur and mild lip cyanosis were detected. The baby appeared healthy and fed well. Its breathing sound was clear. No definite tachypnea or chest retraction was noted. A grade III/VI harsh systolic ejection murmur was heard at the upper left sternal border. Pulse oximetry checked at the right finger and toe showed the same oxygen saturation of around 85%, and after oxygen supply via nasal prong (5 L/min), it registered around 90% at the both sites. The blood pressures in the right arm and right ankle were within the normal limits for the patient's age. EKG showed a QRS axis of 150° and satisfied the voltage criteria for right ventricular hypertrophy. Chest X-ray showed no cardiomegaly or significant lung lesion (Fig. 1A).

This is a typical clinical presentation of a common cyanotic congenital heart disease. The presence of cyanosis and cardiac murmur after birth in this case indicated that the cyanosis had a cardiac origin. The additional findings that indicated CHDs were a blunted response to oxygen supply, abnormal QRS axis and voltage, clear or rather darker lung field, and a typical cardiac silhouette (boot-shape) on chest X-ray (Fig. 1). Echocardiography revealed a typical form of tetralogy of Fallot (TOF), a large malaligned perimembranous VSD, PS (valvular and subvalvar infundibular PS), overriding of the aorta and RV hypertrophy. In TOF, the degree of cyanosis depends on the severity of PS, that is, the pulmonary blood flow reduces with an increase in the severity of PS, thereby causing more severe cyanosis. Normal heart size, the darker lung fields, and slightly indistinct hilar vascular markings on the chest X-ray indicated decreased pulmonary blood flow. If the PS is very severe or the pulmonary artery or valve is atretic (pulmonary atresia (PA) with VSD; an extreme form of TOF, Fig. 1B), patients will present with profound cyanosis when the PDA constricts. Management to maintain the PDA along with adequate hydration should be initiated immediately to maintain pulmonary blood flow. Fluid restriction and dehydration generally aggravate the cyanosis in cyanotic heart diseases, except in the cases of PDA-independent mixing lesions with pulmonary congestion (TGA, truncus arteriosus or TAPVR). The surgical treatment options for a severe form of TOF or PA with VSD are initial palliative procedures such as modified Blalock-Taussig shunt, insertion of a stent into the PDA, or insertion of a stent into the RV outflow track, which is followed by a total repair. In some centers, a total repair during the neonatal period is preferred.

A neonate was referred from a local obstetric clinic because of cyanosis and tachypnea a few hours after birth. The baby was born after a normal full term vaginal delivery and was meconium-stained at birth. On the physical examination, the baby appeared slightly pale, and showed blue lips and nasal flaring. The respiratory rate was 70/min with chest wall retraction. Chest auscultation revealed a coarse breathing sound with fine crackles in both lung fields. Heart rate was 170/min. No remarkable cardiac murmur was detected. Oxygen saturation checked by pulse oximetry was 90% at the right arm and 75% at the leg. The blood pressures at the right arm and leg were the same and within the normal limits for the patient's age. The baby was intubated and received mechanical ventilation. Arterial blood gas analysis during mechanical ventilation with a FiO₂ of 1.0 showed PaO₂ 180 mmHg, PaCO₂ 50 mmHg and oxygen saturation 100%. Chest X-ray showed diffuse haziness in both lung fields with air bronchograms, mild cardiomegaly, and large thymic shadow (Fig. 2).

This case was slightly confusing, but there were some clues to the cause of cyanosis. The baby had a history of meconium staining, and showed cyanosis and severe respiratory symptoms with an abnormal breathing sound. There was no remarkable cardiac murmur or EKG finding. In the chest X-ray (Fig. 2), the heart shadow was slightly large but the main mediastinal shadow was the thymus. A diffuse haziness in both lung fields with an air bronchogram rather than increased vascular markings suggested that primary pulmonary problems were the cause of cyanosis and respiratory distress. Another finding important in differential diagnosis is differential cyanosis, i.e., higher O₂ saturation in the right arm than in the leg, which indicates a right-to-left shunt through the PDA. Differential diagnoses in this situation are PPHN and severe coarctation of the aorta or arch interruption. The patient showed a profound response to 100% oxygen supplementation. Echocardiography showed a structurally normal heart with RV dilatation, moderate TR with a velocity of 4 m/sec, RA dilatation, bi-directional shunt (mainly right-to-left shunt during ventricular systole) through the PDA, and right-to-left shunt via PFO. The final diagnosis was PPHN caused by pneumonia and possibly by meconium aspiration. Fortunately, this baby showed rapid improvement after supportive management. Pulmonary vasodilators such as inhaled nitric oxide (iNO), sildenafil, bosentan, or iloprost are good options for severe cases. However, if the condition is intractable to medical management and caused by reversible lung problems, an extracorporeal membrane oxygenation (ECMO) will rescue the patient⁷⁾.

This baby presented with severe cyanosis just after delivery at a local clinic and was transferred to a tertiary care center with an oxygen supply via a nasal prong. The reported oxygen saturation monitored by pulse oximetry during transfer was around 50-60%. On admission, the baby was mildly tachypneic and mildly lethargic. Whole body cyanosis was noticed, and it did not improve after O₂ supplementation (SaO₂ around 40%). After intubation and mechanical ventilation with a FiO₂ 1.0, arterial blood gas analysis showed pH 7.34, PaO₂ 30 mmHg (O₂ saturation 66%), and PaCO₂ 28 mmHg. Chest examination revealed grade II/VI systolic murmur at the lower sternal border without definite rale or wheezing in the lung fields. The liver was palpable at a 1-finger-breadth. EKG showed a QRS axis of 120°, a tall p wave and right ventricular hypertrophy. Chest radiography showed cardiomegaly but clear lung fields and decreased pulmonary vascular markings (Fig. 3A).

This was a rare case of severe cyanotic CHDs intractable to oxygen therapy and mechanical ventilation alone. Initial physical examination showed clear breathing sound and cardiac murmur, thereby implying the cardiac origin of cyanosis. Chest X-ray showed no evidence of lung problem, but it did show clearer or darker lung fields, decreased pulmonary vascular markings, and cardiomegaly. These findings indicated a lesion with ductal-dependant pulmonary circulation, which necessitated an immediate empirical therapy with prostaglandin infusion to rescue this baby even before echocardiagraphic diagnosis was done (O₂ saturation was around 40% and decreasing). Generally, in cases of CHDs, the heart size increases along with an increase in pulmonary blood flow. If there is a cardiomegaly in CHDs with suspected severe PS or PA (conditions with decreased pulmonary blood flow), the possible mechanisms of cardiomegaly would be myocardial dysfunction, severe atrioventricular valve regurgitation (usually involving tricuspid valve), and/or enlargement of the atria. The common cardiac defects of such cases are Ebstein's anomaly of the tricuspid valve, congenital TV dysplasia, and PA with intact ventricular septum (PA IVS) with severe TR. Echocardiography in this patient revealed severe TR (Fig. 3B) due to flail anterior and posterior leaflets, moderate dilatation of the RV, RA enlargement with a right-to-left shunt through the PFO, pulmonary atresia and small PDA. Particularly in this patient, the morphology of the atretic pulmonary valve appeared normal, but the leaflets did not open during systole. There was no antegrade flow through the pulmonary valve during systole, but trivial regurgitation was observed during diastole, thereby implying "functional pulmonary atresia". Functional pulmonary atresia, a relatively uncommon clinical condition, occurs in neonates with severe TR associated with Ebstein's anomaly, tricuspid valve dysplasia, or transient myocardial dysfunction with normal intracardiac anatomy8-¹⁰⁾. In patients with increased perinatal pulmonary vascular resistance and severe TR, the RV cannot generate adequate pressure and forward flow to open the pulmonary valve. Therefore, administration of pulmonary vasodilators to lower the pulmonary vascular resistance along with early closure of the PDA, which further elevates the pulmonary artery pressure, may rescue a neonate in a critical clinical state¹⁰⁾. In the cases of anatomic pulmonary atresia or critical pulmonary stenosis, balloon valvotomy (valvuloplasty) or surgical treatment is required.

This term baby was born without any apparent perinatal problems and was discharged home 2 days after birth. At home, the baby was reported to be doing well for one or two days after discharge, but it appeared blue and showed tachypnea and poor feeding. The baby was brought to the local clinic at which it was born, and it was transferred emergently to a tertiary care center. On admission, the baby looked pale and cyanotic and showed tachypnea. Oxygen saturation values at the right fingers and toes were around 60% initially and 75% after O₂ supplementation. The respiratory rate was 70/min with chest wall retraction. Chest auscultation revealed fine crackles in the lung fields but did not reveal any remarkable cardiac murmur. The blood pressures at the right arm and the right ankle were 60/45 mmHg. EKG showed no remarkable findings, and chest radiograph showed cardiomegaly and diffuse haziness and increased pulmonary vascular markings (Fig. 4A).

This patient showed profound cyanosis and respiratory difficulty that did not respond to 100% oxygen supply, thereby implying the cardiac origin of the cyanosis. The chest X-ray (Fig. 4A) showed cardiomegaly and pulmonary congestion indicating increased pulmonary blood flow. Because the severe cyanosis was observed with pulmonary over-circulation (no PS) in this patient, this case can be considered to be quite different from the previous cases of right-sided obstructive lesions (case 1 or case 3), which presented with decreased pulmonary blood flow and intracardiac right-to left shunt.

The most common diagnosis for this case could be a simple TGA (with no VSD and PS), in which parallel rather than serial systemic and pulmonary circulation causes severe cyanosis (the result of inadequate intercirculatory mixing) and pulmonary congestion. A similar situation can occur in cases of TAPVR or truncus arteriosus, which are ductal-independent mixing lesions. In obstructive type TAPVR with severe cyanosis, the pulmonary venous congestion or edema is striking and the heart size is usually normal. In truncus arteriosus, pulmonary congestion with cardiomegaly is evident, but cyanosis is usually mild because of adequate mixing of the blood via the large VSD.

In this case, after initial empirical therapy with prostaglandin infusion and diuretics, echocardiography confirmed the diagnosis of TGA with a constricting PDA and restrictive mixing of blood through the PFO. Because of persistent severe cyanosis and pulmonary congestion, an emergency balloon atrial septostomy was done on the day of admission (Fig. 4B), and an arterial switch operation (the Jatene procedure) was performed two days later.

This baby was born at a gestational age of 35 weeks and had birth weight of 2.5 kg. At birth, it showed cyanosis and mild tachypnea and was admitted to an intensive care unit for close observation and oxygen supplementation. At 3-4 h after birth, the patient's cyanosis and tachypnea aggravated, and it underwent intubation and mechanical ventilation. Oxygen saturation values before and after mechanical ventilation (FiO₂, 1.0) were 65% and 85%, respectively. Chest auscultation revealed no remarkable cardiac murmur. Fine crackles were heard in both lung fields. EKG was unremarkable. Chest X-ray (Fig. 5) showed severe and diffuse haziness with obliteration of the right cardiac silhouette and a left-sided cardiac apex. Respiratory distress syndrome (RDS) was initially suspected, and a surfactant was administered. However, the clinical conditions did not improve after the surfactant treatment and the ventilator support.

This preterm baby presented with progressively worsening severe cyanosis and respiratory difficulty a few hours after birth, and was suspected to have RDS. The remarkable finding in the chest radiograph was a severe and diffuse haziness in both lung fields that nearly obliterated the cardiac silhouette (Fig. 5). It is quite reasonable to suspect RDS in this preterm neonate, although other causes such as bacterial pneumonia should be considered. However, in cases with severe cyanosis and respiratory distress that do not respond to oxygen supplementation and positive mechanical ventilation, and/or surfactant administration, TAPVR with severe pulmonary venous obstruction should be ruled out by immediate echocardiographic examination, because TAPVR with severe pulmonary venous obstruction will require immediate surgical repair. This case was diagnosed as an infracardiac type of TAPVR (in which common pulmonary venous channel drains into the portal system) with severe obstruction, and the patient was sent to the operating room for surgical repair.

A 9-day-old neonate was transferred to the neonatal intensive care unit for the evaluation of lethargy and respiratory distress. The full-term baby was born by cesarean section at a local obstetric clinic and was discharged home two days after birth. The baby was reported to have done "quite well" at home until the 6^th day after birth, when her mother noticed that her breathing was very fast with chest retraction and that she appeared pale and lethargic. On admission, the baby looked pale and lethargic. The skin on the abdomen and legs was mildly cyanotic, icteric, and mottled. Skin turgor was decreased. The blood pressures were 70/45 mmHg (right arm) and 50/30 mmHg (leg). Oxygen saturations were 95% (right finger) and 85% (toes). Respiration rate was 70/min and heart rate was 160/min. Body temperature was 37℃. Chest auscultation revealed grade II-III/VI ejection-type cardiac murmur at the upper left sternal border and no remarkable rale or wheezing in the lung fields. EKG showed a sinus rhythm and biventricular hypertrophy. Chest radiography (Fig. 6) showed cardiomegaly and increased pulmonary vascular markings. Arterial blood gas analysis showed pH 7.30, pCO₂ 27mmHg, pO₂ 68 mmHg, and HCO₃ 15 mmol/L. The blood urea nitrogen (BUN) and creatinine (Cr) were 20.3 mg/dL and 1.24 mg/dL, respectively. Serum glutamic-oxaloacetic transaminase (GOT) and glutamic-pyruvic transaminase (GPT) were 746 and 154 U/L, respectively. The serum creatine phosphokinase (CPK) and lactate dehydrogenase (LDH) were 1,720 and 6,410 U/L, respectively. No urine output was observed for the first 2 hours after admission.

This patient's main clinical manifestation was a sudden deterioration of systemic circulation, which was followed by acute renal failure and respiratory distress. However, cyanosis was not remarkable in this patient. The characteristic findings on physical examinations were differential cyanosis and different blood pressures in the preductal (right upper extremity) and postductal (leg) area. The higher blood pressure in the preductal part of the body indicated lesions with aortic arch obstruction or interruption, although similar blood pressures in both parts of the body cannot rule out aortic arch obstruction or interruption in the presence of a large PDA. The differential cyanosis (higher O₂ saturation in the right arm) indicates the right-to-left shunt through the PDA. Regardless of the anatomic diagnosis in detail, these patients should be resuscitated immediately by using advanced life support and empirical therapy, including mechanical ventilation with sedation and paralysis, infusion of prostaglandin, adequate fluid therapy and diuretic administration, and inotropic support. This patient was diagnosed as an interruption of the aortic arch (type A), a constricting PDA, and a large subarterial VSD. However, this complicated CHD had not been recognized at birth and the patient had been discharged home. Not a small proportion of neonates with critical CHD may appear normal or have subtle signs; these signs may escape the clinician's notice in a routine neonatal examination1, 4, 11, ¹²⁾.

The most common potentially fatal defects missed at birth discharge are left-sided obstructive lesions such as HLHS and coarctation of the aorta4, 11, ¹²⁾. In the majority of patients showing left-sided obstructive lesions just after birth, the systemic circulation is maintained by blood flow through the large PDA; pulmonary overflow is not profound because of elevated pulmonary vascular resistance; and cyanosis is usually mild, especially in the upper part of the body. A decrease in pulmonary vascular resistance and the PDA size may result in sudden systemic hypotension or shock and severe pulmonary congestion. Therefore, in routine clinical practice, clinicians should be alert to subtle signs of heart failure, such as tachypnea, tachycardia, unexplained cough or irritability, poor and interrupted feeding, excessive sweating, or pallor.