Age: 14 years
Gender: Female
Occupation: Student
Working diagnosis: Hypoplastic left heart syndrome
HISTORY
The patient was born at term gestation by normal delivery. She had normal Apgar scores and her birth weight was 3.2 kg. Her mother did not have an antenatal fetal echocardiogram.
She developed tachypnea and cyanosis 30 hours after birth. Clinical examination at that time revealed a saturation of 68% on 70% oxygen, a gallop rhythm, a grade 2/6 systolic murmur at the left upper sternal edge, and a clear chest. Arterial blood gases showed severe hypoxia with a P o 2 of 35 mm Hg. CXR demonstrated borderline cardiomegaly.
The baby was started on a prostaglandin E1 infusion and then transferred to a tertiary children’s hospital for further management. Her oxygen saturation improved to 90% on the prostaglandin E1 infusion. An echocardiogram on arrival revealed situs solitus with normal systemic and pulmonary venous connections. The LV was markedly hypoplastic with a patent mitral valve and intact interventricular septum. There was subaortic atresia. A restrictive secundum ASD was noted with a single right SVC. The ascending aorta and arch were of reasonable size measuring 50 mm at the sinuses and 35 mm at the transverse arch. There was no aortic coarctation. A PDA with right-to-left shunting was noted.
She underwent a successful first-stage Norwood procedure on day 7 under hypothermic circulatory arrest. She had an uneventful postoperative period and was discharged home on digoxin, furosemide, and amiloride.
She remained well at home with normal development and satisfactory weight gain. Her resting O 2 saturation gradually dropped and was 68% at the age of 3 months. Cardiac catheterization revealed a good caliber neoaorta with no coarctation. There was some stenosis of the left pulmonary artery. The RV angiogram revealed good systolic function.
The patient underwent elective stage II palliation (bidirectional cavopulmonary shunt, see Fig. 68-7 ) at 3.5 months of age, along with further enlargement of the ASD and bovine pericardial patch repair of the left pulmonary artery. At the time of discharge her resting oxygen saturation was 80% on room air and her ventricular function was good by echocardiography.
She remained under close clinical follow-up. By the age of 3 years, her parents expressed concern that her exercise tolerance and oxygen saturations had decreased. Cardiac catheter assessments were done at 1.5 and 3 years of age. These revealed good cavopulmonary connection with good-sized branch pulmonary arteries and a transpulmonary gradient of 8 mm Hg.
At the age of 3.5 years, she had her third staged palliative procedure: elective Fontan surgery (total cavopulmonary connection, see Fig. 68-8 ). In this procedure the RA-PA connection was completed with a pulmonary homograft patch. A lateral tunnel, constructed using Gore-Tex with a 3.5 mm fenestration, directed the IVC flow into the pulmonary artery.
She was extubated on the day of operation and was transferred to the ward on the following day. She remained hemodynamically stable with a resting oxygen saturation of 90% on room air. She had a significant pleural effusion requiring drainage. A transthoracic echocardiogram performed at the time of discharge showed good ventricular function, trivial tricuspid regurgitation, a patent fenestration, and no pericardial or pleural effusions. Prior to discharge she was fully anticoagulated.
Repeat cardiac catheterization at age 5 showed the oxygen saturation in the RV and aorta to be 92% with an RA mean pressure of 17 mm Hg and a left atrial mean pressure of 13 mm Hg. This did not change significantly with balloon occlusion of the lateral tunnel fenestration. There were no veno-venous collaterals. The treating cardiologist opted not to close the fenestration.
Several years later, further cardiac catheterization revealed satisfactory Fontan circulation hemodynamics with mean pressures in the IVC, Fontan tract, SVC, and branch pulmonary arteries all reading 15 mm Hg. The fenestration in the Fontan pathway remained patent.
At age 14, she returned for routine clinical follow-up.
Comments: Infants with hypoplastic left heart syndrome (HLHS) are usually normal in appearance at birth. Symptoms are commonly noted after 24 to 48 hours but may appear in an hour or two in response to ductus arteriosus constriction, as the circulation is duct-dependent.
Clinical features in the early neonatal period are influenced by the severity of obstruction at the foramen ovale. Babies with severe obstruction of the foramen ovale usually have severe early symptoms with severe cyanosis and metabolic acidosis. Usually there is no initial significant respiratory distress, but tachypnea and dyspnea may develop. With severe hypoxemia and metabolic acidosis, hypoglycemia and hypocalcaemia can occur.
In HLHS, constriction of the arterial duct leads to reduced tissue perfusion with anaerobic metabolism and oliguria. In the presence of moderate restriction of the foramen ovale, pulmonary edema develops progressively as pulmonary vascular resistance falls. Constriction of the ductus arteriosus in this setting will dramatically decrease systemic perfusion and increase pulmonary blood flow further aggravating pulmonary edema. If there is evidence of constriction of the arterial duct, prostaglandin E1 is indicated to maintain duct patency and to increase systemic blood flow and perfusion.
Norwood and his colleagues achieved the initial surgical palliation of HLHS. This first operation is usually performed within the first week of life. The procedure involves transection of the pulmonary trunk proximal to its bifurcation and its anastomosis to the hypoplastic ascending aorta, incorporating a patch of homograft material to augment the ascending aorta, arch, and distal aorta. An atrial septectomy is performed, and a Blalock-Taussig shunt constructed (see Fig. 68-6 ).
Recent data from Toronto demonstrated consistent improvement in the mortality rate for first-stage surgery from 1990 through 2000. For the period 1998–2000, the mortality rate was 19%, lower than the 59% mortality for the period 1990–1993.
Risk factors for poor outcome from a Norwood procedure include low birth weight, diminutive ascending aorta, atresia of both aortic and mitral valves, severe extracardiac anomalies, poor preoperative clinical status, Turner syndrome, RV dysfunction, and older age at the time of first palliation. Factors contributing to perioperative morbidity and mortality are recurrent obstruction of the aortic arch (11%–37% incidence), acute shunt thrombosis, and tricuspid valve regurgitation.
During the stage II bidirectional cavopulmonary anastomosis the SVC is divided and its cranial end is anastomosed to an incision in the superior aspect of right pulmonary artery. The cardiac end of the SVC is oversewn. This operation is usually performed at the age of 3 to 6 months. It facilitates ventricular volume unloading as well as promoting regression of the ventricular mass and reducing any atrioventricular valve regurgitation.
Risk factors identified with early mortality in patients having the stage II bidirectional cavopulmonary shunt include younger age at the time of surgery (<2 months), mean pulmonary artery pressure more than 18 mm Hg, abnormal pulmonary venous connection, heterotaxy, and severe atrioventricular valve regurgitation.
There is no unanimous agreement as to the optimum age for stage III Fontan surgery but it is usually performed between 4 and 6 years in HLHS. This surgery may carry more risk in the adult and in the infant, although it can be carried out in children as young as 2 years and in adults with potentially excellent results. In patients younger than 10 years there is a favorable decrease in ventricular dimensions, volumes, and wall stress after Fontan-type surgery as compared to those undergoing the surgery after age 10 years.
Fenestration in the Fontan tract results in lower superior and IVC and RA pressures and an improved cardiac output, at the expense of usually mild desaturation. It may also reduce the severity and duration of postoperative pleural effusions.
Thromboembolic events have been well documented both acutely and late after Fontan surgery. Varma and colleagues demonstrated clinically silent pulmonary emboli in 17% of an adult population with Fontan surgery. Rosenthal and colleagues documented an overall rate of 3.9 per 100 patient years of thromboembolic events with a time from Fontan operation to the thrombotic event of 6.1 ± 5 years.
CURRENT MEDICATIONS
Warfarin 5 mg daily
Lisinopril 5 mg daily
Comments: ACE inhibitors such as lisinopril are not established therapy in patients with Fontan procedures. There are no clinical trial data to suggest they are effective in protecting ventricular function or preserving favorable ventricular shape, but they are often used on clinical grounds.
PHYSICAL EXAMINATION
BP 98/68 mm Hg, HR 75 bpm, oxygen saturation 92%, falling to 82% on exertion
Height 144 cm, weight 43 kg, BSA 1.31 m 2
Surgical scars: Midline sternotomy scar
Neck veins: Hard to evaluate and a waveform not seen
Lungs/chest: Clear to auscultation
Heart: Rhythm was regular, there was a normal S1, a single S2, and no murmur.
Abdomen: Liver edge palpable
Extremities: Normal without edema, skin was warm
Comments: This physical exam is favorable for a Fontan patient. A saturation of 90% to 95% on room air is typical, dropping on exercise. The absence of edema argues against both heart failure and PLE. The absence of a murmur is as expected, and argues against substantial AV valve regurgitation.
LABORATORY DATA
| Hemoglobin | 15.4 g/dL (11.5–15.0) |
| Hematocrit/PCV | 45% (36–46) |
| MCV | 86 fL (83–99) |
| Platelet count | 203 × 10 9 /L (150–400) |
| Sodium | 140 mmol/L (134–145) |
| Potassium | 4 mmol/L (3.5–5.2) |
| Creatinine | 0.8 mg/dL (0.6–1.2) |
| Blood urea nitrogen | 4 mmol/L (2.5–6.5) |
Comments: Mild degree of erythrocytosis may relate to the mild desaturation at rest (due to the fenestration) that is exacerbated with exercise.
ELECTROCARDIOGRAM
FINDINGS
Heart rate: 83 bpm
QRS axis: +91°
QRS duration: 102 msec
Normal sinus rhythm. Incomplete RBBB, RV hypertrophy, nonspecific ST-T wave abnormalities.
Comments: RV hypertrophy is present. The prominent R-waves in the left precordial leads are hard to explain since the LV is hypoplastic. It should be remembered that the RV occupies a dominant portion of the left hemithorax; hence much of the depolarization represented by these leads is still right ventricular.
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