Age: 15 years
Gender: Female
Occupation: Student
Working diagnosis: D-transposition of the great arteries
HISTORY
The diagnosis of D-TGA was made in utero. Postnatally, the infant had a good-sized ASD, and she underwent arterial switch operation (ASO) at day 6 of life uneventfully. Aortopulmonary collaterals were detected several days later, and these were successfully ligated.
At age 1, the patient had a follow-up echocardiogram demonstrating a high gradient through the RVOT. Catheterization confirmed the presence of supravalvular pulmonary stenosis, and a catheter balloon dilatation was performed with resolution of the pressure gradient. Five years later, however, restenosis above the pulmonary valve was noted and this was again treated with catheter balloon dilatation.
At age 10, she had no significant complaints during follow-up, but echocardiography demonstrated recurrent supravalvular pulmonary stenosis. Given the prior two attempts at balloon dilatation, it was decided to repair the area surgically. She underwent relief of the supravalvar pulmonary stenosis with placement of a T-shaped patch of bovine pericardium and closure of a residual ASD. The operation was uncomplicated, and the patient was discharged home within a week.
Over the past few years she noted progressive shortness of breath compared to her peers and mentioned this during her routine follow-up visit at the tertiary cardiac center.
Comments: Whereas most patients with D-TGA in today’s adult cardiology clinics will have been repaired with an atrial switch procedure (i.e., Mustard or Senning repair), those treated with an arterial switch are just now reaching adulthood. The successful anatomic correction for TGA was first described in 1975 by Jatene and colleagues in Brazil. The procedure involves the transection of the aorta and pulmonary artery (PA) at a level above the sinuses of the semilunar valves and reimplantation in their normal position. The coronary arteries are detached from the aorta with a surrounding “button” of aortic wall and reimplanted into the neoaorta. The procedure is usually performed within the first 2 weeks of life and should be undertaken within the first 4 to 6 weeks of life at the latest, while the LV is still capable of sustaining the systemic load.
Although the very long-term outcomes of patients with an ASO are unknown, complications of ASO are now known to include endocarditis, RVOT obstruction (as with our patient), and coronary artery disease/obstruction.
CURRENT SYMPTOMS
The patient is breathless when climbing stairs at school. Her parents are convinced that she is more breathless than others on light exertion and that she has slowed down recently. She has occasional short-lived palpitations without any history of dizziness or syncope.
NYHA class: I–II
Comments: Patients tend to underestimate their own symptoms, although occasionally parents may be unduly concerned about signs or symptoms. Objective assessment with exercise testing, for example, is often necessary and recommended as a real tool for assessing functional capacity and cardiac output.
PHYSICAL EXAMINATION
BP 110/62 mm Hg, HR 74 bpm, oxygen saturation at rest 99%
Height 172 cm, weight 56 kg, BSA 1.64 m 2
Surgical scars: Midline sternotomy
Neck veins: 1 cm above the sternal angle, with a normal waveform
Lungs/chest: Normal on examination
Heart: Regular sinus rhythm. There was a mild parasternal lift, normal first and second heart sounds, and a grade 3/6 ejection systolic heart murmur heard maximally at the second left intercostal space.
Abdomen: Normal
Extremities: Normal. No edema seen, and the skin was warm. There was no cyanosis or clubbing.
Comments: Examination in patients with arterial switch repair should focus on signs of PA stenosis and neoaortic valve stenosis or regurgitation. The murmur heard here is consistent with further stenosis of either outflow tract.
LABORATORY DATA
| Hemoglobin | 11.9 g/dL (11.5–15.0) |
| Hematocrit/PCV | 36% (36–46) |
| MCV | 83 fL (83–99) |
| Platelet count | 321 × 10 9 /L (150–400) |
| Sodium | 137 mmol/L (134–145) |
| Potassium | 3.6 mmol/L (3.5–5.2) |
| Creatinine | 0.6 mg/dL (0.6–1.2) |
| Blood urea nitrogen | 5 mmol/L (2.5–6.5) |
OTHER RELEVANT LAB RESULTS
| Albumin | 4.3 g/dL |
ELECTROCARDIOGRAM
FINDINGS
Heart rate: 79 bpm
QRS axis: +119°
QRS duration: 94 msec
Normal sinus rhythm, right-axis deviation, nonspecific ST segment changes in the inferior leads. Prominent R-wave in V1.
Comments: It is important to exclude signs of myocardial ischemia in a patient with prior arterial switch, as the coronary arteries and ostia were reimplanted. Right-axis deviation and the tall R in V1 are not unexpected. RV hypertrophy would suggest RVOT obstruction.
CHEST X-RAY
FINDINGS
Cardiothoracic ratio: 58%
The cardiac size is mildly enlarged. The cardiac apex is elevated suggesting RV overload, in keeping with the ECG. Sternal wires are noted. The lungs and pleural spaces are clear.
Comments: Patients with TGA have a narrow mediastinal shadowing due to the parallel anteroposterior relationship of the great arteries. Ordinarily, the cardiothoracic ratio is normal in D-TGA patients without ventricular dilatation, and pulmonary vascular markings should be normal in the absence of PAH.
EXERCISE TESTING
| Exercise protocol: | Bruce |
|---|---|
| Duration (min : sec): | 12 : 57 |
| Reason for stopping: | Dyspnea |
| ECG changes: | None |
| Rest | Peak | |
|---|---|---|
| Heart rate (bpm): | 74 | 203 |
| Percent of age-predicted max HR: | 99 | |
| O 2 saturation (%): | 99 | 98 |
| Blood pressure (mm Hg): | 110/62 | 140/50 |
| Peak V o 2 (mL/kg/min): | 36 | |
| Percent predicted (%): | 75 | |
| Ve/V co 2 : | 24 | |
| Metabolic equivalents: | 10.3 | |
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