Age: 27 years
Gender: Female
Working diagnosis: Down syndrome
HISTORY
The patient has Down syndrome and was suspected to have cardiac disease shortly after birth. Echocardiography, however, showed only a subaortic membrane with a peak gradient of 43 mm Hg across the LVOT. The atrial and ventricular septa were intact, and no other lesions were seen.
She was assessed again at the age of 18. She had a good exercise capacity (498 m walked in 6 minutes) without significant desaturation during exercise. Echocardiography showed an unchanged gradient across the LVOT, as well as normal LV and RV dimensions and function. The patient was subsequently lost to follow-up.
A blood count arranged by her local general practitioner 1 year before presentation showed an elevated hematocrit and hemoglobin. There was a normal white cell and platelet count. She was seen by a hematologist, who found no other abnormality.
She began to experience increasing dyspnea on exertion and was referred for further workup.
Comments: Down syndrome, or trisomy of chromosome 21, is present in approximately 0.7 out of 1000 live births and accounts for 95% of all syndromic congenital malformations. The various types of congenital heart defects seen include ventricular septal defect, PDA, atrioventricular septal defect, and atrial septal defect.
The hematologic finding of increased hemoglobin/hematocrit with a normal white cell and platelet count is consistent with erythrocytosis, rather than polycythemia (in which all cell lines are increased). This finding therefore should alert the physician to look for evidence of hypoxemia due to a right-to-left shunt.
CURRENT SYMPTOMS
The patient notes dyspnea after walking 200 m on level ground and becomes breathless when climbing stairs. The patient denies chest pain, palpitations, or syncope. She sleeps well and does not snore.
NYHA class: III
Comments: Snoring may be important, since sleep apnea, common in patients with Down syndrome, can contribute to PAH, heart failure, and stroke risk.
PHYSICAL EXAMINATION
BP 110/60, HR 86 bpm, oxygen saturation 96% on room air (right hand) and 83% in left foot
Height 152 cm, weight 87 kg, BSA 1.92 m 2
Surgical scars: None
Neck veins: JVP was not elevated, and there was a normal waveform.
Lungs/chest: Clear
Heart: An RV impulse was palpable. There was variable splitting of the second heart sound with a loud pulmonary component. There was a grade 3 systolic ejection murmur loudest at the upper right sternal edge.
Abdomen: No hepatomegaly
Extremities: Peripheral pulses were all easily palpable. Clubbing was seen in the toes, but not the fingers.
Comments: In any patient such as this it is imperative to look for evidence of differential cyanosis. Lower body cyanosis was present in this patient. If the oximetry data and physical findings are correct, the diagnosis must be a pulmonary hypertensive PDA.
A loud second heart sound is a cardinal clinical sign in patients with pulmonary hypertension.
In this patient the systolic murmur was best heard in the aortic area and it is most likely related to the subaortic ridge described in previous echocardiograms.
LABORATORY DATA
| Hemoglobin | 20.2 g/dL (11.5–15.0) |
| Hematocrit | 58% (36–46) |
| MCV | 104 fL (83–99) |
| MCH | 36 pg (27–32.5) |
| Platelets | 157 × 10 9 /L (150–400) |
| WBC | 6.7 × 10 9 /L (3.5–10.8) |
| Sodium | 138 mmol/L (134–145) |
| Potassium | 4.2 mmol/L (3.5–5.2) |
| Creatinine | 0.9 mg/dL (0.6–1.2) |
| Blood urea nitrogen | 4.4 mmol/L (2.5–6.5) |
| Iron | 21 µg/L (12.6–26.0) |
| Ferritin | 37 ng/mL (20–186) |
| TIBC | 73 µmol/L (50–80) |
| Transferrin saturation | 29% (20–45) |
| Vitamin B 12 | 449 ng/L (180–914) |
| Folate | >20 (>20) |
Comments: The elevated hemoglobin concentration in this patient represents secondary erythrocytosis. Secondary erythrocytosis is seen in chronically cyanotic patients. The term secondary erythrocytosis refers to an isolated increase in red blood cells (as opposed to polycythemia, in which all cell lines proliferate) and is a physiologic adaptation to chronic hypoxemia.
The oxygen saturation on room air is 96% in the upper extremity and does not explain a hemoglobin value as high as 20 g/dL. However, there is clinical evidence of lower body cyanosis. Therefore, low renal saturations may account for elevated erythropoietin levels leading to her raised hemoglobin.
There is no evidence of iron, vitamin B 12 , or folate deficiency in this patient. Macrocytosis is common in patients with Down syndrome and is not necessarily related to other deficiencies.
ELECTROCARDIOGRAM
FINDINGS
Heart rate: 84 bpm
PR int: 170 msec
QRS axis: +160°
QRS duration: 99 msec
Sinus rhythm. Marked right axis deviation. RV hypertrophy with strain pattern in V1–4.
Some peaking of P-waves in I and II
Comments: There is voltage evidence of RV hypertrophy (R/S V 1 > 1; R V 1 > 7 mm, R/S V 6 < 1). There is also right axis deviation and T-wave inversion anteroseptally, consistent with RV “strain.”
CHEST X-RAY
FINDINGS
Cardiothoracic ratio: 54%
Mild cardiomegaly, predominantly due to enlargement of the RA. Mildly prominent central pulmonary arteries.
Comments: From what is known so far in this case, the provider should look for evidence of pulmonary hypertension. Abnormal findings in patients with PAH usually include prominent central pulmonary arteries and attenuation of peripheral vascular markings (pruning). Signs of RA and RV enlargement may also be present. Calcification of the PDA should also be sought.
EXERCISE TESTING
Sinus rhythm throughout
| Exercise protocol: | Modified Bruce |
|---|---|
| Duration (min:sec): | 5 : 48 |
| Reason for stopping: | Dyspnea |
| ECG changes: | None |
| Rest | Peak | |
|---|---|---|
| Heart rate (bpm): | 86 | 164 |
| Percent of age-predicted max HR: | 85 | |
| O 2 saturation (%): | 96 (83 in foot) | 92 (36 in foot) |
| Blood pressure (mm Hg): | 110/60 | 150/80 |
| Double product: | 24,600 | |
| Peak V o 2 (mL/kg/min): | 11.3 | |
| Percent predicted (%): | 58 | |
| Ve/V co 2 : | 60 | |
| Metabolic equivalents: | 4.5 | |
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