Age: 28 years
Gender: Female
Occupation: Flight attendant
Working diagnosis: Transposition of the great arteries and Mustard procedure
HISTORY
The patient had transposition of the great arteries, and received a successful atrial switch (Mustard procedure) in early life. Recovery and follow-up were uneventful.
At age 16, the patient had her first episode of palpitations; atrial flutter was diagnosed, which self-terminated. Because of several recurrences, she was started on bisoprolol 5 mg once daily. Apart from occasional palpitations, she felt fine.
She married and wanted to start a family, and thus was referred to an ACHD clinic for prepregnancy advice. She was again in atrial flutter. Baseline imaging studies including a transthoracic echocardiogram, and cardiac MRI revealed patent pulmonary and systemic pathways and good systemic RV function, with no atrial thrombus. Sinus rhythm was restored by direct current cardioversion and maintained with sotalol 80 mg twice daily. She also performed well in cardiopulmonary exercise testing.
She became pregnant 6 months later, and the pregnancy was well tolerated. Warfarin was stopped when pregnancy was confirmed.
She had two episodes of` breakthrough atrial flutter with hemodynamic compromise requiring electrical cardioversion, both occurring during the third trimester. Amiodarone was added for the remainder of pregnancy to prevent arrhythmia recurrences. She delivered uneventfully at 38 weeks of gestation.
She had frequent palpitations and dizzy spells in the 6 months after delivery, and returned to the outpatient clinic.
A Holter recording showed paroxysmal sustained atrial flutter with, occasionally, a slow ventricular response of 33 to 50 bpm and sinus pauses (longest was 2.5 seconds). She received a dual-chamber pacemaker implantation for symptomatic bradycardia. She was restarted on amiodarone (in combination with bisoprolol), but this failed to prevent recurrence of symptomatic fast atrial flutter. She was at that point advised to have electrophysiological evaluation of the tachycardia and radiofrequency ablation.
Comments: The Mustard procedure redirects blood at the atrial level using a baffle. The systemic venous return is directed to the LV and the pulmonary venous blood is directed to the RV. The surgery achieves physiological correction, but the RV remains the systemic pumping chamber. The overall survival of patients with atrial switch is about 75% at 25 years.
Atrial arrhythmia occurs in 20% of patients by age of 20.
Successful pregnancies have been reported in patients with atrial switch procedures, that is, Mustard or Senning operations. Imaging studies may identify significant baffle obstruction or leakage that should be dealt with before conception (see Case 49 ). Furthermore, RV function may deteriorate during and after pregnancy, and there is reported maternal mortality, albeit the experience is relatively small.
Our patient should be a relatively low risk subject during pregnancy, as she has a normal functional class and good systemic RV function. She is, however, at high risk for atrial arrhythmia recurrence during pregnancy. Pharmacological or electrical strategy to restore/maintain sinus rhythm before conception may be advisable. Beta-blockers in this respect have a good safety profile for the mother and the fetus.
Warfarin or Coumadin need not always be stopped in a pregnant patient, although concerns about warfarin embryopathy certainly have been discussed. Furthermore, there is an underreported incidence of fetal cerebral bleeding with warfarin therapy, which may be of greater concern (see Case 14 for a more thorough discussion of the options).
If needed, DC cardioversion during pregnancy is a very low risk procedure.
CURRENT SYMPTOMS
The patient is asymptomatic apart from intermittent palpitations. She describes several distinct episodes of a rapid, regular pulse lasting several hours. However, she can climb two to three flights of stairs without difficulty, and actively participates in horseback riding and swimming.
NYHA class: I
PHYSICAL EXAMINATION
BP 110/70 mm Hg (right arm), HR 110 bpm, oxygen saturation 98% on room air
Height 160 cm, weight 55 kg, BSA 1.56 m 2
Surgical scars: Median sternotomy scar
Neck veins: JVP was visible 3 cm above the sternal angle, with no visible V-wave.
Lungs/chest: Chest was clear.
Heart: She had an irregular rhythm. A marked RV heave was noted. Her first heart sound was normal with a single and loud second heart sound. There was a grade 2/6 pan-systolic murmur best heard at the left lower sternal border compatible with tricuspid regurgitation.
Abdomen: Her abdomen was soft, and no organomegaly was detected.
Extremities: No peripheral edema
Comments: A resting heart rate above 100 bpm in a Mustard (or Senning) patient with previous atrial switch procedures or other surgery for ACHD should not be assumed to be sinus tachycardia (it is more likely to be atrial flutter or atrial reentry tachycardia).
The irregularity of the rapid pulse does not necessarily exclude atrial flutter.
The murmur of tricuspid regurgitation in a Mustard patient would not increase with inspiration since the tricuspid valve is in the systemic rather than the pulmonary circuit.
LABORATORY DATA
| Hemoglobin | 13.9 g/dL (11.5–15.0) |
| Hematocrit/PCV | 40% (36–46) |
| MCV | 91 fL (83–99) |
| Platelet count | 199 × 10 9 /L (150–400) |
| Sodium | 138 mmol/L (134–145) |
| Potassium | 3.9 mmol/L (3.5–5.2) |
| Creatinine | 0.6 mg/dL (0.6–1.2) |
| Blood urea nitrogen | 5.7 mmol/L (2.5–6.5) |
Comments: Blood laboratory results were normal.
ELECTROCARDIOGRAM
FINDINGS
Heart rate: 110 bpm
QRS axis: +145°
QRS duration: 93 msec
Atrial flutter, or intra-atrial reentry (see P-waves, best seen in lead V3), with variable ventricular response. RV pressure overload with RV strain.
Comments: RV hypertrophy and right-axis deviation are typical for patients with a Mustard or Senning procedure and a systemic RV.
Atrial arrhythmia in Mustard patients is usually due to intra-atrial reentry or atrial flutter. Atrial flutter is a common result of prior extensive atrial surgery and/or may reflect atrial dilatation and stretch due to systemic tricuspid regurgitation or ventricular decompensation. Mustard patients are also prone to sick sinus syndrome and junctional rhythm for the same reasons.
CHEST X-RAY
FINDINGS
Cardiothoracic ratio: 49%
Situs solitus, levocardia, left aortic arch with borderline cardiomegaly and normal pulmonary vascular markings.
Comments: The vascular pedicle is narrow with an oblong cardiac silhouette (“egg on string”), which is fairly typical for transposition of the great arteries.
EXERCISE TESTING
| Exercise protocol: | Modified Bruce |
|---|---|
| Duration (min:sec): | 11:35 |
| Reason for stopping: | Leg fatigue |
| ECG changes: | Junctional rhythm at baseline, sinus rhythm restored at exercise stage 2 |
| Rest | Peak | |
|---|---|---|
| Heart rate (bpm): | 45 | 139 |
| Percent of age-predicted max HR: | 72 | |
| O 2 saturation (%): | 98 | 98 |
| Blood pressure (mm Hg): | 110/70 | 170/80 |
| Peak V o 2 (mL/kg/min): | 26.7 | |
| Percent predicted (%): | 85 | |
| Ve/V co 2 : | 40 | |
| Metabolic equivalents: | 7.6 | |
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