Age: 30 years
Gender: Female
Occupation: Student
Working diagnosis: Congenitally corrected transposition of the great arteries
HISTORY
At age 11, transposition was diagnosed after evaluation of a murmur. The patient was also found to have a VSD and pulmonary stenosis. No intervention was offered.
When the patient was 22 years old, she had an episode of lightheadedness and was found to have second-degree AV block. An epicardial pacemaker was implanted, and 2 years later, it was changed to a transvenous dual-chamber system.
The patient returned for routine follow-up. She reported completing her education, announcing plans for marrying soon, and was making future plans, including possibly starting a family. She wondered whether anything should be done for her to improve her long-term prospects.
Comments: CCTGA is an uncommon form of congenital heart disease first described by von Rokitansky in 1875.
It accounts for less than 1% of all forms of congenital heart disease and is characterized by AV and ventriculoarterial discordance. There are two forms of CCTGA, depending on whether situs is normal (situs solitus, L-loop, L-transposition [S, L, L]) or inverted (situs inversus, D-loop, D-transposition [I, D, D]).
Associated abnormalities occur frequently and include VSD (usually a large, nonrestrictive conoventricular defect), LVOT obstruction (valvar and subvalvar pulmonary stenosis), AV conduction abnormalities, and an Ebstein-like left AV valve. Therefore, the need for a pacemaker in this patient is somewhat typical.
While these differ from the figures in infants, the relative frequency of associated lesions in adulthood from one study are given below:
Any associated lesion: 50%
VSD: 20%
ASD: 23%
LVOT obstruction: 32%
Ebstein-like systemic AV valve (tricuspid): 27%
3–4+ systemic AV valve (tricuspid) regurgitation: 59%
Dextrocardia: 16%
High-grade AV block: 32%
Permanent pacemaker: 14%
3–4+ pulmonary AV valve (mitral) regurgitation: 7%
3–4+ aortic valve regurgitation: 7%
Transvenous pacing in a patient with an intracardioc shunt carries a risk of systemic thromboembolism (see Case 48 ).
CURRENT SYMPTOMS
Generally the patient reported no symptoms. Occasionally, with severe emotional stress, she became acutely dyspneic and blue, although the symptoms usually settled spontaneously within minutes. Her reported exercise capacity was unlimited on flat ground, and she could climb two flights of stairs without stopping. She had no sustained palpitations.
NYHA class: II
CURRENT MEDICATIONS
Warfarin 6.25 mg per day (target INR 2–3)
Perindopril 2 mg once daily
Comments: The patient was put on warfarin because of her transvenous pacing leads (potentially with thrombus formation) in the setting of some right-to-left shunting to reduce the prospect of a paradoxic embolus.
There are few clinical data on the use of ACE inhibitors in patients with a systemic RV. Thus, their use is not evidence-based and not routinely recommended.
PHYSICAL EXAMINATION
BP 95/60 mm Hg, HR 80 bpm, oxygen saturation 95% on room air
Height 161 cm, weight 54 kg, BSA 1.55 m 2
Surgical scars: Present from pacemaker implantations
Neck veins: JVP was not elevated, and waveform was normal.
Lungs/chest: Clear
Heart: The heart rate was regular. There was a left parasternal lift with no apical displacement. There was a palpable thrill in the pulmonary area, a normal first heart sound, and a single second heart sound. A grade 4/6 quite-late-peaking ejection systolic murmur was maximal at the upper left sternal edge. There was no diastolic murmur.
Abdomen: No signs of hepatomegaly
Extremities: Good peripheral pulses, no cyanosis or clubbing, no edema
Comments: The patient is not cyanotic at rest, despite the diagnosis of a large VSD. The loud ejection systolic murmur at the upper left sternal edge indicates pulmonary stenosis at one or more levels, which limits excessive pulmonary blood flow and raises the systolic pressure in the pulmonary ventricle. The minimal desaturation fits with a nicely balanced pulmonary stenosis and VSD or a small VSD in the setting of pulmonary stenosis.
LABORATORY DATA
| Hemoglobin | 14.0 g/dL (11.5–15.0) |
| Hematocrit/PCV | 40% (36–46) |
| MCV | 94 fL (83–99) |
| Platelet count | 262 × 10 9 /L (150–400) |
| Sodium | 144 mmol/L (134–145) |
| Potassium | 3.9 mmol/L (3.5–5.2) |
| Creatinine | 0.9 mmol/dL (0.6–1.2) |
| Blood urea nitrogen | 3.1 mmol/L (2.5–6.5) |
Comments: No abnormalities were seen. The patient has a normal hemoglobin, which argues that her oxygen saturation stays in a fairly normal range with her usual activities.
ELECTROCARDIOGRAM
FINDINGS
Sinus rhythm at 100 bpm. Atrial sensing, ventricular pacing with an LBBB pattern, suggesting RV pacing.
Comments: Heart block is common in CCTGA, and this patient has a functioning sinus node. One P-wave seems not to be sensed, and the pacemaker escapes before resuming atrial tracking.
CHEST X-RAY
FINDINGS
Cardiothoracic ratio: 30%
There is a narrow cardiac silhouette in the center of the chest, with likely mesocardia. A dual-chamber pacemaker is present with leads in the RA and LV (pulmonary ventricle). A third epicardial lead from the former epicardial pacing system is also present. Some excessive vascularity is suggested in the right lower lung field, which may reflect bronchiectasis.
Comments: There are no signs of pulmonary vascular congestion or pulmonary hypertension despite the presence of a large VSD (see Fig. 60-3 ), which emphasizes the balanced nature of the patient’s lesions. Pulmonary stenosis (valvular or subvalvular) is preventing excessive pulmonary blood flow and subsequent pulmonary arterial hypertension. Bronchiectasis may be present from abnormal ciliary motility (Kartagener’s syndrome), which can accompany various forms of ACHD, including CCTGA and dextrocardia.
Though somewhat semantic in this case, the position of the ventricular apex determines dextro- versus levocardia. Here, the position is somewhat ambiguous. The left hemidiaphragm is lower than the right, which argues in favor of levocardia. However, the position of the LV pacing wire seems to favor dextrocardia. The term mesocardia is often employed in such cases.
EXERCISE TESTING
| Exercise protocol: | Bruce |
|---|---|
| Duration (min:sec): | 11:10 |
| Reason for stopping: | Fatigue |
| ECG changes: | None |
| Rest | Peak | |
|---|---|---|
| Heart rate (bpm): | 80 | 105 |
| Percent of age-predicted max HR: | 55 | |
| O 2 saturation (%): | 95 | 94 |
| Blood pressure (mm Hg): | 110/70 | 150/80 |
Comments: Reasons for reduced exercise capacity may include abnormal chronotropic response, ventricular dysfunction, poor lung function, poor effort, poor fitness, or other factors. There is a rate response program in the pacemaker, which should allow the exercise rate to rise further. One cannot be certain that the patient’s effort was maximal. The ECGs should be examined.
A notable finding here is that the oxygen saturation did not fall significantly with exercise. Despite having a VSD, the patient maintains very reasonable pulmonary blood flow relative to systemic blood flow, and shunting is minimized. This is enabled by the pulmonary stenosis, which in this patient’s case is severe enough to limit excessive left-to-right shunt at rest and protect against pulmonary vascular disease, but not so severe as to limit pulmonary blood flow at the expense of more right-to-left shunting, even during exercise. As above, it is difficult to say whether the patient’s effort was maximal, and whether further desaturation would have occurred with more vigorous exercise.
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