Age: 29 years
Gender: Male
Occupation: Chef
Working diagnosis: Congenitally corrected transposition of the great arteries
HISTORY
A childhood murmur brought the patient to attention at a young age, and echocardiograms showed congenitally corrected TGA. At age 9, cardiac catheterization had documented his CCTGA, secundum ASD (shunt ratio of 1.5 : 1), mild subvalvular pulmonary stenosis with moderate pulmonary regurgitation, and a very dilated main pulmonary artery (PA).
Investigation of exertional dyspnea at age 16 revealed AV conduction abnormalities and resulted in placement of an endocardial DDD pacemaker.
At age 19, he was admitted with congestive heart failure (CHF) and was found to have severe impairment of the systemic RV. There was still only a small gradient across the pulmonary valve. He was started on captopril and improved clinically. Warfarin was also started.
Three years later, at age 22, he was admitted with worsening dyspnea and fatigue. There was further worsening of his systemic RV function. He had several episodes of atrial fibrillation and was started on amiodarone. Cardiac catheterization revealed a large increase in his ASD shunt with ratio of 3.5 : 1. He was referred for consideration of heart transplantation. He responded to intensification of his ongoing medical therapy, and it was decided to not yet pursue transplantation.
Over the subsequent 6 years, he had gradual worsening of dyspnea and fatigue with increasing abdominal girth and discomfort, despite escalation of his medical therapy. At age 29, he was referred to the ACHD clinic for consideration of other interventions, notably closure of the ASD and/or possible use of cardiac resynchronization therapy (CRT).
Comments: CCTGA is an uncommon defect accounting for only about 0.5% of all congenital heart disease. It is defined by AV discordance and ventriculoarterial discordance, so that the pulmonary and systemic circuits are correctly in series but the morphologic RV becomes the systemic ventricle and the LV is in the subpulmonary position. Although extracardiac anomalies are infrequent, associated cardiac anomalies are very common, as exemplified by this patient’s anatomy. The most common defects include VSD (60%–80%) and pulmonary outflow tract obstruction (30%–50%). Systemic tricuspid valve dysplasia, including Ebstein anomaly, is frequently noted at autopsy. These intrinsic tricuspid valve anomalies, in conjunction with systemic RV dysfunction, are responsible for the tricuspid regurgitation incidence of up to 80% in CCTGA. Despite being called “congenitally corrected” TGA, it must be recognized for its common late complications and need for regular follow-up.
ASDs are uncommonly seen and will overload the pulmonary ventricle rather than the systemic ventricle. Although an ASD will result in right-sided volume overload with dilatation of the atria and the subpulmonary ventricle, the size of the shunt in this case would not have been expected, in the presence of subpulmonary stenosis, to give rise to significant chamber enlargement and certainly not to the marked dilatation of the PA.
In CCTGA, the AV node is positioned more anteriorly in the RA (near the junction of the right AV valve and the pulmonary valve), and the bundle of His follows a long course anteriorly across the infundibular septum to reach the bundle branches. This results in a high rate of complete heart block (about 2% per year), especially in patients who have had VSD or tricuspid valve surgery.
The presence of an endocardial pacemaker has been shown to be a significant risk factor for thromboembolism, which may cause arterial embolization in the setting of an intracardiac shunt. A recent long-term follow-up study reported more thromboembolic complications associated with endocardial leads versus epicardial leads in patients with an intracardiac shunt. Although there are no published studies regarding the routine use of anticoagulants in such individuals, the use of warfarin seems prudent, but in this particular study, warfarin was not protective. Other recent studies have not reached similar conclusions about endocardial leads in Fontan patients (see Case 64 ). Alternatively, epicardial leads have a higher failure rate than endocardial leads, and hence a balance of risk must be considered in each patient.
ACE inhibitors are frequently used for medical therapy for systemic RV failure, although there are not yet good data for their elective, prophylactic application in this setting.
The increase in the size of the left-to-right shunt across the ASD is not surprising in the face of worsening systemic ventricular function with rising LA pressures and consequently higher driving forces across the atrial septum from left to right.
CURRENT MEDICATIONS
Warfarin as directed
Amiodarone 100 mg daily
Bisoprolol 2.5 mg daily
Digoxin 125 μg daily
Lisinopril 20 mg daily
Furosemide 160 mg daily
Amiloride 5 mg daily
Metolazone 2.5 mg daily
Spironolactone 25 mg daily but only three times a week
Slow K 2 tabs three times daily
Comments: Warfarin is indicated for the prevention of thromboembolism in the presence of atrial fibrillation. The amiodarone is being used to keep the patient out of atrial fibrillation, since patients with CCTGA tend to tolerate atrial arrhythmias poorly.
Spironolactone can be symptomatically beneficial in patients with elevated venous pressure and hepatic congestion. Caution against hyperkalemia is especially important in patients with compromised renal function. This patient has developed gynecomastia and therefore is taking the spironolactone only three times a week.
PHYSICAL EXAMINATION
BP 90/60 mm Hg, HR 76 bpm, oxygen saturation 97%
Height 176 cm, weight 69 kg, BSA 1.84 m 2
Surgical scars: None
Neck veins: 5 cm above the sternal angle
Lungs/chest: No deformity of the chest wall; the chest was clear.
Heart: Heart rate was 76 bpm and regular. The first heart sound was normal with fixed splitting of the second heart sound. There was a pan-systolic murmur along both sternal borders followed by a low-pitched diastolic murmur. Carotid upstroke was normal with normal peripheral pulses.
Abdomen: The abdomen was soft with normal bowel sounds. There was epigastric tenderness, and the liver edge was palpable 2 cm below the costal margin and was slightly tender.
Extremities: There was no peripheral edema. No clubbing was seen.
Comments: One expects to hear fixed splitting of S2 in the presence of a large ASD because of delayed pulmonary valve closure throughout the respiratory cycle. However, the pacemaker in the pulmonary ventricle would be expected to cause delayed aortic valve closure, thereby narrowing the S2 split. The pan-systolic murmur is likely due to the systemic tricuspid valve regurgitation. Its unusual location is probably due to the unusual position of the heart itself, as is obvious in the CXR and CT scans. The diastolic murmur may be secondary to pulmonary regurgitation or represent an inflow rumble associated with the ASD.
LABORATORY DATA
| Hemoglobin | 11.8 g/dL (13.0–17.0) |
| Hematocrit/PCV | 34% (41–51) |
| MCV | 92 fL (83–99) |
| Platelet count | 191 × 10 9 /L (150–400) |
| Sodium | 133 mmol/L (134–145) |
| Potassium | 4.0 mmol/L (3.5–5.2) |
| Creatinine | 2.8 mg/dL (0.6–1.2) |
| Blood urea nitrogen | 51 mg/dL (7–18.2) |
| INR | 3 |
Comments: The cause of the anemia may not be directly linked to the congenital cardiac defect. There is no evidence of intravascular hemolysis, and the indices do not support the diagnosis of iron deficiency. The anemia may be associated with chronic Coumadin use, although one would expect iron deficiency if that were true. Alternately, anemia is nearly always present in patients with subacute infective endocarditis, and endocarditis must always be considered in any congenital heart patient presenting with anemia and nonspecific systemic symptoms. A thorough assessment of his anemia will be necessary.
Renal dysfunction is likely due to overtreatment of his CHF against a background of chronically low cardiac output. This is commonly seen in patients with systemic LV failure therapy. He is on four diuretics and lisinopril.
Special attention needs to be paid to his digoxin dose. It should be determined whether there is sufficient benefit from the digoxin to continue its use in the face of renal insufficiency.
ELECTROCARDIOGRAM
FINDINGS
Heart rate: 72 bpm
QRS axis: −30°
QRS duration: 200 msec
This shows a paced atrial and ventricular rhythm with a very wide QRS complex. The P-waves are very prolonged and notched, suggesting LA overload. We are also reminded that amiodarone tends to prolong cardiac electrical activity.
Comments: This very wide QRS complex indicates delays in depolarization that can form the basis for discoordinate ventricular contraction. In patients with morphologic RV pacing, such pacing-induced electromechanical dissynchrony has been associated with a higher incidence of LV dysfunction. In a similar fashion, pacing of the subpulmonary LV may contribute to systemic RV desynchronization and consequent RV dysfunction.
The common ECG features of CCTGA are not present in this case because of the paced rhythm. Commonly one sees a QS or QR pattern in V1, with absence of Q-waves in V5 and V6. This is because the septal depolarization occurs from right to left due to the ventricular inversion. There may be enlarged P-waves as a result of atrial dilatation linked to systemic AV valve regurgitation. First-degree AV block may be present in up to 50% and complete heart block may occur in up to 50% of patients with CCTGA. Delta waves may be present, since Wolff-Parkinson-White syndrome is found in 2% to 4% of patients.
CHEST X-RAY
FINDINGS
Cardiothoracic ratio: 70%
Marked enlargement of the cardiac silhouette with a very prominent right heart border and PA enlargement. The atrial pacing lead was in the RA and the ventricular lead was sitting in the apex of the morphologic LV that was to the right of the midline. There was some pulmonary plethora noted but no evidence of pulmonary edema.
Comments: In CCTGA, the prominent upper left heart border is due to the side-by-side configuration of the ascending aorta and the PA. This is evident on the coronal slice of the CT scan (see Fig. 56-5 ). In this case, the upper left border is further accentuated by the enlarged PA, and the prominent right heart border is actually due to the enlarged subpulmonary LV that sits to the right of the midline.
EXERCISE TESTING
| Exercise protocol: | Modified Bruce |
|---|---|
| Duration (min:sec): | 4:22 |
| Reason for stopping: | Fatigue and dyspnea |
| ECG changes: | Paced |
| Rest | Peak | |
|---|---|---|
| Heart rate (bpm): | 76 | 103 |
| Percent of age-predicted max HR: | 54% | |
| O 2 saturation (%): | 95 | 98 |
| Blood pressure (mm Hg): | 90/60 | 106/80 |
| Peak V o 2 (mL/kg/min): | 10.6 | |
| Percent predicted (%): | 26 | |
| Ve/V co 2 : | 51 | |
| Metabolic equivalents: | 3.1 | |
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