Age: 31 years
Gender: Female
Occupation: Schoolteacher
Working diagnosis: Tricuspid atresia, Fontan repair
HISTORY
This patient with tricuspid atresia underwent a classic right BT shunt at 5 months of age. At 12 years of age, she underwent a modified Fontan procedure and division of her right BT shunt with an uncomplicated postoperative course. Her atriopulmonary Fontan operation consisted of anastomosis of the dome of the RA to the underside of the RA.
At 24 years of age, she developed atrial arrhythmias with ventricular rates reaching 200 to 220 bpm. Medical treatment for tachycardia included digoxin and beta-blockers. She had multiple episodes of tachycardia requiring direct current cardioversion.
The following year she had a left-sided cerebrovascular accident, with transient left hemiparesis. Cardiac catheterization showed a mean RA pressure of 14 mm Hg (A-wave 20, V-wave 16), pulmonary artery mean pressure of 14, and an LV pressure of 110/5 bpm; a wedge pressure could not be obtained. The RA was markedly dilated with sluggish flow, with a right-to-left shunt noted at the atrial level. Ventricular function was described as “good,” with mild atrioventricular valve regurgitation. Procainamide was initiated. She had exercise intolerance and depression at this time.
At 28 years of age she underwent the first of three catheter ablation procedures. At her first electrophysiology study, RA macroreentrant tachycardia of two different morphologies was easily inducible. Lengthy lines of ablation were delivered in the RA inferior isthmus region, between the SVC and the atriopulmonary anastomosis, and between the SVC and the ASD patch. Tachycardia recurred promptly after a rather long ablation procedure. Propafenone was initiated.
Her second ablation was attempted the following year, at 29 years of age, using a CARTO 3D mapping system. She was again noted to have intra-atrial reentry tachycardia with a cycle length of 315 msec. Ablation was performed at the lateral right atrial wall between the area of the crista terminalis and the previous surgical atriotomy scar, and within the coronary sinus. The procedure was considered acutely successful. Her antiarrhythmic medications other than digoxin were discontinued. Following the second ablation, she experienced daily frequent short bursts of tachycardia, at slower rates of 120 to 140 bpm, with dizziness after termination of episodes. She was noted to have marked sinus bradycardia with 3 to 4 second pauses after termination of tachycardia.
She had a second cerebrovascular accident with transient hemiparesis at 30 years of age. Exercise intolerance was progressive. She experienced abdominal fullness and swelling of her lower extremities, as well as brawny induration of both lower legs. She had frequent loose stools.
Her third catheter ablation was attempted, at 31 years of age. At this time, she had sustained intra-atrial tachycardia that was easily induced, with 1 : 1 AV conduction and an atrial cycle length of 350 msec. A high-energy radiofrequency generator was used and lesions were placed in regions near the tricuspid valve, without affecting the tachycardia. Three additional tachycardia circuits were identified, and after termination of sinoventricular tachycardia a >6-second asystolic pause occurred. Of note, despite multiple attempts, the coronary sinus could not be entered during this procedure. The patient was discharged on antiarrhythmic therapy and referred for arrhythmia surgery.
Comments: In older Fontan-type patients, tricuspid atresia is the most common underlying congenital heart defect. This surgical approach was later extended to patients with more complex lesions, including heterotaxy syndromes, and hypoplastic left heart syndrome.
The technique of doing a BT shunt has changed over time. The classic BT shunt involves an end-to-side anastomosis between a severed subclavian artery and the ipsilateral pulmonary artery. The current technique does not interrupt the subclavian artery. A Gore-Tex graft is placed between the subclavian and pulmonary arteries with end-to-side connections of each anastomosis. The pulse and blood pressure are absent or reduced in the classic BT shunt, and normal or reduced with the modern technique.
Initial palliation consisting of systemic pulmonary shunt at several months of age suggests the presence of pulmonary stenosis; patients with pulmonary atresia would undergo initial palliation during the first week of life. Patients with excessive pulmonary flow would have undergone pulmonary artery banding as the initial procedure.
Typically, sinoventricular tachycardia develops about 8 years after Fontan repair. Although the patient became symptomatic at age 24 years, continuous 24-hour electrocardiographic monitoring likely would have shown the development of sinus bradycardia, atrial ectopy, and nonsustained atrial tachycardia prior to the development of sustained tachycardia.
The development of a cerebrovascular accident suggests right atrial thrombus due to sluggish atrial flow, in addition to right-to-left atrial-level shunting.
Fontan patients typically do not complain of exercise intolerance until fatigue has progressed significantly; they usually have maintained a sedentary lifestyle. They may be able to walk on a flat surface for lengthy periods, but they are usually unable to run, or to go up a flight of stairs quickly, due to their inability to augment cardiac output abruptly.
The most common mechanism of sinoventricular tachycardia in Fontan patients is a macroreentrant atrial tachycardia in the RA. Atrial dilatation and prior surgical incisions/patches create the environment for conduction slowing and reentry. Focal atrial tachycardia, which may represent microreentrant circuits, may occur in up to 10% of patients.
In patients with lateral-tunnel-type Fontan repairs, or patients with double-inlet LVs with prior partitioning of the atria, the tachycardia circuit may be localized on the pulmonary venous side of the atrial partition, and thus not be easily accessible to an ablation catheter.
The acute success rates of ablation in patients with congenital heart disease are improved by the use of 3D mapping techniques, as well as noncontact mapping systems allowing mapping of single beats of atrial tachycardia. However, the short-term recurrence of tachycardia during the first 6 months is greater than 60%.
CURRENT SYMPTOMS
Daily palpitations, associated with faintness; weight loss (10 pounds over the last year); increasing exertional fatigue. Hypothyroidism had developed 8 years previously, and the patient was on replacement.
Our patient stopped working as a schoolteacher due to progressive fatigue. She took daily naps and had abdominal swelling and lower extremity edema if she had a busy day in the house.
She reported feeling depressed much of the time.
NYHA class: III–IV
Comments: Weight loss is common in patients with right heart failure due to a sensation of abdominal fullness and nausea after eating small amounts of food.
Change in work status/habits may be indicative of exercise intolerance. Daily naps are frequent; again, patients rarely volunteer the information about napping.
Depression is very common among adult Fontan patients with arrhythmias and exercise intolerance; at least half of patients report the use of antidepressant medications.
CURRENT MEDICATIONS
Digoxin 0.125 mg daily
Lasix 20 mg daily
Potassium chloride 80 mEq daily
Lisinopril 15 mg daily
Warfarin 4 mg daily
Aspirin 81 mg daily
Synthroid 150 µg daily
Comments: Anticoagulation is essential in Fontan patients with dilated atria and/or atrial arrhythmias, due to the increased risk of thrombus formation and strokes (see Case 61 ).
There is an increased incidence of thyroid disorders in Fontan patients, in addition to amiodarone-induced thyroid disease.
PHYSICAL EXAMINATION
Overall well-appearing adult female in no distress with thin arms
BP 110/70 mm Hg, HR 65 bpm, oxygen saturation 93%
Height 163 cm, weight 61 kg, BSA 1.66 m 2
Surgical scars: Midline sternotomy scars and right lateral thoracotomy scar
Neck veins: Jugular veins could not be seen.
Lungs/chest: Mild rhonchi over the right lower lobe
Heart: The LV impulse was increased, and a regular rhythm present with a single S1 and S2, with no gallop, and a grade 1/6 systolic murmur was audible at the apex.
Abdomen: The abdomen was protuberant, with the liver 3 cm below the right costal margin. No venous distension over the abdomen.
Extremities: There was digital erythema with mild clubbing. Mild dark brownish discoloration of lower extremities was seen. There was trace edema.
PERTINENT NEGATIVES
There was no goiter, ascites, or scoliosis.
Comments: Muscle wasting in the upper extremities is common in Fontan patients with advanced congestive failure.
Mild desaturation at rest is common in Fontan patients due to right-to-left shunting at the atrial level and/or intrapulmonary shunting.
Cardiomegaly may result in decreased aeration of the right lower lobe.
Single first and second heart sounds reflect AV valve atresia and single ventricular outflow (since pulmonary outflow is obliterated when a Fontan procedure is performed).
Mitral regurgitation is progressive with ventricular dilatation, and frequently abnormal mitral valve morphology is present. Hepatomegaly is often difficult to appreciate due to the degree of hepatic enlargement and general abdominal fullness.
Chronic desaturation results in clubbing; dependent edema and sluggish venous return produce plethora of the extremities. In patients with a “failed Fontan,” chronic venous stasis changes of the lower extremities are more common than edema.
Ascites is an advanced finding, often associated with PLE.
Scoliosis is common in patients with repeated thoracotomies and contributes to restrictive lung disease.
LABORATORY DATA
| Hemoglobin | 15.8 g/dL (11.5–15.0) |
| Hematocrit/PCV | 46.5% (36–46) |
| MCV | 89.7 fL (83–99) |
| Platelet count | 170 × 10 9 /L (150–400) |
| Sodium | 139 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 | 10 mmol/L (2.5–6.5) |
OTHER RELEVANT LAB RESULTS
| Magnesium | 1.6 mg/dL (1.8–2.4) |
| Phosphorus | 3.3 mg/dL (3.0–4.5) |
| Calcium | 9.8 mg/dL (8.8–10.8) |
| Free T4 | 1.6 ng/dL (0.89–1.76) |
| TSH | 1.76 mU/L (0.35–5.10) |
| Total protein | 8.1 g/dL (6.0–8.0) |
| Albumin | 4.5 g/dL (3.1–4.6) |
| AST | 31 IU/L (16–52) |
| ALT | 28 IU/L (2–30) |
| Alk Phos | 142 IU/L (55–274) |
| Total bilirubin | 2.2 mg/dL (0.2–1.0) |
| Direct bilirubin | 0.4 mg/dL (<0.3) |
Comments: Mild erythrocytosis is not uncommon in Fontan patients. Erythropoiesis is stimulated by the low cardiac output and typical mild desaturation.
ELECTROCARDIOGRAM
