Age: 26 years
Gender: Female
Occupation: Laboratory technician
Working diagnosis: Pulmonary atresia with ventricular septal defect
HISTORY
The patient was born with a diagnosis of pulmonary atresia, large subaortic VSD, overriding aorta, large aortopulmonary collateral arteries, and distal right pulmonary artery stenosis. A modified left BT shunt was performed at the age of 3 to increase her pulmonary blood flow.
Two years later she was found to have intermittent complete heart block with a junctional escape rhythm at a rate of 60 bpm. However, she remained asymptomatic and was followed. She had no clinical problems. For various reasons she was not felt suitable for more definitive repair of her congenital heart lesion.
By the age of 22 years, the patient had gradually developed fatigue, exertional dyspnea, and a low working capacity. A 24-hour ECG recording at the time showed a complete heart block, with atrial rates up to 115 bpm and a narrow complex escape rhythm with a rate of 30 to 45 bpm.
Four years later at age 26 the patient participated in an exercise study as part of her clinical follow-up. Her heart rate response was blunted, the exercise capacity was only 36% of predicted, and she desaturated to 47% at peak exercise. A DDD pacemaker was implanted with epicardial leads placed via a subxiphisternal incision and tunneled to an abdominal pocket. A 5-day course of antibiotics was given. The wire thresholds were low (1.4 and 1.3 volts, respectively).
Five days later ventricular capture was not obtained even at maximal output. At the removal of the system, the ventricular lead seemed not to be properly secured. A new ventricular lead was tunneled to the site of the old pacing box. Appropriate doses of flucloxacillin and amoxicillin were given pre- and postoperatively.
Shortly thereafter, pacing thresholds had greatly increased. After 3 weeks the pacemaker did not work. Blood and pus from the abdominal scar appeared, and the patient was admitted to the hospital.
Comments: Patients with pulmonary atresia and VSD usually have a normal sinus node. The AV node occupies its normal position, and the bundle of His is closely related to the posterior rim of the membranous defect. Complete heart block is therefore not a common complication, particularly in patients who have not had intracardiac repair. The etiology of the heart block in this patient is, therefore, unknown. A pacemaker would not necessarily be required in the absence of symptoms.
Epicardial pacing is often preferred in children and adolescents with complex congenital defects and limited vascular access. Yet, compared to endocardial pacing, epicardial leads have traditionally had higher thresholds and thus shorter longevity. In the presence of an intracardiac (especially right-to-left) shunt, as in this patient, there is also the potential for systemic thromboembolism (see Case 64 ). The risk may be small but has been consistently reported in recent studies even among patients with simple septal defects. Another rationale for using epicardial leads in this patient population is to preserve venous access for later use, as patients with early onset of block require lifelong pacing.
Pacemaker revisions are identified as predictors of infection. Patients undergoing pacemaker replacements are 2.5 times more likely to have a pacemaker infection compared to those undergoing a primary implantation.
In our case, placement of another epicardial pacing system would seem unlikely to be successful. Previous surgical procedures combined with healed infection will create some degree of damage to the epicardial wall, resulting in more fibrosis, scarring, and adhesions, which all carry the risk of higher ventricular thresholds and early battery depletion.
CURRENT SYMPTOMS
The patient currently complains of mild shortness of breath with exertion and loss of energy and appetite. She has had intermittent fevers and shivers for the past 5 days. She has not experienced palpitations or syncope, and does not have a cough.
NYHA class: II
Comments: Fever and shivers in a patient with a permanent pacemaker should alert the physician to the possibility of pacemaker infection.
PHYSICAL EXAMINATION
BP 89/56 mm Hg, HR 55 bpm, oxygen saturation 69%, temperature 36.5° C
Height 169 cm, weight 33 kg, BSA 1.24 m 2
Surgical scars: There was an old left thoracotomy scar and a transverse abdominal incision. From the left end of the abdominal incision there was some discharge noted.
Neck veins: Mildly elevated with visible cannon waves
Lungs/chest: Chest was clear to auscultation. A continuous murmur from the aortopulmonary collateral(s) was best heard on the dorsal aspect of the chest.
Heart: There was an RV lift with a normal first heart sound, a loud single second heart sound, and a 2/6 ejection murmur at the upper right sternal edge with no diastolic murmur.
Abdomen: Tenderness around the pulse generator pocket was evident and again some discharge was noted. The liver was not enlarged.
Extremities: There was no peripheral edema. Digital clubbing was seen in both hands and feet.
Comments: The patient is very small for a mature adult, which is not uncommon in patients with severe cyanosis. The very low oxygen saturations here imply inadequate overall pulmonary blood flow from her collaterals and the BT shunt.
Signs at the pacemaker pocket site on admission suggested infection. Local symptoms at the site of pacemaker implantation often mirror an infective process involving the entire pacing system even though the infection seems to be local.
LABORATORY DATA
| Hemoglobin | 15.8 g/dL (11.5–15.0) |
| Hematocrit/PCV | 49% (36–46) |
| WBC | 12.8 × 10 9 /L (3.5–10.8) |
| Neutrophils | 83% |
| MCV | 97 fL (83–99) |
| Platelet count | 279 × 10 9 /L (150–400) |
| Sodium | 135 mmol/L (134–145) |
| Potassium | 3.9 mmol/L (3.5–5.2) |
| Creatinine | 72 mg/dL (60–120) |
| Blood urea nitrogen | 5.5 mmol/L (2.5–6.5) |
OTHER RELEVANT LAB RESULTS
| CRP | 90 g/L (0–10) |
| Albumin | 31 g/L (37–53) |
| Total protein | 61 g/L (62–82) |
| Total bilirubin | 32 µmol/L (3–24) |
| INR | 1.7 |
PERTINENT NEGATIVES
Wound swab cultures were negative.
Swabs from epicardial pacing box were negative.
Blood cultures were negative.
Comments: The patient was relatively anemic despite her raised hemoglobin. With an oxygen saturation of 69% one would have expected the hemoglobin to be over 20 g/dL. Explanations for the low hemoglobin need to be sought, but may be related to infection. The MCV is high, though this does not necessarily exclude iron deficiency.
The abnormal liver function test may reflect the abnormal hemodynamics of this patient, but may also relate to her nutrition and chronic ill health.
When a lead is infected, the whole length of the lead is usually involved. The absence of positive cultures does not exclude active infection.
ELECTROCARDIOGRAM
FINDINGS
Heart rate: 55 bpm
QRS axis: +100°
QRS duration: 108 msec
Complete AV block with a junctional escape rhythm. There is RA overload and nonspecific repolarization abnormalities.
Comments: The atrial rate is about 75 bpm. Although the ventricular rate is currently acceptable, it can contribute to exertional intolerance and poses a risk of syncope. Pacemaker therapy is recommended even for symptom-free adults, and would seem all the more appropriate in someone with ACHD.
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