Pacemaker-associated cyanosis in an adolescent: The answer hiding behind shadows
A 13 year-old female with congenital complete atrioventricular (AV) block presented to cardiology clinic with progressive exertional fatigue. She had a permanent dual-chamber transvenous PM that was implanted at 5 years of age, and the generator wasreplaced 5 years later. On TTE there was mild tricuspid valve inflow obstruction deep in the RA at the level of the atrial lead with mean Doppler gradient of 3.9 mmHg. The tricuspid valve appeared normal and there was no valvular stenosis or regurgitation. There was no atrial shunt detected. The estimated RV systolic pressure was 20.4 mmHg above RA pressure. A cardiopulmonary stress test demonstrated decreased exercise capacity with 94% oxygen saturation at rest, decreasing to 77% with exercise, but was otherwise unremarkable. Chest CT with contrasts did not reveal evidence of pulmonary arterio-venous malformations or thromboemoblism. The chest CT was confounded by a significant amount of metal artifact caused by the transvenous pacing leads. A stress echocardiogram was performed to further assess the hypoxemia with exercise. No evidence of pulmonary hypertension during exercise was noted, but there was a right-to-left shunt through a small intra-atrial communication that only became evident at peak exercise. Acoustic shadowing from the pacing leads again obscured any detailed assessment of the tricuspid inflow obstruction.\nDuring the next few months she experienced an interval worsening of fatigue at rest as well as dizziness and headaches. She was scheduled for cardiac catheterization to measure right heart and pulmonary artery (PA) hemodynamics and to determine candidacy for PFO closure. At the onset of the study angiography was performed and a large calcified mass at the superior vena cava-right atrium (SVC-RA) junction created a filling defect ().\nPA pressures were normal. There were no filling defects in the pulmonary segments. A transesophageal echocardiogram (TEE) confirmed two atrial thrombi; one at the SVC-RA junction associated with the pacing leads, measuring 1. 9 × 0. 6 cm, and the other at the inferior atrial septum, measuring 1. 7 × 0. 8 cm ().\nThe mean gradient across the SVC-RA junction was 3 mmHg. Closure of the PFO was delayed and the patient was started on enoxaparin. A hypercoagulability work-up was negative.\nThe case was discussed at cardiac surgery conference and one week later she went to the operating room for a right atrial thrombectomy, primary closure of the PFO, and conversion to an epicardial pacing system. Intraoperative inspection within the RA showed the atrial and ventricular pacing leads surrounded by a calcified thrombus measuring 3 × 2 cm (). Complete surgical extraction was performed along with successful placement of the epicardial pacing system. The patient's hospital course was complicated by a mild left-sided pleural effusion which resolved on diuretics. On follow-up 4 months post-operatively the patient had resolution of dizziness and fatigue. She had normal resting oxygen saturations and TTE showed normal tricuspid inflow and no recurrence of thrombus.