Ann Thorac Surg 2004;78:e1-e2
© 2004 The Society of Thoracic Surgeons
Case report
Successful surgical management of a neonate with a saddle pulmonary embolus
Lorraine E. De Blanche, MDa,
Michael L. Schmitz, MDb,
Charles E. Johnson, RN, CCPa,
Thomas H. Best, MDc,
Jonathan J. Drummond-Webb, MD*a
a Section of Pediatric and Congenital Heart Surgery, Little Rock, Arkansas, USA
b Section of Pediatric Cardiovascular Anesthesiology, Little Rock, Arkansas, USA
c Department of Pediatric Cardiology, Arkansas Children's Hospital, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA
Accepted for publication November 25, 2003.
* Address reprint requests to Dr Drummond-Webb, Department of Pediatric Cardiology, Arkansas Children's Hospital, 800 Marshall St, #677, Little Rock, AR 72202-3591, USA
e-mail: drummond-webbjonathan{at}uams.edu
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Abstract
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A female neonate presented with evidence of a massive ventilation-perfusion mismatch. She was subsequently found to have a saddle pulmonary embolus. The infant successfully underwent surgical pulmonary embolectomy.
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Introduction
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Pulmonary embolus (PE) is well-documented as a dreaded and frequent cardiovascular emergency in the adult population. The incidence of first-time thromboembolism increases with age, with much more prevalence in the elderly [1]. The incidence of pulmonary embolism is estimated at 69 cases per 100,000 population per year, but the condition is rare in children (< 5 cases per 100,000 per year) [2]. Often the diagnosis is made postmortem in children as it may be an unrecognized cause of respiratory distress or failure [3]. We believe this is the first reported case of a neonate with a saddle PE who survived surgical intervention.
The patient was delivered at 39 weeks gestational age by Caesarian section for failure to descend. After delivery, the patient's left arm appeared mottled and hypotonic. The left brachial and radial pulses were not palpable. A complete blood count was normal aside from a platelet count of 35,000/µL. Twenty-four hours later her left arm improved and the radial pulse was palpable. The platelet count normalized at 72 hours. She was discharged 4 days later with a diagnosis of "arterial spasm."
Five days after discharge, the patient presented to the family's physician in an acutely hypoxic condition. She was immediately transferred to our center. A chest and abdomen roentgenogram showed bilaterally reduced pulmonary vascular markings. An arterial blood gas had a pH 7.08, PaCO2 57 Torr, PAO2 52 Torr, HCO3– 17 mEq/dL, with a calculated base excess of minus 13, which suggested a significant ventilation-perfusion mismatch. The electrocardiogram showed 1 to 1.5 mm anterior lead segment elevation depression in V2, V3, and V3R. Transthoracic echocardiography revealed a large echogenic mass in the main pulmonary artery (PA) extending to the left and right PAs (Fig 1).
A patent foramen ovale and patent ductus arteriosus were also noted. The infant had no signs of peripheral venous obstruction, and venous ultrasonography did not reveal evidence of thrombosis in other venous structures. Her right arm, although adequately perfused, was hypotonic. A head ultrasound showed evidence of a right middle cerebral artery stroke.
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Fig 1. Preoperative transthoracic echocardiogram showing the saddle embolus in the main pulmonary artery. (Ao = aorta; LPA = left pulmonary artery; MPA = main pulmonary artery; RPA = right pulmonary artery.)
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The infant was urgently transferred to the operating room where exposure was achieved through a median sternotomy. Manipulation of the PA was minimized (a "no-touch" technique) to reduce the risk of dislodging the emboli. Tapes were placed around the PA branches. Cardiopulmonary bypass (CPB) was established through the ascending aorta and right atrial appendage. The tapes around the PA branches were tightened, preventing propagation of distal clotting. The infant was cooled to a nasopharyngeal temperature of 25°C. The patent ductus arteriosus was ligated. At 25°C, crystalloid cardioplegia was administered and circulatory arrest was established. The right atrium was opened, and through the tricuspid annulus a large clot was seen to be obstructing 75% of the right ventricular outflow tract. This clot was easily removed. The patent foramen ovale was closed with a running suture. Cardiopulmonary bypass was reinstituted after a circulatory arrest period of less than 5 minutes. The main PA was opened transversely, and the snares on the right and left PAs were sequentially released. An organized thrombus was extricated from the main PA and each PA branch. The thrombus was adherent to the PA wall, but was separated easily, yielding a clean intimal surface that was not contiguous with the clot previously extracted from the right ventricular outflow tract. Repeated irrigation with heparinized normal saline and suctioning continued until no thrombus was returned with suctioning. The PA was closed. The patient was easily separated from CPB at 36°C. No intracardiac or pulmonary lines were placed. Nitric oxide at 40 ppm was commenced after the right ventricle appeared under strain after cessation of CPB.
A heparin infusion was started in the immediate postoperative period. Nitric oxide was discontinued 72 hours later, and she was extubated, remaining hemodynamically stable. However, postoperative evidence of hypotonia persisted, and magnetic resonance imaging subsequently confirmed the stroke. She was discharged on postoperative day 12 on daily subcutaneous enoxaparin (4 mg).
All coagulation studies remained normal (prothrombin time, 13.6 seconds; international normalized ratio, 1.2; activated partial thromboplastin time, 35 s; fibrinogen, 132 mg/dL). Follow-up studies have shown normal levels of antithrombin (59.0%), proteins C and S (protein C antigen, 50%; function, 45%; protein S total, 49.0%; function, 36%), and no factor V Leiden or prothrombin 20210A mutations. Tests for anticardiolipin antibodies revealed insignificant levels (3 IgM phospholipids units and 3 IgG phospholipids units). Homocysteine levels were not elevated (3.99 micromol/L). The primary cause of the PE remains unknown.
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Comment
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We have only been able to document one similar case to our present case in the pediatric population. Moreno-Cabral and Breitweser [4] reported a neonate that was born with cyanosis, hypoxia, and right heart failure, who underwent a cardiac catheterization that suggested severe pulmonary valvular stenosis with intact ventricular septum. At 6 days of age, the infant was taken to surgery, and the pulmonary artery was opened with the aid of CPB. After an uneventful embolectomy, the infant expired 30 hours later from distal arterial PE.
The cause of the PE in our case remains undetermined. In the pediatric population, PE is associated with central venous catheters, administration of hyperalimentation, L-asparaginase treatment, use of oral contraceptives, nephrotic syndrome, antiphospholipid antibodies (such as with lupus erythematosis), intracardiac anomalies, or inherited thrombotic disorders [5–7]. Inherited prothrombotic diseases include deficiencies of the anticoagulant proteins (protein C, protein S, and antithrombin), as well as activated protein C resistance (factor V Leiden), the MTHFR C677T genotype, elevated lipoprotein (a), and the prothrombin gene G20210A variant [7]. The child we have described had normal proteins C and S function and normal antithrombin activity, but did not have the factor V Leiden or prothrombin G20210A mutations.
Nitric oxide was used to offset the load of what appeared to be post-CPB pulmonary hypertension. A pulmonary artery catheter was intentionally omitted to avoid furnishing a surface for new clot formation within the same vessel that the original clot had formed. Nitric oxide can attenuate the effects of mediators (eg, endothelin-1 and thromboxane A2) thought to cause pulmonary vasoconstriction and cardiac depression seen in patients with PE [8]. Also, nitric oxide may have an inhibitory effect on platelet adhesion and aggregation that could reduce the potential for clot growth for residual emboli [9].
We believe this is the first documented neonatal survivor of a massive PE and surgical embolectomy. Definitive management including early, aggressive surgical intervention, a no touch surgical technique, the use of nitric oxide to facilitate and normalize endothelial pulmonary artery function, unload the right ventricle, and early anticoagulation may have all contributed to survival. The surgical strategy of a no-touch technique, immediate control of the PA branches, and circulatory arrest is a recommendation from the senior author's experience with the adult population.
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References
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Abstract
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