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* From the Center for Lung Research (Drs. Holcomb, Loyd, Robbins, and Mss. Casey-Cato and Mason), and Division of Cardiovascular Medicine (Drs. Byrd and Wilsdorf), Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN.
Correspondence to: Ivan M. Robbins, MD, Center for Lung Research, Vanderbilt University School of Medicine, Room T-1219, MCN, Nashville, TN 37232; e-mail: Ivan.Robbins.{at}mcmail.vanderbilt.edu
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Abstract |
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Key Words: contrast echocardiography • Eisenmenger’s syndrome • paradoxical systemic air embolism • patent foramen ovale • pulmonary hypertension
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Introduction |
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Precapillary pulmonary hypertension (PH; mean pulmonary artery pressure of > 25 mm Hg at rest, or > 30 mm Hg with exercise) occurs in an idiopathic form, primary pulmonary hypertension (PPH), or in association with a number of other disorders including congenital heart defects.3 Eisenmenger’s syndrome (ES) refers to the secondary development of irreversible PH with bidirectional or right-to-left shunting in patients with defects at the ventricular, atrial, or great vessel levels. Pathologically, PPH and ES are virtually indistinguishable.4
Echocardiography is frequently employed in the evaluation and management of PH to estimate the degree of PH, to assess right ventricular (RV) function, and to monitor the effects of therapy. Agitated-saline contrast echocardiography (ASCE) is often performed in unexplained PH to rule out an unrecognized congenital or acquired intracardiac shunt, especially if the patient is hypoxemic.
Epoprostenol, the synthetic salt of prostacyclin, is used in the treatment of both PPH as well as ES. It has been shown in PPH patients to improve hemodynamics, exercise tolerance, quality of life, and survival.5 6 Because of its short half-life in vivo, epoprostenol must be administered by continuous IV infusion through a long-term indwelling venous catheter. These catheters have certain risks, including infection, thrombosis, and catheter fracture.7 Case reports have described PAE in association with the use of central venous catheters and have cited catheter malfunction as the source for embolism.2 8 Although paradoxical thromboembolism has been described in association with epoprostenol therapy,9 PAE has never been reported. We report four cases of PH-associated PAE encountered at our institution over the last 5 years, related either to ASCE or to multilumen catheter use with epoprostenol therapy.
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Case Reports |
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Paradoxical air emboli occurring after flushing of the unused catheter port was suspected. The double-lumen catheter was replaced with a single-lumen catheter in August and neurologic symptoms resolved. She continued to receive continuous IV epoprostenol until she underwent double lung transplantation in November, 1999. She has had no further neurologic events after transplantation.
Case 2
A 37-year-old white woman with a history of ES associated with a
secundum ASD and severe PH (Table 1)
presented in April, 1999 with
progressive dyspnea, weakness, and severe hypoxemia. Her history was
significant for a paradoxical thromboembolism in 1992, for which she
was receiving long-term anticoagulation therapy with warfarin.
Continuous IV epoprostenol was initiated after placement of a
double-lumen Hickman catheter in her right subclavian vein. Three weeks
after initiation of therapy, the patient presented with complaints of
multiple episodes of left-sided facial numbness and tingling, as well
as left-upper-extremity numbness, occurring immediately after routine
flushing of the unused lumen of the indwelling catheter. All symptoms
completely resolved within minutes of onset.
Physical examination findings were significant for an SaO2 of 78% on 4 L/min of supplemental oxygen, peripheral and perioral cyanosis, jugular venous distention to 16 cm, a prominent RV heave, 2+ peripheral edema, and profound digital clubbing. Neurologic examination findings were normal. Laboratory studies revealed a therapeutic INR of 2.2 and a hematocrit of 59%. Head CT findings were within normal limits. ASCE, with agitated saline solution injected through the unused catheter port, demonstrated contrast bubbles traversing the ASD (Fig 1 , top, and bottom) with recurrent facial numbness. The patient underwent catheter replacement with a single-lumen Hickman catheter. Her neurologic symptoms did not recur after catheter replacement. However, the patient developed progressive hypoxemia and cor pulmonale, and died 6 weeks after initiation of epoprostenol treatment.
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Case 4
A 53-year-old white woman presented to Vanderbilt Medical Center
in August, 1994 for further evaluation and management of suspected PPH.
As part of her evaluation, ASCE was performed, which revealed a PFO
during a Valsalva maneuver. After ASCE, the patient experienced acute
onset of right-lower quadrantanopia, as well as left-hand numbness and
ataxia. Head CT as well as MRI were performed, with normal findings for
both. The patient denied any previous episodes of focal neurologic
deficits.
Physical examination findings were significant for a resting SaO2 of 92% on room air, a 2/6 tricuspid regurgitation with a prominent P2, and an RV heave. Extremity examination findings were negative for cyanosis or clubbing. Neurologic examination findings revealed right temporal lower-field quadrantanopia, without deficits in strength, sensation, or cerebellar function. Laboratory study results were remarkable only for mild renal insufficiency, with a serum creatinine level of 1.5 mg/dL.
Over the next 24 h, the patient’s visual deficits completely resolved, and subsequent neurologic examination findings were normal. Additional workup revealed no secondary causes of PH, and subsequent right-heart catheterization confirmed the diagnosis of PPH (Table 1) . Despite intensive therapy with multiple vasodilators, the patient developed severe cor pulmonale and died 3 weeks after presentation.
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Discussion |
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PFO associated with paradoxical thromboemboli or air emboli has been discussed extensively in the literature.10 11 Previous autopsy series have found the prevalence of PFO to be 25 to 35%, although the majority of these are clinically silent because left atrial pressure usually remains higher than right atrial pressure.10 However, certain situations, such as initiation of a Valsalva maneuver, can increase right atrial pressure and create a right-to-left shunt, even in patients with only mild PH. Both patients in our series who experienced PAE during ASCE had no clinical, radiographic, or routine two-dimensional and color Doppler echocardiographic evidence of intracardiac right-to-left shunting. PAE occurred only after injection of agitated saline solution contrast with a concomitant Valsalva maneuver.
Echocardiography continues to be an invaluable tool in evaluation and monitoring of PH, and the use of ASCE to exclude intracardiac shunting poses a very low risk of even transient complications. Over the last year, approximately 75 patients evaluated for PH at our center underwent ASCE without complications, confirming that the incidence of PAE associated with this test is very low. Clearly, cyanotic patients are at increased risk for PAE after ASCE, although neurologic complications are almost always transient. As advised by the American Society of Echocardiography, because of this risk, ASCE should only be performed if the diagnosis underlying arterial hypoxemia is uncertain clinically and after careful study with two-dimensional and Doppler flow echocardiography for defects at the septal or great vessel level. If PAE does occur, treatment should include 100% supplemental oxygen therapy to promote air-emboli resorption until symptoms have resolved. Additionally, if PAE-like symptoms occur during or after ASCE despite negative study findings, transesophageal echocardiography should be considered to rule out occult intracardiac shunting.12
PAE is a rare complication of central venous catheterization, with < 10 cases reported in the literature. It has been associated with hemodialysis catheters, in which symptoms occurred after manipulation of the line.8 PAE has also been described with conventional central venous catheters developing a crack in the line or left open to air, and with introducer sheaths in which the obturator was not placed.2
PAE associated with continuous IV epoprostenol therapy has not been reported. Raffy et al9 reported a case of paradoxical thromboembolism occurring during acute vasodilator testing with epoprostenol in a patient with PPH; however, the thromboembolic source was not discussed. Both of the patients we report were receiving long-term epoprostenol therapy through a multilumen, central venous catheter. Symptoms occurred in both patients when air was introduced into the venous system through the unused port of the catheter, and did not recur once single-lumen catheters were placed. There have been no other episodes of PAE among the 45 patients currently receiving epoprostenol therapy at our center, although only three of our patients have a double-lumen catheter in place, none of whom have an intracardiac defect. Epoprostenol therapy for ES has only recently been reported,13 and continued use of multilumen catheters in these patients will likely result in additional cases of PAE. Given the potential morbidity and mortality associated with PAE, the continued use of multilumen catheters should be avoided in patients with significant right-to-left shunts.
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Footnotes |
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Abbreviations: ASCE = agitated-saline contrast echocardiography; ASD = atrial septal defect; ES = Eisenmenger’s syndrome; INR = international normalized ratio; PAE = paradoxical systemic air embolism; PFO = patent foramen ovale; PH = pulmonary hypertension; PPH = primary pulmonary hypertension; RV = right ventricular; SaO2 = arterial oxygen saturation
Received for publication July 27, 2000. Accepted for publication October 3, 2000.
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