CARDIOVASCULAR ANESTHESIA: Case Report
The introduction of intraoperative transesophageal echocardiography (TEE) into cardiac surgery has been demonstrated to change the planned surgical procedure (1–3). This case report highlights the importance of performing a complete intraoperative TEE examination as defined by current standards (4). We describe a patient who was originally scheduled to undergo pulmonary embolectomies for bilateral pulmonary emboli as well as a right atrial thrombectomy for an impending paradoxical embolus that is a thrombus lodged in a patent foramen ovale. Use of intraoperative TEE permitted identification of a previously undiagnosed aortic thrombus at the level of the ligamentum arteriosum that presumably paradoxically embolized from a deep venous thrombosis (DVT); an unplanned aortic thrombectomy was subsequently performed.
An active, previously healthy 33-yr-old white male presented to a community hospital with the chief complaint of shortness of breath. His medical history was unremarkable. The initial medical evaluation included a computerized tomographic scan of the chest that revealed massive bilateral pulmonary emboli. The patient was systemically heparinized after diagnostic laboratory studies were drawn to exclude a hypercoagulable disorder. The tests included screening for protein C deficiency, protein S deficiency, antithrombin III deficiency, homocystinemia, prothrombin gene 20210, lupus anticoagulant, and factor V Leiden. After admission, a lower extremity noninvasive ultrasound scan revealed a left popliteal DVT. A transthoracic echocardiographic (TTE) examination performed to investigate a diastolic murmur demonstrated a large, mobile thrombus saddling a patent foramen ovale, right atrial/ventricular dilation, moderate to severe tricuspid insufficiency, and profound pulmonary hypertension with estimated pulmonary arterial pressures of more than 100 mm Hg.
The patient was then transferred to our institution for emergent surgical intervention. He underwent awake surgical preparation to allow for the immediate initiation of cardiopulmonary bypass (CPB) in anticipation of the potential hemodynamic collapse that can be associated with the induction of general anesthesia in patients with right heart pressure overload. Additionally, the initiation of positive pressure ventilation may also contribute to the development of hemodynamic collapse in patients with right heart pressure overload. The CPB cannulae were inserted into the right femoral vessels under local anesthesia. General anesthesia was uneventfully induced with midazolam, fentanyl, and vecuronium. The intraoperative TEE examination was completed under general anesthesia before the initiation of CPB. Intraoperative TEE examination revealed the previously mentioned echocardiographic findings (Figure 1/Video 1). Right to left shunting across the patent foramen ovale was noted using color Doppler. Evaluation of the aorta demonstrated a previously undiagnosed, large, extremely mobile thrombus anchored in the proximal descending thoracic aorta at the level of the ligamentum arteriosum (Figure 2/Video 2). There was no evidence of a patent ductus arteriosus or aortic atheromatous disease by the TEE examination.
The CPB arterial cannulation site was then changed to the ascending aorta to avoid retrograde dislodgement of the aortic thrombus. The operative procedure included bilateral pulmonary embolectomies, aortic thrombectomy under deep hypothermic circulatory arrest, atrial thrombectomy, and primary closure of the patent foramen ovale. The patient was separated from CPB on milrinone, norepinephrine, and prostaglandin E1 infusions with diffuse right ventricular hypokinesis. Post-CPB TEE examination did not reveal any residual thrombus. Postoperatively, the patient received anticoagulation with heparin followed by warfarin and an inferior vena cava filter as well as a ventricular epicardial pacemaker for paroxysmal third-degree heart block. Postoperative pulmonary arterial systolic pressures remained high (70–80 mm Hg). He was discharged to home on postoperative Day 17 taking nifedipine and atenolol to treat his pulmonary hypertension. At 9-mo follow-up, he had fully resumed his active lifestyle and continued on the same medications. A TTE examination performed at the same time demonstrated an estimated pulmonary arterial systolic pressure of 46 mm Hg (assuming a right atrial pressure of 5 mm Hg). The initial laboratory studies to rule out a hypercoagulable disorder were nondiagnostic, thus he was given the diagnosis of idiopathic DVT. He did not experience any additional complications related to his DVT.
This patient had multiple thromboemboli that seemed to be from a single source in the left popliteal vein. Approximately two million Americans develop a DVT each year, and roughly 600,000 Americans will develop a pulmonary embolus annually (5). The incidence of paradoxical emboli in such patients may be as frequent as 34%(6). We postulate that in our patient, the initial emboli likely traveled to the pulmonary circulation and increased right heart pressures. This increased pressure may have opened a previously sealed foramen ovale or created a right to left atrial shunt through a preexisting patent foramen ovale, thus creating the potential for the formation of an impending paradoxical embolus. Thrombus saddling a patent foramen ovale, an impending paradoxical embolus, is a recognized clinical phenomenon that has been reported in both postmortem and antemortem series (7). Aortic thrombus at the level of the ligamentum arteriosum in the absence of aneurysmal disease or aortic atheromatous disease has also been reported (8,9). A review of these reports show that this clinical phenomenon is rare and determination of its etiology limited by the surgical corrective technique used. One manuscript described a case of aortic thrombus at the level of the ligamentum arteriosum in a patient who received an interposition Dacron graft after intersegmental aortectomy; histopathological examination of the aortic specimen revealed focal atheromatous disease despite the TEE report of the remainder of the aortic examination being unremarkable (8). After establishing deep hypothermic circulatory arrest, an aortotomy was made just proximal to the level of the ligamentum arteriosum. This approach did not allow us direct examination of the affected segment of aortic wall, and it is therefore difficult to comment on potential etiologies of the arterial thrombus discovered in our patient.
Intimal irregularity secondary to tumor or another cause (e.g., traumatic disruption or connective tissue disorders) may form the nidus for an aortic thrombus in a nonaneurysmal, nonatheromatous aorta. Although arterial emboli originate most often from a cardiac source, it is possible that our patient’s thrombus developed on the aortic wall in situ. In our patient, the cardiac source was clear. The process by which the embolus may have become fixed on the aortic wall was not. Our case is unusual in that the paradoxical embolus was arrested in transit at two separate and unique anatomic locations: in the patent foramen ovale and in the descending thoracic aorta at the level of the ligamentum arteriosum. Intraoperative TEE did not reveal evidence of a patent ductus arteriosus.
This case highlights the importance of performing a complete intraoperative TEE examination despite the completion of a preoperative TTE examination. A complete TEE examination should include both anatomical and functional evaluation of all four heart valves as well as examination of the four cardiac chambers for pathology and functional status. The aortic examination is especially important in cardiac surgical patients to reduce the potential risk of stroke. Additionally, this case demonstrates the potential for an embolus in transit to arrest at two unique anatomic locations, a clinical phenomenon previously unreported.
We would like to gratefully acknowledge the help of Dr Marielle Scherrer-Crosbie who obtained the intraoperative echocardiographic images during the course of a complicated surgery and anesthetic.
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© 2002 International Anesthesia Research Society
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