Intraoperative Diagnosis of Left Atrial Myxoma

The intraoperative indications for transesophageal echocardiography (TEE) remain unclear, particularly in patients without known left-ventricular dysfunction or valvular heart disease [1-3]. We describe a patient who developed hypoxemia and hypotension during anesthesia for revascularization of an occluded popliteal artery. TEE and fiberoptic bronchoscopy were used to diagnose the cause of the problems, whereupon a previously undiagnosed left atrial myxoma was identified. Case Report A 53-yr-old male was admitted after acute occlusion of his left popliteal artery. Past medical history was significant for heavy smoking and essential hypertension. The patient was a stout, 90-kg, bearded man 168 cm tall. Significant physical findings included a Mallampatti Class 3 airway, expiratory wheezes with forced exhalation, and diminished breath sounds bilaterally. Cardiac auscultatory findings were normal. The left foot was pale with absent pulses distal to the left femoral artery. There was electrocardiographic evidence of an incomplete right bundle branch block with left atrial enlargement. Angiography demonstrated aneurysmal dilation of the left common femoral artery which was suspected to be the source of the embolic occlusion of the popliteal artery. Preoperative medications included inhaled albuterol and intravenous (IV) heparin and urokinase. The activated partial thromboplastin time was 49.5 (control 23.7). The patient presented for urgent thrombectomy and possible revascularization of the left leg. A rapid sequence induction of general anesthesia using IV fentanyl 250 micro gram, ketamine 75 mg, and succinylcholine 120 mg was performed. The patient was orally intubated with moderate difficulty; however, there was no evidence of regurgitation during the laryngoscopy. Auscultation of the chest after intubation revealed expiratory wheezing over the right lung field and diminished breath sounds over the left lung field. A right mainstem bronchial intubation with bronchospasm was suspected, whereupon the endotracheal tube was withdrawn 3.0 cm and suctioned. Nebulized metaproterenol was administered. General anesthesia was maintained with 1.0% isoflurane, vecuronium (7.0 mg), and oxygen (FIO2 = 0.99). Although bronchospasm resolved, the patient's arterial oxygen saturation (by finger-pulse oximetry) remained only 90%. Arterial blood gas analysis showed PaO2 = 62 mm Hg, PaCO2 = 45 mm Hg, and pH = 7.37. Fiberoptic bronchoscopy confirmed that the endotracheal tube tip was properly positioned above the carina and that there were no secretions in the major bronchi. During this time, systolic blood pressure decreased from 135 mm Hg to 90 mm Hg, and heart rate increased from 85 bpm to 110 bpm. Despite infusion of 500 mL 5% hetastarch and 800 mL lactated Ringer's solution and reduction of the inspired isoflurane concentration to 0.5%, phenylephrine infusion (40 micro gram/min) was required to maintain systolic blood pressure at approximately 100 mm Hg. Urine output during the first hour of the case was 20 mL. Because of concern about left-ventricular function and whether fluid administration had been either inadequate or excessive, TEE was performed, revealing vigorous, symmetric contraction of the right and left ventricles, no segmental wall motion abnormalities, and decreased end-diastolic left-ventricular area indicative of hypovolemia. Mitral, tricuspid, aortic, and pulmonic valve functions were normal. A 2 times 2 cm mobile mass was identified in the left atrium Figure 1 and Figure 2. Based on the echocardiographic examination, an additional 750 mL of lactated Ringer's solution (rather than inotropic drug support) was administered with resolution of hypotension and tachycardia. Positive end-expiratory pressure (5 cm H2 O) and intermittent sigh breaths were added (to treat presumed atelectasis), increasing the PaO2 (on 100% oxygen) from 62 mm Hg to 390 mm Hg. The remainder of the surgery and anesthesia was uneventful, and afterward the trachea was extubated without difficulty. At operation, the popliteal artery was found to be completely thrombosed, necessitating bypass grafting. No specimen was obtained; therefore, we could not determine whether the inciting cause had been an embolus from the myxoma. One week later, the patient underwent removal of the left atrial myxoma and made an unremarkable recovery.Figure 1: Transesophageal echocardiography (TEE), four-chamber view showing a myxoma (M) in the left atrium (LA). RA = right atrium, RV = right ventricle, LV = left ventricle.Figure 2: This is an expanded view of the four-chamber TEE image showing the myxoma (M) attached to the atrial septum. LA = left atrium, RA = right atrium.Discussion This case illustrates how TEE can provide critical diagnostic information and help manage unstable patients. TEE has been touted as a useful intraoperative monitor for assessing wall motion, left-ventricular contractility, and the need for infusion of IV fluid. For these reasons, we performed our examination [4-6]. The effectiveness of TEE as a monitor, and whether its use improves patient outcome, remains unclear. At issue is the quality of data interpretation when TEE is performed by anesthesiologists. In this case, the TEE study quickly ruled out ventricular failure, volume overload, and acute valve dysfunction as causes of the high alveolar-to-arterial oxygen gradient, and confirmed the need for additional fluid administration. Additionally, TEE identified the patient's left-atrial myxoma. Placement of a pulmonary artery catheter may have helped in the hemodynamic management of the patient, but could not have provided a diagnosis of left atrial myxoma or detailed direct information regarding cardiac function. Clearly, TEE is not needed for routine monitoring of patients undergoing general anesthesia; however, this case illustrates how TEE can be helpful in diagnosing and managing patients who have an unstable cardiovascular status. It is important to remember TEE's diagnostic power, as well as its usefulness as a monitor, particularly when it is not possible to perform a thorough preoperative cardiovascular evaluation.