Unsuspected aortic valve vegetation detected during intraoperative transesophageal echocardiographic monitoring for coronary artery bypass grafting

Unsuspected Aortic Valve Vegetation Detected During lntraoperative Transesophageal Echocardiographic Monitoring for Coronary Artery Bypass Grafting Martin J. London, MD, James M. Brown, MD, David N. Campbell, MD, and Mark E. Keller, MD N T R A O P E R A T I V E transesophageal echocardiography

I (TEE) is being used increasingly for monitoring of ventricular function and wall motion during coronary artery bypass grafting (CABG). Although the exact frequency of its use has not been well documented in the literature, a recent survey administered by the Society of Cardiovascular Anesthesiologists at their 1993 Annual Meeting indicated that nearly 39% of the respondents (n = 202) used TEE "routinely" during cardiac cases (although no distinction was made between CABG and valve surgery).* Although the respondents to this survey represent a biased sample of cardiovascular subspecialists, it appears that the intraoperative use of TEE has become popular. With the use of such a sensitive imagmg modality, the chance of detecting incidental abnormalities unrelated to the primary surgical procedure increases. A case is reported of an unsuspected finding on TEE that led to additional surgical intervention in an already high-risk patient undergoing CABG. CASE REPORT A 65-year-old man was admitted to the Denver Veterans Affairs Medical Center for evaluation of 3 weeks of progressive angina with exertion and at rest. An exercise thallium treadmill test performed 4 days before admission showed reversible anteroseptal and mferoposterior ischemia, a fixed apical defect, and stress-induced left ventricular failure. He was admitted to the cardiac intensive care umt where intravenous heparin and nitroglycerin paste were instituted for unstable angina. Physical examination on admission was unremarkable with no neurologic abnormahties noted. The patient reported a history of prior myocardial infarction 15 years before admission. Other medical condations included longstanding non-insulin-dependent diabetes mellitus and an undocumented history of a cerebrovascular accident (CVA) requiring hospitalization, also 15 years before admission. Medications included glyburide and low-dose aspirin. Normal sinus rhythm, right bundle-branch block, and Q waves in V1-V3 were present on the electrocardiogram (ECG). The heart and lungs were normal on physical examination and on a portable chest x-ray. Serial creatine kinase isoenzymes were negative for acute Infarction. Cardiac catheterization with coronary cineangiography performed 2 days after admission showed a normal left main coronary artery, 100% proximal occlusion of the left anterior descending and right coronary arteries with collateral filling, high-grade proximal lesions of the obtuse marginals, and a normal posterior descending artery. The contrast ventriculogram showed a dilated left ventricle with anteroseptal and apical akinesis and a calculated ejection fraction of 35%. The aortic valve appeared normal with no

~R.E. Buckingham: 1993 Practice Trend Survey Results Sooety of Cardiovascular Anesthesiologists Newsletter, April 1994, p 2

evidence of regurgitation of contrast or dilation of the aortic root. CABG was recommended. Vital signs in the hospital before surgery were stable and the patient was afebrde. Intravenous heparln therapy was continued until the night before surgery. The preoperative hematocrit was 48.7%, the white blood cell count 4,700/ixL, and the platelet count 123,000/1~L. Ten days after hospital admission, the patient was brought to the operating suite after premedication with morphine and lorazepam. Vancomycin, 1 g, was administered intravenously before skin incision. After placement of a radial artery catheter and a mixed venous oxygen saturation pulmonary artery catheter via the right internal jugular vein, anesthesia was induced with sufentanil, 200 t~g, and pipecuronium, 10 rag. Anesthesia was maintained with additional doses of sufentanil, midazolam, and low inspired concentrations of isoflurane. A multihertz (3.5, 5.0, 7.0 Mhz) biplane transesophageal echo probe (V501B, Acuson, Mountain View, CA), interfaced to a 128 XP ultrasound scanner, was placed after endotracheal mtubation. Examination by the attending anesthesiologist showed a dilated left ventricle with anteroseptal akmesis and severe hypokinesia of the inferior and lateral walls in the transgastric midpapillary short-axis imaging plane. The distal septum and lateral walls were akinetic in the four-chamber transverse long-axis view. Examination of the aortic valve and left ventncular outflow tract in both the transverse and longitudinal long-axis orientations at a 7.0-MHz frequency using the "zoom" (RES) function, showed a tricuspid valve with a 0.5 x 0.75 cm mobile, pendulating lesion on the noncoronary cusp (Fig 1). In the transverse long-axis view, it appeared to be "shaggy" and irregular (Fig 2). The lesion appeared to arise from the inferior surface of the valve leaflet and was noted to prolapse above and below the point of coaptation of the valve leaflets (Fig 3). The gain of the ultrasound system was lowered to the mimmum possible for visualization to minimize the possibility that this observation was artifactual. The motion of the lesion was carefully assessed on a frame-by-frame basis using the on-board digital cineloop capability of the ultrasound system. M-mode examination of the aortic valve showed normal leaflet excursion, and the lesion could be seen as a marked thickening of the normal valve coaptation during diastole. Color-flow Doppler imaging of the left ventricular outflow tract in both the longitudi-

From the Umversay of Colorado Health Sctences Center; and the Veteran Affatrs Medical Center, Denver, CO Address repnnt requests to Martm J London, MD, Chtef, Anesthesia Sectton (112A), Veterans Affatrs Medtcal Center, 1055 Clermont St, Denver, CO 80220 Copyright © 1996 by W.B Saunders Company 1053-0770/96/1002-001853 00/0 Key words transesophageal echocardiography, aorttc valve, endocardttts, mtraoperattve penod

Journal of Cardtothorac/c and VascularAnesthesta, Vo110, No 2 (February), 1996 pp 253-257

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Fig 1. Intraoperatwe TEE image of an apparent vegetation arising from the aortic valve noted on the transverse long-axis view at 7 0 MHz with zoom magnification and cine frame capture {late diastole as shown in the lower left corner ECG trace), The distance between the white dot markers on either edge of the image is 1 cm. The lesion is approximately 0.75 x 0 5 cm in its largest dimension. Note its prolapse into the left ventncular outflow tract (right side of image under the anterior mitral valve leaflet, which is the linear structure on the upper portion of the image) during diastole

nal and transverse long-aras views failed to show any evidence of aortic regurgitation. The mitral valve apparatus was normal with trace--1 + mitral regurgitation by Doppler color-flow imaging. The finding of a suspected vegetation on the aortic valve was relayed immediately to the surgeon. After consultation with the attending cardiologist in the operating room, it was agreed that endocarditis could not be excluded, despite a lack of fever or an elevated white count. After institution of

Fig 2. Similar anatomy as Fig 1 but at a slightly different angle of interegation (also in diastole). Note the similarity of the lesion in this image to its appearance on direct inspection (Fig 4)

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Fig 3. Evaluation of the lesion during late systole in the longitudinal long-axis view of the left ventricular outflow tract, The lesion can be seen to arise from the inferior surface of the upper valve leaflet (noncoronary cusp),

hypothermic cardiopulmonary bypass and administration of cold blood cardioplegia by the anterograde and retrograde routes, the aorta was cross-clamped, the aortic root opened, and the valve examined. A flat fibrotic lesion that appeared to be an old organized vegetation was noted on the noncoronary cusp (Fig 4). There was no thrombus present on the lesion or in the aortic root. Given the normal functioning of the aortic valve by Doppler color-flow and M-mode examination, it was elected to leave the lesion in situ and the aortotomy was closed. Saphenous vein grafts were placed to two obtuse marginals, the diagonal, and the right coronary arteries during a single period of aortic cross-clamping. The left internal mammary artery was anastomosed to the left anterior descending coronary artery. The ischemlc time was 121 minutes. CPB was successfully terminated after 150 minutes despite transient global deterioration of wall motion and an increase in mitral regurgitation to 2 to 3+, which was treated with low-dose nitroglycerin and sodium nitroprusside infusions. The patient was taken to the surgical intensive care unit where the hematocrit was 30%, platelet count 101,000/jxL, I N R (international normalized ratio) 1.0 (normal, 0 . 7 7 - 1.27), and PTT 37 seconds (normal, 28 to 37 seconds). Mediastinal drainage was brisk (approximately 1 L) over the first 8 hours. He was transfused 2 units of packed red blood cells and 20 units of platelets with a subsequent decrease in drainage. He was extubated 13 hours after surgery, transferred to the ward on postoperative day 3 and discharged on postoperatwe day 7 in good condition. One month after discharge, the patient complained of syncopal episodes when arising from bed in the morning on two occasions. No localizing neurologic signs were present. A 24-hour Holter recording was performed but was unremarkable. Two months postdischarge, he was feeling well

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Fig 4. Direct inspection of the aortic valve after aortotomy during bypass. The chronic fibrotic lesion arises from the inner surface of the noncoronary cusp. The right coronary ostia is apparent above the right aortic leaflet. Note the otherwise normal appearance of the valve leaflets and their sinuses

without shortness of breath or chest pain. However, he related gait instability (falhng to his right). Neurologic examination by his primary physician showed a shuffling gait with a positive Rhomberg sign. Computerized tomography (CT) of the head performed as an outpatient showed evidence of an old right frontal lobe infarction, minor volume loss in the cerebellum, and diffuse involvement of the right cerebellum by abnormal hypodense nonenhancing tissue. Rewew of the patient's medical records documented a spontaneous intracerebellar hematoma in 1979, treated by suboccipital craniectomy with evacuation, requiring a hospital stay of 6 weeks. During that hospitalization, no infectious complications were noted. There was no documentation of a CVA. The current CT scan findings were believed to be most likely related to the old cerebellar hematoma and surgical evacuation. DISCUSSION

Incidental abnormalities detected by intraoperative TEE performed for monitoring purposes may fall into two categories: incidental with no immediate life-threatening consequences (ie, asymptomatic mitral valve prolapse) or those with potentially serious consequences 0e, previously undetected asymmetric septal hypertrophy). In rare circumstances such as presented here, incidental findings may result in additional surgical intervention that may increase the risk of perioperative complications. The finding of a large mobile lesion, consistent with a vegetation on the aortic valve, was completely unexpected. Given that contrast ventrlculography performed at the time of cardiac catheterization showed impaired ventncular function, an absence of mitral or aortic regurgitation, and a normal-sized aortic root, a preoperative transthoracic echocardiogram (TI'E) was not performed. When presented with the abnormal TEE findings in the operating room, it

was the authors' opinion that a missed diagnosis of acute endocarditis, although a very remote possibility given the absence of any clinical symptoms and a normal laboratory profile, could not be excluded. If it were present, embohzation or extension of infection into the aortic root could have severe untoward consequences, especially with mampulation of the aortic valve during insertion of the aortic cannula and with administration of anterograde cardioplegia. Thus, it was believed that there was no alternative to direct inspection of the aortic valve, despite the fact that any additional surgical intervention and/or prolongation of ischemic time in this already high-risk patient might increase his surgical and perioperative risk. The patient's vague undocumented history of a CVA 15 years before admission, which could have been embolic in origin perhaps from endocarditis, led to the suspicion that if a vegetation were present, it would be old (and not infectious). Alternate diagnoses that must be considered in this setting include the presence of ultrasound artifact and a neoplastic process. Artifact is a serious consideration, particularly when imaging the aorta. Neustein and Narang describe a case in which a circular density 1.3 cm in diameter was seen at the level of the aortic valve in a patient scheduled for CABG. 1 Aortotomy showed a normal aortic valve. Although they report that longitudinal imaging demonstrated thickening of the valve leaflet, they do not report specifically whether this abnormality was present and apparently did not perform an M-mode examination. They also briefly present two other cases with smaller densities at this level. Appelbe et al present both in vitro and m vivo observations on the presence of artifacts during TEE of the aorta. 2 They observed linear artifacts in 44% of patients in the ascending aorta. In vitro, using water-filled balloons and porcme aortas suspended in saline, these were shown to be multiple path artifacts caused by reflection of ultra-

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sound within the left atrium. In the present case, the authors were confident that this lesion was not artifact because it was present in at least three different imaging planes using high-resolution (7 MHz) imaging. As well, it was confirmed by M-mode examination, a technique with better temporal resolution than two-dimensional (2-D) imaging. Use of the on-board digital cineloop capability allowed for tracking its motion precisely frame by frame. An additional diagnosis that has been reported and that was not specifically excluded was a papillary fibroelastoma. Narang et al have also reported a case in which a 1-cm2 tumor attached to the upper margin of the right coronary cusp of the aortic valve was the cause of ostial obstruction of the right coronary artery and the patient's angina) Although a subtle abnormality was present on the cineangiogram, its significance was not appreoated preoperatively, and the patient was scheduled to undergo CABG. Detection of this abnormality prevented the patient from undergoing the (erroneous) planned procedure. Review of the literature by Narang et al shows that this is a very rare entity accounting for less than 1% of primary cardiac masses. As well, the morphologic appearance usually consists of a multilobulated pedicle with papillary fronds radmting from its surface. It was believed that any form of neoplastic process was extremely unlikely in the present patient, and, therefore, the lesion was not biopsied. It is possible that the aortotomy performed to evaluate this incidental finding may have contributed to the brisk early postoperative mediastlnal drainage that required administration of homologous blood products. These products increased his risk of contracting an infectious bloodborne pathogen. However, the patient's preoperative thrombocytopenia (possibly related to prolonged intravenous heparin therapy), which worsened in the early postoperative period, is a more likely etiologic factor. Once the aortotomy was performed and the suspected abnormality found to be chronic, it was decided to leave the lesion in situ. Although culturing the lesion or taking a biopsy could have been performed, it was believed the morphologic appearance was not consistent with an active infection. Because a biopsy was not performed, a tumor cannot be completely excluded. However, the flat, organized surface with no excresences or lobulatlon was believed to be inconsistent with a neoplastic process. The decision whether to excise it was based on concerns that it could act as a subsequent nidus for refection (should the patient ever become septic) or that it could possibly embolize (either the lesion or an attached thrombus) In addition, surgical excision might induce valvular dysfunction, which would be poorly tolerated In this patient with already impaired ventricular function. Since evaluation by 2-D, M-mode and color-flow Doppler demonstrated normal valvular function, fears of inducing poor coaptation of the valve leaflets possibly causing regurgitation or stimulating an inflammatory response possibly causing stenosis led to the decision not to excise the lesion. As well, the need to proceed in a timely manner to minimize the period of cardiopulmonary bypass and ischemic time in this high-risk

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patient was a major factor in the surgical decision-making process. Despite the risks involved, identification of this abnormality did have some potential benefit to the patient. The patient's primary care physician was notified because he is at risk for endocarditis with dental or surgical procedures. Thus, It is likely that he will receive appropriate antibiotic prophylaxis according to American Heart Association guidelines. On follow-up, the patient has done well with resolution of angina and improvement in his exercise tolerance. His reported neurologic symptoms of gait instabihty appear to be cerebellar in ongm and are most hkely related to progression of damage from his old cerebellar hematoma rather than embolic phenomena from his abnormal aortic valve. Vegetations are rather "sessile" (ie, completely attached to the valve leaflet) or "mobile or pendulating" (ie, a portion of the vegetation extends off the valve leaflet and prolapses Into the atrium, ventricle, or aorta). In this case, the latter was present. Clinically silent, histologically documented, active endocarditls can occur, but xt is rare. Mugge et al, in a prospective study of 80 patients with histologically documented endocarditis at surgery or autopsy, reported that all but 2.5% of patients had clinical signs. 4 The large size of this residual vegetation, in the absence of a history of clinical symptoms and without any associated valvular dysfunction, is distinctly unusual. Differentiation between an acute or chronic vegetation using echocardiographlc criteria alone is difficult. The presence of "shaggy" or "fuzzy" echoes on M-mode or 2-D imaging is believed to be consistent with acute infection. Sophisticated computer processing may be of value in this differentiation. Tak et al prospectively studied 22 patients with overt clinical signs of infectious endocardltis, using digital signal processing of the transthoracic echocardiogram to measure mean pixel intensity (MPI) of the vegetation acutely and after a mean of 9 weeks of antibiotic therapy (the chronic stage)5 They noted a statistically significant increase in MPI in the chronic stage in all patients who responded favorably to therapy (ie, resolution of chnical signs). In several patients who either did not respond, relapsed, or required surgery, MPI was either unchanged or decreased. They attribute the expected increase in MPI to morphologic changes in the vegetation from the acute infectious stage (neutrophils, organisms, erythrocytes, fibrin, and platelet thrombi) to the noninfectious chronic stage (fibroblast infiltration, collagen deposition, hyalinlzatlon, calcification, and finally endothellalizatlon). Although mean vegetation size decreased by 25% in the chronic phase (a significant change), in 6 patients no change, or a shght increase in size of the vegetation, was noted. Thus, in contrast to measurement of MPI, changes in vegetation size are not a reliable indicator of success of therapy. In the present case, such an approach, even if it were technically feasible (ie, the analysis of Tak et al required extensive off-line computer processing), would not

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be of value as a change in MPI over time, rather than a single static measurement, is required. In addition, Tak's analysis was performed using transthoracic echocardiography, which may not be freely extrapolated to images obtained using TEE, which has much greater sensitivity than TTE. 6 Finally, in echocardiographic evaluation of a lesion suspicious for endocarditls, the damage the infecnous process may cause to the valve apparatus should also be considered, as well as supporting and adjacent structures. This may lead to ruptured chordae tendineae (mitral or tricuspid valves), ruptured valve leaflets (with or without thrombotic material attached), or aneurysm of the valve leaflets, all of which may be difficult to differentiate from a vegetation. As well, fibrin strands (excrescences) have been reported to occur on the left ventricular side of the aortic valve caused by degeneration and denuding of the endothe-

lial layers. 7 They appear as short, thin, fluttering linear densaties. Their potential to embolize is controversial. The ability to image the myocardmm and valves on a routine clinical basis enhances the role of the anesthesiologist in the operating room. With the continued refinement of TEE transducers and ultrasound scanners (ie, 7 MHz frequency, on-board digital cmeloop capture, high frame rate magmfication, multiplane imaging) the ability to detect even minor anatomic abnormalities is increased. With it comes increased responsibility to recognize and report incidental anatomic findings. Such observations must be put into the context of the patient's overall medical condition and the type of surgery. Hopefully, careful observation and perioperative consultation with the appropriate specialists and postoperative follow-up with the primary care physician when an incidental finding is noted may lead to enhanced patient outcome.

REFERENCES

1. Neustein SM, Narang J. Transesophageal echocardlographlc artifact mimicking an aortic valve tumor J Cardlothorac Vasc Anesth 6"724-727, 1992 2. Appelbe AF, Walker PG, Yeoh JK, et al. Clinical significance and origin of artifacts in transesophageal echocardiography of the thoracic aorta. J Am Coil Cardlo121:754-760, 1993 3. Narang J, Neusteln S, Israel D: The role of transesophageal echocardiography in the diagnosis and excision of a tumor of the aortic valve. J Cardlothorac Vasc Anesth 6'68-69, 1992 4. Mugge A, Daniel WG, Frank G, et al: Echocardiography in infective endocarditlS' Reassessment of prognostic implications of

vegetation size determined by the transthoraclc and the transesophageal approach JAm Coll CardIol 14 631-638, 1989 5 Tak T, Rahimtoola SH, Kumar A. et al' Value of digital image processing of two-dimensional echocardiograms in differentiating active from chronic vegetations of infective endocardltls Circulation 78.116-123, 1988 6. YvorchukKJ, Kwan-LeungC: Applicationof transthoraclc and transesophagealechocardiographyin the diagnosisand managementof infectiveendocarditls J Am Soc Echocardlogr 14.294-308,1994 7. Goldman ME Chnical atlas of transesophageal echocardiography. Mt. gasco, NY, Futura, 1993, pp 110