Ann Thorac Surg 1996;62:1141-1145
© 1996 The Society of Thoracic Surgeons
Original Articles: Cardiovascular
"Incisura" of the Ascending Aorta and Vascular Pedicle Width in the Cardiac Transplant Patient
Andy C. Chiou, MD,
Christopher J. Abularrage,
Paul N. Olson, MD,
Larissa Hood, MD,
Christopher E. Engeler, MD,
Harry J. Griffiths, MD,
Sara J. Shumway, MD
Departments of Surgery and Radiology, University of Minnesota, Minneapolis, Minnesota
Accepted for publication May 7, 1996.
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Abstract
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Background. The purpose of this study was to evaluate three findings in cardiac transplant patients: the appearance, etiology, and incidence of "incisura" (a characteristic indentation) of the ascending aorta; the vascular pedicle width, which usually appears enlarged on standard chest radiographs; and clearing of the retrosternal clear space.
Material. Two hundred sixty-one cardiac transplantations were performed at the University of Minnesota before December 31, 1992. The appearance, etiology, and incidence of an incisura were studied; the vascular pedicle width was measured; and the rate of clearing of the retrosternal clear space was determined.
Results. Forty-six percent of the patients whose ascending aorta could be visualized on the lateral chest radiogram showed an incisura. Approximately one third of the patients showed continued opacification of the retrosternal space postoperatively. The width of the vascular pedicle in this series of cardiac transplant patients measured 60.9 ± 22.8 mm (standard deviation, 11.4 mm), in comparison to a normal of 48 ± 5.0 mm.
Conclusions. An incisura of the ascending aorta and the widened vascular pedicle are normal postoperative chest radiographic findings in cardiac transplant patients and should not be misconstrued as abnormalities.
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Introduction
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During a routine evaluation of the postoperative radiograms of cardiac transplant patients, an indentation of the ascending aorta is sometimes identified that gives the appearance of a coarctation. This "incisura" was identified on several lateral chest radiograms, but visualization of this incisura was hindered in some patients by persistent opacification of the retrosternal clear space. It was also noted that the vascular pedicle was widened in most of these patients. This study was therefore undertaken to evaluate these findings and to determine their frequency.
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Methods
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Two hundred sixty-one cardiac transplantations were performed at the University of Minnesota between March 4, 1978, and December 31, 1992. Postoperative chest radiograms were retrospectively evaluated to (1) determine whether there was an incisura, (2) determine the appearance and rate of clearing of the retrosternal clear space, and (3) measure the vascular pedicle width, according to the method of Milne [1–4].
Once discharged, these patients are followed up biweekly for 4 weeks, weekly for 4 weeks, and every other week for 4 months. The follow-up was then extended as the time from transplantation increased. All postoperative chest radiographs were reviewed by P.O., along with A.C. or L.H.
Thirty patients were excluded because (1) death occurred before posteroanterior and lateral upright radiograms were obtained after transplantation, (2) follow-up was conducted at a different institution, or (3) films were not available. In a small number of cases, the films had been destroyed.
An incisura was defined as a kink or indentation along the anterior wall of the ascending aorta seen above the level of the aortic root on the lateral radiogram (Figs 1, 2
). This usually occurred at a point midway between the aortic root and the origin of the right subclavian artery. The postoperative radiogram series for each patient was evaluated for this finding.
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Fig 1. . Lateral chest radiogram obtained after cardiac transplantation. Arrow indicates the site of the incisura.
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All patients undergo cardiac and coronary catheterization as well as myocardial biopsy during routine follow-up. The results of these studies, if available, were reviewed in many patients. In addition, 25 cardiac transplant patients underwent magnetic resonance imaging to obtain T2 values for the evaluation of myocardial rejection. These studies were also evaluated for the appearance of an incisura.
During evaluation of the postoperative chest radiograms, a variability in the rate of clearing of the retrosternal clear space was also noted. Therefore the time it took for the retrosternal space to clear was also evaluated in routine postoperative radiograms in cardiac transplant patients. Complete data were not available for 39 patients. The patients were divided into two groups: (1) those who had had a previous sternotomy and (2) those who had not.
The vascular pedicle was measured in 221 of the 261 patients (Fig 3). Forty patients were excluded because of (1) death before a baseline postoperative radiogram could be obtained, (2) age less than 16 years, and (3) unavailability of posteroanterior upright films. The measurement was made according to Milne's criteria for vascular width and involves measuring the distance from the point where the superior vena cava crosses the right mainstem bronchus to a line drawn vertically from the site of origin of the left subclavian artery from the aortic arch.
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Fig 3. . (A, B) Preoperative posteroanterior and lateral chest radiograms. The vascular pedicle width is 56 mm. Note that coronary artery bypass grafting markers are present. (C, D) Posteroanterior and lateral chest radiograms obtained after cardiac transplantation. The vascular pedicle width is now 70 mm and the coronary artery bypass grafting markers are elevated. The lateral radiogram also shows the incisura.
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Results
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In the cardiac transplant patient, the lateral chest radiograms show an irregular contour of the ascending aorta similar to that seen in aortic coarctation. This incisura of the ascending aorta occurs at the anastomosis of the native and donor aortas (see Fig 1, 2
). However, evaluation of the ascending aorta on the lateral radiograms is often hindered by postoperative changes in the retrosternal clear space. The ascending aorta could be identified in only 69% (159/231) of the patients. Of these 159 patients, an incisura of the ascending aorta was seen in 46% (73/159) (Figs 4, 5).
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Fig 4. . (A) Lateral chest radiogram showing an aortic incisura (arrow). (B) Magnetic resonance imaging study (T2-weighted axial image) obtained above the aortic anastomosis; the aorta measures 5 cm. (C) Magnetic resonance imaging study (T2-weighted axial image) obtained below the aortic anastomosis (graft aorta); the aorta measures 3 cm. (D) Coronal magnetic resonance image shows this change in the caliber of the aorta to occur at the site of the anastomosis.
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The retrosternal clear space was evaluated to determine the time it took for the space to clear postoperatively. This was found to be dependent on whether the patient had had a previous sternotomy. One hundred fifty-six patients had had no previous sternotomies, and in 77.6% (121/156) of these patients, the retrosternal space cleared in an average of 4.3 months; in the remaining 22.4% (35/156), the space remained opacified at the time of evaluation. Sixty-six patients had had a previous sternotomy, and of these, the space cleared in 50% (33/66) in an average of 6.5 months; however, the other 50% (33/66) of these patients showed persistent opacification after cardiac transplantation.
The vascular pedicle width measured an average of 60.9 ± 22.8 mm (range, 34–96 mm). This compares with a normal mean of 48 ± 5.0 mm [5]. Twenty-two patients were considered normal on the basis of their body habitus. These measurements were obtained in patients who were considered to show a normal postoperative cardiac transplant appearance and had no evidence of pulmonary edema (see Fig 3). Numerous patients were noted to have fractures of the first and second ribs postoperatively, and occasionally these could be misdiagnosed as pulmonary nodules (Fig 6).
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Comment
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During cardiac transplantation, the atrial anastomoses are performed first (the left and then the right). Once established, the great vessels are then anastomosed. Generally the pulmonary arterial end-to-end anastomosis is done first, with both the donor and the recipient pulmonary arteries kept relatively short to prevent torsion or twisting. The donor and recipient aortas are anastomosed in an end-to-end fashion with running 4-0 monofilament suture in the usual adult cardiac transplant recipient. The aortic end-to-end anastomosis is done with both the donor and the recipient aortas left relatively long to allow for examination of the undersurface of the neoaorta should bleeding be a problem. However, once the two atrial and pulmonary arterial anastomoses are completed, the two aortas, once approximated, may lie in a different plane than the original aorta.
Few papers have been written regarding the postoperative appearance and resultant contours of the heart and pulmonary vasculature after cardiac transplantation [1–4]. These papers primarily discuss the irregular contours of the cardiac silhouette. Silverman and associates [4] noted the presence of a step-off in the contour of the ascending aorta after cardiac transplantation but did not indicate the frequency with which this incisura was observed. This incisura occurs at the site of the surgical anastomosis of the native and graft aorta. After noting the existence of an incisura, particular attention was paid to the size difference between the native and graft aorta. Patients with a known size discrepancy at operation were generally found to show an incisura postoperatively. However, patients whose surgical size discrepancy was not as great also showed some degree of incisura, and this may be due in part to compliance variations between the more pliable graft aorta and the more rigid native aorta. This is supported by the fact that most patients showing an incisura were more than 40 years of age. The etiology of this incisura is probably multifactorial and could be due to the extra length of aorta used to allow for mobility at operation, the different plane of the neoaorta, and the size disparity between the normal donor aorta (smaller) and the diseased recipient aorta (larger).
The enlargement of the vascular pedicle can also be related to the technique used for the atrial and aortic anastomoses. The additional length of the aorta, the additional volume of the right atrium, and the new plane of alignment for the neoaorta will all cause an apparent widening of the vascular pedicle. Elevation and elongation of the aorta and enlargement of the atria were clearly demonstrated in a patient who had had a previous coronary artery bypass operation, with metallic clips and markers outlining the aorta (see Fig 4).
The time it took for the retrosternal clear space to clear in patients with and without sternotomies was not significantly different; however, patients who had had a previous sternotomy were more likely to have an opacified retrosternal space. The appearance of the retrosternal space and the rate of clearing are important in the routine follow-up evaluation of these patients. In many patients the retrosternal space cleared in approximately 1 month. The opacification may be partially explained by the postoperative presence of edema, serous fluid, or hemorrhagic fluid within the mediastinum. These postoperative changes were evaluated using magnetic resonance imaging, which showed the T2 signal decreased with time postoperatively, reflecting decreasing amounts of fluid within the mediastinum [6].
Because cardiac transplant patients receive immunosuppressant treatment to decrease the risk of rejection, these patients need to be monitored carefully for the development of retrosternal or mediastinal infections and transplant lymphomas. Reopacification of the retrosternal space may be an early indication of such a complication, and this must be differentiated from opacification caused by the presence of edema, serous fluid, or hemorrhagic fluid.
One additional observation was made during the evaluation of the chest radiograms. The first and second ribs showed callous formation bilaterally and symmetrically approximately 4 to 8 months after the transplantation (see Fig 6). This has been noted in many patients who have undergone median sternotomy and is thought to represent the healing of stress fractures resulting from retraction at the time of the surgical procedure [7, 8].
In summary, the following chest radiographic findings should be considered normal in cardiac transplant patients: (1) An incisura can be identified in approximately 50% of the patients whose ascending aorta can be visualized; (2) the mean vascular pedicle width in this series is increased; therefore, a new vascular pedicle width should be established for each patient postoperatively; (3) clearing of the retrosternal space is dependent on many factors, including previous sternotomy, adipose tissue, hematoma, the development of infection, or lymphoma formation; and (4) sclerosis may occur in the first and second ribs 4 to 8 months after median sternotomy and should not be misdiagnosed as pulmonary nodules.
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Footnotes
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Address reprint requests to Dr Chiou, Department of Surgery, The New York Hospital/Cornell Medical Center, 525 E 68th St, Box 207, New York, NY 10021.
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References
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- Florence SH, Hutton LC, McKenzie FN, Kostuk WJ. Cardiac transplantation: postoperative chest radiographs. Can Assoc Radiol J 1988;39:115–7.[Medline]
- Murayama S, Ikezoe J, Godwin JD, Allen MD. Radiographic changes in cardiac contours following cardiac transplantation: clarification by MRI. Acta Radiol 1991;32:183–6.[Medline]
- Shirazi KK, Amendola MA, Tisnado J, Cho SR, Beachley MC, Lower RR. Radiographic findings in the chest of patients following cardiac transplantation. Cardiovasc Intervent Radiol 1983;6:1–6.[Medline]
- Silverman JF, Griepp RB, Wexler L. Radiographic changes in cardiac contour following cardiac transplantation. Radiology 1974;111:303–6.[Medline]
- Milne ENC, Pistolesi M, Miniati M, et al. The vascular pedicle of the heart and the vena azygos: Part 1: The normal subject. Radiology 1984;152:9–17.[Abstract/Free Full Text]
- Randal PA, Transolini NC, Kohman LJ, et al. MR imaging in the evaluation of the chest after uncomplicated median sternotomy. Radiographics 1993;13:329–40.[Abstract]
- Curtis JA, Libshitz HI, Dalinka MK. Fracture of the first rib as a complication of sternotomy. Radiology 1975;115:63–5.[Abstract]
- Gumbs RG, Peniston RL, Nabhani HA, et al. Rib fractures complicating median sternotomy. Ann Thorac Surg 1991;51:952–5.[Abstract]
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[Abstract]
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Abstract
Introduction
