Ann Thorac Surg 2004;78:782-785
© 2004 The Society of Thoracic Surgeons
Original article: cardiovascular
Redo-aortic valve replacement after previous bilateral internal thoracic artery bypass grafting
Hitoshi Hirose, MDa,*,
Inderjit S. Gill, MDa,
Bruce W. Lytle, MDa
a Department of Thoracic and Cardiovascular Surgery, Cleveland Clinic Foundation, Cleveland, Ohio, USA
Accepted for publication February 10, 2004.
* Address reprint requests to Dr Gill, Department of Thoracic and Cardiovascular Surgery, Cleveland Clinic Foundation, ME90, 3rd Floor, Hamann Bldg, 2500 Metro Health Dr, Cleveland, OH 44109-1998, USA
gillis{at}ccf.org
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Abstract
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BACKGROUND: Aortic valve replacement (AVR) after coronary artery bypass using bilateral internal thoracic arteries (ITAs) is a challenge. Management of these patent grafts and myocardial protection are important issues. Moreover the risk and outcome of these complex operations have not been clearly defined.
METHODS: Eighteen consecutive patients (all male) who exhibited previous bilateral ITA grafts underwent subsequent AVR surgery from 1990–2001 at the Cleveland Clinic Foundation. Their medical records were retrospectively analyzed.
RESULTS: At the time of reoperation, the mean age of the patients was 67 ± 6.4 years and 33 out of 36 (92%) ITAs were patent. The interval between previous coronary bypass and aortic valve surgery was 10.3 ± 5.3 years. All patients underwent redo-median sternotomy with aortic cannulation in 12 patients (67%) and femoral or axillary artery cannulation in 6 patients (33%). The patent ITAs were clamped during aortic cross-clamping in 15 patients. In 3 patients the ITAs were not dissected. These 3 patients underwent deep hypothermic arrest for myocardial protection. Concomitant coronary revascularization was performed in 8 patients (44%). There were no hospital deaths. One stroke occurred but there were no other major complications. Average intubation time was 23.1 ± 27.1 hours, intensive care unit stay was 2.3 ± 3.1 days, and postoperative hospital stay was 10.3 ± 7.6 days.
CONCLUSIONS: Reoperative aortic valve surgery in the patients with patent bilateral ITA grafts can be performed safely.
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Introduction
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Aortic valve replacement (AVR) after coronary artery bypass grafting (CABG) using bilateral internal thoracic artery (ITA) is a challenge. Technical difficulties regarding this procedure include the risk of graft injury during sternal reentry, myocardial protection during AVR, and the management of progression of arteriosclerosis in native coronary arteries and grafts. In patients with previous bilateral ITA grafting, the right ITA (RITA) often crosses the midline over the ascending aorta. Injuries of these ITAs may be catastrophic. Careful dissection is required to identify these previously placed grafts. Myocardial protection while the aorta is cross-clamped is another issue regarding patients with patent ITA grafts. Because of the persistent blood flow from the ITA graft, routine administration of cardioplegia may not be enough to achieve adequate myocardial protection unless these ITAs are isolated and clamped. Coronary artery disease and vein graft disease may progress over time and patients may require further coronary artery bypass procedures in addition to the AVR, which makes the procedure more complex. Prophylactic AVR in patients with mild aortic stenoses who undergo primary coronary artery bypass is controversial. The risk and outcome of redo AVR for the patient with prior bilateral ITA grafting has not been clearly defined. This has prompted a reexamination of these issues.
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Material and methods
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Consecutive patients who underwent reoperation for AVR between January 1990 and December 2001 at the Cleveland Clinic Foundation after previous bilateral ITA grafting were identified by a query of the prospective Cardiovascular Information Registry. The Institutional Review Board has approved this registry for research and it identified 18 patients (all male, mean age of 67 ± 6.4 years at the time of reoperation) who met the above criteria. Details of these original operations and redo-AVRs were reviewed. The results were expressed as incidences and percentages for categorical variables or with a mean ± standard deviation for continuous variables as appropriate.
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Results
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Previous CABG
The previous CABG using the bilateral ITAs was performed 10.3 ± 6.4 years before AVR. Both left ITAs (LITAs) and RITAs were used as an in-situ pedicle graft in all of the patients. The mean number of distal anastomoses at the time of previous CABG was 3.1 ± 0.9. In 10 out of 18 patients (56%), the RITAs crossed the midline to the left anterior descending artery (LAD) in 8 patients, the diagonal artery in 1 patient, and the circumflex artery in 1 patient. Of these one RITA was placed via the transverse sinus to the circumflex artery and others were placed anterior to the ascending aorta. The distributions of previously placed bypass are presented in Table 1.
The characteristics of the aortic valve were available in 16 patients at the time of CABG. Of these 3 out of 16 patients (19%) were diagnosed as having mild aortic stenosis with pressure gradients of 10 mm Hg or less. The other 13 out of 16 patients (81%) were diagnosed as having a normal aortic valve, which was determined by echocardiography or angiography. In 7 patients, measurements of the aortic pressure gradient were available at least twice by the time of reoperation for AVR. The calculated linear yearly progression of the pressure gradient for the aortic stenosis was 6.6 ± 1.9 mm Hg per year (4.4–9.3 mm Hg per year).
Reoperation
Indication for AVR regarded aortic stenosis in 16 patients (89%) with a mean pressure gradient of 44 ± 10.2 mm Hg and an aortic valve area of 0.7 ± 0.2 cm2 and severe aortic regurgitation in 2 patients (11%). The pathology of the aortic valve was degenerative in 12 patients, bicuspid in 1 patient, and rheumatic in 1 patient. At the time of AVR the mean age of the patients was 67 ± 6.4 years. Three patients indicated a history of two previous CABG. An angiogram was performed on all patients before AVR. The previously placed bilateral ITA grafts were patent except for three occluded RITA grafts including the RITA-circumflex artery graft passing though the transverse sinus. Three patients exhibited diffuse saphenous vein disease but all the LITAs were patent. The preoperative patient demographics are presented in Table 2.
Preoperative angiograms were reviewed to identify the route of the previously placed grafts. Femoral artery exposure was performed in all cases. If the lateral chest roentgenogram revealed the graft to be adherent to the sternum and to be at high risk for graft injury during sternotomy, cannulation of the femoral artery was performed before sternotomy to decompress the heart (5 out of 18, 28%). After redo-median sternotomy, the right side of the heart and ascending aorta were dissected first and then crossover grafts were dissected free. The aorta was cannulated and cardiopulmonary bypass was established between the right atrium and ascending aorta (12 out of 18, 67%). One patient (1 out of 18, 5.6%) who exhibited severe calcific aorta was cannulated via the axillary artery instead. This particular patient underwent deep hypothermic fibrillatory arrest without clamping the aorta during replacement of the aortic valve and ascending aorta. After establishment of cardiopulmonary bypass the ITAs and vein grafts were further dissected. In 3 patients (17%) the ITAs (3 LITAs and 1 RITA) were not able to be isolated because of heavy adhesions. Thus the RITA was clamped during the aortic cross-clamp in 13 patients, not dissected and left perfused in 1 patient, dissected but unclamped because of previously mentioned information (circulatory arrest) in 1 patient, and transected because of documented angiographical occlusion in 3 patients. On the other hand the LITA was dissected and clamped in 14 patients, not dissected and left perfused in 3 patients, and dissected but unclamped in 1 patient because of circulatory arrest. One RITA injury occurred during dissection (1 out of 15 patent RITA grafts, 6.7%), which was reimplanted on the ascending aorta.
Except for 1 patient who underwent redo-AVR without clamping the aorta under hypothermic circulatory arrest, the aorta was clamped and cardioplegia was given via combination of antegrade and retrograde manner in 11 out of 17 patients (64.7%), retrograde alone in 4 out of 17 patients (24%), or antegrade alone in 2 out of 17 patients (12%). During the cardiopulmonary bypass, bladder temperature was controlled normothermia (36°C) in 1 patient, mild hypothermia (30°–34°C) in 4 patients, moderate hypothermia (25°–29°C) in 3 patients, and deep hypothermia (< 25°C) in 9 patients. Three patients in whom the ITAs could not be dissected, 1 patient whose aorta was heavily calcified and could not clamped, and 1 patient who suffered graft injury underwent deep hypothermic arrest. In 4 other patients hypothermic arrest was used at the surgeon's preference (complexity of surgery, difficult dissection, hypertrophic heart, etc).
Concomitant CABG was performed in 8 patients. Occluded RITAs (3 patients) and diseased saphenous vein grafts (3 patients) were replaced with new saphenous vein grafts. New lesions were bypassed with vein (1 patient) or radial artery (1 patient).
The aortic valve was replaced with a pericardial valve in 14 out of 18 patients (78%) and a mechanical valve in 4 out of 18 patients (22%). Mean pump time was 122 ± 60 minutes, clamp time was 69 ± 28 minutes, and operation time was 7.3 ± 1.8 hours.
Outcome
There were no hospital deaths (0%, 70% confidence limits 0%–10%) in this series. One patient suffered a postoperative stroke (6%, 70% confidence limits 0.7%–18%) related to atrial fibrillation and required long-term rehabilitation. No postoperative myocardial infarction, mediastinitis, respiratory failure, or renal failure were observed. The postoperative courses are presented in Table 3.
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Comment
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Reoperation
Redo-AVR after bilateral ITA grafting is a relatively uncommon procedure. Bilateral ITA grafting is not performed as often as single ITA grafting, but the reason for this may be the hesitation for referral caused by an overestimation of the risk associated with the procedure. In addition to the risk of standard reoperative open-heart surgery, patients undergoing redo-AVR after bilateral ITA grafts manifest several special technical considerations. These include the dissection and preservation of the previously placed ITAs—especially the grafts crossing the midline—and adequate myocardial protection during cardiac arrest. Unlike redo-CABG or redo-mitral valve surgery that can be accomplished with a thoracotomy, redo-AVR usually requires a sternotomy. Because of the presence of crossover ITAs, these patients require a full sternotomy as a partial sternotomy would not be adequate for exposure.
The previously reported hospital mortality of redo-AVR post-CABG is 6.4%–17% [1–3], which is slightly higher than redo-CABG where mortality is reported to be in the range of 4.3%–9.6% [4, 5]. In our series of redo-AVR after bilateral ITA grafting, no mortality was observed although our study group was limited and the selection of patients may have been biased. Byrne studied 94 patients who had undergone redo-AVR with previously placed single ITA grafts and determined an operative mortality of 6.4%; perioperative myocardial infarction occurred in 7%, stroke occurred in 11%, and ITA injury occurred in 6.8% [2]. Univariable analysis revealed urgent procedures, concomitant aorta or aortic root surgery, and longer pump time to be associated with hospital mortality, however none of these were an independent predictor by multivariable analysis [2].
Careful interpretation of preoperative angiography for the routing of ITA is essential for these redo operations. If the ITA is suspected to be adherent to the sternum on lateral view of the chest roentgenogram, femoral cannulation and decompression of the heart before the sternotomy should be considered.
Myocardial protection
There are multiple strategies regarding the management of myocardial protection with patent ITA grafts. Ideally the patent ITA graft should be dissected free and occluded temporarily during aortic cross-clamping to avoid cardioplegia washout via the patent ITAs [4, 6]. However dissection of the ITAs may be difficult because of dense adhesions and may result in injury, which occurs at a frequency of 3.5%–12.5% [2, 6, 7]. In these circumstances establishing deep hypothermia is a reasonable alternative [2, 6]. Theoretically all patients with open ITA graft(s) where temporary occlusion is not achieved should have profound hypothermia (< 20°C) to obtain complete circulatory arrest and minimize oxygen demands. Adequate myocardial protection may be achieved with a combination of antegrade and/or retrograde cardioplegia and moderate hypothermia (25°–28°C). These strategies can be effective with regard to providing efficient myocardial protection, but the application of a particular protection technique should be individualized.
We recommend that patent ITA grafts be clamped, if possible, during the aortic cross-clamping to achieve complete cardioplegic arrest. Retrograde cardioplegia alone may not be enough for myocardial protection in a hypertrophic heart, which is often observed in patients with aortic valve disease and additional antegrade cardioplegia and/or mild hypothermia may be necessary to ensure myocardial protection [8]. If the ITAs are difficult to dissect, the alternatives are to cool to 20°C and perform AVR under deep hypothermic arrest. Moreover if the aorta is heavily calcified, the femoral artery or axial artery should be cannulated, deep hypothermic fibrillatory arrest without clamping the aorta should be employed, and then the aortic valve and ascending aorta should be replaced. However these techniques regarding myocardial protection are based on individual anatomy and intraoperative judgment of the surgeon. Inadequate myocardial protection during surgery often results in postoperative cardiac failure [9], which should be avoided.
Concomitant CABG at the time of redo-AVR is indicated in all of the patients with saphenous vein disease and new coronary artery lesions. The diseased saphenous vein should be replaced with new saphenous vein because of the risk of distal emboli and postoperative myocardial infarction [10] To avoid the risk of hypoperfusion the use of the radial artery should be limited to patents with a lack of venous conduit or native coronary artery disease and should not be used for graft re-replacement [9, 11].
Progression of aortic valve lesion
Aortic stenosis is reported to progress at the rate of 5–10 mm Hg per year with a decrease of aortic valve area by 0.08–0.12 cm2 per year [1, 12, 13]. Our study was limited to only 7 patients with a degenerative valve, however the literature indicates that the pathology of the aortic valve exhibits a major effect on the progress of aortic stenosis. A study has revealed that degenerative trileaflet valves progress faster and have the highest calcification rates, whereas rheumatic valve disease progresses slowly and congenital bicuspid valves fall in a category between rheumatic and degenerative [14]. Lower left ventricular function, hyperlipidemia, and diabetes may further enhance the progression of aortic stenosis. A follow-up study of mild aortic stenosis at the time of CABG by Collins demonstrated that symptoms and signs of severe aortic stenosis occurred in more than 50% of patients by 5 years post-CABG [13]. On the other hand a patient who undergoes CABG using bilateral ITA grafting has an 80% 10-year predicted survival [15]. Thus during his or her lifetime hemodynamically considerable aortic stenosis is most likely to develop in a patient with mild aortic stenosis at the time of CABG who is undergoing bilateral ITA grafting, although severe aortic stenosis symptoms developing in individual patients is difficult to predict. However prophylactic AVR for mild aortic stenosis in patients whose primary symptoms are coronary artery disease is controversial. Combined prophylactic AVR will increase the operative risk as well as remote valve-related events [13]. Young individuals with mild aortic valve stenosis and minimum comorbidity should be considered for prophylactic AVR at the time of CABG. On the contrary in elderly patients or patients with substantial comorbidity prophylactic AVR should be avoided, although each case should be accessed individually.
Study limitations
This study was analyzed retrospectively at a single institution. The number of study patients was limited because this procedure is not performed frequently. Follow-up study was not obtained because most patients were examined postoperatively by physicians outside of our institution.
Conclusion
If aortic stenosis reaches clinical significance after bilateral ITA grafting, this study supports the idea that redo-AVR can be performed safely. However these decisions should be individually tailored.
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References
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- Odell JA, Mullany CJ, Schaff HV, et al. Aortic valve replacement after previous coronary artery bypass grafting. Ann Thorac Surg. 1996;62:1424–1430[Abstract/Free Full Text]
- Byrne JG, Karavas AN, Filsoufi F, et al. Aortic valve surgery after previous coronary artery bypass grafting with functioning internal mammary artery grafts. Ann Thorac Surg. 2002;73:779–784[Abstract/Free Full Text]
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- Nava D, Cosgrove DM, Lytle BW, et al. Is the internal thoracic artery the conduit of choice to replace a stenotic vein graft? Ann Thorac Surg. 1994;57:40–44[Abstract]
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Abstract
Introduction
