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Ann Thorac Surg 2003;75:1476-1480
© 2003 The Society of Thoracic Surgeons

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Original article: cardiovascular

Three or more median sternotomies for patients with valve disease: role of computed tomography

^a Department of Thoracic and Cardiovascular Surgery, Sapporo Medical University School of Medicine, Sapporo, Japan

Accepted for publication November 11, 2002.

^* Address reprint requests to Dr Morishita, Department of Thoracic and Cardiovascular Surgery, Sapporo Medical University School of Medicine, South 1 West 16, Chuo-ku, Sapporo 060-8556, Japan.
e-mail: kmori{at}sapmed.ac.jp

	Abstract

Top Abstract Introduction Patients and methods Results Comment References

 
BACKGROUND: We evaluated the effects of computed tomographic (CT) scan-guided third or fourth median sternotomies for valve operations on the incidence of resternotomy-related complications and early mortality.

METHODS: Ninety patients undergoing valve replacement with third or fourth time sternotomy were divided into two groups. One group (CT group) consisted of 64 patients who had undergone routine CT scans preoperatively after 1991 to assess the possibility of sternotomy-related bleeding, and the other group (no CT group) comprised the remaining 26 patients who did not receive CT scans.

RESULTS: Hospital death occurred in 4 patients (6%) in the CT group and in 6 patients (23%) in the no CT group (p = 0.0309). Multivariate analysis indicated NYHA class 4 (odds ratio [OR] = 6.99) and year of operation (OR = 1.05) to be predictors of hospital death. Preoperative CT scans revealed that 8 patients were considered to be high risk for resternotomy, they underwent femorofemoral bypass before sternal division was performed. Hemorrhage occurred upon sternal reentry in 2 of these 8 patients. The incidences of sternotomy-related injury were 19% (5/26) in the no CT group and only 3% (2/64) in the CT group (p = 0.0198). Multivariate analyses demonstrated a fourth sternotomy (OR = 4.31) to be a predictor of resternotomy-related injury.

CONCLUSIONS: CT scans provide preoperative information on retrosternal adhesions. When a distended heart or expanded aorta has adhered to the sternum, femorofemoral cannulation should be performed before sternotomy. Third and fourth sternotomies, though demanding procedures, can be performed safely using the described strategy.

	Introduction

Top Abstract Introduction Patients and methods Results Comment References

 
More than 40 years has passed since the introduction of valvular operations in our institution, and an increasing number of patients are undergoing second and subsequent operations. Third or fourth operations are not rare now. For such operations, median sternotomy is used as first operations because it provides good exposure. However, reoperative median sternotomy is technically more demanding [1]. In addition, adhesions become denser with an increase in the number of previous operations. Consequently, a third or fourth median sternotomy increases the rate of complications related to sternal reentry and the rate of operative mortality. Surgeons may have recently more frequently been observing significant sternotomy-related hemorrhage as they have been forced to operate on more patients requiring third or fourth median sternotomy. To solve this problem, the possibility of sternotomy-related bleeding has been assessed by the use of preoperative computed tomographic (CT) scans since 1991. In high-risk cases for hemorrhage, the femoral artery and vein should be routinely cannulated. Thus, patients in which a third and fourth median sternotomy was performed for valve replacement in our institution were reviewed to evaluate the effects of CT scan-guided sternotomy on the incidence of resternotomy-related complications and early mortality.

	Patients and methods

Top Abstract Introduction Patients and methods Results Comment References

 
Patients
Data from 90 consecutive patients who had undergone valve replacement with third or fourth time median sternotomy in our institution during the period January 1981 to September 2001 were used for analysis in this study. The patients were divided into two groups. One group (CT group) consisted of 64 patients who had undergone routine CT scans preoperatively after early 1991 to define the space between the sternum and heart, and the other group (no CT group) comprised the remaining 26 patients who did not receive preoperative CT scans.

Demographic information of the two groups is depicted in Table 1. There was no difference between both groups with respect to age, sex distribution, New York Heart Association functional class (NYHA), and ejection fraction.

Previous operative procedures in two groups are listed in Table 2. Of them, 5 were performed elsewhere (2%). Previous operations had been performed at mean intervals of 7.9 years between the last and current operations in the no CT group, and 8.9 years in the CT group.

Surgical technique
A skin incision for the standard median sternotomy was made. If patients had a wide previous scar, the scar was excised. Initially, only the external lamina and medulla of the sternum were divided using an oscillating saw after the sternal wires had been removed. With the partially divided sternum elevated using towel clips, the remaining posterior lamina was divided (Fig 1). Theoretically, this elevation increases the distance between the retrosternum and the heart to reduce the possibility of heart injury. Elevating the cut sternum by two rake retractors, retrosternal tissues were directly removed from the back of the sternum. This allows for the insertion of a sternal spreader. The retractor was spread slowly to avoid stretching any underlying tissues. Only minimal areas necessary for cannulation were dissected. When there was firm adhesion between the pericardium and thin right atrial wall, an alternative was to open the right pleural cavity and perform atrial cannulations. Basically, the ascending aorta was selected as the initial site for arterial perfusion. Right atrial or bicaval cannulation was performed for venous return, according to planned procedures. Bleeding during dissection could be well controlled with the fingers. After completion of the procedures, an air needle was inserted into the ascending aorta for evacuation of any residual air, with the patient in the Trendelenburg position. We are currently using two-dimensional transesophageal echocardiography to monitor intracardiac air.

View larger version (49K): [in this window] [in a new window]   Fig 1. Sternotomy technique. With the partially divided sternum elevated using towel clips, the remaining posterior lamina is divided.

Since January 1991, preoperative CT scans have been used routinely to define the retrosternal region. Patients in which the ascending aorta or right ventricle had adhered to the sternum (Fig 2) were considered high-risk cases. For a high-risk operation, bypass was initially started and the aorta and the heart were decompressed before performing the median sternotomy. If the heart was very close to the sternum but there was a fatty tissue between the sternum and heart (Fig 3), the femoral artery and vein were exposed but not cannulated. Once the extracorporeal bypass had been started, additional sternal division and repair of torn tissues were completed using core cooling with reduced bypass flow.

View larger version (117K): [in this window] [in a new window]   Fig 2. Thoracic computed tomography revealed that the ascending aorta was adherent to the sternum.

View larger version (107K): [in this window] [in a new window]   Fig 3. Thoracic computed tomography visualized a layer of fatty tissue between the heart and the sternum.

	Results

Top Abstract Introduction Patients and methods Results Comment References

 
Operative data
For myocardial protection, all patients in the CT group received cold blood cardioplegia, whereas 20 patients (77%) in the no CT group had cold blood cardioplegia (p = 0.0004). Nine patients (14%) in the CT group and 5 (19%) in the no CT group underwent femoral vessel cannulation. The rest of patients had the ascending aorta cannulated. The averaged total cardiopulmonary bypass time of CT group and no CT group was 185 ± 60 minutes and 179 ± 64 minutes, respectively. The two groups did not differ in cross-clamp time (110 ± 41 minutes in CT group vs 110 ± 37 minutes in no CT group). No patients required deep hypothermic circulatory arrest.

Mortality and morbidity
Hospital death occurred in 4 patient (6%) in the CT group and in 6 patients (23%) in the no CT group (p = 0.0309). Three of 4 patients in the CT group died of multisystem organ failure and one patient died from low cardiac output syndrome. Causes of death in the no CT group were low cardiac output syndrome in 4 patients, cerebral bleeding in 1 patient, and persistent cardiac failure in 1 patient. Eight patients who underwent a fourth sternotomy in both groups survived the operations. Five patients in the CT group and 6 patients in the no CT group required intraaortic balloon pump (IABP) support. Four of these 5 patients in the CT group survived, whereas only 1 of the 6 patients in the no CT group survived. One patient in the CT group required implantation of a left ventricular assist device and finally died. Mechanical ventilation of more than 72 hours was required in 15 patients (23%) in the CT group and 8 patients (31%) in the no CT group, stroke occurred in 3 patients in the CT group and in 2 patients in the no CT group, hepatic dysfunction occurred in 4 patients in the CT group, and gastrointestinal bleeding occurred in 1 patient in the no CT group. Nine patients (14%) in the CT group and 6 patients (23%) in the no CT group experienced renal dysfunction (creatinine > 2 mg/dL). In univariate analyses, nonutilization of preoperative CT scans (p = 0.0309) and NYHA class 4 (p = 0.0024) were significantly associated with hospital deaths. However, multivariate analysis revealed NYHA class 4 and year of operation to be predictors of hospital death (Table 3).

Lateral chest radiography was performed on all of the patients in the CT group, but none of the lateral chest radiographs illustrated a clear retrosternal space. In contrast, all but two CT scans enabled identification of adhesion of the heart or great vessels to the sternum. The two CT scans that did not enable identification of adhesion had many artifacts that interfered with interpretation.

Hemorrhage occurred in 7 patients (27%) in the no CT group. The hemorrhage was associated with resternotony in 5 of these patients, all of whom required immediate femorofemoral bypass. However, hemostasis was successfully performed in the above 5 patients. Bleeding occurred during dissection of the heart in the remaining 2 patients. Reexploration for postoperative bleeding was not required in any patients. The average volume of intraoperative blood loss was 2331 ± 1361 mL, which was not significantly from blood loss in the CT group. The incidences of sternotomy-related injury were 19% (5/26) in the no CT group and only 3% (2/64) in the CT group (p = 0.0198).

Univariate analyses demonstrated that the significant factors for risk of resternotomy-related injury were nonutilization of preoperative CT scans (p = 0.0198), and femorofemoral bypass (p < 0.0001). However, both of these risk factors disappeared after multivariate analyses, which indicated a fourth sternotomy to be a predictor of resternotomy-related injury (Table 3).

	Comment

Top Abstract Introduction Patients and methods Results Comment References

 
This study demonstrated that a hospital mortality and the incidence of bleeding with reentry dropped after the routine use of preoperative CT scans. The hospital mortality rate has declined from 23% to 6% and the incidence of sternotomy-related injury was 3%, down from 19% earlier. Lytle and coworkers [2] reported 15% hospital mortality in patients undergoing second valvular reoperations. Other clinical investigations have also indicated similar results [3, 4]. However, clinical data from 131 surgeons revealed that surgical mortality rose to 37% when catastrophic hemorrhage occurred during redo-sternotomy [1]. Rizzoli and colleagues [5] also reported that operative heart lacerations occurred in 20 of 863 patients undergoing reoperations, with 50% perioperative mortality and a death hazard ratio of 7.6. Accordingly, hemorrhage should be prevented during redo-sternotomy and dealt appropriately when it occurs.

A third or fourth operation appears to carry a high risk compared with that of a primary one. The reason can be that median sternotomy used for a third or fourth operation is technically more demanding because of dense adhesions. To prevent catastrophic hemorrhage, Dobell and Jain [1] recommended that the pericardium should be closed at the first operation, the risk of sternotomy hemorrhage should be assessed preoperatively, the groin should be prepared, and the perfusion lines should be primed and positioned in a sterile field. We agree with their recommendations, though there is some doubt as to whether the closure of the pericardium will prevent catastrophic hemorrhage. Most importantly, the condition of retrosternal adhesion should be routinely checked preoperatively.

CT scans provide information on distension of the right atrium or right ventricle, position and size of the ascending aorta, and presence of a pseudoaneurysm. Our decision to perform femorofemoral cardiopulmonary bypass before sternal division has been based on this information obtained from CT scans. Even if the heart is very close to the sternum, CT scans can indicate whether or not there is a fatty tissue between the heart and the sternum. If fatty tissue exists, there is less risk of hemorrhage with reentry. Although presternotomy bypass lowers the incidence of resternotomy-related hemorrhage by decompression of the distended heart and the enlarged aorta, prolonged bypass time is highly associated with postoperative complications. Therefore, an unnecessary presternotomy bypass should be eliminated.

The routine use of preoperative CT scans requires debate. From a cost-benefit point of view, CT scans should be considered in patients for whom a decision as to whether presternotomy bypass is necessary is required. Unfortunately, it is difficult to select such patients preoperatively. On the other hand, conventional chest radiography is suitable for routine study because it is cheap. However, in the present study, the necessity of presternotomy bypass could not be determined on the basis of chest radiographs because the radiography did not provide any information on adhesions between the heart and sternum. The quantitative superiority of CT scanning and the difficulty in selection of appropriate patients may justify routine use of preoperative CT scans.

The reported incidences of hemorrhage during redo sternotomy range from 0% to 6% [1, 5–7]. The incidence of injuries in our series of patients, however, was slightly higher (8%). The higher incidence can be partly explained by the fact that our patients underwent a third or fourth sternotomy, whereas other series included many patients who had undergone a second sternotomy. After initiation of routine study with CT scans, the incidence of injuries dropped to 3%, the same as that previously reported.

Refinement of the technique of redo sternotomy is another possible means for prevention of sternotomy-related injury. Numerous techniques to reduce the incidence of injury have been developed [4, 6–11]. Some investigators reported 0% injury with their techniques [9, 11]. Nevertheless, we believe that the incidence of resternotomy-related injury cannot be reduced to 0% because there is still a high probability of occurrence of injury. Our multivariate analysis demonstrated that a fourth sternotomy is associated with a high incidence of heart or great vessel injury. For such high-risk patients, presternotomy bypass should be considered on the basis of information obtained from preoperative CT scans, whatever technique for resternotomy is used.

Despite the fact that there were no deaths resulting from hemorrhage in our series, the mortality rate was still high. Our multivariate analysis indicated NYHA 4 to be the significant predictor of hospital mortality. The high mortality rate can be partly explained by a general tendency to delay third and fourth operations until NYHA 4 because such operations are believed too risky. The hospital mortality rate decreases to 7% if NYHA 4 patients are excluded from our patients, indicating that a third or fourth sternotomy itself does not carry a high risk. Moreover, recent improvements in surgical techniques and postoperative care have resulted in a decrease in hospital mortality rate. Therefore, it is important to perform operations when necessary.

The main limitations of this study arise from the small size of the patient group. Other limitations are the retrospective nature and the long duration of the study. Because of these limitations, it is difficult to make a definite conclusion about the effect of preoperative CT scans on incidence of resternotomy-related complications and early mortality of patients undergoing third and fourth sternotomies. Nonetheless, our study has provided some information on how third and fourth sternotomies can be performed safely, information that has been lacking in previous reports.

In conclusion, CT scans provide preoperative information on retrosternal adhesions. When a distended heart or expanded aorta has adhered to the sternum, femorofemoral cannulation should be performed before sternotomy. Third and fourth sternotomies, though demanding procedures, can be performed safely using the described strategy.

	References

Top Abstract Introduction Patients and methods Results Comment References

 

1. Dobell A.R.C., Jain A.K. Catastrophic hemorrhage during redo sternotomy. Ann Thorac Surg 1984;37:273-278.[Abstract]
2. Lytle B.W., Cosgrove D.M., Taylor P.C., et al. Reoperations for valve surgery: perioperative mortality and determinants of risk for 1000 patients, 1958–1984. Ann Thorac Surg 1986;42:632-643.[Abstract]
3. Piehler J.M., Blackstone E.H., Bailey K.R., et al. Reoperation on prosthetic heart valves. Patient-specific estimates of in-hospital events. J Thorac Cardiovasc Surg 1995;109:30-48.[Abstract/Free Full Text]
4. Follis F.M., Pett S.B., Jr, Miller K.B., Wong R.S., Temes R.T., Wernly J.A. Catastrophic hemorrhage on sternal reentry: still a dreaded complication?. Ann Thorac Surg 1999;68:2215-2219.[Abstract/Free Full Text]
5. Rizzoli G., Bottio T., De Perini L., Scalia D., Thiene G., Casarotto D. Multivariate analysis of survival after malfunctioning biological and mechanical prosthesis replacement. Ann Thorac Surg 1998;66:S88-S94.
6. Najafi H., Guynn T., Najafi C., Alden T. Declining risk of reoperative valvular surgery. J Card Surg 1995;10:185-197.[Medline]
7. Temeck B.K., Katz N.M., Wallace R.B. An approach to reoperative median sternotomy. J Card Surg 1990;5:14-25.[Medline]
8. Culliford A.T., Spencer F.C. Guidelines for safely opening a previous sternotomy incision. J Thorac Cardiovasc Surg 1979;78:633-638.[Abstract]
9. Garrett H.E., Matthews J. Reoperative median sternotomy. Ann Thorac Surg 1989;48:305.[Abstract]
10. Eddy A.C., Miller D., Johnson D., et al. Anterior sternal retraction for reoperative median sternotomy. Am J Surg 1991;161:556-559.[Medline]
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