|Home | About | Journals | Submit | Contact Us | Français|
Although the term “complex aortic surgery” has come into increasing use, it has not been defined. We propose the following definition: replacement or remodeling (not resuspension of commissures) of the aortic root, together with either an intracardiac procedure or a replacement of more than 1 segment of aorta, all of which require cerebral protection.
We retrospectively analyzed data pertaining to 152 patients (mean age, 56 ± 12 years) who underwent surgery for thoracic aortic disease with aid of cardiopulmonary bypass from October 2000 through December 2005. The replaced segment was the ascending aorta with or without the root in 106 patients, the aortic arch in 15, and the descending aorta in 31. Among these patients, 10 met our proposed criteria and constituted the complex group. In this group, in addition to the aortic root, the entire thoracic aorta (ascending, arch, and descending) was replaced in 4 patients, the total arch in 2, and a partial arch in 1. The remaining 3 underwent valve or coarctation repair. Their outcomes were analyzed as a sub-group within the overall outcome.
The in-hospital mortality rate was 12.5% in the overall group (19/152), 4.1% in elective cases (3/73), and 10% in the complex group (1/10). Duration of cardiopulmonary bypass, myocardial ischemia, and total cerebral protection times were significantly longer in the complex group (P <0.0001). Total cerebral protection time over 40 minutes was the only predictor of neurologic morbidity (P = 0.003; odds ratio, 4.7).
Procedural complexity, as we defined it, increased neurologic morbidity, but not the mortality rate.
Although the term “complex aortic surgery” has come into increasing use, it has not been defined. We propose the following definition: replacement or remodeling (not resuspension of commissures) of the aortic root, together with either an intracardiac procedure or a replacement of more than 1 segment of aorta, all of which require cerebral protection. We present our results in a series of patients who met the proposed criteria. Patients not requiring cerebral protection and those requiring aortic cross-clamping were excluded. The outcomes of the series of patients were analyzed as a subgroup within the overall outcomes.
We retrospectively analyzed the data concerning 152 patients (mean age, 56 ± 12 years) who had undergone operation for thoracic aortic disease with cardiopulmonary bypass from October 2000 through December 2005. Among these patients, 10 met our proposed criteria and thereby constituted the complex group. Some of the preoperative and operative variables of the entire group of 152 are given in Table I.
In all patients in the complex group, the aortic root and the ascending aorta were replaced and a period of deep hypothermic circulatory arrest (HCA) (mean, 34 ± 10 min) was imposed. In addition, the entire thoracic aorta (the ascending, arch, and descending segments) was replaced in 4 patients, the total arch in 2 patients, and a partial arch in 1 patient. In the remaining 3 patients, the mitral valve was replaced in 1, the tricuspid valve was repaired in another, and an ascending–descending aorta bypass was performed in the last. Coexisting diseases were hypertension in 5 patients and Marfan syndrome in 2. Previous aortic operation had been performed in 3 patients. Some of the demographic, operative, and outcome data on the complex group are provided in Table II.
Exposure was obtained by sternotomy, clamshell incision (bilateral anterior thoracotomy and transverse sternotomy) (Fig. 1), or posterolateral thoracotomy. Cannulation was performed after systemic heparinization; the arterial cannulation sites are shown in Table I. After the institution of cardiopulmonary bypass, patients who would require HCA were cooled to a rectal temperature of 16 °C. The remaining patients were cooled to 28 °C. The ascending aorta was clamped and the proximal repair was accomplished during cooling. Cold blood cardioplegic solution, administered antegrade and retrograde, was used for myocardial protection. The right superior pulmonary vein was used for venting. Gelatin-coated Dacron grafts were used for aortic segment replacement, and bileaflet mechanical valves were used in the course of aortic root replacement. Teflon felt was used for graft-to-aorta anastomosis. In patients who had descending aortic disease, resection was performed by mobilizing the aorta and clipping the intercostal arteries externally. None of the intercostal arteries was reimplanted. The left ventricular apex was used for venting in the thoracotomy approach.
Among patients who required HCA, 7 patients in the complex group and 10 patients in the noncomplex group received antegrade cerebral perfusion through the arch graft at a rate of 10 mL/(kg·min), in order to maintain a radial artery pressure of 50 mmHg. Perfusion times with comparisons between the groups are given in Table III. The mean numbers of transfused blood and fresh frozen plasma units per patient for the entire group of 152 were 3.2 ± 1.9 and 2.4 ± 1.4 units, respectively.
Statistical Analysis. Statistical analyses were performed by using the SPSS/PC+ (version 10.0) computer program (SPSS Inc.; Chicago, Ill). A P value <0.05 was con-sidered significant. Frequency and percentage values of categoric variables, and mean, average, and standard deviation values of continuous variables were determined. Patient characteristics and outcomes were compared by using t tests for continuous variables and the χ2 or Fisher exact test for categoric variables. Pre- and intraoperative variables that might affect death or morbidity were analyzed by univariate analysis, which was followed by multivariate stepwise logistic regression analyses. Factors that reached significance in the univariate analysis were entered into the multivariate analysis. Values were expressed as mean ± standard deviation.
The in-hospital mortality rate of the entire group was 12.5% (19/152). The mortality rate was 4.1% (3/73) in elective cases. Eighteen patients (11.8%) developed temporary neurologic dysfunction (confusion, agitation, or lethargy) or minor temporary neurologic events (such as diplopia or monoparesis); 4 (2.6%) developed major stroke. Neurologic events were documented by a consulting neurologist and an intensive-care physician. Computed tomographic scans of the brain could not be performed in the 4 patients with major stroke due to logistic reasons, and all these patients died. Eight patients developed renal failure that required dialysis, and 6 developed respiratory failure that required tracheostomy. In the complex group, the death rate was 10% (1/10). Some of the operative and outcome data for the complex group are shown in Table II.
Univariate analysis revealed that emergency operation (P = 0.011), aortic dissection (P = 0.017), use of HCA (P = 0.042), and transfusion of more than 4 units of blood (P = 0.037) or more than 3 units of fresh frozen plasma (P = 0.017) were associated with death. Advanced age (P = 0.012), complex group (P = 0.039), arch replacement (P = 0.002), use of HCA (P = 0.02), cerebral ischemic time longer than 30 min (P = 0.044), and total cerebral protection time longer than 40 min (P = 0.003) were associated with neurologic morbidity. In multivariate analysis, there was no single factor associated with death. Total cerebral protection time (TCPT) longer than 40 min was the only predictor of neurologic morbidity (P =0.003; odds ratio, 4.76; confidence intervals, 1.72–13.11). Duration of cardiopulmonary bypass, myocardial ischemia, and TCPT were significantly long-er in the complex group (Table III).
Traditionally, thoracic aortic cases have been reported according to the location of the replaced segment. Thoracoabdominal aortic aneurysms, which are beyond the scope of this article, have been well classified.1 Replacement of the thoracic aortic segments (namely, the root, ascending aorta, arch, and descending aorta) requires perfusion methods that vary with the segment. Aortic root and arch replacement require long periods of myocardial and cerebral protection, respectively. Similarly, ascending aorta and root replacement under circulatory arrest—performed together with an intracardiac procedure (not 1- or 2-vessel coronary artery bypass grafting)—prolongs the protection time. Therefore, we consider the combination of such procedures to be complex. Cardiopulmonary bypass and myocardial and cerebral protection times were significantly long-er in our complex group. Long periods of myocardial ischemia or cardiopulmonary bypass emerged as incremental risk factors for death in our previous analysis of patients with acute dissection,2 but not in this study. One might regard aortic reoperations as complex, but we regard them as difficult, rather than complex, because they prolong dissection time but not perfusion or organ protection times.
We define complexity on the basis of procedural risk, not on the basis of patient- or disease-related risk. One can perform a low-risk (low-complexity) operation on a high-risk patient: for example, replacement of the ascending aorta with a tubular graft in a patient who pre-sents with visceral malperfusion or rupture in association with acute type A dissection. The univariate factors that we mention above in association with risk of death (emergency operation, aortic dissection, use of HCA, and the requirement of substantial amounts of transfused blood or fresh frozen plasma) are well-known risk factors that are encountered in patients who present with acute type A aortic dissection. Our mortality and complication rates compare favorably with those of the 2 recent series reported by Harrington3 and Schepens4 and their associates.
Because most of the non-neurologic morbidity resulted in death, we would like to focus here on neurologic outcomes. Neurologic morbidity, especially temporary neurologic dysfunction—described by Ergin and associates5 as a reflection of subtle brain injury—was higher in our complex group, probably due to prolonged periods of cerebral ischemia. It has been shown that HCA affords adequate protection for up to 30 min.6 If a long-er period of cerebral ischemia is expected, then an additional protection measure, preferably antegrade cerebral perfusion, should be used.7 Total cerebral protection time is the sum of time required for HCA and either antegrade or retrograde cerebral perfusion.7 Longer periods of TCPT, as seen in our complex group, constitute the only incremental risk factor for neurologic events, according to our analysis.
The variables that have emerged as risk factors from some previous aortic surgery studies support the ration-ale behind our definition of “complex aortic surgery.” In their analysis of brain protection techniques, Hagl and colleagues7 reported that performing mitral valve replacement or other concomitant procedures in addition to an aortic procedure was an independent risk factor for stroke, along with the duration of TCPT. Harrington and coworkers3 reported that, among patients who underwent aortic root replacement, length of stay in the intensive care unit was prolonged in those who underwent total arch replacement.
One important issue is hemostasis. It has been reported that prolonged cardiopulmonary bypass time, but not the use of profound hypothermia, is associated with increased postoperative hemorrhage after proximal aortic surgery.3 Telescopic aortic anastomosis, when supported by Teflon felt, is very hemostatic and durable.8 This technique, which we used in most of our patients, might counterbalance the bleeding associated with long cardiopulmonary bypass times.
In conclusion, we wish to emphasize the need to define procedural risk in operations on the thoracic aorta, for the purpose of risk stratification. Some have reported complex procedures (for example, Bentall plus total arch) as a subgroup, without giving specific mortality rates.3,4 In our study, procedural complexity increased neurologic morbidity, but not the mortality rate. Large-scale analyses from high-volume centers are needed for risk stratification in thoracic aortic surgery. Our suggested definition of complex aortic surgery may help delineate procedural risk.
Address for reprints: Anil Apaydin, MD, Department of Cardio-vascular Surgery, Ege University Medical School, Bornova–Izmir 35100, Turkey. E-mail: email@example.com