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a Department of Cardiothoracic Surgery, Mount Sinai School of Medicine, New York, New York
b Department of Anesthesiology, Mount Sinai School of Medicine, New York, New York
Accepted for publication April 28, 2009.
* Address correspondence to Dr Etz, Department of Cardiothoracic Surgery, Mount Sinai School of Medicine, One Gustave L. Levy Pl, New York, NY 10029 (Email: christian.etz{at}mountsinai.org).
Presented at the Forty-fifth Annual Meeting of The Society of Thoracic Surgeons, San Francisco, CA, Jan 26–28, 2009.
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Abstract |
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Methods: Sixty patients (34 male, mean age 54.4 years) underwent redo thoracotomy for DTA (22 patients) or extended thoracoabdominal incision for reoperative TAAA (38 patients) from March 1988 to June 2007, after 1.7 ± 0.9 previous cardioaortic procedures. Forty-one patients were hypertensive (68%), 18 were smokers (30%), 9 had Marfan syndrome (15%), 9 had coronary artery disease (15%), 5 had chronic obstructive pulmonary disease (8%), and 3 had diabetes mellitus (5%). In all, 45% (27 patients) had previous dissection, 30% (18) had atherosclerotic aneurysms, 15% had coarctation surgery (9), and 6 patients had other etiologies. Mean follow-up, 100% complete, was 6.5 years.
Results: Hospital mortality for reoperative DTA/TAAA was 13.3% (8 patients). Although 6.3 ± 2.9 (0 to 14) segmental artery pairs were sacrificed at reoperation—and 6.2 ± 2.3 (1 to 12) initially—for a total of 10.6 ± 3.9 (2 to 15) segmental artery pairs sacrificed, only 1 patient had paraplegia (1.6%). Four patients had a 2-day procedure, with 12 to 24 hours of intensive care unit recovery after lysis of extensive adhesions: all survived. Respiratory complications occurred in 13 patients (21.6%), and permanent dialysis was required in 2 (3.3%), but there were no strokes. Adverse outcome—1-year mortality, stroke, permanent dialysis, or paraplegia—occurred in 13 patients (21.6%). Adverse outcome was marginally associated (p < 0.2) with increased age, atherosclerotic aneurysms (33% versus 17% other), TAA incision (30% versus 9%), and greater aneurysm extent, and was significantly associated with perfusion technique (p = 0.02). Adverse outcome occurred in 3 of 4 patients who had clamp-and-sew technique, 6 of 21 using partial cardiopulmonary bypass (28.6%), and 3 of 17 with partial left heart bypass (17.7%), but only 1 of 18 with hypothermic circulatory arrest (5.6%).
Conclusions: Reoperative DTA/TAAA repair was significantly safer with hypothermic circulatory arrest rather than partial cardiopulmonary bypass, partial left heart bypass, or clamp-and-sew strategy. A 2-day procedure may be advisable for patients with extensive adhesions.
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Introduction |
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Reoperative patients have been reported to be an average of 7 years older than patients presenting for primary procedures, and appear to present more often with renal failure, cerebrovascular disease, atherosclerotic heart disease, more extensive aneurysms (Crawford II/III), and rupture, and are more often symptomatic and likely to have preexisting spinal cord injury [3]. Their preoperative risk profile predicts a likelihood of significant operative mortality and postoperative morbidity. We suspect that the fear of an adverse outcome has often led to the reluctance of surgeons to undertake even indicated reoperations in some patients.
Increasing life expectancy and initial surgical treatment of aortic disease at an advanced age are likely further to increase the mean age of patients in need of reoperation, since patients with thoracic aortic aneurysms are at a substantial risk of having subsequent aneurysms in previously unoperated segments of the aorta [4]. Natural history studies have demonstrated that a separate aneurysm involving the abdominal aorta develops in at least 25% of patients initially presenting with a thoracic aortic aneurysm. Pressler and McNamara [5] found separate abdominal aortic aneurysms in 26 of 90 patients (28.9%) with nondissecting thoracic aortic aneurysms: 4 of these 26 patients (15.4%) died of a ruptured abdominal aortic aneurysms.
Patients with multilevel or recurrent aortic aneurysmal disease thus represent a complex cardiovascular therapeutic challenge as rupture of a second aneurysm is a frequent cause of death after successful aortic aneurysm repair [6, 7]. In patients who originally presented with aortic aneurysms involving the ascending, transverse arch, or descending segments, Crawford and coworkers [7] reported that multiple aneurysms developed in nearly 60%; in contrast, multiple aneurysms developed in only 12% of patients who initially had abdominal aortic aneurysms. New or recurrent aortic aneurysms accounted for about 30% (36 of 130) of thoracic aortic reoperations reported by Carrel and colleagues [8].
Because alternatives to surgery are often not available for complex aortic disease, innovative strategies to manage the technical challenges are mandatory to allow reoperative procedures to be successful. At present, although surgical treatment is usually necessary to prevent rupture and improve survival in patients with multiple aneurysms, data regarding the risks associated with multiple aortic operations have been conflicting. Most present the results of more proximal aortic operations after infrarenal abdominal aortic aneurysm repair [9]. Previous reports of small series have described early mortality rates ranging from 25% to 28.6% [10-12]. A contemporary series describes a 30-day mortality of 11.4% [4].
The reported outcomes after surgical repair of multilevel and recurrent aortic aneurysms vary widely. Specific information regarding the results of TAAA repair after previous thoracic aneurysm repair through a left thoracotomy are limited, and thus the safety of TAAA repair in patients with previous thoracic aneurysm repair through left thoracotomy remains somewhat uncertain. To clarify these issues—and to establish a standard against which future endovascular and hybrid approaches can be compared—we retrospectively evaluated our 20-year experience with TAAA repair in patients with previous thoracic aneurysm repair through a left thoracotomy.
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Material and Methods |
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Patient Demographics
Thirty-four were male (56.7%); mean age was 54.4 ± 16.7 years (median 55; range, 13 to 80). Forty-one patients (68%) were hypertensive, 18 (30%) were smokers, 9 (15%) had Marfan syndrome, 9 (15%) had coronary artery disease, 5 (8%) had chronic obstructive pulmonary disease, and 3 (5%) were diabetic. Table 1
summarizes the clinical characteristics of all patients who underwent redo lateral thoracotomy. The average number of previous cardioaortic procedures was 1.7 ± 0.9. Most of the reoperated patients had undergone one previous operation, but 18 had had two previous procedures, 9 had had three, and 2 had undergone four previous aortic procedures, of which at least one was carried out through a left lateral thoracotomy.
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Previous Procedures in Reoperated Patients
Sixty consecutive patients underwent redo lateral thoracotomy after a total of 102 previous cardioaortic procedures, of which more than 90% involved the thoracic or abdominal aorta. Eighty-six were previous thoracic aortic aneurysm repairs: 3 ascending aortic aneurysm repairs, 8 Bentall procedures, 11 coarctation repairs, 12 complete arch repairs (7 as the first stage of an elephant trunk procedure), 39 descending thoracic aortic operations, 13 thoracoabdominal operations, and 6 abdominal aortic aneurysm repairs. The remaining patients had, in addition, aortic valve replacements (2), coronary artery bypass graft surgery (4), and various other procedures (4). The interval between the first and the last thoracotomy was 7.6 years on average (median interval 5.2; interquartile range, 0 to 32).
Surgical Management
Arterial cannulation
Arterial cannulation was carried out either through the femoral artery (n = 50; 89%), the distal transverse arch/previously placed aortic graft (n = 5; 9%), or (in 1 patient; 2%) through the right axillary artery. Venous cannulation was established with a wire-directed catheter placed in the right atrium through the femoral vein.
Hypothermic circulatory arrest
Hypothermic circulatory arrest (HCA) was used in 18 patients (30%) and was effected by surface (cooling blanket) and perfusion cooling. The decision to utilize HCA was prompted by technical considerations, often involving the feasibility and safety of clamping the aorta proximal to the repair. If HCA was anticipated early in the procedure, the patient was cooled during the initial period of cardiopulmonary bypass. A minimum of 30 minutes of cooling was utilized. In some patients in whom HCA was instituted later in the operative procedure, the patient was maintained at a perfusion temperature of 20°C until about 15 minutes before HCA, after which the blood temperature was lowered to 10°C. Adequate cerebral cooling was assured in all cases by a jugular venous saturation greater than 95% and an esophageal temperature of 12° to 15°C. In all patients for whom more than 20 minutes of HCA was anticipated, the head was packed circumferentially in ice. The average cerebral ischemia time during HCA was 37 ± 9 minutes (median 36; range, 22 to 57) at a mean esophageal temperature of 13.4 ± 1.9°C. Perfusion warming was carried out at the end of the procedure, with the gradient between the esophageal and blood temperature maintained at less than 10°C. Warming was maintained until esophageal temperature reached 35°C, and bladder temperature was greater than 32°C. Downward drift, however, resulted in most patients leaving the operating room at esophageal and bladder temperatures of 32°C. Warming was usually accomplished in 1 hour of perfusion; during the last 15 or 20 minutes, partial bypass was frequently utilized to take advantage of improved warming with pulsatile perfusion. Intraoperative details for the entire series are summarized in Table 2.
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Partial cardiopulmonary bypass
Partial cardiopulmonary bypass was used in 21 patients (35%). In all cases, right atrial drainage was established through the common femoral vein and the catheter position monitored by transesophageal echocardiography. A centrifugal pump and cardiopulmonary bypass circuit without a reservoir was utilized at flows of 2,000 to 4,000 cc/min. The mean esophageal temperature during partial cardiopulmonary bypass was 30.9 ± 1.9°C, with an average duration of perfusion of 122 ± 64 minutes. For visceral perfusion, additional catheters were used in 13 patients for the kidneys, for the superior mesenteric artery, and for the celiac trunk.
Partial left heart bypass
Left heart bypass (LHB) was used in 17 patients (28%). Left atrial to femoral artery bypass was adjusted to maintain equal pressures above and below. Arterial cannulation was through a common femoral artery in 15 patients (88%), and through a central cannula (namely, in the proximal descending aorta or the distal arch) in 2 patients (12%). The left atrium was drained directly in 5 patients (29%) and through the left inferior pulmonary vein in 12 patients (71%) using a BioMedicus circuit (Medtronic Biomedicus Inc, Eden Prairie, MN) without a reservoir. Flows varied from 1,500 to 4,000 cc/min, and the average duration of LHB was 60 ± 36 minutes at a mean esophageal temperature of 32 ± 1.4°C.
DTA/TAAA Repair Technique
The aneurysm was dissected free from mediastinal tissue. The intercostal and lumbar arteries remaining after the previous aortic repair were dissected and temporary occluded. If MEP and SSEP remained unchanged, the segmental vessels were sacrificed before opening the aneurysm to avoid backbleeding and possible steal from the spinal cord circulation. In general—in view of their importance in supporting spinal cord perfusion—clamping of the subclavian artery was avoided, and the internal mammary artery and the superior epigastric axis were preserved. If clamping of the distal aorta was not feasible or unsafe, the distal anastomosis was performed first, and distal perfusion restored after cross clamping of the graft. Vascular Dacron grafts (Hemashield; Boston Scientific, Natick, MA), 18 to 34 mm, with as many as three additional side arms, were implanted in an end-to-end fashion. For the visceral segment, a beveled anastomosis was frequently utilized. If the visceral segment required circumferential replacement, the visceral vessels were occluded with a balloon catheter and intermittently perfused with cold blood before being directly anastomosed to the graft or connected utilizing intervening graft segments (8 to 12 mm Dacron).
Revascularization of the Visceral Segment
A total of 30 patients (50%) underwent reimplantation of at least one visceral vessel: in these cases, partial cardiopulmonary bypass was used in 17 patients (57%); LHB was performed in 7 patients (23%); a clamp-and-sew repair was performed in 4 patients (13%); and 2 patients (7%) underwent deep HCA. The superior mesenteric artery and the celiac trunk were reimplanted in 27 patients: the preferred technique for reimplantation was through an additional side arm in the main graft (n = 18; 67%) followed by a Carrel patch (n = 9; 30%). The renal arteries were reimplanted in 28 patients: in 20 cases (71%), an additional graft was utilized; in 8 cases (22%), a button technique was preferred.
Motor Evoked Potential Monitoring
After induction, volatile anesthetics were discontinued, as were muscle relaxants, and narcotic anesthesia was substituted. Motor evoked potentials (MEPs) were elicited by a train of nine transcranial electrical pulses delivered from a Digitimer D185 cortical stimulator (Welwyn, Garden City, UK). The stimuli were applied through two disposable corkscrew electrodes (Nicolet Biomedical, Madison, WI) anchored in the scalp overlying the left and right motor cortices, respectively, approximately 6 to 8 cm lateral from vertex. In response to stimulation, MEPs (composed of compound muscle action potentials) were recorded from the skin over the tibialis anterior (leg) and abductor pollicis (hand) muscles through subdermal needle electrodes. The recordings from the hands permit evaluation of the effects of anesthesia and temperature on the amplitudes of the MEPs. The signals were amplified, filtered, digitized, and saved to hard drive. The stimulation intensity was set to 10% above the level that elicited the maximal MEP amplitude for each patient. A decrease of 50% in amplitude of the leg MEPs in the presence of stable hand MEPs was considered to reflect a lower body ischemic event. The MEP monitoring has been performed in 20 patients since 2002.
Somatosensory Evoked Potential Monitoring
Somatosensory evoked potentials (SSEPs) were elicited by stimulation of the left and right posterior tibial nerves through two surface disk electrodes placed approximately 2.0 cm apart below the medial malleolus at the ankle. Recordings were made from the scalp overlying the somatosensory cortex using subdermal needle electrodes placed approximately 3 to 4 cm behind vertex and referenced to an electrode at FPz on the forehead. A ground electrode was placed on the shoulder. The recorded signals were amplified, filtered, and saved to hard drive. The responses to 200 to 300 stimuli were averaged. Ischemic spinal cord dysfunction was defined as a decrease in SSEP amplitude of more than 50%. The SSEP monitoring has been performed in 46 patients since 1993. In 45 of 46 cases, MEP and SSEP remained unchanged during the course of serial segmental artery sacrifice, or could be returned to baseline levels by anesthetic and blood pressure manipulation. One patient had loss of SSEPs and MEPs late intraoperatively, and is discussed below.
Segmental Artery Sacrifice and MEP/SSEP
An average of 10.6 ± 3.9 segmental artery (SA) pairs (median 12; range, 2 to 15) were sacrificed overall—6.2 ± 2.3 during previous aortic procedures (median 6; range, 1 to 12) and 6.3 ± 2.9 during the redo lateral thoracotomy (median 6; range, 0 to 14). In 83% of patients, almost 90% of all SAs (in average 6.1 ± 1.7 SA pairs) were sacrificed between T7 and L1, where the artery of Adamkiewicz is presumed to arise. In 80% of patients (47 of 60), an average of 5.9 ±1.8 SAs were sacrificed between T9 and L3—an area of the spinal cord that has been suggested to be particularly important by Biglioli and coworkers—without MEP/SSEP loss [13]. During the early period of this study, 5 patients had SA reimplantation, 1 after SSEP loss. The extent of segmental artery sacrifice in each patient, and the level of intersegmental artery resection, are shown in Figure 1, with the patients in chronological order.
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Postoperative Management
The SSEPs were monitored until the patient awakened. Thereafter, hourly brief neurological examinations were performed for 72 hours. High normal blood pressures were maintained, aiming for a mean aortic pressure of 90 mm Hg. The CSF drainage was continued for 48 to 72 hours, and methylprednisolone was used for 72 hours (1,000 mg, day 0; 375 mg, day 1; 250 mg, day 2).
Follow-Up
Patients were followed by their referring cardiologist and contacted periodically by our research personnel. Annual computed tomography scans were scheduled for all patients. Postoperative events were compiled and analyzed according to the Guidelines for Reporting Morbidity and Mortality after Cardiac Valvular Operations and our institutional check list. For this study, the follow-up was closed on December 13, 2007, and was 100% complete. Follow-up time for the entire cohort (n = 60) ranged from 0 to 19 years (median 4), with an average of 4.8 ± 4.3 years. Long-term survival was evaluated for the 48 patients still alive 1 year postoperatively (median follow-up 3.7 years; range, 0.1 to 18).
Statistical Methods
Data were entered in Excel spreadsheets and transferred to a SAS file (SAS Institute, Cary, NC) for data description and analysis. Patient and disease characteristics are described as percents, median (range) or means (standard deviation). The two major outcomes considered are adverse outcome among all patients in the sample, and long-term survival among patients who were alive 1 year after their surgery. For the latter, follow-up time started 1 year after the procedure date and terminated at the earliest of death or last contact alive.
Factors were tested for association with adverse outcome by 
2 tests or logistic regression, as appropriate. Long-term survival probabilities were estimated from a Kaplan-Meier life table. We also estimated the annual death rate for this group per person-year of follow-up, as well as the standardized mortality ratio. This gives the observed numbers of deaths relative to the number that would be expected based on New York State population death rates for comparable age, sex, and follow-up times. Statistical significance of the standardized mortality ratio was tested under a Poisson model, implemented with SAS Proc Genmod.
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Results |
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Postoperative Course
Hospital mortality—defined as death in the hospital or within 30 days postoperatively— for reoperative DTA/TAAA was 13.3% (8 patients; Table 3).
The mean age of the patients who died was 61 ± 13.2 years. Three patients died intraoperatively: 2 had cardiac failure, and 1 patient had uncontrollable bleeding from the pulmonary artery and was found only at autopsy to have had an extensive histiosarcoma mimicking a pseudoaneurysm.
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Postoperative Complications
Serious bleeding requiring reoperation occurred in 3 patients (5%). Severe respiratory complications required tracheotomy in 5 patients. Extracorporeal membrane oxygenation support was necessary in 1 patient; 7 patients (11.6%) had prolonged initial intubation or required reintubation.
Only 1 patient (1.6%) had spinal cord injury. This hypertensive patient had been operated on with LHB, and delayed onset paraparesis was detected on the second postoperative day. All aortic segmental arteries had been sacrificed: T9 to L4 during reoperation, and T3 to T8 during the first procedure, 4 years earlier. Cerebrospinal fluid drainage could not be established during the second operation, and equivocal intraoperative SSEP recordings with a poor signal were attributed to technical problems. A magnetic resonance imaging scan performed 2 days after the procedure showed spinal cord injury at the level of T8. After a short period of rehabilitation, the patient recovered some motor function, and he was able to ambulate with assistance at the time of discharge, but currently is wheelchair bound.
Adverse Outcome
Adverse outcome was defined as paraplegia, permanent hemodialysis, or stroke within 30 days after operation, or death within 1 year after operation. An adverse outcome occurred in 13 patients (21.6%). Adverse outcome was marginally associated—but without reaching statistical significance (0.05 < p > 0.2)—with increased age, atherosclerotic aneurysms, thoracoabdominal incision, and greater aneurysm extent. Perfusion technique was the only variable with a significant (p = 0.02) impact upon adverse outcome (Table 5). Adverse outcome occurred in 3 of 4 patients (75%) who had clamp-and-sew technique, in 6 patients (28.6%) using partial cardiopulmonary bypass, and in 3 patients (17.7%) with partial LHB. Only 1 patient of the 18 with HCA (5.6%), however, experienced an adverse outcome.
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The higher annual death rates of 1-year survivors resulted in estimated long-term survival probabilities of 98% 1 year later, 93% 2 years later, and 69% 5 years later. Corresponding survival rates for the age- and sex-matched New York State population are 99%, 99%, and 96%, respectively (Fig 3).
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Comment |
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Gloviczki and colleagues [14] reviewed the Mayo Clinic experience of 102 consecutive patients with multiple aortic aneurysms who underwent 201 aortic reconstructions. The initial operations involved the thoracic aorta in 65 patients (63.7%), and were limited to the lower abdominal aorta in 37 (36.3%); TAAA repair was performed as a subsequent procedure in 37 patients (36.3%). Overall operative mortality increased with the number of procedures: 4.4% for the first operation, 10.4% for the second, and 33.3% for the third. In contrast, of the 1,509 patients in Crawford's complete TAAA experience, reported by Svensson and colleagues [15], 181 (12%) had a previous proximal aortic operation: compared with the patients without previous thoracic aortic repair, this group was characterized by a lower 30-day mortality rate (4% with previous thoracic aortic repair versus 9% without previous thoracic aortic repair; p < 0.025) and a lower incidence of postoperative renal failure (8% versus 19%; p < 0.0004), although there was an increased incidence of paraplegia (20% versus 15%; p < 0.05). The Crawford series statistics suggest the possibility that some patients with high risk factors were denied operation for fear of a high operative mortality, and raise the specter of a higher risk of paraplegia in these patients.
Our experience suggests that the overall mortality and morbidity are within acceptable ranges, especially given that there is at present no real alternative to surgery in terms of preventing rupture, which is a potent threat. Endovascular approaches in this situation hold out some promise, but are likely to be complicated endeavors, given the need in 50% of the current cohort for vascularization of visceral vessels, and the risks associated with an additional debranching procedure. Furthermore, suitable landing zones to permit stent placement are not likely to be present in all patients. Stent placement may not be appropriate in patients with connective tissue disorders. The long-term results with stent placement are an especial concern in this cohort, which included a relatively high proportion of younger patients.
With regard to spinal cord injury, we did not find what appears to be a significantly enhanced risk: only 1 patient experienced parapaplegia. In this patient, a magnetic resonance imaging study showed localized spinal cord injury at the level of T8, one segmental level away from the center of all the segmental arteries sacrificed. This supports our theory, derived from experimental studies, suggesting that the collateral network's flow reserve declines progressively toward the middle of the longitudinal center of SAs sacrificed, while it supplies sufficient blood flow at the cranial and caudal margins of the resected aneurysm [16, 17]. The occurrence of spinal cord injury in this case also supports the concept of direct measurement of spinal cord perfusion pressure: low levels of spinal cord perfusion pressure might have alerted the surgical team to take more seriously the equivocal SSEP readings that had been observed intraoperatively [18]. The occurrence of spinal cord injury in this patient also underscores the importance of meticulous postoperative as well as intraoperative neuromonitoring, and the value of CSF drainage.
From this retrospective review, we have made the arguably surprising observation that reoperative DTA/TAAA repair seems to be significantly safer with HCA rather than partial cardiopulmonary bypass, partial LHB, or a clamp-and-sew strategy. Recent experience with direct spinal cord perfusion pressure monitoring has suggested that spinal cord perfusion pressures are not as high with either of these nonpulsatile distal perfusion techniques as with cardiopulmonary bypass. It is possible that deep HCA may provide better protection for both the viscera and the spinal cord during prolonged procedures than any form of partial bypass under moderate hypothermia. Many surgeons avoid use of deep HCA for fear of excessive bleeding, but this has not been a problem in our experience or in other large series utilizing HCA for DTA/TAAA repair [19–21].
The success of the 2-day approach to patients with extensive adhesions is very encouraging. In addition to allowing bleeding to subside after lysis of extensive adhesions, this technique also allows the surgical team to approach the critical portions of the reconstructive operation with fresh energy and attention, rather than after many hours of frustrating but necessary preliminary dissection. The 2-day strategy may have contributed to the successful use of deep HCA in conjunction with extensive thoracoabdominal aneurysm repair, as neither of the 2 patients in whom both techniques were used had serious bleeding complications.
Although an overall mortality of 13% and an adverse outcome of 22% are still far from ideal, these results must be viewed in relation to the substantial risk of not operating: the 60 patients in this patient cohort had an overall average aneurysm diameter of 6.8 ± 1.2 cm (6.6 ± 1.4 cm among those with dissection, and 6.9 cm in those with nondissecting aneurysms). We think that these operative results will prove useful for evaluating studies of outcomes using endovascular or hybrid approaches, which may become more appealing alternatives in the future. An awareness of the natural history of these lesions—that subsequent operation or endovascular intervention may be needed—should prompt greater use of creative strategies, such as placement of antegrade and reverse elephant trunks, as well as transposition of visceral vessel attachments, during initial operations for thoracic aortic aneurysms, specifically to facilitate later interventions.
But even those patients in this series who underwent successful operation and survived the first postoperative year still suffered an accelerated death rate thereafter, compared with an age- and sex-matched control population. The finding that the observed mortality for this redo lateral thoracotomy cohort was relatively high (4.2% per patient/year), exceeding the expected death rate of an age- and sex-matched control population almost 2.5-fold, suggests that careful assessment of a patient's long-term benefits is needed before opting for elective surgery, especially for patients who have several preoperative risk factors. Long-range planning at the time of initial surgery, further technical innovations, and use of endovascular techniques will undoubtedly improve the immediate risk of reoperation, but may have limited impact on the long-term outlook.
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DR ETZ: Our strategy since 1993 has been—and continues to be—not to reattach segmental arteries. We use MEP monitoring and CSF drainage in pretty much all patients except for a few in whom it is technically very difficult. And we believe that segmental artery reattachment is not necessary.
It seems as though in this specific patient cohort, spinal cord perfusion has had some priming, or there is some compensation which takes place after the primary procedure, because we see that paraplegia rates in the redo patients are lower than in comparable primary procedures: that has been shown by your group, I think, and by Dr Kouchoukos as well. The low paraplegia rate in our redo cases underscores the success of the nonreattachment strategy.
DR COSELLI: We found in our own work that patients undergoing redo operations certainly had no increased risk of paraplegia. Although the results for this group were not statistically significantly different, the redo patients' risk was numerically actually somewhat less than that of the primary patients.
DR YUTAKA OKITA (Kobe, Japan): The left lung is always a problem in this kind of cohort. So how many patients did you have with chronic obstructive lung disease preoperatively? And how often do you have endobronchial bleeding especially in the patients who have hypothermic circulatory arrest? And how do you prevent lung complication during operation?
DR ETZ: In this cohort there were 8 patients who presented with chronic obstructive pulmonary disease, about 15%. The risk of endobronchial bleeding certainly is a major concern, and this is in partly why we advocate the 2-day procedure for patients in whom extensive manipulation of the lung is required and a severe problem with pulmonary secretions often develops. The extra day allows time for extensive suctioning of the lung and for bleeding to subside. Otherwise, other than really careful handling, there is not much I can recommend.
DR PETER T. MORTENSEN (Copenhagen, Denmark): Congratulations with your results on a very sick patient population I must say. It was very nice that you compared your patient group with a background population of New York. But what would be more interesting, at least to me, is to see what would have happened if you did not operate on this patient group. Would you have any comments on the foreseeing events for these patients if you had not operated on them.
DR ETZ: This is another difficult question that revolves around the issue of what is the optimal diameter at which to operate on patients with thoracic aneurysms. The average diameter in this cohort was 7 cm, including the dissections. It was even a little higher in the patients who did not have a dissection. I cannot answer from the data we have, since our computed tomography scan follow-up includes few patients with aneurysms larger than 7 cm because that is beyond the threshold at which we would routinely recommend operation. We suspect from natural history studies that the mortality rate would have been much higher in these patients if we had not operated.
DR ERIC E. ROSELLI (Cleveland, OH): I agree. I think you'd have a lot more dead people than live ones. Congratulations on a great presentation and great experience.
I wasn't surprised to see that folks who had the clamp-and-sew technique had a higher risk of adverse events. But I thought that it was interesting to note that the folks with deep circulatory arrest seemed to be different than the others. And I think that Gene Blackstone would say that we'd have to probably look closer at that bias for making a choice of using that technique to determine the propensity of undergoing circulatory arrest. Do you have some sense or can you give us some idea how you choose circulatory arrest over partial bypass or left heart bypass in this group?
DR ETZ: I would agree that it is certainly a valid concern that the groups having repair with different techniques might not be comparable. We felt reasonably comfortable with the conclusions from this study because there were generally very sick patients in the HCA group: it includes patients with unclampable aortas, and with more severe atherosclerotic disease. In Dr. Coselli's group, HCA was used in a very high percentage of urgent and emergent procedures, I think 51%. The proportion of urgent and emergent procedures was not as high in our group. Nevertheless, the HCA patients were high risk patients as compared with the LHB and partial cardiopulmonary bypass patients, although the selection of technique was based on technical factors rather than on risk profile.
DR CHRIS ROKKAS (Athens, Greece): My question relates to the management of the airway, do you use a double-lumen endotracheal tube in all your cases? We have found that the left lung should stay deflated the entire time and only be reinflated after administration of protamine. This decreases the incidence of intraparenchymal hematomas. I wonder whether you have a policy regarding the state of inflation of the lung for this procedure.
DR ETZ: We use double lumen intubation in all patients as well. During DHCA there is usually no reinflation of the lungs. The 2-day procedure in part is an attempt to address this issue: to have the ability to reinflate the lungs and clear the secretions. But there is no protocol as far as I know. We inflate the lungs whenever the technical progression of the procedure allows it.
DR JOSEPH E. BAVARIA (Philadelphia, PA): A follow-up comment: if we're doing redo thoracic aortic surgery or redo thoracoabdominal, on patients with FEV1 less than 60%, we use elective "on-the-table" tracheostomy just for the airway. Do you have any policy like that?
DR ETZ: Doctor Griepp is a proponent of early tracheostomy with any respiratory complication, but there is no protocol for prospective elective tracheostomy. We do it early postoperatively if there is any problem.
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