Jan D. Galla

Prospective Study of the Natural History of Thoracic Aortic Aneurysms

BACKGROUND The decision whether or not to recommend resection of moderately large descending thoracic and thoracoabdominal aneurysms requires weighing the relatively high mortality and significant risk of paraplegia associated with operation against the likelihood that the aneurysm will rupture spontaneously, with an almost invariably fatal outcome. To better define the risk of aneurysm rupture, we undertook a prospective study of patients who had not had operation on their moderately large descending thoracic and thoracoabdominal aneurysms. METHODS Patients were enrolled at the time of their second computed tomographic scans: three-dimensional computer-generated reconstructions allowed determination of several dimensional parameters for each study, including diameters and cross-sectional areas at the site of maximal dilatation in the descending aorta and in the abdomen as well as total thoracoabdominal surface area. Comparisons of serial studies permitted calculation of yearly rates of change in these dimensions. RESULTS Of 114 patients, 8 died of causes unrelated to the aneurysm, 26 died of rupture, 20 met previously determined criteria for operation, and 60 survived without operation or rupture. Multivariate regression analysis identified maximal diameter in the descending and in the abdominal aorta as independent risk factors for rupture, as well as older age, the presence of even uncharacteristic pain, and a history of chronic obstructive pulmonary disease. A piecewise exponential model enabled construction of an equation allowing calculation of rate of rupture in patients in whom the values of the risk factors are known, and also of the probability of rupture in a given individual over a specified time interval. CONCLUSIONS Because using this equation--based on easily determined risk factors (age, pain, chronic obstructive pulmonary disease, maximal thoracic and maximal abdominal aortic diameter)--allows the risk of aneurysm rupture within a given interval to be estimated fairly accurately for each individual patient, it is our current practice to recommend operation when the calculated risk of rupture within 1 year exceeds the anticipated mortality of elective operation, rather than relying on general operative guidelines based almost exclusively on aneurysm size.

The natural history of thoracic aortic aneurysms.

Because improved understanding of the natural history of thoracic aneurysms would enhance our ability to determine in which cases the risk of surgical treatment is justified, the rate of enlargement of thoracic aneurysms and thoracoabdominal aneurysms was studied in 67 patients by means of serial computer-generated three-dimensional reconstructions of computed tomographic scans. Patients were followed for a mean of 1.5 +/- 0.15 years (0.2 to 5.35 years) with an average interval between examinations of 0.9 +/- 0.1 year (0.2 to 5.0 years). Thirty-nine patients continue to be followed; 7 were lost to follow-up; 14 died during follow-up (4 after aneurysm rupture), and 10 underwent an operation. Indications for operation included the presence of pain, an absolute aortic diameter larger than 8 cm, an increase in aortic diameter of more than 1 cm per year, or marked irregularity of aneurysm contour. Aortic diameter and volume data were generated from the aortic silhouette obtained by tracing each computed tomographic slice with a translucent digitizing tablet. Estimated change in aortic diameter after 1 year was 0.43 cm; estimated change in aortic volume was 88.1 ml. The impact of possible risk factors on the enlargement of aneurysms was examined by analysis of variance (p < 0.05). A significantly higher rate of aneurysm expansion was found in patients with a larger aortic diameter (> 5 cm) at diagnosis (change in diameter = 0.17 cm versus 0.79 cm; change in volume = 40 ml versus 141.8 ml), and in smokers (change in diameter = 0.35 cm versus 0.70 cm; change in volume = 78.3 ml versus 120.8 ml). Changes in diameter and volume for aneurysms of different initial diameters and volumes was predicted by exponential regression by the equations: change in diameter = 0.0167 (initial aortic diameter)2.1; change in volume = 0.0356 (initial aortic volume)1.322. No correlation was noted between the rate of enlargement and age, sex, or the presence of dissection. A history of hypertension correlated with a greater aortic diameter at diagnosis but did not significantly affect the rate of enlargement.(ABSTRACT TRUNCATED AT 250 WORDS)

Risk factors for rupture of chronic type B dissections

OBJECTIVE This study was an attempt to determine risk factors for rupture and to improve management of patients with type B aortic dissection who survive the acute phase without operation. METHODS We studied 50 patients by means of serial computer-generated 3-dimensional computed tomographic scans. All patients who did not undergo operative treatment before the completion of at least 2 computed tomographic scans a minimum of 3 months apart after an acute type B dissection were included in the study. The median duration of follow-up was 40 months (range 0.9-112 months). Only 1 patient died of causes unrelated to the aneurysm during follow-up. Nine patients had fatal rupture (18%); 10 patients underwent elective aneurysm resection because of rapid expansion or development of symptoms, and 31 patients remained alive without operation or rupture. Possible risk factors for rupture in patients in the rupture, operative, and event-free groups were compared, as were dimensional data from first follow-up and last computed tomographic scans. RESULTS Older age, chronic obstructive pulmonary disease, and elevated mean blood pressures were unequivocally associated with rupture (rupture versus event-free survival, P <.05), and pain was marginally significantly associated. Analysis of dimensional factors contributing to rupture was complicated by the fact that patients who underwent elective operation had significantly larger aneurysms and faster expansion rates than did either of the other groups, leaving comparisons of aneurysmal diameter between groups with and without rupture showing only marginal statistical significance. The last median descending aortic diameter before rupture in the rupture group was 5.4 cm (range 3.2-6. 7 cm). CONCLUSIONS In an environment in which patients with large and rapidly expanding aneurysms are usually referred for surgical treatment, older patients with chronic type B dissections, especially if they have uncontrolled hypertension and a history of chronic obstructive pulmonary disease, are significantly more likely to have rupture than are younger, normotensive patients without lung disease. Neither the presence of a persistently patent false lumen nor a large abdominal aortic diameter appears to increase the risk of rupture. Overall, our nondimensional data strikingly resemble the natural history of patients with nondissecting aneurysms, suggesting that calculations derived from data on chronic descending thoracic and thoracoabdominal aneurysms would provide an overly conservative individual estimate of rupture risk for patients with chronic type B dissection, who tend toward earlier rupture of smaller aneurysms. A more aggressive surgical approach toward treatment of patients with chronic type B dissection seems warranted.

Natural history of descending thoracic and thoracoabdominal aneurysms

BACKGROUND A review of 165 patients with chronic dissecting and degenerative aneurysms of the descending thoracic and thoracoabdominal aorta initially managed nonoperatively was carried out to ascertain factors associated with a high risk of rupture. METHODS Changes in the aneurysms were followed with three-dimensional reconstructions of computed tomograph scans. Risk factors were compared in patients with dissecting and nondissecting aneurysms who experienced rupture, in whom operation was recommended during the course of follow-up, and in those without rupture or operation. RESULTS Nondimensional variables associated with an enhanced risk of rupture include age, the presence of chronic obstructive pulmonary disease, and even uncharacteristic continued pain. Patients with rupture of dissections had significantly higher blood pressures than survivors, and significantly smaller maximal descending thoracic aortic diameters (median 5.4 cm) than patients with rupture of degenerative aneurysms (median 5.8 cm). The extent of the aneurysm, as reflected by the maximal abdominal aortic diameter, was a significant risk factor for rupture only in nondissecting aneurysms. Mortality from rupture was significantly higher in patients with chronic dissections than in patients with nondissecting aneurysms: 9/10 vs 26/34 (p = 0.004). CONCLUSIONS Almost 20% of patients followed nonoperatively succumbed to rupture, suggesting that a more aggressive surgical approach toward patients with chronic aneurysms of the descending thoracic and thoracoabdominal aorta is warranted. An individualized risk of rupture within 1 year can now be calculated, and patients whose operative risk is lower than their calculated risk should be offered elective surgery.

Is the bentall procedure for ascending aorta or aortic valve replacement the best approach for long-term event-free survival?

BACKGROUND This retrospective analysis of a selected series of Bentall procedures may be useful in evaluating the results of valve-sparing operations, an increasingly popular alternative for replacement of the ascending aorta and aortic valve. METHODS One hundred forty-two elective patients younger than 65 years without concomitant procedures who underwent replacement of the thoracic aorta and aortic valve between 1989 and 2000 were studied; 85% were men, and the median age was 46 years (range, 13 to 64 years). Degenerative disease of the aorta was the most common cause requiring operation (86%, including 46% with a bicuspid aortic valve); 8% had chronic dissection, and 6% had atherosclerotic aneurysms. The ascending aorta was replaced in 94 patients (66%); 45 patients (32%) underwent hemiarch replacement, and in 3 patients (2%) the total arch was replaced. A mechanical valve was used in 88%, and a biologic valve, in 12%. RESULTS There were no intraoperative deaths. Two patients had a stroke postoperatively, one of which was fatal. Complications during follow-up included 2 cases of endocarditis, 1 peripheral thromboembolic event, and 10 instances of significant bleeding (requiring hospitalization or transfusion). Surgery for distal aortic segments was performed in 4 patients, but no patient required reoperation in the proximal aorta. Kaplan-Meier curves show overall survival is 0.95 (95% confidence intervals, 0.9 to 0.99) at 5 years and 0.93 (95% confidence intervals, 0.86 to 0.99) at 8 years, and event-free survival is 0.85 (95% confidence intervals, 0.78 to 0.92) at 5 years and 0.78 (95% confidence intervals, 0.68 to 0.88) at 8 years. CONCLUSIONS The button Bentall procedure can be performed with excellent short-term and long-term results in relatively uncomplicated elective patients in whom aortic valve disease is combined with dilatation of the ascending aorta. Results of this traditional operation are the standard against which the long-term outcome of newer approaches, such as valve-sparing operations, should be compared.

Technical advances in total aortic arch replacement

BACKGROUND We compared the effects of using hypothermic circulatory arrest (HCA) alone, HCA combined with selective cerebral perfusion (SCP), and use of SCP with a trifurcated graft (T) on outcome after aortic arch repair. METHODS One hundred fifty patients, median age 66 years (range, 27 to 85), underwent total arch replacement between 1988 and 2002; 75 were female. We retrospectively compared the results of three patient groups roughly comparable with regard to preoperative risk factors: 45 patients using HCA beginning in 1988; 67 patients using HCA/SCP beginning in 1994; and 38 patients utilizing a trifurcated arch graft in conjunction with SCP through the axillary artery (HCA/SCP/T) since 2000. The groups were well matched with regard to median age (66, 68, and 66 years), urgency (emergent 11%, 13%, 5%; urgent 24%, 9%, 18%; and elective 64%, 78%, 76%), and several other known risk factors (p = not significant). RESULTS An adverse outcome-hospital death or permanent stroke-occurred in 14%: in 16% with HCA, in 16% with HCA/SCP, and in 8% with HCA/SCP/T. Transient neurologic dysfunction among patients surviving without stroke was lower with HCA/SCP/T (11%) than with HCA (33%) or HCA/SCP (17%). Mean duration of HCA was 52 +/- 16 minutes with HCA alone versus 45 +/- 10 minutes with HCA/SCP and 31 +/- 7 minutes with HCA/SCP/T (p < 0.0001 for groups HCA and HCA/SCP combined versus HCA/SCP/T). Mean duration of SCP was 57 +/- 25 minutes with HCA/SCP versus 62 +/- 24 minutes with HCA/SCP/T (p = not significant). Comparison of the groups of patients who had comparable preoperative risk factors for adverse outcome showed a trend toward lower adverse outcome and transient neurologic dysfunction rates using HCA/SCP/T; a significant reduction in respiratory (p < 0.001), infectious (p = 0.015) and cardiac (p = 0.005) complications in HCA/SCP/T compared with the earlier groups; and significantly shorter durations of intensive care (p < 0.0001) and hospitalization (p = 0.004). CONCLUSIONS Our results suggest that HCA/SCP is superior to HCA alone for preventing cerebral injury during operations on the aortic arch. By further reducing embolic risk as well as duration of HCA, HCA/SCP/T with axillary artery cannulation may be the optimal technique for averting adverse outcomes, reducing complications, and shortening hospital stay after aortic arch repair.

Replacing the ascending aorta and aortic valve for acute prosthetic valve endocarditis: is using prosthetic material contraindicated?

BACKGROUND The use of prosthetic material (rather than a homograft) for ascending aorta/aortic valve replacement (Bentall procedure) in cases of acute prosthetic valve endocarditis is controversial. We report favorable results using this technique almost exclusively (a homograft was used in only 3 patients with hematological problems) during a 12-year interval. METHODS Twenty-eight patients (55 +/- 14 years; 22 male) underwent a Bentall procedure for acute prosthetic valve endocarditis between 1988 and 2000. Twenty-five patients had undergone previous aortic valve replacement (1 with concomitant mitral valve replacement, 4 with coronary artery bypass grafting), and 3 had had a previous Bentall operation. The median interval between initial surgery and reoperation was 13 months (range, 1 to 106). Sixty-eight percent of operations were urgent or emergencies. Ninety-three percent of patients had significant aortic regurgitation; complete annuloaortic dehiscence occurred in 71%, and in 57%, an abscess was found. Causative organisms were identified in 25 of 28 patients: Staphylococcus epidermidis (9), Staphylococcus aureus (7), Streptococcus viridans (6), Pseudomonas (2), and Legionella (1). RESULTS Twenty-three patients had mechanical and 5 had biological valves implanted during the Bentall procedure. Hypothermic circulatory arrest was used in 64%. Hospital mortality was 11%: there was one intraoperative death, and two before discharge (one cardiac, one sepsis). Eighty-nine percent survived without stroke. During follow-up (median, 44.5 months; complete in 92%), 1 patient died of recurrent endocarditis at 4 months. CONCLUSIONS These results indicate that prosthetic root replacement may be superior to use of a homograft for acute aortic prosthetic valve endocarditis, with only a 4% incidence of recurrent endocarditis and reoperation.

Acute type B aortic dissection: surgical therapy

BACKGROUND Surgery for acute type B aortic dissection is associated with significant mortality. We report the results for 34 consecutive patients who underwent urgent surgery because they met criteria for operation during the acute phase (< 14 days) of acute type B dissection. METHODS The average patient age was 64 (32 to 88) years. Indications for surgery were persistent pain (12), threatened exsanguination (18), malperfusion (renal [3], limb [3]), rapid aortic enlargement (4), and uncontrolled hypertension (1). The mean interval from onset of pain to operation was 7 (1 to 14) days. Resection included the proximal descending aorta in 32, the distal aortic arch in 10, extension to the diaphragm in 10, and involved a thoracoabdominal procedure in 3. Surgical techniques included hypothermic circulatory arrest (16 [47%]), distal bypass, monitoring of somatosensory-evoked potentials, sequential intercostal sacrifice (average, 5.6 pairs), cerebrospinal fluid drainage, and steroid administration. RESULTS There was no hospital mortality. Important complications occurred in 16 patients (47%): 10 respiratory requiring tracheostomy, six infectious, four dialysis, two myocardial infarctions, and two neurologic (one transient stroke, one paraplegia). Mean intensive care unit and hospital stays were 10 (3 to 32) and 35 (7 to 107) days. Survival at 5 and 10 years was 80% and 57%, respectively (mean follow-up, 5.8 years). CONCLUSIONS Patients meeting criteria for urgent surgery have a low perioperative risk for mortality and paraplegia, and are relatively free from long-term aorta-related complications. These findings warrant consideration of earlier surgery for appropriate patients with acute type B aortic dissection.

Radical replacement of the aortic root in acute type A dissection: indications and outcome

OBJECTIVE Failure of the repair at the proximal aorta is an important cause of morbidity and mortality following surgical treatment of acute type A dissection. This review was undertaken to determine the influence of total composite replacement of the ascending aorta and the root on the operative risk and long-term survival. METHODS In a consecutive series of 73 patients with acute type A dissections between 1985 and 1994, 19 (26%) patients with radical root replacement (group I) were compared with 54 patients who had conventional valve-preserving root reconstruction (group II). RESULTS Group I represented a higher operative risk with the presence of significant aortic regurgitation (13/19 68.4% vs 23/54 42.5% P < 0.05), aortic dilatation (19/19 100% vs 32/54 59.2% P < 0.00), and coronary dissection (13/19 68.4% vs 3/54 5.5% P < 0.000). In spite of this there was no difference in operative mortality (3/19 15.7% vs 7/54 12.9%, NS) or the occurrence of major postoperative complications: bleeding (3/19 15.7% vs 7/54 12.9%, NS), respiratory (5/19 26.3% vs 11/54 20.3%, NS), stroke (2/19 10.5% vs 3/54 5.5%, NS). Patients with radical root replacement had substantially better event-free survival at 5 years (87.5% +/- 11.7% vs 67.1% +/- 8.9%) and 9 years (87.5% +/- 21.9% vs 63.0% +/- 19.2%). CONCLUSIONS This experience confirms that, in the treatment of acute type A dissection, an aggressive approach to aortic root pathology is indicated for specific indications, and can be carried out with good early and excellent long-term results.

Acute Dissections of the Aorta: Current Surgical Treatment

Tremendous progress has been made in the treatment of acute aortic dissections as a result of advances in surgical, medical, and diagnostic modalities. Rapid clinical diagnosis should be followed by aggressive monitoring, pharmacologic manipulation, and definitive elucidation of the anatomy of the disorder. Ultrasonography and CT scanning may provide valuable information on the anatomy of the dissection, but contrast arteriography remains the preferred method for demonstrating the anatomy. Surgical correction is now recommended for both type A and type B dissections during the acute stage. The exact approach is dictated by the location of the intimal tear and the extent of the dissection. The complexity of the operation may extend from interposing an intraluminal graft to full cardiopulmonary bypass with profound hypothermia, circulatory arrest, and replacement of the ascending aorta, aortic arch, or aortic valve apparatus. The rapid advancement of management techniques for acute aortic dissections now offers patients a reasonable expectation of survival without complications. Future improvements in early, noninvasive, and rapid diagnostic methods, as well as increased utilization of invasive monitoring and nonporous graft materials, promise to increase survival for a patient afflicted with acute aortic dissection.