What is the appropriate size criterion for resection of thoracic aortic aneurysms?

Aortic arch replacement for recurrent cerebral embolization

Replacement of the aortic arch for atheroma with cerebral embolization is in its infancy. The appropriateness of such intervention is controversial. Over a 10-month period, a 58-year-old woman suffered multiple debilitating cerebral vascular accidents manifested by motor, sensory, and memory deficits and documented by computed tomographic scanning and magnetic resonance imaging. Carotid and vertebral arteries were free of arteriosclerotic disease. Transesophageal echocardiography demonstrated two large atheromas with friable, pedunculated forms, one in the aortic arch and one in the very proximal descending thoracic aorta. Transcranial ultrasound revealed recurrent cerebral microembolic events. Cerebrovascular events continued, and the atheromas increased in size, despite treatment with Coumadin and aspirin. Under deep hypothermic arrest, the segment of the aortic arch harboring the atheroma was excised and replaced with a Dacron graft. Repeat transcranial ultrasound revealed cessation of embolic signals. All cerebrovascular events ceased. No further anticoagulation therapy was required. The patient has made substantial recovery from the preoperative deficits and continues to do well 1 year after aortic arch replacement. Resection of mobile aortic arch atheromas is likely to become increasingly important in the future as transesophageal echocardiography leads to their more common identification as a cause of cerebral ischemic events.

Yearly rupture or dissection rates for thoracic aortic aneurysms: simple prediction based on size

BACKGROUND

Prior work has clarified the cumulative, lifetime risk of rupture or dissection based on the size of thoracic aneurysms. Ability to estimate simply the yearly rate of rupture or dissection would greatly enhance clinical decision making for specific patients. Calculation of such a rate requires robust data.

METHODS

Data on 721 patients (446 male, 275 female; median age, 65.8 years; range, 8 to 95 years) with thoracic aortic disease was prospectively entered into a computerized database over 9 years. Three thousand one hundred fifteen imaging studies were available on these patients. Five hundred seventy met inclusion criteria in terms of length of follow-up and form the basis for the survival analysis. Three hundred four patients were dissection-free at presentation; their natural history was followed for rupture, dissection, and death. Patients were excluded from analysis once operation occurred.

RESULTS

Five-year survival in patients not operated on was 54% at 5 years. Ninety-two hard end points were realized in serial follow-up, including 55 deaths, 13 ruptures, and 24 dissections. Aortic size was a very strong predictor of rupture, dissection, and mortality. For aneurysms greater than 6 cm in diameter, rupture occurred at 3.7% per year, rupture or dissection at 6.9% per year, death at 11.8%, and death, rupture, or dissection at 15.6% per year. At size greater than 6.0 cm, the odds ratio for rupture was increased 27-fold (p = 0.0023). The aorta grew at a mean of 0.10 cm per year. Elective, preemptive surgical repair restored life expectancy to normal.

CONCLUSIONS

This study indicates that (1) thoracic aneurysm is a lethal disease; (2) aneurysm size has a profound impact on rupture, dissection, and death; (3) for counseling purposes, the patient with an aneurysm exceeding 6 cm can expect a yearly rate of rupture or dissection of at least 6.9% and a death rate of 11.8%; and (4) elective surgical repair restores survival to near normal. This analysis strongly supports careful radiologic follow-up and elective, preemptive surgical intervention for the otherwise lethal condition of large thoracic aortic aneurysm.

Aortic root replacement in patients with Marfan's syndrome: the Southampton experience

BACKGROUND

The purpose of this study was to evaluate the early and late clinical outcome after aortic root replacement (ARR) in patients with Marfan's syndrome.

METHODS

A total of 65 consecutive patients with Marfan's syndrome (mean age 41.7 +/- 10.7 years, range 15 to 76 years) undergoing ARR between 1972 and 1998 in Southampton were studied. Of the patients, 45 had a chronic aneurysm of the ascending aorta and 20 had a type A dissection (16 acute and 4 chronic). The operations were elective in 38 and nonelective in 27 cases (emergency in 22 and urgent in 5). Mean size of the ascending aorta was 6.3 +/- 1.4 cm (3.8 to 12 cm). A Bentall procedure was performed in 62 and a homograft root replacement in 3 patients. Mean follow-up was 8 +/- 4.1 years (0 to 22.9 years).

RESULTS

Operative mortality was 6.1% (4 deaths) (for the elective vs nonelective procedures it was 2.6% vs 11%, p = 0.2). The 10-year freedom from thromboembolism, hemorrhage, and endocarditis was 88%, 89.8%, and 98.4% (0.9%, 0.9%, and 0.2% per patient-year) and from late aortic events it was 86.3% (1.3% per patient-year). Aortic root replacement for dissection was an independent predictor of occurrence of late aortic events (p = 0.01). Five patients had a reoperation with one early death. The 10-year freedom from reoperation was 89.2% (1.1% per patient year) (for elective and nonelective procedures, 90.8% vs 84.6%, p = 0.6). The 10-year survival, including operative mortality, was 72.7% (for elective and nonelective procedures, 78% vs 66.5%, p = 0.6). Late aortic events was an independent adverse predictor of survival (p = 0.02).

CONCLUSIONS

In patients with Marfan's syndrome, elective ARR, usually for chronic aneurysm, is associated with a low mortality, low rate of aortic complications, and good late survival. Nonelective ARR, mostly for dissection, has a greater operative risk and a significantly higher incidence of late catastrophic aortic events. Early prophylactic surgery in these patients is therefore recommended. Long-term clinical and radiologic follow-up to prevent or to treat late aortic events is highly desirable.

Penetrating atherosclerotic ulcers of the aorta

BACKGROUND

Penetrating aortic ulcers burrow into the aortic wall and can have fatal consequences. Although they were first described as long ago as 1934 they have only recently been recognized as a distinct pathological entity.

METHOD

A review of the current literature was undertaken, based primarily on an English language Medline search with secondary references obtained from key articles.

RESULTS

Penetrating aortic ulcer is principally a disease of elderly hypertensive men. It may run a benign course or may produce complications such as aortic rupture, embolization and aneurysm formation. Presentation may be identical to that of classical aortic dissection, but the distinction is important because an ulcer may be more likely to cause rupture.

CONCLUSION

Open surgical repair has been the 'gold standard' of treatment but endovascular stenting is an attractive option in this group of frail patients.

Aortic root replacement versus aortic valve replacement: a case-match study

BACKGROUND

There is increasing evidence that patients with aortic valve disease and dilatation of the ascending aorta are at risk for later dissection or rupture of the aortic wall when the dilated ascending aorta is not replaced or reinforced at the time of aortic valve replacement. In order to find out whether the more complex surgical procedure of aortic root replacement carries a higher early or late postoperative risk than isolated aortic valve replacement, we conducted a matched-pair study with patients of both groups.

METHODS

Between June 1993 and August 1998, 100 consecutive patients with aortic valve disease and ectasia/aneurysm of the ascending aorta underwent replacement of the aortic valve and the ascending aorta with a CarboSeal composite graft (CarboSeal; Sulzer Carbo-Medics Inc, Austin, TX). Identical bileaflet valve prostheses (CarboMedics; Sulzer CarboMedics Inc, Austin, TX) were implanted during the same time period in 928 patients for aortic valve disease. On the basis of various preoperative clinical variables 100 patients with aortic valve replacement were matched to the 100 patients with replacement of the aortic root. The duration of follow-up for both groups was similar with 37 + 17 months (range, 9 to 70) for the CarboSeal group and 38 + 14 months (range, 13 to 65) for the CarboMedics group. Survival and morbidity were calculated by Kaplan-Meier analysis and risk-adjusted mortality was evaluated by multivariate analysis in a Cox regression model.

RESULTS

The early postoperative mortality of 1% in the CarboSeal group and 4% in the CarboMedics group was insignificantly different. Although the overall survival rate at 5 years was lower (60.7% vs 86.3%; p = 0.13) in the CarboSeal group, the freedom from cardiac mortality and valve-related morbidity was similar in the two groups.

CONCLUSIONS

Replacement of the ascending aorta and aortic valve can be performed with similar operative risk, valve-related morbidity, and late cardiac mortality as isolated aortic valve replacement.

Endovascular repair of lesions of descending thoracic aorta: aneurysms and dissections

The morbidity and mortality of open repair of descending thoracic aortic lesions remains uncomfortably high. Shortly after the advent of an endovascular approach for infrarenal abdominal aortic aneurysms, attempts have been made to apply similar technologies to the thoracic aorta. Early experiences with endovascular grafts for thoracic aortic aneurysms have met with good to moderate success but have provided a framework for development of improved technologies specifically designed for this anatomic region. Early studies with second generation devices have shown more promise. Aortic dissections, a disease state associated with an exceptionally high morbidity and mortality, represent another condition that is readily treated with an endovascular approach.

Ascending thoracic aortic aneurysm in an elite runner

A 41-year-old ultramarathon runner presented to his physician after having exercise-related chest pain that radiated down his left arm and seemed typical for myocardial ischemia. The patient had only a single risk factor. Extensive testing revealed a large thoracic aortic aneurysm. This case illustrates how the standard workup could miss this and other potentially lethal conditions in an extremely well-conditioned athlete.

Surgical treatment for a ruptured thoracic aortic aneurysm

OBJECTIVE

The treatment for a ruptured thoracic aortic aneurysm remains controversial. This study was undertaken to assess the outcome from surgery.

METHODS

Between 1993 and 1998, we have performed 19 operations for a ruptured thoracic aortic aneurysm. Patients with an impending rupture or a chronic false aneurysm were excluded. There were 11 men and 8 women, with a mean age of 70.5 +/- 6.7 years. The aneurysm was caused by dissection in 8 patients. Of these, 7 were acute (Stanford type A, 6; type B, 1), and the other one was chronic (type B). Aortic rupture occurred into the pericardial cavity (n = 7), into the left lung (n = 6), the mediastinum (n = 3), the pleural cavity (n = 2), or into the esophagus (n = 1). Severely unstable hemodynamics were noted in 12 patients with a rupture into the pericardium, mediastinum, or pleural cavity (Group A). Inotropic support was required in each of these patients. Metabolic acidosis developed all but 1 patient. The 7 patients with a rupture into the lung or esophagus coughed or vomited blood (Group B). The operative approach was anterior (n = 17) or lateral (n = 2). Grafts were placed in the ascending aorta (n = 4), ascending and transverse arch aorta (n = 7), transverse arch aorta (n = 3), or in the descending thoracic aorta (n = 5). Selective cerebral perfusion was used in 13 patients.

RESULTS

There were 5 hospital deaths (26.3%). The postoperative complications included central nervous system dysfunction (n = 3), low cardiac output syndrome or cardiac arrhythmias (n = 3), respiratory failure (n = 4), acute renal failure (n = 1), and local or systemic infections (n = 4). The perioperative event-free rate was 36.8% overall, 25% in Group A, and 57.1% in Group B.

CONCLUSIONS

Patients with unstable hemodynamics require prompt operative intervention. Rupture into the esophagus is associated with a high mortality rate. Rupture in a thoracic aortic aneurysm can be successfully treated with emergency surgery.

Evolution of aortic dissection after surgical repair

Patients after aortic dissection repair still have long-term unfavorable prognosis and need careful monitoring. The purpose of this study was to analyze the evolution of aortic dissection after surgical repair in correlation to anatomic changes emerging from systematic magnetic resonance imaging (MRI) follow-up. Between January 1992 and June 1998, 70 patients underwent surgery for type A aortic dissection. Fifty-eight patients were discharged from the hospital (17% operative mortality) and were followed by serial MRI for 12 to 90 months after surgery. In all, 436 postoperative MRI examinations were analyzed. In 13 patients (22.5%) no residual intimal flap was identified, whereas 45 patients (77.5%) presented with distal dissection, with a partial thrombosis of the false lumen in 24. The yearly aortic growth rate was maximum in the descending aortic segment (0.37 +/- 0.43 cm) and was significantly higher in the absence of thrombus in the false lumen (0.56 +/- 0.57 cm) (p <0.05). There were 4 sudden deaths, with documented aortic rupture in 2. Sixteen patients underwent reoperation for expanding aortic diameter. In all but 1 patient, a residual dissection was present (in 13 without any thrombosis of the false lumen). Close MRI follow-up in patients after dissection surgical repair can identify the progression of aortic pathology, providing effective prevention of aortic rupture and timely reoperation. Thrombosis of the false lumen appears to be a protective factor against aortic dilation.

Early surgery versus conservative management of dissecting aneurysms of the descending thoracic aorta

BACKGROUND

Optimal management for patients who present acutely with uncomplicated type III dissections of the descending thoracic aorta remains controversial. Patients with dissecting aneurysms represent a subgroup at high risk of rupture who may benefit from early elective surgery as an alternative to standard medical therapy. METHODS. The authors constructed a Markov decision model to compare the following clinical strategies: 1) early elective surgery immediately after diagnosis (EARLY SURGERY), 2) medical therapy with periodic computed tomography and with elective surgery when aortic diameter is projected to reach 6 cm (CT FOLLOW-UP), and 3) medical therapy with urgent surgery for dissection-related complications (WATCHFUL WAITING). Data sources included Medline (1966-1995) and a case series of patients with type III dissecting aneurysms who received medical therapy with radiographic follow-up.

RESULTS

For a typical 60-year-old patient with an acute, uncomplicated 5-cm dissecting aneurysm of the descending thoracic aorta and an operative 30-day mortality rate of 14% for EARLY SURGERY, the model predicts that EARLY SURGERY improves survival compared with CT FOLLOW-UP (9.91 vs 9.44 QALYs). Conservative management may be preferred for patients who have maximum aneurysm diameters < or = 4 cm, are elderly (> or = 75 years), or have higher-than-expected risk of operative mortality.

CONCLUSIONS

The choice between early surgery and medical therapy for uncomplicated dissecting aneurysm of the descending thoracic aorta should be tailored to the individual patient's operative risk, risk of dissection-related events, and age. Early surgery may be a reasonable alternative to medical therapy for carefully selected patients at centers with favorable perioperative mortality rates.

Clinical and patho-anatomical factors affecting expansion of thoracic aortic aneurysms

OBJECTIVE

To examine the expansion of aneurysmal aortic segments (> or = 35 mm) and to assess the impact of clinical and patho-anatomical factors on aneurysm expansion.

DESIGN

87 consecutive patients (mean age 63.6 years, range 22-84 years) were studied using serial (six month intervals) computed tomographic or magnetic resonance imaging to monitor progression of thoracic aortic aneurysms. Aortic diameter was measured at seven predetermined segments and at the site of maximum aortic dilatation (MAX).

RESULTS

780 segment intervals were identified. The median overall aneurysm expansion rate was 1.43 mm/year. This increased exponentially with incremental aortic diameter (p < 0.01) and varied by anatomical segment (p < 0.05). The presence of intraluminal thrombus (p < 0.01) but not dissection or calcification was associated with accelerated growth. Univariate analysis identified thrombus (p < 0.001), previous stroke (p < 0.002), smoking (p < 0. 01), and peripheral vascular disease (p < 0.05) as factors associated with accelerated growth in MAX. Dissection, wall calcification, and history of hypertension did not affect expansion. beta Blocker treatment was not associated with protection. Multivariate analysis confirmed the positive effect of intraluminal thrombus and previous cerebral ischaemia, and the negative effect of previous aortic surgery on aneurysm growth. These findings translated into a mathematical equation describing exponential aneurysm expansion.

CONCLUSIONS

Aneurysmal thoracic aortic segments expand exponentially according to their initial size and their anatomical position within the aorta. The presence of intraluminal thrombus, atherosclerosis, and smoking history is associated with accelerated growth and may identify a high risk patient group for close surveillance.

Replacement of the aortic valve and ascending aorta with a valved stentless composite graft: technical considerations and early clinical results

BACKGROUND

Replacement of the aortic valve and the ascending aorta with a conduit consisting of a mechanical valve and a Dacron tube has become a fairly common procedure. Commercially available conduits employing xenografts are rarely used for the same purpose, because if a reoperation becomes necessary due to degeneration of the valve prosthesis, usually the entire conduit must be replaced. A composite graft with a stentless valve, such as we describe in this article, avoids this problem, because in case of reoperation only the valve cusps need to be resected and the tube graft may be left in place.

METHODS

Surgical technique of replacement of the aortic valve and the ascending aorta with a stentless composite graft and early results of the procedure are presented.

RESULTS

Hemodynamics of the graft soon after surgery were excellent, with an average systolic gradient of 8 mm Hg and no regurgitation across the valve. There were two reoperations for bleeding in the early postoperative period.

CONCLUSIONS

The stentless composite graft we describe provides excellent hemodynamics, has no need for anticoagulation, and is expected to offer a benefit in case of reoperation.

The Marfan syndrome

The Marfan syndrome (MFS), initially described just over 100 years ago, was among the first conditions classified as a heritable disorder of connective tissue. MFS lies at one end of a phenotypic continuum, with people in the general population who have one or another of the features of MFS at the other end, and those with a variety of other conditions in between. Diagnosis of MFS and these other conditions remains based on clinical features. Mutations in FBN1, the gene that encodes fibrillin-1, are responsible for MFS and (in a few patients) other disorders in the continuum. In addition to skeletal, ocular, and cardiovascular features, patients with MFS have involvement of the skin, integument, lungs, and muscle tissue. Over the past 30 years, evolution of aggressive medical and surgical management of the cardiovascular problems, especially mitral valve prolapse, aortic dilatation, and aortic dissection, has resulted in considerable improvement in life expectancy.

Reduced survival in women after valve surgery for aortic regurgitation: effect of aortic enlargement and late aortic rupture

OBJECTIVE

We sought to investigate the relationship of female sex, aortic pathology, and left ventricular function to outcome after an operation for aortic regurgitation.

METHODS

One hundred nine women underwent aortic valve replacement (n = 92) or repair (n = 17) for pure aortic regurgitation between 1985 and 1996. Mean follow-up was 5.7 +/- 2.6 years. New York Heart Association functional class III-IV symptoms were present in 70 patients, whereas left ventricular function was normal in 60 patients. Ascending aortic diameter in 97% exceeded the 90th percentile for a size-matched healthy population. A concomitant aortic operation was performed by means of root replacement in 31 patients and by means of interposition graft in 28 patients. Of 50 patients undergoing isolated valve procedures, 19 had aortas of 4.0 cm or larger.

RESULTS

At 5 and 10 years, survival was 78% and 44%, respectively. Fatal aortic rupture occurred in 13 patients, and 2 others underwent emergency operations for impending aortic rupture, for a total of 15 late aortic events. Freedom from aortic events was 87% and 76% at 5 and 10 years, respectively. Risk factors for aortic events were older age (P =.07) and increasing ascending aortic diameter indexed to body surface area (P =.03) in women who had not undergone replacement of the ascending aorta. Rupture location was at the ascending aorta in 71% without ascending replacement and the descending aorta in 62% with ascending grafts.

CONCLUSION

In women, late survival after an operation for aortic regurgitation is importantly decreased by coexisting aortic pathology with subsequent aortic rupture. Aortic replacement at the time of a valve operation should be considered on the basis of indexed aortic size.

Magnetic resonance imaging of the thorax. Past, present, and future

Magnetic resonance imaging is a valuable modality of extreme flexibility for specific problem-solving capability in the thorax. This article reviews MR applications in the imaging of great vessels, which are currently the most important applications in the thorax; other established applications in the thorax; and pulmonary functional MR imaging.

[Surgical treatment of cardiovascular manifestations of Marfan's syndrome]

Patients with Marfan's syndrome suffer mainly from the cardiovascular manifestations of the disease, in particular the acute dissection or rupture of the dilated aorta. Due to improved diagnostic and early surgical intervention the life expectancy of these patients could be considerably improved. However, rupture is still the most frequent and dissection the second frequent cause of death. Life threatening complications of aortic dissection are pericardial effusion, aortic insufficiency and malperfusion syndrome, due to obstruction of aortic branches. Dissection of the ascending aorta is treated by implantation of a valved conduit with reimplantation of the coronary arteries. Some surgeons favor the complete replacement of the ascending aorta with preservation of the aortic valve, although long-term results show some development of aortic insufficiency after this procedure. Based on the experience of the last years, most surgeons prefer the prophylactic replacement of the aorta in Marfan patients, i.e. before complications have occurred. A special treatment algorithm helps to define the indication for the operative treatment in different manifestations of the disease. The low mortality of the elective replacement of the ascending aorta in contrast to replacement in emergency cases speaks in favor of the early operative treatment. For the long-term prognosis of the patient a closed and continuous cardiologic surveillance is mandatory. The patient should be close to a center with the necessary diagnostic tools and with sufficient experience with the medical and surgical treatment, in order to further improve the life expectancy in the future.

Magnetic resonance imaging of the thorax. Past, present, and future

Magnetic resonance is a valuable modality of extreme flexibility for specific problem-solving capability in the thorax. This article reviews MR applications in the imaging of great vessels, which are currently the most important applications in the thorax; other established applications in the thorax; and pulmonary functional MR imaging.

Pathologic variants of thoracic aortic dissections. Penetrating atherosclerotic ulcers and intramural hematomas

This article confirms the existence of two variants of acute aortic pathology, the penetrating atherosclerotic ulcer (PAU) and the intramural hematoma (IMH), which are radiologically distinct from classic aortic dissection. Table 4 reviews the characteristics distinguishing PAU from classic aortic dissection and IMH. We took as a matter of definition that classic aortic dissection involves a flap which traverses the aortic lumen. We defined PAU and IMH as nonflap lesions, with PAU demonstrating a crater extending from the aortic lumen into the space surrounding the aortic lumen. This categorization can be summarized with the expression, "no flap, no dissection." With these definitions made, re-review of the imaging studies for the present report identified 36 such lesions out of 214 cases originally read as aortic dissection. Therefore, these variant lesions accounted for over 1 out of 8 acute aortic pathologies. Besides confirming the existence of the conditions, PAU and IMH, as distinct radiographic lesions, this series strongly suggests that these two conditions constitute distinct clinical entities as well. Table 4 summarizes the clinical patterns of these two entities as apparent from the present study, and contrasts them with classic aortic dissections. In particular, the following observations, some of which are consonant findings in smaller series, can be made regarding the typical patient profiles of PAU and IMH from the present study: The patients with PAU and IMH are distinctly older than those with type A aortic dissection (74.0 and 73.9 versus 56.5 years, P = 0.0001). Although not statistically significant, PAU and IMH patients tend to be older than patients with type B aortic dissections as well. For PAU and IMH, unlike aortic dissection, the concentration in the elderly is manifested in a very small standard deviation of the mean age (see Fig. 13); these two entities, PAU and IMH, are essentially diseases of the seventh, eighth, and ninth decades of life. Patients with PAU and IMH are almost invariably hypertensive (about 94% of cases). The pain of PAU and IMH mimics that of classic aortic dissection, with anterior symptoms in the ascending aortic lesions and intrascapular or back pain with descending aortic lesions. Unlike classic dissection, PAU and IMH do not produce branch vessel compromise or occlusion and do not result in ischemic manifestations in the extremities or visceral organs. PAU and IMH are more focal lesions than classic aortic dissection, which frequently propagates for much or the entire extent of the thoracoabdominal aorta. PAU is uniformly associated with severe aortic arteriosclerosis and calcification, whereas classic dissection often occurs in aortas with minimal arteriosclerosis and calcification. PAU and IMH tend to occur in even larger aortas than classic aortic dissection (6.2 and 5.5 versus 5.2 cm, P = 0.01). PAU and IMH are strongly associated with AAA, which is seen concomitantly in 42.1% of PAU patients and 29.4% of IMH patients. PAU and IMH are largely diseases of the descending aorta (90% for PAU and 71% for IMH). Although our pathology data is limited, we do feel that an inherent difference in the histologic intramural level of the hematoma may underlie the pathophysiologic process that determines which patient develops a typical dissection and which develops an intramural hematoma. In particular, we feel that the level of blood collection is more superficial, closer to the adventitia, in IMH than in typical aortic dissection. This may explain why the inner layer does not prolapse into the aorta on imaging studies or when the aorta is opened in the operating room. This more superficial location would also explain the high rupture rates as compared to classic aortic dissection (Fig. 14, Table 3). We did find PAU and IMH to behave much more malignantly than typical descending aortic dissection. As seen in Figure 6, the rupture rate is much higher than for aortic dissection. Docume

Interpreting data on thoracic aortic aneurysms. Statistical issues

Reliable information on growth rates and risk factors for growth of thoracic aortic aneurysms (TAA) is important for managing patients with this potentially lethal condition. This article reviews existing procedures for ascertaining TAA growth rates and describes improved statistical methodologies. Using data from the Yale Center for Thoracic Aortic Disease, the article demonstrates that the statistical procedure of instrumental variables (IV) estimation leads to substantially more precise and robust estimates of TAA growth rates and associated risk factors. We recommend that IV estimation be routinely employed in estimating the progression of thoracic aortic aneurysms and in identifying risk factors for growth. The article also discusses the issue of sample selection effects that arise when patients receive graft surgery and therefore are removed from the data set, and describes statistical procedures fro addressing this issue.

Natural history, pathogenesis, and etiology of thoracic aortic aneurysms and dissections

The natural history of thoracic aortic aneurysms and dissections is diverse, reflecting a broad spectrum of etiologies which include increasing aortic size, hypertension, and genetic factors. The pathogenesis is related to defects or degeneration in structural integrity of the adventitia, not the media, which is required for aneurysm formation. The ascending and descending aorta appear to have separate underlying disease processor that lead to a weakened vessel wall and an increased susceptibility for dissection. Etiologic factors for aortic aneurysms and dissections are multifactorial, reflecting genetic, environmental, and physiologic influences.

Medical treatment of the aorta. I

Diseases of the thoracic aorta are serious conditions that require close observations. Impressive advances in imaging modalities such as magnetic resonance imaging, computed tomography sacs, and transesophageal echocardiography have aided diagnosis and provided insights into the pathogenesis and natural history of thoracic aortic aneurysms, dissection, and atherosclerosis. The current review highlights the etiology, epidemiology, and pathophysiology of these disorders and focuses on the diagnostic approach and suggested medical therapies in the current era.

Surgical techniques. Ascending aorta

Aneurysm and dissection are the most common diseases affecting the ascending aorta. Graft replacement of the ascending aorta is a straightforward cardiovascular procedure with excellent early and late results. When aneurysm or dissection extends into the aortic sinuses or arch, management becomes more complex and may entail replacement of the aortic root, aortic valve, or a portion of the aortic arch using hypothermic circulatory arrest. The optimal root prosthesis depends on several patient- and procedure-related variables. Valve-sparing procedures confer many long-term advantages and should be considered in all cases where the aortic valve leaflets are normal. The Ross procedure, although ideally suited for isolated aortic valve disease in young patients, may be applicable to some patients with combined aortic valve and ascending aortic disease, unless there is evidence of a systemic connective tissue disorder.

Developing surgical intervention criteria for thoracic aortic aneurysms

In summary, the development of intervention criteria is a complex and challenging endeavor. Specific examination of this issue is crucial to the appropriate clinical care of patients. With these objectives in mind, we have drawn upon our clinical experience to design, by way of statistical analysis, reasoned size criteria for intervention. These intervention criteria must be carefully weighed against the patient's age, overall physical condition, and anticipated life expectancy. We have approached the development of criteria for intervention using statistical methodology from the standpoint of preventing complications (i.e., dissection and rupture). Symptomatic states, organ compression, concomitant aortic insufficiency, and acute ascending aortic dissection are well-accepted general indications for surgical intervention regardless of aortic size. The appendix incorporates the size criteria developed in the present study as an integral component within a comprehensive strategy for managing patients with TAA. This study confirms that aneurysms of the thoracic aorta are potentially lethal, that attentive follow-up is critical, and that adverse events can be anticipated based on size criteria. As we continue to expand our database, we hope to refine further statistically-based recommendations for surgical intervention. Multi-institutional patient enrollment, with the concomitant statistical power of larger patient numbers, would considerably strengthen this type of analysis.

Giant unruptured aneurysm of the thoracic aorta--a case report

An asymptomatic 88-year-old woman underwent a screening medical examination. The chest x-ray film showed a large mediastinal mass with calcification. Both chest computed tomography and nuclear magnetic resonance imaging revealed an unruptured aortic aneurysm, predominantly affecting the ascending aorta and the proximal part of the aortic arch. Its maximum diameter was 10.5 cm. An ascending aortic aneurysm more than 10 cm in diameter is very rare. She died of acute pulmonary embolism unrelated to the aneurysm, and autopsy indicated that the etiology of the aneurysm was atherosclerotic degeneration. Retrospectively, the natural progression of the aneurysm was able to be followed on a series of chest x-ray films obtained over 18 years.

Clinical outcome in the Marfan syndrome with ascending aortic dilatation followed annually by echocardiography

This study reviewed the utility of echocardiography in following patients with the Marfan syndrome for whom cardiovascular complications, especially aortic root dilatation, dissection and rupture, are the major causes of morbidity and mortality. We conclude that echocardiography can be used to follow asymptomatic patients with the Marfan syndrome.

Reproducibility of thoracic aortic diameter measurement using computed tomographic scans

OBJECTIVES

Decisions to recommend elective surgical repair of thoracic aortic aneurysms (TAA) may be based on size or expansion rate, which are used as indices of the risk of rupture. Measurement error may thus affect clinical decision-making. In order to evaluate the reproducibility of aortic diameter measurements of TAA, we assessed departmental inter- and intra-observer variability of measurement of pre-selected computed tomographic scan images of aneurysmal segments of the thoracic aorta.

METHODS

We compared measurements of minimum aortic diameter made by four observers in 50 pre-selected scans and at different times by two observers using a calliper method and a measurement tool within the scan. Differences in measured dimension were analysed using Wilcoxon's signed ranks test and the repeatability assessed using the method of Bland and Altman.

RESULTS

There were no significant inter-observer differences among three observers but there were significant differences between another observer and two other observers (P < 0.05). No significant intra-observer differences existed. The best intra-observer repeatability was 2.25 while the worst inter-observer repeatability was 4.37. The mean and maximum difference in measurement were +/-0.88 mm and +/-8.0 mm, respectively. Variability of measurement increased with aortic diameter.

CONCLUSIONS

Calliper measurement of TAA is an acceptable measurement method for surveillance of TAA but appears most accurate with a single observer. Increasing error is seen with increasing diameter which may compound error in estimation of expansion rate. Standardisation of technique is advisable for multiple observers and aortic units should adopt quality assurance protocols to minimise error.

Prediction of thoracic aortic aneurysm expansion: validation of formulae describing growth

BACKGROUND

The expansion rate of thoracic aortic aneurysms may be an important and clinically relevant index of the risk of rupture. The aims of this study were to assess the validity of three published exponential equations that predict expansion rate in a separate sample population, and to calculate an expansion rate formula for this cohort of patients.

METHODS

We studied 88 consecutive patients undergoing serial computed tomographic or magnetic resonance imaging scanning to monitor thoracic aortic aneurysm progression. In interval scans of at least 6 months, we measured minimum coronal aortic diameter at seven set levels and maximal diameter, yielding 780 segment-intervals.

RESULTS

The linear expansion rate (mean 2.6 mm/year) increased with incremental aortic diameter (aortic diameter < 40 mm: 2.0; 40-49 mm: 2.3; 50-59 mm: 3.6; > or = 60 mm: 5.6 mm/year; p < 0.01). Regression analysis showed close correlation between predicted and sample data, but there were significant differences between observed and expected measurements. The Yale formula underestimated growth by 0.8 mm, while Mt. Sinai and Osaka formulae overestimated actual change by 1.5 and 0.2 mm, respectively. The expansion rate derived from our population was: last diameter = initial diameter x e(0.00367 x time) (r = 0.617).

CONCLUSIONS

Although formulae derived from one thoracic aortic aneurysm sample population may not extrapolate exactly to others, there is close concordance of results for patient populations in three different continents.

Surgical intervention criteria for thoracic aortic aneurysms: a study of growth rates and complications

BACKGROUND

Evidence regarding the behavior of thoracic aortic aneurysm (TAA) is limited. This study reviews our ongoing efforts to understand the factors influencing aortic growth rates and the complications of rupture and dissection in order to define scientifically sound criteria for surgical intervention.

METHODS

Data from 370 patients with TAA treated at Yale University School of Medicine from January 1985 to June 1997 were analyzed. This computerized data base included 1063 imaging studies (magnetic resonance imaging, computed tomography, and echocardiography).

RESULTS

The mean size of the thoracic aorta in these patients at initial presentation was 5.2 cm (range 3.5-10). The mean growth rate was 0.10 cm/year. Median size at the time of rupture or dissection was 5.9 cm for ascending and 7.2 cm for descending aneurysms. The incidence of dissection or rupture increased with aneurysm size. Multivariable regression analysis to isolate risk factors for acute dissection or rupture revealed that size > or = 6.0 cm increased the probability of these devastating complications by 25.2% for ascending aneurysms (p = 0.006 compared with aneurysms 4.0-4.9 cm). For descending aneurysms > or = 7.0 cm, risk of dissection or rupture was increased by 37.3% (p = 0.031).

CONCLUSIONS

If the median size at time of dissection or rupture had been used as the indication for intervention, half the patients would have suffered a devastating complication before surgery. Accordingly, a criterion lower than the median is appropriate. We recommend 5.5 cm as an acceptable size for elective resection of ascending aortic aneurysms because this operation can be performed with relatively low mortality. For aneurysms of the descending aorta, where perioperative complications are greater and the median size at the time of complication is larger, we recommend intervention at 6.5 cm.

Management of descending aortic dissection

BACKGROUND

Experience with 100 consecutive patients with acute dissection of the descending aorta seen at the Yale Center for Thoracic Aortic Disease over a 10-year period is reported.

METHODS

Clinical records from the Yale Center for Thoracic Aortic Disease from 1988 to 1998 were analyzed. This computerized data base included information regarding patients' demographics, history, presenting symptomatology, diagnostic imaging, early hospital course, treatment strategy, and long term follow up (office visits, echocardiography, computerized tomography, magnetic resonance imaging, and home phone calls).

RESULTS

The average size of the aorta at the time of dissection was 5.05 cm. Nine patients died (six of complications directly related to the thoracic aorta). Sixty of the 91 surviving patients had a benign course, and 31 had a course complicated by rupture (8), vascular occlusion (17), early expansion or extension (12), and continued pain (4); multiple complications were seen in some patients. Forty-two patients came to operation (22 early and 20 late): 32 direct aortic replacements, 6 fenestration procedures, and 4 thromboexclusions. There were six postoperative deaths and six paraplegias. Clinical experience with the alternative procedures of fenestration and thromboexclusion found both procedures safe and effective for selected categories of patients. Review of the literature indicated that direct aortic replacement in the setting of acute descending aortic dissection continues to carry a very high mortality (28%-65%) and paraplegia rate (30%-35%), leaving room for consideration of alternative procedures.

CONCLUSIONS

We recommend a "complication-specific" approach to acute descending aortic dissection: medical management with "antiimpulse therapy" for uncomplicated acute descending dissections and surgical intervention for complicated dissections. Surgical therapy varies for the specific complication: for rupture, direct aortic replacement is recommended; for vascular occlusion, fenestration; and for acute expansion or impending rupture, direct aortic replacement, with thromboexclusion as an option. Chronic descending aortic dissection is treated according to general guidelines for descending aortic aneurysms, with operation for symptoms or enlargement > 6.5 cm.

Surgical treatment of the dilated ascending aorta: when and how?

BACKGROUND

The aorta is considered pathologically dilated if the diameters of the ascending aorta and the aortic root exceed the norms for a given age and body size. A 50% increase over the normal diameter is considered aneurysmal dilatation. Such dilatation of the ascending aorta frequently leads to significant aortic valvular insufficiency, even in the presence of an otherwise normal valve. The dilated or aneurysmal ascending aorta is at risk for spontaneous rupture or dissection. The magnitude of this risk is closely related to the size of the aorta and the underlying pathology of the aortic wall. The occurrence of rupture or dissection adversely alters natural history and survival even after successful emergency surgical treatment.

METHODS

In recommending elective surgery for the dilated ascending aorta, the patient's age, the relative size of the aorta, the structure and function of the aortic valve, and the pathology of the aortic wall have to be considered. The indications for replacement of the ascending aorta in patients with Marfan's syndrome, acute dissection, intramural hematoma, and endocarditis with annular destruction are supported by solid clinical information. Surgical guidelines for intervening in degenerative dilatation of the ascending aorta, however, especially when its discovery is incidental to other cardiac operations, remain mostly empiric because of lack of natural history studies. The association of a bicuspid aortic valve with ascending aortic dilatation requires special attention.

RESULTS

There are a number of current techniques for surgical restoration of the functional and anatomical integrity of the aortic root. The choice of procedure is influenced by careful consideration of multiple factors, such as the patient's age and anticipated survival time; underlying aortic pathology; anatomical considerations related to the aortic valve leaflets, annulus, sinuses, and the sino-tubular ridge; the condition of the distal aorta; the likelihood of future distal operation; the risk of anticoagulation; and, of course, the surgeon's experience with the technique. Currently, elective root replacement with an appropriately chosen technique should not carry an operative risk much higher than that of routine aortic valve replacement. Composite replacement of the aortic valve and the ascending aorta, as originally described by Bentall, DeBono and Edwards (classic Bentall), or modified by Kouchoukos (button Bentall), remains the most versatile and widely applied method. Since 1989, the button modification of the Bentall procedure has been used in 250 patients at Mount Sinai Medical Center, with a hospital mortality of 4% and excellent long-term survival. In this group, age was the only predictor of operative risk (age > 60 years, mortality 7.3% [9/124] compared with age < 60, mortality 0.8% [1/126], p = 0.02).

CONCLUSIONS

This modification of the Bentall procedure has set a standard for evaluating the more recently introduced methods of aortic root repair.

Replacement of the aortic root in patients with Marfan's syndrome

BACKGROUND

Replacement of the aortic root with a prosthetic graft and valve in patients with Marfan's syndrome may prevent premature death from rupture of an aneurysm or aortic dissection. We reviewed the results of this surgical procedure at 10 experienced surgical centers.

METHODS

A total of 675 patients with Marfan's syndrome underwent replacement of the aortic root. Survival and morbidity-free survival curves were calculated, and risk factors were determined from a multivariable regression analysis.

RESULTS

The 30-day mortality rate was 1.5 percent among the 455 patients who underwent elective repair, 2.6 percent among the 117 patients who underwent urgent repair (within 7 days after a surgical consultation), and 11.7 percent among the 103 patients who underwent emergency repair (within 24 hours after a surgical consultation). Of the 675 patients, 202 (30 percent) had aortic dissection involving the ascending aorta. Forty-six percent of the 158 adult patients with aortic dissection and a documented aortic diameter had an aneurysm with a diameter of 6.5 cm or less. There were 114 late deaths (more than 30 days after surgery); dissection or rupture of the residual aorta (22 patients) and arrhythmia (21 patients) were the principal causes of late death. The risk of death was greatest within the first 60 days after surgery, then rapidly decreased to a constant level by the end of the first year.

CONCLUSIONS

Elective aortic-root replacement has a low operative mortality. In contrast, emergency repair, usually for acute aortic dissection, is associated with a much higher early mortality. Because nearly half the adult patients with aortic dissection had an aortic-root diameter of 6.5 cm or less at the time of operation, it may be prudent to undertake prophylactic repair of aortic aneurysms in patients with Marfan's syndrome when the diameter of the aorta is well below that size.

Clinical decision making and operative approaches to thoracic aortic aneurysms

The care of the patient with thoracic aneurysms is quite complicated. The decision to treat an aneurysm must be based on the risk of rupture and the patient's life expectancy. The preoperative evaluation must include detailed imaging to allow proper preoperative planning. This is especially important to determine the need for hypothermic circulatory arrest or the potential to treat a descending aneurysm with an endovascular approach. Thorough preoperative preparation and intraoperative care are as important as surgical decision making and meticulous technique. Although significant advances have been made in operative approaches, cerebral and myocardial preservation, and postoperative care, the management of complicated aneurysms of the thoracic aorta is frequently a humbling experience.

Operation for chronic traumatic aortic aneurysm: when and how?

BACKGROUND

There are few guidelines for surgical intervention late after unoperated traumatic aortic rupture. We reviewed our experience and the literature to determine when and how to operate.

METHODS

Between 1987 and 1997, we treated 9 patients aged 22 to 82 years with chronic traumatic aneurysm. Seven patients underwent aneurysm resection. Two patients have not been operated on. The injury-to-operation interval ranged from 8 weeks to 18 years (mean, 4.1 years). One patient underwent median sternotomy and patch repair during hypothermic circulatory arrest. Six patients underwent left thoracotomy: 2 were operated on with left atrio-femoral bypass, and 4 with hypothermic circulatory arrest and ascending aortic cannulation.

RESULTS

There was no surgical mortality or morbidity. The 2 patients who were not operated on remained asymptomatic without radiologic change in the aneurysm after follow-up of 2 and 9 years.

CONCLUSIONS

From this limited experience and literature review, we make the following subjective observations: (1) all patients with new symptoms should be operated on promptly, and (2) asymptomatic densely calcified aneurysms detected more than 2 years after the accident can be observed by repeated tomography unless new symptoms arise.

Procedures for estimating growth rates in thoracic aortic aneurysms

Thoracic aortic aneurysms (TAAs) are potentially lethal medical conditions often requiring surgical intervention. Reliable information on TAA growth rates and associated risk factors is important for managing this challenging patient population. Unfortunately, a number of studies have employed questionable statistical methods, leading to biased and imprecise estimates. The present study describes these statistical problems in existing studies and delineates procedures for obtaining more reliable results. Using data from the Yale Center for Thoracic Aortic Disease, the study compares TAA growth rate estimates using conventional methods versus the recommended approach of instrumental variables (IV) estimation. The IV approach is designed to mitigate problems of measurement errors inherent in existing estimates of TAA growth. The results demonstrate that IV estimation yields more robust and precise estimates of TAA growth rates and risk factors for TAA growth. For example, the conventional approach yields TAA growth rates that fluctuate substantially-from 0.12 cm/yr to 0.90 cm/yr-depending on (1) the minimum serial follow-up period for patient inclusion in the study and (2) how subjects with negative measured growth rates are handled. In contrast, growth rate estimates using the IV approach are much more robust, ranging from 0.12 to 0.13 cm/yr. The 95% confidence intervals of estimated TAA growth are much more compact using the IV approach as well. We conclude that the IV estimation procedure yields more reliable estimates of TAA growth than does the conventional approach.