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Dissecting Aneurysms of the Aorta
Dissecting Aneurysms of the Aorta MICHAEL E. DE BAKEY, M.D.; ARTHUR C. BEALL, JR., M.D. DENTON A. COOLEY, M.D.; E. STANLEY CRAWFORD, M.D. GEORGE C. MORRIS, JR., M.D. H. EDWARD GARRETT, M.D.; JIMMY F. HOWELL, M.D.
Among all forms of aortic disease, dissecting aneurysms are probably the most lethal, causing death in the majority of patients within a few hours or days after onset. Indeed, studies on the natural course of the disease have demonstrated that less than 10 per cent of patients survive one year after onset. No effective method of treatment was available until a little over a decade ago when successful surgical treatment was first employed. Since then an increasing number of reports have appeared providing evidence that the natural course of the disease can be altered favorably by surgical treatment. With increasing surgical experience in the management of this grave condition a much better understanding of the clinical and pathologic patterns of the disease has been obtained, providing the basis for the development of specific and more effective methods of surgical treatment for each of the different patterns of the disease. Accordingly, this report is concerned with our current approach to the surgical management of this disease.
CLASSIFICATION Although numerous methods of classifying dissecting aneurysms have been proposed on the basis of the various anatomic and pathologic features of disease, from the standpoint of surgical therapy most, if not all, of the various patterns can be divided into three basic types (Fig. 1). From the Cora and Webb Mading Department of Surgery, Baylor University College of Medicine, Houston, Texas Supported in part by the U.S. Public Health Service (HE-03137) and (HE-05435) and the Houston Heart Association.
1045
1046
DE BAKEY, BEALL, COOLEY, CRAWFORD, MORRIS, GARRETT, HOWELL
Figure 1. Drawings illustrating classification of dissecting aneurysms of aorta: (a) Type I dissections, in which intimal tear occurs in ascending aorta and dissecting process extends for variable distance, usually throughout entire aorta, (b) Type II dissections, in which intimal tear occurs in ascending aorta but dissecting process is limited to ascending aorta, and (c and d) Type III dissections, in which intimal tear occurs in proximal descending thoracic aorta. Dissecting process may be limited to descending thoracic aorta (c) or extend for variable distance into abdominal aorta and even its terminal branches (d).
Type I dissecting aneurysms begin with an intimal tear in the ascending aorta, and the dissecting process then extends for a variable distance, usually throughout the entire aorta and even into its major terminal branches (Fig. 1, a). Circumferential involvement of the aorta is usually incomplete, while support of aortic valve commissural attachment frequently is disrupted, producing aortic regurgitation. Type II dissecting aneurysms begin with an intimal tear in the ascending aorta similar to Type 1. However, the dissecting process in this form is limited to the ascending aorta, and the relatively thin outer layer in this type of dissection often produces the appearance of a fusiform aneurysm of the ascending aorta (Fig. 1, b). Aortic valve regurgitation often is present, secondary to loss of valve commissural support or to dilatation of the annulus. Type III dissecting aneurysms begin with an intimal tear in the
DISSECTING ANEURYSMS OF THE AORTA
1047
descending thoracic aorta, usually at or just distal to the origin of the left subclavian artery in the region of attachment of the ligamentum arteriosus. The dissecting process extends distally for a varying distance throughout the aorta and even beyond the bifurcation but in some instances it is limited to the descending thoracic aorta (Fig. 1, c). Circumferential involvement of the aorta is variable and usually is incomplete. When the dissecting process extends distally into the abdominal aorta, its diameter usually decreases prior to passage through the diaphragm (Fig. 1, d), and it is the upper thoracic segment proximal to this area of narrowing in which progressive dilatation of the outer layer with ultimate rupture usually occurs.
OPERATIVE APPROACH
Type I dissecting aneurysms tend to progress rapidly toward a fatal termination unless surgical therapy is applied. Therefore, operation should be performed as soon after onset as possible. Immediate availability of cardiopulmonary bypass using disposable plastic oxygenators* primed with 5 per cent dextrose in distilled water now provides the means whereby such an approach is feasible. The chest is entered through a median sternotomy incision. Cardiopulmonary bypass is instituted and a sump is placed in the left ventricle (Fig. 2, a). The ascending aorta is occluded just proximal to the origin of the innominate artery and is transected in the region of the intimal tear. Special catheters for coronary perfusion are then inserted into the orifices of the coronary arteries to maintain myocardial viability (Fig. 2, b). The intimal tear then is repaired and the false lumen obliterated by approximation of the inner and outer walls of the dissecting process by means of a continuous suture proximally and distally (Fig. 2, c). Resuspension of the aortic valve commissural attachment in this manner usually provides satisfactory correction of aortic valve regurgitation. Should this not prove to be the case, however, the valve should be excised and replaced with a caged-ball prosthesis. Operation is completed by end-to-end anastomosis of the transected aorta (Figs. 2, d, and 3). This procedure, consisting essentially in the repair of the intimal tear and obliteration of the false lumen, is designed to restore mural integrity and normal circulation through the true aortic lumen, thus preventing further progression of the dissecting process. It is particularly applicable in the early stages of the disease when there is minimal anatomic disruption at the site of the intimal laceration. At a later stage when more extensive mural disruption occurs, it may be necessary to modify the procedure by partial or complete excision of the diseased segment of ascending aorta with restoration of vascular continuity using a woven Dacron patch or tube graft. Type II dissecting aneurysms also are approached through a median • Travenol Laboratories, Inc., Morton Grove. Illinois.
1048
DE BAKEY, BEALL, COOLEY, CRAWFORD, MORRIS, GARRETT, ROWEL
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Figure 2. Drawings illustrating technique of operation for Type I dissecting aneurysms: (a) circuit diagram of temporary cardiopulmonary bypass, (b) aorta occluded proximal to innominate artery and transected in region of intimal tear. Perfusion of coronary arteries instituted, (c) repair of intimal tear and obliteration of false lumen by continuous suture proximally and distally, and (d) coronary perfusion continued until end-to-end anastomosis of transected aorta is almost completed.
sternotomy incision and require use of temporary cardiopulmonary bypass (Fig. 4, a). Operation then consists essentially in resection and graft replace-ment of the ascending aorta (Figs. 4, b-d, and 5). Owing to the usually chronic nature of this form of the disease in contrast to the more acute onset of Type I dissections, however, distortion of the aortic valve annulus often is severe. Although resuspension of the valve sometimes is effective in relief of aortic regurgitation, valve replacement with a caged-ball prosthesis occasionally is required. Attempts to correct valve regurgitation by various forms of annuloplasty used in the past have not proved as satisfactory as valve replacement in patients with more than minimal annular dilatation. In certain instances the dissecting process in Type II dissecting aneurysms involves only a portion of the circumference of the ascending aorta and an alternate technique of repair may be considered (Fig. 6).
DISSECTING ANEURYSMS OF THE AORTA
1049
During a period of cardiopulmonary bypass similar to that illustrated in Figure 4, the intimal tear and area of dissection are excised (Fig. 6, a). Coronary artery perfusion then is utilized (Fig. 6, b) while aortic continuity is re-established by application of a patch (Fig. 6, b, c). Type III dissecting aneurysms present an entirely different situation in regard to the type of temporary bypass required for operation. As this form of the disease invariably arises distal to the left common carotid artery,
Figure 3. A 40 year old man with Type I dissecting aneurysm: (a) drawing illustrating and (b) angiogram demonstrating dissecting process arising in ascending aorta and extending throughout aorta, (c) drawing illustrating and (d) angiogram 2 years following operation demonstrating Burgical repair.
1050
DE BAKEY, BEALL, COOLEY, CRAWFORD, MORRIS, GARRETT, HOWELL
Figure 4. Drawings illustrating technique of operation for Type II dissecting aneurysms: (a) circuit diagram of temporary cardiopulmonary bypass, (b) aorta clamped proximal to innominate artery and divided distal to dissecting process. Clamp on distal extent of aneurysm allows heart to perfuse itself through aneurysm using coronary sinus return and bronchial arterial flow, (c) graft anastomosed end-to-end to distal cut end of aorta, and (d) aneurysm excised, perfusion of coronary arteries instituted, and graft ansstomosed to proximal cut end of aorta.
heart action itself continues to perfuse the brachiocephalic vessels. The technique of bypass used in these patients, therefore, consists in left atrial to femoral artery bypass with a pump (Fig. 7, a), a method which has proved far more satisfactory than the use of hypothermia during temporary arrest of circulation through this segment of aorta. These dissections are preferably approached through a left posterolateral incision, which provides excellent exposure of the descending thoracic aorta. Once the pump bypass is in operation, the aorta is clamped proximal
DISSECTING ANEURYSMS OF THE AORTA
1051
to the area of intimal tear. Should it be necessary to place this clamp between the left common carotid and the left subclavian artery, care must be exercised not to compromise blood flow through the left common carotid artery by encroachment or twisting of the aortic clamp during the period of bypass. The aorta also is clamped distal to the dissecting process (Fig. 7, b), or where the circumferential extent of the dissecting process has narrowed as the descending thoracic aorta approaches the aortic diaphragmatic hiatus (Fig. 7, e). Aortic continuity then is re-established by graft replacement (Fig. 7, c, d). However, in those instances in which the dissection extends into the abdominal aorta, the distal false lumen is obliterated by approximating the inner and outer wall of the dissecting process with a continuous suture prior to performing the distal anastomosis (Figs. 7, j, g, and 8).
Figure 5. A 43 year old man with Type II dissecting aneurysm: (a) drawing illustrating and (b) angiogram demonstrating dissecting process arising in and limited to ascending aorta, (c) drawing illustrating and (d) angiogram 2 years following operation demonstrating surgical repair.
1052
DE BAKEY, BEALL, COOLEY, CRAWFORD, MORRIS, GARRETT, HOWELL
Figure 6. Drawings illustrating alternate technique of operation for Type II dissecting aneurysms when dissecting process involves only portion of circumference of ascending aorta: (a) during period of cardiopulmonary bypass ascending aorta occluded proximal to innominate artery, (b) coronary artery perfusion instituted, intimal tear and area of dissection excised, and aortic continuity re-established by use of patch graft, and (c) completed operation.
COMMENT
Almost all dissecting aneurysms of the aorta fall into one of the three basic patterns described. Application of surgical therapy then is based upon the extent and location of the dissecting process and consists essentially in repairing or excising the area of intimal tear with obliteration or excision of the false lumen. Occasionally, however, the dissecting process does not fit entirely into one of these basic patterns, but the principles of operative technique remain the same. Type III aneurysms rarely are associated with variable amo'unts of dissection progressing retrograde into the transverse arch from the area of intimal tear just distal to the left subclavian artery. Surgical therapy in such a case consists in excision of the area of intimal tear in the usual manner, obliteration of the proximal false lumen by reapproximation of the inner and outer walls of the dissecting process with a continuous suture, then graft replacement as usually employed in Type III forms of the disease. In still other cases of Type III dissecting aneurysms, extensive dissection into the upper abdominal aorta may occur, producing severe symptoms from compression of adjacent upper abdominal structures. While the usual procedure employed for Type III may be applicable and followed by relief of pressure symptoms once the false lumen is isolated from aortic blood flow, other forms of surgical therapy may be preferable. One such technique consists in the attachment of a graft from the thoracic aorta proximal to the dissecting process to the abdominal aorta distal to the
DISSECTING ANEURYSMS OF THE AORTA
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dissecting process, following which the descending thoracic aorta containing the intimal tear and the upper abdominal aorta are excised. Should such an extensive dissection involve the upper abdominal visceral branches of the aorta, techniques similar to those employed for fusiform thoracoabdominal aneurysms may be applicable consisting in graft attachments to each of the major visceral arteries. Regardless of the specific surgical technique required, however, effectiveness of surgical therapy in preventing the extremely high mortality expected from dissecting aneurysms of the aorta without treatment has been demonstrated clearly. While less than 1 per cent of unoperated patients can be expected to be alive five years after onset of the disease, follow-up studies of patients in whom surgical therapy was employed show that 50 per cent are still alive after this same period of time. Our surgical experience with dissecting aneurysms of the aorta now exceeds 250 cases, and operative mortality rate progressively has been reduced to approximately 10 per cent in the last five years. With further passage of time, this reduction in opera-
Figure 7. Drawings illustrating technique of operation for Type III dissecting aneurysms: (a) circuit diagram of temporary left atrial to femoral artery bypass with pump, (b) aorta clamped proximal and distal to dissecting process and intimal tear with entire area of dissection excised, (c) graft anastomosed end-to-end to proximal cut end of aorta, (d) graft anastomosed to distal cut end of aorta, (e) aorta clamped proximal to dissecting process and distally as dissecting process narrows followed by excision of intimal tear and major portion of dissection, (f) graft anastomosed to proximal cut end of aorta and false lumen obliterated distally by continuous suture, and (g) graft anastomosed to distal cut end of aorta.
1054
DE BAKEY, BEALL, COOLEY, CRAWFORD, MORRIS, GARRETT, HOWELL
Figure 8. A 65 year old man with Type III dissecting aneurysm: (a) drawing illustrating and (b) angiogram demonstrating dissecting process arising in proximal descending thoracic aorta, (c) drawing illustrating and (d) angiogram 5 years following operation demonstrating surgical repair.
tive mortality rate, related both to improved surgical techniques and to their more appropriate application in various forms of the disease, will be reflected in further improvement in long-term survival rates.
SUMMARY
Experience with surgical management of more than 250 patients with
DISSECTING ANEURYSMS OF THE AORTA
1055
dissecting aneurysms of the aorta has allowed development of certain concepts in regard to their anatomic and pathologic patterns. Based on these conceptual developments, dissecting aneurysms can be divided into three basic types, and specific and rational surgical techniques now are available for each. Results of operation have been most gratifying, and effectiveness of surgical therapy for dissecting aneurysm of the aorta has been demonstrated clearly. Type I dissecting aneurysms arise from an intimal tear in the ascending aorta and the dissecting process extends for a varying distance throughout the aorta. Operation requires temporary cardiopulmonary bypass and consists essentially in repair of the intimal tear with obliteration of the false lumen. Associated aortic valve insufficiency usually is corrected by resuspension of aortic valve commissural attachment during repair of the intimal tear. Type II dissecting aneurysms arise in a similar manner, but the dissecting process is limited to the ascending aorta. Operation in this group consists essentially in resection and graft replacement of the ascending aorta during a period of temporary cardiopulmonary bypass. Aortic annular distortion usually is more severe in this form of the disease than in Type I, and concomitant aortic valve replacement with a caged-ball prosthesis more often is required. Type III dissecting aneurysms arise from an intimal tear at or just distal to the origin of the left subclavian artery, and the dissecting process extends distally for a varying distance, but may be limited to the descending thoracic aorta. Temporary left atrial to femoral artery bypass with a pump is used in this group, and operation consists essentially in resection and graft replacement of the area of intimal tear and as much as possible of the dissecting process with obliteration of any distal false lumen remaining.
Among all forms of aortic disease, dissecting aneurysms are probably the most lethal, causing death in the majority of patients within a few hours or days after onset. Indeed, studies on the natural course of the disease have demonstrated that less than 10 per cent of patients survive one year after onset. No effective method of treatment was available until a little over a decade ago when successful surgical treatment was first employed. Since then an increasing number of reports have appeared providing evidence that the natural course of the disease can be altered favorably by surgical treatment. With increasing surgical experience in the management of this grave condition a much better understanding of the clinical and pathologic patterns of the disease has been obtained, providing the basis for the development of specific and more effective methods of surgical treatment for each of the different patterns of the disease. Accordingly, this report is concerned with our current approach to the surgical management of this disease.
CLASSIFICATION Although numerous methods of classifying dissecting aneurysms have been proposed on the basis of the various anatomic and pathologic features of disease, from the standpoint of surgical therapy most, if not all, of the various patterns can be divided into three basic types (Fig. 1). From the Cora and Webb Mading Department of Surgery, Baylor University College of Medicine, Houston, Texas Supported in part by the U.S. Public Health Service (HE-03137) and (HE-05435) and the Houston Heart Association.
1045
1046
DE BAKEY, BEALL, COOLEY, CRAWFORD, MORRIS, GARRETT, HOWELL
Figure 1. Drawings illustrating classification of dissecting aneurysms of aorta: (a) Type I dissections, in which intimal tear occurs in ascending aorta and dissecting process extends for variable distance, usually throughout entire aorta, (b) Type II dissections, in which intimal tear occurs in ascending aorta but dissecting process is limited to ascending aorta, and (c and d) Type III dissections, in which intimal tear occurs in proximal descending thoracic aorta. Dissecting process may be limited to descending thoracic aorta (c) or extend for variable distance into abdominal aorta and even its terminal branches (d).
Type I dissecting aneurysms begin with an intimal tear in the ascending aorta, and the dissecting process then extends for a variable distance, usually throughout the entire aorta and even into its major terminal branches (Fig. 1, a). Circumferential involvement of the aorta is usually incomplete, while support of aortic valve commissural attachment frequently is disrupted, producing aortic regurgitation. Type II dissecting aneurysms begin with an intimal tear in the ascending aorta similar to Type 1. However, the dissecting process in this form is limited to the ascending aorta, and the relatively thin outer layer in this type of dissection often produces the appearance of a fusiform aneurysm of the ascending aorta (Fig. 1, b). Aortic valve regurgitation often is present, secondary to loss of valve commissural support or to dilatation of the annulus. Type III dissecting aneurysms begin with an intimal tear in the
DISSECTING ANEURYSMS OF THE AORTA
1047
descending thoracic aorta, usually at or just distal to the origin of the left subclavian artery in the region of attachment of the ligamentum arteriosus. The dissecting process extends distally for a varying distance throughout the aorta and even beyond the bifurcation but in some instances it is limited to the descending thoracic aorta (Fig. 1, c). Circumferential involvement of the aorta is variable and usually is incomplete. When the dissecting process extends distally into the abdominal aorta, its diameter usually decreases prior to passage through the diaphragm (Fig. 1, d), and it is the upper thoracic segment proximal to this area of narrowing in which progressive dilatation of the outer layer with ultimate rupture usually occurs.
OPERATIVE APPROACH
Type I dissecting aneurysms tend to progress rapidly toward a fatal termination unless surgical therapy is applied. Therefore, operation should be performed as soon after onset as possible. Immediate availability of cardiopulmonary bypass using disposable plastic oxygenators* primed with 5 per cent dextrose in distilled water now provides the means whereby such an approach is feasible. The chest is entered through a median sternotomy incision. Cardiopulmonary bypass is instituted and a sump is placed in the left ventricle (Fig. 2, a). The ascending aorta is occluded just proximal to the origin of the innominate artery and is transected in the region of the intimal tear. Special catheters for coronary perfusion are then inserted into the orifices of the coronary arteries to maintain myocardial viability (Fig. 2, b). The intimal tear then is repaired and the false lumen obliterated by approximation of the inner and outer walls of the dissecting process by means of a continuous suture proximally and distally (Fig. 2, c). Resuspension of the aortic valve commissural attachment in this manner usually provides satisfactory correction of aortic valve regurgitation. Should this not prove to be the case, however, the valve should be excised and replaced with a caged-ball prosthesis. Operation is completed by end-to-end anastomosis of the transected aorta (Figs. 2, d, and 3). This procedure, consisting essentially in the repair of the intimal tear and obliteration of the false lumen, is designed to restore mural integrity and normal circulation through the true aortic lumen, thus preventing further progression of the dissecting process. It is particularly applicable in the early stages of the disease when there is minimal anatomic disruption at the site of the intimal laceration. At a later stage when more extensive mural disruption occurs, it may be necessary to modify the procedure by partial or complete excision of the diseased segment of ascending aorta with restoration of vascular continuity using a woven Dacron patch or tube graft. Type II dissecting aneurysms also are approached through a median • Travenol Laboratories, Inc., Morton Grove. Illinois.
1048
DE BAKEY, BEALL, COOLEY, CRAWFORD, MORRIS, GARRETT, ROWEL
o.
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Figure 2. Drawings illustrating technique of operation for Type I dissecting aneurysms: (a) circuit diagram of temporary cardiopulmonary bypass, (b) aorta occluded proximal to innominate artery and transected in region of intimal tear. Perfusion of coronary arteries instituted, (c) repair of intimal tear and obliteration of false lumen by continuous suture proximally and distally, and (d) coronary perfusion continued until end-to-end anastomosis of transected aorta is almost completed.
sternotomy incision and require use of temporary cardiopulmonary bypass (Fig. 4, a). Operation then consists essentially in resection and graft replace-ment of the ascending aorta (Figs. 4, b-d, and 5). Owing to the usually chronic nature of this form of the disease in contrast to the more acute onset of Type I dissections, however, distortion of the aortic valve annulus often is severe. Although resuspension of the valve sometimes is effective in relief of aortic regurgitation, valve replacement with a caged-ball prosthesis occasionally is required. Attempts to correct valve regurgitation by various forms of annuloplasty used in the past have not proved as satisfactory as valve replacement in patients with more than minimal annular dilatation. In certain instances the dissecting process in Type II dissecting aneurysms involves only a portion of the circumference of the ascending aorta and an alternate technique of repair may be considered (Fig. 6).
DISSECTING ANEURYSMS OF THE AORTA
1049
During a period of cardiopulmonary bypass similar to that illustrated in Figure 4, the intimal tear and area of dissection are excised (Fig. 6, a). Coronary artery perfusion then is utilized (Fig. 6, b) while aortic continuity is re-established by application of a patch (Fig. 6, b, c). Type III dissecting aneurysms present an entirely different situation in regard to the type of temporary bypass required for operation. As this form of the disease invariably arises distal to the left common carotid artery,
Figure 3. A 40 year old man with Type I dissecting aneurysm: (a) drawing illustrating and (b) angiogram demonstrating dissecting process arising in ascending aorta and extending throughout aorta, (c) drawing illustrating and (d) angiogram 2 years following operation demonstrating Burgical repair.
1050
DE BAKEY, BEALL, COOLEY, CRAWFORD, MORRIS, GARRETT, HOWELL
Figure 4. Drawings illustrating technique of operation for Type II dissecting aneurysms: (a) circuit diagram of temporary cardiopulmonary bypass, (b) aorta clamped proximal to innominate artery and divided distal to dissecting process. Clamp on distal extent of aneurysm allows heart to perfuse itself through aneurysm using coronary sinus return and bronchial arterial flow, (c) graft anastomosed end-to-end to distal cut end of aorta, and (d) aneurysm excised, perfusion of coronary arteries instituted, and graft ansstomosed to proximal cut end of aorta.
heart action itself continues to perfuse the brachiocephalic vessels. The technique of bypass used in these patients, therefore, consists in left atrial to femoral artery bypass with a pump (Fig. 7, a), a method which has proved far more satisfactory than the use of hypothermia during temporary arrest of circulation through this segment of aorta. These dissections are preferably approached through a left posterolateral incision, which provides excellent exposure of the descending thoracic aorta. Once the pump bypass is in operation, the aorta is clamped proximal
DISSECTING ANEURYSMS OF THE AORTA
1051
to the area of intimal tear. Should it be necessary to place this clamp between the left common carotid and the left subclavian artery, care must be exercised not to compromise blood flow through the left common carotid artery by encroachment or twisting of the aortic clamp during the period of bypass. The aorta also is clamped distal to the dissecting process (Fig. 7, b), or where the circumferential extent of the dissecting process has narrowed as the descending thoracic aorta approaches the aortic diaphragmatic hiatus (Fig. 7, e). Aortic continuity then is re-established by graft replacement (Fig. 7, c, d). However, in those instances in which the dissection extends into the abdominal aorta, the distal false lumen is obliterated by approximating the inner and outer wall of the dissecting process with a continuous suture prior to performing the distal anastomosis (Figs. 7, j, g, and 8).
Figure 5. A 43 year old man with Type II dissecting aneurysm: (a) drawing illustrating and (b) angiogram demonstrating dissecting process arising in and limited to ascending aorta, (c) drawing illustrating and (d) angiogram 2 years following operation demonstrating surgical repair.
1052
DE BAKEY, BEALL, COOLEY, CRAWFORD, MORRIS, GARRETT, HOWELL
Figure 6. Drawings illustrating alternate technique of operation for Type II dissecting aneurysms when dissecting process involves only portion of circumference of ascending aorta: (a) during period of cardiopulmonary bypass ascending aorta occluded proximal to innominate artery, (b) coronary artery perfusion instituted, intimal tear and area of dissection excised, and aortic continuity re-established by use of patch graft, and (c) completed operation.
COMMENT
Almost all dissecting aneurysms of the aorta fall into one of the three basic patterns described. Application of surgical therapy then is based upon the extent and location of the dissecting process and consists essentially in repairing or excising the area of intimal tear with obliteration or excision of the false lumen. Occasionally, however, the dissecting process does not fit entirely into one of these basic patterns, but the principles of operative technique remain the same. Type III aneurysms rarely are associated with variable amo'unts of dissection progressing retrograde into the transverse arch from the area of intimal tear just distal to the left subclavian artery. Surgical therapy in such a case consists in excision of the area of intimal tear in the usual manner, obliteration of the proximal false lumen by reapproximation of the inner and outer walls of the dissecting process with a continuous suture, then graft replacement as usually employed in Type III forms of the disease. In still other cases of Type III dissecting aneurysms, extensive dissection into the upper abdominal aorta may occur, producing severe symptoms from compression of adjacent upper abdominal structures. While the usual procedure employed for Type III may be applicable and followed by relief of pressure symptoms once the false lumen is isolated from aortic blood flow, other forms of surgical therapy may be preferable. One such technique consists in the attachment of a graft from the thoracic aorta proximal to the dissecting process to the abdominal aorta distal to the
DISSECTING ANEURYSMS OF THE AORTA
1053
dissecting process, following which the descending thoracic aorta containing the intimal tear and the upper abdominal aorta are excised. Should such an extensive dissection involve the upper abdominal visceral branches of the aorta, techniques similar to those employed for fusiform thoracoabdominal aneurysms may be applicable consisting in graft attachments to each of the major visceral arteries. Regardless of the specific surgical technique required, however, effectiveness of surgical therapy in preventing the extremely high mortality expected from dissecting aneurysms of the aorta without treatment has been demonstrated clearly. While less than 1 per cent of unoperated patients can be expected to be alive five years after onset of the disease, follow-up studies of patients in whom surgical therapy was employed show that 50 per cent are still alive after this same period of time. Our surgical experience with dissecting aneurysms of the aorta now exceeds 250 cases, and operative mortality rate progressively has been reduced to approximately 10 per cent in the last five years. With further passage of time, this reduction in opera-
Figure 7. Drawings illustrating technique of operation for Type III dissecting aneurysms: (a) circuit diagram of temporary left atrial to femoral artery bypass with pump, (b) aorta clamped proximal and distal to dissecting process and intimal tear with entire area of dissection excised, (c) graft anastomosed end-to-end to proximal cut end of aorta, (d) graft anastomosed to distal cut end of aorta, (e) aorta clamped proximal to dissecting process and distally as dissecting process narrows followed by excision of intimal tear and major portion of dissection, (f) graft anastomosed to proximal cut end of aorta and false lumen obliterated distally by continuous suture, and (g) graft anastomosed to distal cut end of aorta.
1054
DE BAKEY, BEALL, COOLEY, CRAWFORD, MORRIS, GARRETT, HOWELL
Figure 8. A 65 year old man with Type III dissecting aneurysm: (a) drawing illustrating and (b) angiogram demonstrating dissecting process arising in proximal descending thoracic aorta, (c) drawing illustrating and (d) angiogram 5 years following operation demonstrating surgical repair.
tive mortality rate, related both to improved surgical techniques and to their more appropriate application in various forms of the disease, will be reflected in further improvement in long-term survival rates.
SUMMARY
Experience with surgical management of more than 250 patients with
DISSECTING ANEURYSMS OF THE AORTA
1055
dissecting aneurysms of the aorta has allowed development of certain concepts in regard to their anatomic and pathologic patterns. Based on these conceptual developments, dissecting aneurysms can be divided into three basic types, and specific and rational surgical techniques now are available for each. Results of operation have been most gratifying, and effectiveness of surgical therapy for dissecting aneurysm of the aorta has been demonstrated clearly. Type I dissecting aneurysms arise from an intimal tear in the ascending aorta and the dissecting process extends for a varying distance throughout the aorta. Operation requires temporary cardiopulmonary bypass and consists essentially in repair of the intimal tear with obliteration of the false lumen. Associated aortic valve insufficiency usually is corrected by resuspension of aortic valve commissural attachment during repair of the intimal tear. Type II dissecting aneurysms arise in a similar manner, but the dissecting process is limited to the ascending aorta. Operation in this group consists essentially in resection and graft replacement of the ascending aorta during a period of temporary cardiopulmonary bypass. Aortic annular distortion usually is more severe in this form of the disease than in Type I, and concomitant aortic valve replacement with a caged-ball prosthesis more often is required. Type III dissecting aneurysms arise from an intimal tear at or just distal to the origin of the left subclavian artery, and the dissecting process extends distally for a varying distance, but may be limited to the descending thoracic aorta. Temporary left atrial to femoral artery bypass with a pump is used in this group, and operation consists essentially in resection and graft replacement of the area of intimal tear and as much as possible of the dissecting process with obliteration of any distal false lumen remaining.