- Email: [email protected]
Technique for the relief of discrete subaortic stenosis
J THORAC CARDIOVASC SURG 84:917-920, 1982
Current Technique
Technique for the relief of discrete subaortic stenosis The technique of enucleation of discrete subaortic stenosis is described.
Roxane McKay, M.D., and Donald N. Ross, M.D., London, England
Discrete subvalvular obstruction of the left ventricular outflow tract has been treated conventionally by sharp excision of the fibrous ring, with'"? or without' myectomy of the adjacent interventricular septum. Operative complications of heart block and injury to the mitral or aortic valves, as well as the late recurrence of subaortic stenosis, 5, 6 suggest that this technique is not ideal. During the past 16 years, the following method of enucleation by blunt dissection has given satisfactory results. 7 Method
The heart is exposed by a vertical, midline sternotomy and cardiopulmonary bypass is established with arterial return to the ascending aorta and venous drainage from a single basket in the right atrium. Moderate hypothermia (28 0 to 300 C) has permitted brief reduction of flow to facilitate exposure when necessary; the left side of the heart has not been vented routinely. After aortic cross-clamping, cardioplegic solution is infused into the root of the aorta, which is then opened with an oblique incision extended into the noncoronary sinus. The subaortic area is exposed by retraction of the aortic cusps. When these are thin and pliable, capillary From The National Heart Hospital and Cardiothoracic Institute, London England. Received for publication June 3, 1982. Accepted for publication June 29, 1982. Address for reprints: Mr. D. N. Ross, F.R.C.S., Department of Surgery, Cardiothoracic Institute, 2 Beaumont St., London WIN 2DX, England. 0022-5223/82/120917+04$00.40/0 © 1982 The C. V. Mosby Co.
action will hold them against the wall of the aorta, but often a retractor is necessary to visualize the junction of the fibrous ring with the ventricular septum (Fig. 1). With the subaortic shelf placed under tension by traction downward and away from the muscular interventricular septum, a Watson-Cheyne dissector* is used to find a plane of cleavage, starting under the commissure between right and left coronary cusps. The fibrous tissue is then peeled off the ventricular septum by blunt dissection, which is done clockwise under the right and noncoronary cusps and onto the anterior leaflet of the mitral valve (Fig. 2). Finger-like projections of tissue that extend down onto the septum and up onto the ventricular aspect of the aortic valve are removed intact with the ring. Similar dissection counterclockwise beneath the left coronary cusp and across the anterior mitral leaflet completes enucleation of the subaortic fibrous tissue, often as a complete ring (Fig. 3). Secondary muscular hypertrophy is usually present and treated by myectomy. The septum is incised just to the right of the commissure between left and right coronary cusps with a No. 12 blade ("hook knife" or "scimitar blade"). The incision is carried upward from the trabecular septum, across the area of enucleated fibrous obstruction, to just below the aortic anulus. A wedge of muscle is then removed from each side. 8 The septum, aortic valve, and mitral valve are inspected to exclude injury and confirm complete removal of obstructive tissue, and the aortotomy is closed with a continuous monofilament suture. After discontinuation of bypass, pressures are measured in the left ventricle *G. U. Manufacturing Company Limited, London, England.
917
9 I 8 McKay and Ross
The Journal of Thoracic and Cardiovascular Surgery
Fig. 1. Exposure of the subaortic obstruction and initiation of dissection under the right aortic sinus with a Watson-Cheyne dissector.
Fig. 2. Relationship of subvalvular structures to the aortic cusp s. Fibrous tissue of discrete subaortic stenosis always involve s the muscular septum and extends variably onto the other parts of the left ventricular outflow tract and aortic valve .
and ascending aorta, before and after administration of isoproterenol (Isuprel) , to document relief of both fixed and dynamic obstruction. Comment
Several observations indicate that discrete subaortic stenosis may be an acquired lesion, possibly resulting from turbulent flow in a deformed left ventricular out-
flow tract. ?"!' Fibrous tissue which has accumulated on the endocardium might be expected to peel away from the heart, analogous to endarterectomy in the peripheral vascular system. On gross inspection , the enucleated ring usually appears to be free of muscle (Fig. 4), but histologic examination has shown that endocardium remains attached, occasionally with a thin layer of myocardial cells (Fig. 5). The technique of blunt dissection consistently develops a subendocardial plane that completely removes the fibrous membrane without causing damage to the conduction or valve tissue. In cases of reoperation for discrete subaortic stenosis, this plane has been found without difficulty, an indication that the original excision was done more superficially. Although the fibroelastic tissue of subaortic stenosis is always found on the muscular interventricular septum beneath the right coronary cusp, there is considerable variation in its thickness, length, orientation in the left ventricular outflow tract, and its relation to the aortic valve." 12 Protrusions frequently extend onto the ventricular septum and often involve the ventricular side of aortic cusps. Because they follow the curvature of the heart and lie in several planes, sharp excision of the ring would tend to amputate these extensions where they pass onto the septum or valve at an angle (Figs. 4 and 5). Such residual islands of fibrous tissue may contribute to recurrence of subaortic obstruction by causing areas of turbulent flow.
Volume 84 Number 6 December, 1982
Discrete subaortic stenosis
9 19
Fig. 4. Lateral view of an enucleated ring showing the contour of the surface which was attached to the muscular septum and the long, finger-like extensions of fibrous tissue.
bottom).
Fig. 5. Photomicrograph of a subaortic ring cut in cross section at the area of septal attachment. Fibrous tissue from the ventricular surface of the right coronary cusp and a thin layer of muscle from the septum remain attached to the discrete fibrous stenosis. Dotted line indicates where the ring would be cut by sharp excision and shows that a large part of the fibrous tissue would be left on the outflow tract. (Elastic van Gieson stain; original magnification x 3.)
Myectomy for fixed obstruction of the left ventricular outflow tract is somewhat controversial. When the subaortic obstruction is a thin, localized membrane of fibroelastic tissue, muscular hypertrophy tends to be less pronounced, and a good result can be obtained from removal of just the fibrous ring.' More often in our experience, palpation of the ventricular septum
discloses a finn ridge of hypertrophied muscle; when palpated with coronary perfusion and a beating heart, the outflow tract can be felt to close down during ventricular systole, even after complete removal of the fibrous obstruction. Because of this anatomic evidence at operation, as well as the postoperative demonstration of a dynamic component in many patients with residual
Fig. 3. Subaortic rings seen from above, after enucleation from patients ages 2, 7, 31, and 46 years, respectively (top to
920 McKay and Ross
The Journal of Thoracic and Cardiovascular Surgery
or recurrent subaortic obstruction.P combined enucleation and myectomy are now performed in most patients with discrete subvalvular stenosis.
2
3
4
5
REFERENCES Hardesty RL, Griffith BP, Mathews RA, Siewers RD, Neches WH, Park SC, Bahnson HT: Discrete subvalvular aortic stenosis. An evaluation of operative therapy. J THoRAc CARDIOVASC SURG 74:352-361, 1977 Champsaur G, Trusler GA, Mustard WT: Congenital discrete subvalvar aortic stenosis. Surgical experience and long-term follow-up in 20 paediatric patients. Br Heart J 35:443-446, 1973 McGoon DC: Technics of Open-Heart Surgery for Congenital Heart Disease, Chicago, 1968, Year Book Medical Publishers, Inc., p 37 Cooley DA, Beall AC, Hallman GL, Bricker DL: Obstructive lesions of the left ventricular outflow tract. Circulation 31:612-621, 1965 Katz NM, Buckley MJ, Liberthson RR: Discrete membranous subaortic stenosis. Report of 31 patients, review of the literature, and delineation of management. Circulation 56: 1034-1038, 1977
6 Newfeld EA, Muster AJ, Paul MH, Idriss FS, Riker WL: Discrete subvalvular aortic stenosis in childhood. Study of 51 patients. Am J Cardiol 38:53-61, 1976 7 Galloti R, Wain WH, Ross DN: Surgical enucleation of discrete sub-aortic stenosis. Thorac Cardiovasc Surg 29:312-314, 1981 8 Morrow AG, Reitz BA, Epstein SE, Henry WL, Conkle DM, Itscoitz SB, Reedwood DR: Operative treatment in hypertrophic subaortic stenosis. Techniques and the results of pre and postoperative assessment in 83 patients. Circulation 52:88-102, 1975 9 Rosenquist GC, Clark EB, McAllister HA, Bharati S, Edwards JE: Increased mitral-aortic separation in discrete subaortic stenosis. Circulation 60:70-74, 1979 10 Freedom RM, Fowler RS, Duncan WJ: Rapid evolution from "normal" left ventricular outflow tract to fatal subaortic stenosis in infancy. Br Heart J 45:605-609, 1981 11 Somerville J: Congenital heart disease. Changes in form and function. Br Heart J 41: 1-22, 1979 12 Somerville J, Stone S, Ross D: Fate of patients with fixed subaortic stenosis after surgical removal. Br Heart J 43:629-647, 1980
Current Technique
Technique for the relief of discrete subaortic stenosis The technique of enucleation of discrete subaortic stenosis is described.
Roxane McKay, M.D., and Donald N. Ross, M.D., London, England
Discrete subvalvular obstruction of the left ventricular outflow tract has been treated conventionally by sharp excision of the fibrous ring, with'"? or without' myectomy of the adjacent interventricular septum. Operative complications of heart block and injury to the mitral or aortic valves, as well as the late recurrence of subaortic stenosis, 5, 6 suggest that this technique is not ideal. During the past 16 years, the following method of enucleation by blunt dissection has given satisfactory results. 7 Method
The heart is exposed by a vertical, midline sternotomy and cardiopulmonary bypass is established with arterial return to the ascending aorta and venous drainage from a single basket in the right atrium. Moderate hypothermia (28 0 to 300 C) has permitted brief reduction of flow to facilitate exposure when necessary; the left side of the heart has not been vented routinely. After aortic cross-clamping, cardioplegic solution is infused into the root of the aorta, which is then opened with an oblique incision extended into the noncoronary sinus. The subaortic area is exposed by retraction of the aortic cusps. When these are thin and pliable, capillary From The National Heart Hospital and Cardiothoracic Institute, London England. Received for publication June 3, 1982. Accepted for publication June 29, 1982. Address for reprints: Mr. D. N. Ross, F.R.C.S., Department of Surgery, Cardiothoracic Institute, 2 Beaumont St., London WIN 2DX, England. 0022-5223/82/120917+04$00.40/0 © 1982 The C. V. Mosby Co.
action will hold them against the wall of the aorta, but often a retractor is necessary to visualize the junction of the fibrous ring with the ventricular septum (Fig. 1). With the subaortic shelf placed under tension by traction downward and away from the muscular interventricular septum, a Watson-Cheyne dissector* is used to find a plane of cleavage, starting under the commissure between right and left coronary cusps. The fibrous tissue is then peeled off the ventricular septum by blunt dissection, which is done clockwise under the right and noncoronary cusps and onto the anterior leaflet of the mitral valve (Fig. 2). Finger-like projections of tissue that extend down onto the septum and up onto the ventricular aspect of the aortic valve are removed intact with the ring. Similar dissection counterclockwise beneath the left coronary cusp and across the anterior mitral leaflet completes enucleation of the subaortic fibrous tissue, often as a complete ring (Fig. 3). Secondary muscular hypertrophy is usually present and treated by myectomy. The septum is incised just to the right of the commissure between left and right coronary cusps with a No. 12 blade ("hook knife" or "scimitar blade"). The incision is carried upward from the trabecular septum, across the area of enucleated fibrous obstruction, to just below the aortic anulus. A wedge of muscle is then removed from each side. 8 The septum, aortic valve, and mitral valve are inspected to exclude injury and confirm complete removal of obstructive tissue, and the aortotomy is closed with a continuous monofilament suture. After discontinuation of bypass, pressures are measured in the left ventricle *G. U. Manufacturing Company Limited, London, England.
917
9 I 8 McKay and Ross
The Journal of Thoracic and Cardiovascular Surgery
Fig. 1. Exposure of the subaortic obstruction and initiation of dissection under the right aortic sinus with a Watson-Cheyne dissector.
Fig. 2. Relationship of subvalvular structures to the aortic cusp s. Fibrous tissue of discrete subaortic stenosis always involve s the muscular septum and extends variably onto the other parts of the left ventricular outflow tract and aortic valve .
and ascending aorta, before and after administration of isoproterenol (Isuprel) , to document relief of both fixed and dynamic obstruction. Comment
Several observations indicate that discrete subaortic stenosis may be an acquired lesion, possibly resulting from turbulent flow in a deformed left ventricular out-
flow tract. ?"!' Fibrous tissue which has accumulated on the endocardium might be expected to peel away from the heart, analogous to endarterectomy in the peripheral vascular system. On gross inspection , the enucleated ring usually appears to be free of muscle (Fig. 4), but histologic examination has shown that endocardium remains attached, occasionally with a thin layer of myocardial cells (Fig. 5). The technique of blunt dissection consistently develops a subendocardial plane that completely removes the fibrous membrane without causing damage to the conduction or valve tissue. In cases of reoperation for discrete subaortic stenosis, this plane has been found without difficulty, an indication that the original excision was done more superficially. Although the fibroelastic tissue of subaortic stenosis is always found on the muscular interventricular septum beneath the right coronary cusp, there is considerable variation in its thickness, length, orientation in the left ventricular outflow tract, and its relation to the aortic valve." 12 Protrusions frequently extend onto the ventricular septum and often involve the ventricular side of aortic cusps. Because they follow the curvature of the heart and lie in several planes, sharp excision of the ring would tend to amputate these extensions where they pass onto the septum or valve at an angle (Figs. 4 and 5). Such residual islands of fibrous tissue may contribute to recurrence of subaortic obstruction by causing areas of turbulent flow.
Volume 84 Number 6 December, 1982
Discrete subaortic stenosis
9 19
Fig. 4. Lateral view of an enucleated ring showing the contour of the surface which was attached to the muscular septum and the long, finger-like extensions of fibrous tissue.
bottom).
Fig. 5. Photomicrograph of a subaortic ring cut in cross section at the area of septal attachment. Fibrous tissue from the ventricular surface of the right coronary cusp and a thin layer of muscle from the septum remain attached to the discrete fibrous stenosis. Dotted line indicates where the ring would be cut by sharp excision and shows that a large part of the fibrous tissue would be left on the outflow tract. (Elastic van Gieson stain; original magnification x 3.)
Myectomy for fixed obstruction of the left ventricular outflow tract is somewhat controversial. When the subaortic obstruction is a thin, localized membrane of fibroelastic tissue, muscular hypertrophy tends to be less pronounced, and a good result can be obtained from removal of just the fibrous ring.' More often in our experience, palpation of the ventricular septum
discloses a finn ridge of hypertrophied muscle; when palpated with coronary perfusion and a beating heart, the outflow tract can be felt to close down during ventricular systole, even after complete removal of the fibrous obstruction. Because of this anatomic evidence at operation, as well as the postoperative demonstration of a dynamic component in many patients with residual
Fig. 3. Subaortic rings seen from above, after enucleation from patients ages 2, 7, 31, and 46 years, respectively (top to
920 McKay and Ross
The Journal of Thoracic and Cardiovascular Surgery
or recurrent subaortic obstruction.P combined enucleation and myectomy are now performed in most patients with discrete subvalvular stenosis.
2
3
4
5
REFERENCES Hardesty RL, Griffith BP, Mathews RA, Siewers RD, Neches WH, Park SC, Bahnson HT: Discrete subvalvular aortic stenosis. An evaluation of operative therapy. J THoRAc CARDIOVASC SURG 74:352-361, 1977 Champsaur G, Trusler GA, Mustard WT: Congenital discrete subvalvar aortic stenosis. Surgical experience and long-term follow-up in 20 paediatric patients. Br Heart J 35:443-446, 1973 McGoon DC: Technics of Open-Heart Surgery for Congenital Heart Disease, Chicago, 1968, Year Book Medical Publishers, Inc., p 37 Cooley DA, Beall AC, Hallman GL, Bricker DL: Obstructive lesions of the left ventricular outflow tract. Circulation 31:612-621, 1965 Katz NM, Buckley MJ, Liberthson RR: Discrete membranous subaortic stenosis. Report of 31 patients, review of the literature, and delineation of management. Circulation 56: 1034-1038, 1977
6 Newfeld EA, Muster AJ, Paul MH, Idriss FS, Riker WL: Discrete subvalvular aortic stenosis in childhood. Study of 51 patients. Am J Cardiol 38:53-61, 1976 7 Galloti R, Wain WH, Ross DN: Surgical enucleation of discrete sub-aortic stenosis. Thorac Cardiovasc Surg 29:312-314, 1981 8 Morrow AG, Reitz BA, Epstein SE, Henry WL, Conkle DM, Itscoitz SB, Reedwood DR: Operative treatment in hypertrophic subaortic stenosis. Techniques and the results of pre and postoperative assessment in 83 patients. Circulation 52:88-102, 1975 9 Rosenquist GC, Clark EB, McAllister HA, Bharati S, Edwards JE: Increased mitral-aortic separation in discrete subaortic stenosis. Circulation 60:70-74, 1979 10 Freedom RM, Fowler RS, Duncan WJ: Rapid evolution from "normal" left ventricular outflow tract to fatal subaortic stenosis in infancy. Br Heart J 45:605-609, 1981 11 Somerville J: Congenital heart disease. Changes in form and function. Br Heart J 41: 1-22, 1979 12 Somerville J, Stone S, Ross D: Fate of patients with fixed subaortic stenosis after surgical removal. Br Heart J 43:629-647, 1980