- Email: [email protected]
Nomenclatura obscura: Subaortic obstruction in double-inlet left ventricle and related lesions
Nomenclatura Obscura: Subaortic Obstruction in Double-Inlet Left Ventricle and Related Lesions Christopher Lincoln, FRCS, and Robert H. Anderson, FRCPath Royal Brompton National Heart and Lung Hospital, London, England
I
n this issue of The Annals, Ilbawi and colleagues [l] describe excellent surgical results in treating a group of patients unified anatomically because of their potential for development of subaortic stenosis when their atrial chambers are connected exclusively or predominantly to a dominant left ventricle in the presence of a rudimentary and incomplete right ventricle. For us, however, some of the excellence of this account is dissipated by the words used in the description of the anatomic findings. In this short note, therefore, we present the approach to the anatomic description of these hearts that we now prefer and discuss briefly the alternative surgical approach to the anatomic problem addressed. See also page 842. We find the chosen title of Ilbawi and colleagues [l]to be confusing. Practitioners of cardiology in the young have struggled now for more than half a century to determine how best to describe those hearts unified because their atrial chambers are connected to only one ventricle. The problem in describing such hearts has been that, almost always, although the atria connect to only one ventricle, a second rudimentary and incomplete ventricle is present in the hearts that is not connected to the atria [2, 31. Descriptions have been bedeviled throughout this period by an illogical desire, the reason for which we are still unable to determine, to describe the hearts in terms of them having a ”single” ventricle (or else a ”univentricular heart”). In reality, of course, they have one dominant and one rudimentary ventricle. The two ventricles are connected by a defect in the ventricular septum, which is often restrictive. It is such a restrictive defect that, most often, is the major source of the obstructive lesions under consideration by Ilbawi and colleagues [l].We must confess that, in the past, one of us (R.H.A.) has contributed in no small way to the misunderstandings that still surround the anatomic description of these lesions. Thus, at different times, it was suggested that tricuspid atresia is a ”univentricular heart” [4],when it clearly is not, and that “primitive ventricle” is an appropriate description [5], which is also untrue. The root of all these problems, problems that still confront Ilbawi and colleagues [l],remains the illogical convention that permitted hearts with double-inlet venAddress reprint requests to Mr Lincoln, Royal Brompton National Heart and Lung Hospital, Sydney St, London SW3 GNP, England. 0
1991 by The Society of Thoracic Surgeons
tricle to be described as “single ventricle” [6, 71 or “single ventricle equivalents” [l],when they possess one large and one small ventricle. Ilbawi and colleagues argue that “single ventricle equivalent is standard terminology for the group of lesions we described” (Ilbawi MN, personal communication, 1991). We are unaware of this generic title having entered the general surgical lexicon. In anatomic terms, the one thing to which the hearts described are not equivalent is a solitary ventricle. As stated, the very reason that the hearts under discussion give problems in description is because they are made up of one big and one small ventricle. The big ventricle is of either left or right morphology, the small ventricle being of complementary trabecular pattern. Restriction of the ventricular septal defect in such settings occurs almost always when the dominant ventricle is of left morphology and the incomplete ventricle is of right morphology. Then, when there are discordant ventriculoarterial connections, again as is usually the case, such restriction at the ventricular septal defect produces subaortic stenosis. Appreciation of the anatomic problem, therefore, is clarified only when it is noted that the hearts have two ventricles, rather than being a ”single ventricle equivalent.” It does not help, in this respect, to argue that such hearts have been called ”single ventricle” from time immemorial. The term has also been inadequate and illogical from time immemorial. Indeed, it was our attempts to produce logic where none existed that led to such ill-conceived notions as denying ventricular status to the rudimentary and incomplete right ventricle [8]. Experience has now shown that description is simplified markedly by recognizing the chambers in double-inlet left ventricle and tricuspid atresia for what they are-a dominant left and a rudimentary and incomplete right ventricle. By the same token, the interventricular communication can be named for what it is-a ventricular septal defect. The abnormal course of the atrioventricular conduction axis can then be predicted in such hearts with considerable accuracy [9]. All of these matters of clarification stem from the simple step of recognizing that the hearts have one large and one small ventricle. Although we are now able to describe these hearts in simple and unambiguous fashion, it is much harder to determine their optimal surgical treatment. It is hard to quibble with any approach that, in its initial stage, produces only one death in 13 procedures. It is difficult to determine how Ilbawi and colleagues dealt with their solitary patient having a dominant right ventricle. The Ann Thorac Surg 1991;52:73&1
0003-4975/91/$3.50
Ann Thorac Surg
EDITORIAL LINCOLN AND ANDERSON SUBAORTIC OBSTRUCTION IN DILV
1991;52730-1
measurements and evaluation of this patient must have been different from those used in all others. It would have been better if this patient had been excluded, because the anatomic substrate underscoring aortic stenosis (infundibular stenosis within the dominant ventricle) is, quite different from that of all the other cases. A mortality rate of 15% reported previously by others is considered to be high. Yet, if the next patient seen during infancy by Ilbawi and colleagues should die during surgical treatment, their mortality rate would be 20%. Would this sulddenly be considered high, and persuade them from continuing with this very promising technique? We would hope not. The important question raised by this experience is its place when compared with the alternative technique of enlargement of the ventricular septal defect and, if necessary, the outflow tract of the rudimentary right ventricle. Ilbawi and colleagues [l], in our opinion, do less than justice to this alternative surgical approach and seem to have derived different information from the article by Cheung and associates [9] than was our intention to convey when we wrote it. In this respect, each reader must draw his or her own inferences from reading any given report. In contrast to the inferences drawn by Ilbawi and colleagues [l],however, we can state firmly that the ventricular septal defect in such hearts with univentricular connection to a dominant left ventricle can be enlarged adequately with minimal risk of damaging the atrioventricular conduction axis and with acceptable surgical risks.
731
References 1. Ilbawi MN, DeLeon SY, Wilson WR Jr, et al. Advantages of early relief of subaortic stenosis in single ventricle equivalents. Ann Thorac Surg 1991;52:842-9. 2. Anderson RH, Macartney FJ, Tynan MJ, et al. Univentricular atrioventricular connexion-the single ventricle trap unsprung. Pediatr Cardiol 1983;4:273-80. 3. Anderson RH, Becker AE, Tynan M, Macartney FJ, Rigby ML, Wilkinson JL. The univentricular atriventricular connectiongetting to the root of a thorny problem. Am J Cardiol 1984;54: 822-8. 4. Anderson RH, Becker AE, Macartney FJ, Shinebourne EA, Wilkinson JL, Tynan MJ. Is “tricuspid atresia” a univentricular heart? Pediatr Cardiol 1979;51-6. 5. Anderson RH, Becker AE, Wilkinson JL, Gerlis LM. The morphogenesis of univentricular hearts. Br Heart J 1976;38: 55&72. 6. Van Praagh R, Ongley PA, Swan HVC. Anatomic type of single or common ventricle in man. Morphologic and geometric aspects of 60 necropsied cases. Am J Cardiol 1964;13: 367-86. 7. Lev M, Liberthson RR, Kirkpatrick JR, Eckner FAD, Arcilla RA. Single (primitive) ventricle. Circulation 1969;39:577-81. 8. Anderson RH, Becker AE, Freedom RM, et al. Problems in the nomenclature of the univentricular heart. Herz 1979;4:97-106. 9. Cheung HC, Lincoln C, Anderson RH, et al. Options for surgical repair in hearts with univentricular atrioventricular connection and subaortic stenosis. J Thorac Cardiovasc Surg 1990;100:672-81.
I
n this issue of The Annals, Ilbawi and colleagues [l] describe excellent surgical results in treating a group of patients unified anatomically because of their potential for development of subaortic stenosis when their atrial chambers are connected exclusively or predominantly to a dominant left ventricle in the presence of a rudimentary and incomplete right ventricle. For us, however, some of the excellence of this account is dissipated by the words used in the description of the anatomic findings. In this short note, therefore, we present the approach to the anatomic description of these hearts that we now prefer and discuss briefly the alternative surgical approach to the anatomic problem addressed. See also page 842. We find the chosen title of Ilbawi and colleagues [l]to be confusing. Practitioners of cardiology in the young have struggled now for more than half a century to determine how best to describe those hearts unified because their atrial chambers are connected to only one ventricle. The problem in describing such hearts has been that, almost always, although the atria connect to only one ventricle, a second rudimentary and incomplete ventricle is present in the hearts that is not connected to the atria [2, 31. Descriptions have been bedeviled throughout this period by an illogical desire, the reason for which we are still unable to determine, to describe the hearts in terms of them having a ”single” ventricle (or else a ”univentricular heart”). In reality, of course, they have one dominant and one rudimentary ventricle. The two ventricles are connected by a defect in the ventricular septum, which is often restrictive. It is such a restrictive defect that, most often, is the major source of the obstructive lesions under consideration by Ilbawi and colleagues [l].We must confess that, in the past, one of us (R.H.A.) has contributed in no small way to the misunderstandings that still surround the anatomic description of these lesions. Thus, at different times, it was suggested that tricuspid atresia is a ”univentricular heart” [4],when it clearly is not, and that “primitive ventricle” is an appropriate description [5], which is also untrue. The root of all these problems, problems that still confront Ilbawi and colleagues [l],remains the illogical convention that permitted hearts with double-inlet venAddress reprint requests to Mr Lincoln, Royal Brompton National Heart and Lung Hospital, Sydney St, London SW3 GNP, England. 0
1991 by The Society of Thoracic Surgeons
tricle to be described as “single ventricle” [6, 71 or “single ventricle equivalents” [l],when they possess one large and one small ventricle. Ilbawi and colleagues argue that “single ventricle equivalent is standard terminology for the group of lesions we described” (Ilbawi MN, personal communication, 1991). We are unaware of this generic title having entered the general surgical lexicon. In anatomic terms, the one thing to which the hearts described are not equivalent is a solitary ventricle. As stated, the very reason that the hearts under discussion give problems in description is because they are made up of one big and one small ventricle. The big ventricle is of either left or right morphology, the small ventricle being of complementary trabecular pattern. Restriction of the ventricular septal defect in such settings occurs almost always when the dominant ventricle is of left morphology and the incomplete ventricle is of right morphology. Then, when there are discordant ventriculoarterial connections, again as is usually the case, such restriction at the ventricular septal defect produces subaortic stenosis. Appreciation of the anatomic problem, therefore, is clarified only when it is noted that the hearts have two ventricles, rather than being a ”single ventricle equivalent.” It does not help, in this respect, to argue that such hearts have been called ”single ventricle” from time immemorial. The term has also been inadequate and illogical from time immemorial. Indeed, it was our attempts to produce logic where none existed that led to such ill-conceived notions as denying ventricular status to the rudimentary and incomplete right ventricle [8]. Experience has now shown that description is simplified markedly by recognizing the chambers in double-inlet left ventricle and tricuspid atresia for what they are-a dominant left and a rudimentary and incomplete right ventricle. By the same token, the interventricular communication can be named for what it is-a ventricular septal defect. The abnormal course of the atrioventricular conduction axis can then be predicted in such hearts with considerable accuracy [9]. All of these matters of clarification stem from the simple step of recognizing that the hearts have one large and one small ventricle. Although we are now able to describe these hearts in simple and unambiguous fashion, it is much harder to determine their optimal surgical treatment. It is hard to quibble with any approach that, in its initial stage, produces only one death in 13 procedures. It is difficult to determine how Ilbawi and colleagues dealt with their solitary patient having a dominant right ventricle. The Ann Thorac Surg 1991;52:73&1
0003-4975/91/$3.50
Ann Thorac Surg
EDITORIAL LINCOLN AND ANDERSON SUBAORTIC OBSTRUCTION IN DILV
1991;52730-1
measurements and evaluation of this patient must have been different from those used in all others. It would have been better if this patient had been excluded, because the anatomic substrate underscoring aortic stenosis (infundibular stenosis within the dominant ventricle) is, quite different from that of all the other cases. A mortality rate of 15% reported previously by others is considered to be high. Yet, if the next patient seen during infancy by Ilbawi and colleagues should die during surgical treatment, their mortality rate would be 20%. Would this sulddenly be considered high, and persuade them from continuing with this very promising technique? We would hope not. The important question raised by this experience is its place when compared with the alternative technique of enlargement of the ventricular septal defect and, if necessary, the outflow tract of the rudimentary right ventricle. Ilbawi and colleagues [l], in our opinion, do less than justice to this alternative surgical approach and seem to have derived different information from the article by Cheung and associates [9] than was our intention to convey when we wrote it. In this respect, each reader must draw his or her own inferences from reading any given report. In contrast to the inferences drawn by Ilbawi and colleagues [l],however, we can state firmly that the ventricular septal defect in such hearts with univentricular connection to a dominant left ventricle can be enlarged adequately with minimal risk of damaging the atrioventricular conduction axis and with acceptable surgical risks.
731
References 1. Ilbawi MN, DeLeon SY, Wilson WR Jr, et al. Advantages of early relief of subaortic stenosis in single ventricle equivalents. Ann Thorac Surg 1991;52:842-9. 2. Anderson RH, Macartney FJ, Tynan MJ, et al. Univentricular atrioventricular connexion-the single ventricle trap unsprung. Pediatr Cardiol 1983;4:273-80. 3. Anderson RH, Becker AE, Tynan M, Macartney FJ, Rigby ML, Wilkinson JL. The univentricular atriventricular connectiongetting to the root of a thorny problem. Am J Cardiol 1984;54: 822-8. 4. Anderson RH, Becker AE, Macartney FJ, Shinebourne EA, Wilkinson JL, Tynan MJ. Is “tricuspid atresia” a univentricular heart? Pediatr Cardiol 1979;51-6. 5. Anderson RH, Becker AE, Wilkinson JL, Gerlis LM. The morphogenesis of univentricular hearts. Br Heart J 1976;38: 55&72. 6. Van Praagh R, Ongley PA, Swan HVC. Anatomic type of single or common ventricle in man. Morphologic and geometric aspects of 60 necropsied cases. Am J Cardiol 1964;13: 367-86. 7. Lev M, Liberthson RR, Kirkpatrick JR, Eckner FAD, Arcilla RA. Single (primitive) ventricle. Circulation 1969;39:577-81. 8. Anderson RH, Becker AE, Freedom RM, et al. Problems in the nomenclature of the univentricular heart. Herz 1979;4:97-106. 9. Cheung HC, Lincoln C, Anderson RH, et al. Options for surgical repair in hearts with univentricular atrioventricular connection and subaortic stenosis. J Thorac Cardiovasc Surg 1990;100:672-81.