There is so much that is new in Chapter 22, Chapter 23, Chapter 24, Chapter 25, Chapter 26 , it may be helpful to summarize and to integrate this new understanding. The abbreviations, references, and implicit figures in this summary are the same as in Chapter 22, Chapter 23, Chapter 24, Chapter 25, Chapter 26 and will not be reiterated here.
Infundibuloarterial Situs Concordance and Discordance
- 1.
If the situs (pattern of anatomic organization) of the infundibulum and the situs of the great arteries are the same (concordant), the great arteries are normally related (solitus normally related, or inversus normally related).
- 2.
If the situs of the infundibulum and the situs of the great arteries are different (discordant), the great arteries are abnormally related.
Relationships between the great arteries that have infundibuloarterial situs concordance and hence normally related great arteries include:
Solitus normally related great arteries (SNRGA):
SNRGA{S,D,S}=OR+4L
Inverted normally related great arteries (INRGA):
INRGA{I,L,I}=4R+0L
Tetralogy of Fallot (TOF):
TOF{S,D,S}=0R+1L(TOF-atresia)
TOF{S,D,S}=0R+2L(TOF-severe pulmonary stenosis[PS])
TOF{S,D,S}=0R+3L(TOF-mild/moderate PS)
TOF is a hypoplastic, obstructive subpulmonary infundibulum and its sequelae.
Absent subpulmonary infundibulum (AOSPI) and its sequelae, formerly misinterpreted as truncus arteriosus communis (TAC):
AOSPI{S,D,−}=0R+(−L)+APSD(TAC)(type A1)
AOSPI{S,D,−}=0R+(−L)+(−PV)+(−MPA)(TAC)(typeA2)
The third element in the segmental situs set, a horizontal dash, that is { , ̶L} indicates absence of a subarterial muscular infundibulum, both right-sided and left-sided: = 0R + ( ̶L). In Equation 27.6 there is an aortopulmonary window (APW) or aortopulmonary septal defect (APSD).
In Equation 27.7 , there is absence of the main pulmonary artery (MPA). Absence of the MPA is fatal to the idea of truncus arteriosus communis. If the MPA is absent, truncus arteriosus communis cannot be present because truncus arteriosus communis means a very large APW. Hence, if the MPA is absent, there can be no APW.
The symbol zero (0) means that there is no subarterial infundibular muscle. Zero means that there is subarterial fibrous tissue. By contrast, the symbol (–) means that the subarterial region is absent, with no muscle and no fibrous tissue. Consequently, the symbols zero and dash have very different meanings. Zero (0) means subarterial fibrous tissue, whereas dash (–) means no subarterial fibrous tissue or muscular tissue, that is, subarterial tissue is absent. For example, there is no subarterial infundibular muscular tissue and there is no subarterial fibrous tissue such as an intervalvar fibrosa.
TOF and AOSPI appear to be interrelated anomalies. TOF is hypoplasia of the subpulmonary infundibulum, whereas AOSPI is absence of the subpulmonary infundibulum (septum and free wall). The foregoing seven infundibular malformations ( Equations 27.1 to 27.7 ) all have infundibuloarterial situs concordance with essentially normally related great arteries in all except Equation 27.7 , in which the MPA is absent (type A2).
AOAPS{S,D,S}=OR+4L+(−APS)
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