Ventricular septal defect pathophysiology: Difference between revisions

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{{ventricular septal defect}}
{{ventricular septal defect}}


{{CMG}} and Leida Perez, M.D.; '''Associate Editor(s)-in-Chief:''' [[User:KeriShafer|Keri Shafer, M.D.]] [mailto:kshafer@bidmc.harvard.edu], [[Priyamvada Singh]], M.B.B.S
{{CMG}} and Leida Perez, M.D.; '''Associate Editor(s)-in-Chief:''' [[User:KeriShafer|Keri Shafer, M.D.]] [mailto:kshafer@bidmc.harvard.edu]; [[Priyamvada Singh]], M.B.B.S; [[User:Omar Toubat|Omar Toubat]]
 
==Overview==
 
In ventricular septal defect, a persistent opening in the upper [[interventricular septum]] resulting from failure of fusion with the [[aortic septum]] allows blood to flow from the high pressure [[left ventricle]] into the low pressure chamber or [[right ventricle]].  Disruption of the [[septation]] process, from inherited perturbations during embryological development or acquired [[cardiac]] injury, may result in ventricular septal defects ([[VSD|VSDs]]).


==Pathophysiology==
==Pathophysiology==
===Embryology of VSD===
The goal of [[ventricular]] [[septation]] is to permanently divide a single [[ventricular]] cavity into unique right and left chambers. Successful division of the [[ventricles]] necessitates a continuous barrier to ensure [[pulmonary]] and [[systemic]] flow separation in the developed [[heart]]. The true [[interventricular septum]] is a heterogenous structure composed of a [[muscular]] segment and a membranous segment. Disruption of the [[septation]] process, from inherited perturbations during [[embryological]] development or acquired [[cardiac]] injury, may result in [[ventricular septal defect]]<nowiki/>s (VSDs). The most commonly surgically corrected [[VSD|VSDs]] arise in the fibrous membranous [[ventricular septum]].<ref name="pmid25547619">{{cite journal| author=Anderson RH, Sarwark AE, Spicer DE, Backer CL| title=Exercises in anatomy: holes between the ventricles. | journal=Multimed Man Cardiothorac Surg | year= 2014 | volume= 2014 | issue=  | pages=  | pmid=25547619 | doi=10.1093/mmcts/mmu026 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=25547619  }} </ref>
[[Septation]] of the primitive [[ventricle]] into distinct right and left ventricular chambers begins shortly after [[cardiac]] looping. In the early stages of bilateral [[ventricular]] formation there is a large interventricular communication known as the primary interventricular foramen.<ref name="pmid12860885">{{cite journal| author=Anderson RH, Webb S, Brown NA, Lamers W, Moorman A| title=Development of the heart: (2) Septation of the atriums and ventricles. | journal=Heart | year= 2003 | volume= 89 | issue= 8 | pages= 949-58 | pmid=12860885 | doi= | pmc=PMC1767797 | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=12860885  }} </ref> However, this defect is temporary and begins to narrow as [[ventricular]] ballooning creates an upward [[muscular]] growth from the floor of the [[ventricle]].<ref name="pmid24138816">{{cite journal| author=Schleich JM, Abdulla T, Summers R, Houyel L| title=An overview of cardiac morphogenesis. | journal=Arch Cardiovasc Dis | year= 2013 | volume= 106 | issue= 11 | pages= 612-23 | pmid=24138816 | doi=10.1016/j.acvd.2013.07.001 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=24138816  }} </ref> The growth of the primitive [[muscular]] septum from its apical origin towards the [[endocardial cushion]] arrests before closure of the defect is complete, leaving a secondary interventricular foramen.<ref name="pmid24863187">{{cite journal| author=Anderson RH, Spicer DE, Brown NA, Mohun TJ| title=The development of septation in the four-chambered heart. | journal=Anat Rec (Hoboken) | year= 2014 | volume= 297 | issue= 8 | pages= 1414-29 | pmid=24863187 | doi=10.1002/ar.22949 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=24863187  }} </ref> Eventually the secondary interventricular foramen in sealed, accomplishing the bilateral division of the right and left ventricular chambers. Closure of the secondary interventricular foramen requires the proper convergence of three different tissues:<ref name="pmid25307363">{{cite journal| author=Gittenberger-de Groot AC, Calkoen EE, Poelmann RE, Bartelings MM, Jongbloed MR| title=Morphogenesis and molecular considerations on congenital cardiac septal defects. | journal=Ann Med | year= 2014 | volume= 46 | issue= 8 | pages= 640-52 | pmid=25307363 | doi=10.3109/07853890.2014.959557 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=25307363  }} </ref>
# The [[muscular]] interventricular septum
# The [[endocardial cushion]]
# The bulbar septum
Together, the [[endocardial cushion]] and the bulbar [[septum]] contribute to the formation of the membranous septum, which will intersect the muscular [[septum]] and complete the process of [[ventricular]] [[septation]].<ref name="pmid25307363">{{cite journal| author=Gittenberger-de Groot AC, Calkoen EE, Poelmann RE, Bartelings MM, Jongbloed MR| title=Morphogenesis and molecular considerations on congenital cardiac septal defects. | journal=Ann Med | year= 2014 | volume= 46 | issue= 8 | pages= 640-52 | pmid=25307363 | doi=10.3109/07853890.2014.959557 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=25307363  }} </ref>
[[VSD|VSDs]] develop in the membranous or muscular portions of the [[ventricular septum]]. [[Congenital]] muscular septal defects can emerge because of non-compaction of the muscular septum, leaving one of many [[Interventricular foramen|interventricular communications]] in the postnatal heart.<ref name="pmid24863187">{{cite journal| author=Anderson RH, Spicer DE, Brown NA, Mohun TJ| title=The development of septation in the four-chambered heart. | journal=Anat Rec (Hoboken) | year= 2014 | volume= 297 | issue= 8 | pages= 1414-29 | pmid=24863187 | doi=10.1002/ar.22949 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=24863187  }} </ref> Likewise, improper positioning or growth of any component of the membranous septum also results in abnormal [[septation]].<ref name="pmid24863187">{{cite journal| author=Anderson RH, Spicer DE, Brown NA, Mohun TJ| title=The development of septation in the four-chambered heart. | journal=Anat Rec (Hoboken) | year= 2014 | volume= 297 | issue= 8 | pages= 1414-29 | pmid=24863187 | doi=10.1002/ar.22949 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=24863187  }} </ref> Appropriate ventricular [[septation]] is a coordinated effort involving the [[spatiotemporal]] placement of several different tissue components. Morphological defects in this complex process are varied and can occur at any point during [[septation]], accounting for the [[phenotypic]] dynamism in [[VSD|VSDs]].
===Anatomy of Ventricular Septum===
Click [[Ventricular septum anatomy|here]] to learn more about the anatomy of the ventricular septum.
===Diagram of VSD===
[[Image:Ventricular septal defect-en.png|thumb|350px|Ventricular septal defect|left]]
<br clear="left"/>
Please click [[Ventricular septum anatomy|here]] to learn more about the normal ventricular septum anatomy.


*In ventricular septal defect, a persistent opening in the upper [[interventricular septum]] resulting from failure of fusion with the aortic septum allows blood to flow from the high pressure left ventricle into the low pressure chamber or [[right ventricle]].
==Factors Affecting the Pathophysiology of VSD==
*The subsequent natural history and pathophysiology depends on  
*The subsequent natural history and [[pathophysiology]] depends on  
**The size of the defect  
**The size of the defect
**The magnitude of [[left-to-right shunt]]ing.  
**The magnitude of [[left-to-right shunt]]ing.
**Small defects (QP/QS less than 1.5) maybe asymptomatic, but with the high risk for bacterial endocarditis.
**Small defects (QP/QS less than 1.5) maybe [[asymptomatic]], but with the high risk for [[bacterial]] [[endocarditis]].
**Large defects are associated with [[left ventricular failure]].
**Large defects are associated with [[left ventricular failure]].
**Chronic but more moderate [[left-to-right  shunt]]s may lead to pulmonary vascular disease and [[right heart failure|right sided failure]].  
**Chronic but more moderate [[left-to-right  shunt]]s may lead to [[pulmonary]] [[vascular]] disease and [[right heart failure|right sided failure]].


The primary variable is the size of the defect. As a child grows, the relative size of the defect may decrease and the defect may even close spontaneously in early childhood.
The primary variable is the size of the defect. As a child grows, the relative size of the defect may decrease and the defect may even close spontaneously in early childhood.
Line 18: Line 50:
During the first few months of life the PVR decreases, and the magnitude of left-to-right shunt increases. After the first few months the degree of shunting is dependent on the size of the defect.
During the first few months of life the PVR decreases, and the magnitude of left-to-right shunt increases. After the first few months the degree of shunting is dependent on the size of the defect.


'''Presentations in the adult or adolescent''':
===Presentations in the Adult or Adolescent===


a) Small defect without significant left-to-right shunting
a) Small defect without significant left-to-right [[shunting]]


b) Large defect with severe [[pulmonary hypertension]] and [[cyanosis]] due to [[right-to-left shunt]].
b) Large defect with severe [[pulmonary hypertension]] and [[cyanosis]] due to [[right-to-left shunt]].


c) Large defect with a large left-to-right shunt that has induced secondary infundibular stenosis (tough to differentiate from [[tetralogy of Fallot]]).
c) Large defect with a large left-to-right shunt that has induced secondary [[infundibular]] [[stenosis]] (tough to differentiate from [[tetralogy of Fallot]]).


===Small VSDs===
===Small VSDs===


A high resistance to flow across the VSD due to the large pressure difference between the two [[ventricles]]. There is a small left-to-right shunt (Qp/Qs < 1.5) and a normal ratio of PA to systemic pressures.
A high resistance to flow across the [[VSD]] due to the large [[pressure]] difference between the two [[ventricles]]. There is a small left-to-right shunt (Qp/Qs < 1.5) and a normal ratio of PA to systemic [[Pressure|pressures]].


There is little or no increase in the pulmonary vascular resistance. A [[holosystolic murmur]] is present due to the pressure gradient across the defect. The majority of these defects close during the first three years of life.
There is little or no increase in the [[pulmonary]] [[vascular]] resistance. A [[holosystolic murmur]] is present due to the pressure gradient across the defect. The majority of these defects close during the first three years of life.


===Medium-Sized VSDs===
===Medium-Sized VSDs===


There is a moderate [[left-to-right shunt]] present (Qp/Qs = 1.5-2.0) that still has some resistance to flow across the defect. There is also volume overload of the LA and the LV and LVH. There may therefore be a mid diastolic mitral murmur and a [[third heart sound]] (S3). The ratio of the PA systolic pressure to the systemic pressure is < 5.
There is a moderate [[left-to-right shunt]] present (Qp/Qs = 1.5-2.0) that still has some resistance to flow across the defect. There is also volume overload of the LA and the [[LV]] and [[LVH]]. There may therefore be a mid [[diastolic]] [[mitral]] [[murmur]] and a [[third heart sound]] (S3). The ratio of the PA [[systolic]] pressure to the systemic pressure is < 5.


The area of the defect is usually less than 1 cm<sup>2</sup>/m<sup>2</sup> of body surface area and is unusual for this group to have a marked increase in PVR. In some cases and depending on the type of VSD, as the child becomes older, the relative size of the defect will decrease.
The area of the defect is usually less than 1 cm<sup>2</sup>/m<sup>2</sup> of body surface area and is unusual for this group to have a marked increase in [[PVR]]. In some cases and depending on the type of [[VSD]], as the child becomes older, the relative size of the defect will decrease.


===Large VSDs===
===Large VSDs===
Line 42: Line 74:
There is a large defect on the [[ventricular septum]], > 1 cm<sup>2</sup>/m<sup>2</sup> of BSA, with a large shunt left-to-right (Qp/Qs is > 2), causing volume overload of the [[LV]], which may result in its failure. The defect may  approximate the size of the [[aortic orifice]].
There is a large defect on the [[ventricular septum]], > 1 cm<sup>2</sup>/m<sup>2</sup> of BSA, with a large shunt left-to-right (Qp/Qs is > 2), causing volume overload of the [[LV]], which may result in its failure. The defect may  approximate the size of the [[aortic orifice]].


The ratio of the PA pressure to the systemic pressure is > 5. Produce the same clinical findings as moderate sized VSD but also [[pulmonary hypertension]].
The ratio of the [[PA]] [[pressure]] to the [[systemic]] [[pressure]] is > 5. Produce the same clinical findings as moderate sized [[VSD]] but also [[pulmonary hypertension]].


There is rarely spontaneously closure of the defect, and these patients either die, or progress to adolescence or adulthood with severe [[pulmonary hypertension]] or with secondary protective infundibular pulmonary stenosis.
There is rarely spontaneously closure of the defect, and these patients either die, or progress to [[adolescence]] or adulthood with severe [[pulmonary hypertension]] or with secondary protective [[infundibular]] [[pulmonary stenosis]].


In the group with severe pulmonary hypertension, the [[left-to-right shunt]] decreases and the degree of right-to-left shunting increases with accompanying [[cyanosis]] (i.e. they develop [[Eisenmenger's syndrome]]).  
In the group with severe pulmonary hypertension, the [[left-to-right shunt]] decreases and the degree of right-to-left shunting increases with accompanying [[cyanosis]] (i.e. they develop [[Eisenmenger's syndrome]]).  


Protective infundibular stenosis may also result in reversal of the shunt, and may be indistinguishable clinically from [[tetralogy of Fallot]].
Protective [[infundibular]] [[stenosis]] may also result in reversal of the [[shunt]], and may be indistinguishable clinically from [[tetralogy of Fallot]].
 
===Anatomy of ventricular Septum===
 
Click [[Ventricular septum anatomy|here]] to learn more about the anatomy of the ventricular septum.
 
===Diagram of VSD===
 
[[Image:Ventricular septal defect-en.png|thumb|350px|Ventricular septal defect|left]]
<br clear="left"/>
Please click [[Ventricular septum anatomy|here]] to learn more about the normal ventricular septum anatomy.


===Gross Pathology===
==Gross Pathology==


[http://www.peir.net Images courtesy of Professor Peter Anderson DVM PhD and published with permission © PEIR, University of Alabama at Birmingham, Department of Pathology]
[http://www.peir.net Images courtesy of Professor Peter Anderson DVM PhD and published with permission © PEIR, University of Alabama at Birmingham, Department of Pathology]

Latest revision as of 20:08, 18 February 2020

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] and Leida Perez, M.D.; Associate Editor(s)-in-Chief: Keri Shafer, M.D. [2]; Priyamvada Singh, M.B.B.S; Omar Toubat

Overview

In ventricular septal defect, a persistent opening in the upper interventricular septum resulting from failure of fusion with the aortic septum allows blood to flow from the high pressure left ventricle into the low pressure chamber or right ventricle. Disruption of the septation process, from inherited perturbations during embryological development or acquired cardiac injury, may result in ventricular septal defects (VSDs).

Pathophysiology

Embryology of VSD

The goal of ventricular septation is to permanently divide a single ventricular cavity into unique right and left chambers. Successful division of the ventricles necessitates a continuous barrier to ensure pulmonary and systemic flow separation in the developed heart. The true interventricular septum is a heterogenous structure composed of a muscular segment and a membranous segment. Disruption of the septation process, from inherited perturbations during embryological development or acquired cardiac injury, may result in ventricular septal defects (VSDs). The most commonly surgically corrected VSDs arise in the fibrous membranous ventricular septum.[1]

Septation of the primitive ventricle into distinct right and left ventricular chambers begins shortly after cardiac looping. In the early stages of bilateral ventricular formation there is a large interventricular communication known as the primary interventricular foramen.[2] However, this defect is temporary and begins to narrow as ventricular ballooning creates an upward muscular growth from the floor of the ventricle.[3] The growth of the primitive muscular septum from its apical origin towards the endocardial cushion arrests before closure of the defect is complete, leaving a secondary interventricular foramen.[4] Eventually the secondary interventricular foramen in sealed, accomplishing the bilateral division of the right and left ventricular chambers. Closure of the secondary interventricular foramen requires the proper convergence of three different tissues:[5]

  1. The muscular interventricular septum
  2. The endocardial cushion
  3. The bulbar septum

Together, the endocardial cushion and the bulbar septum contribute to the formation of the membranous septum, which will intersect the muscular septum and complete the process of ventricular septation.[5]

VSDs develop in the membranous or muscular portions of the ventricular septum. Congenital muscular septal defects can emerge because of non-compaction of the muscular septum, leaving one of many interventricular communications in the postnatal heart.[4] Likewise, improper positioning or growth of any component of the membranous septum also results in abnormal septation.[4] Appropriate ventricular septation is a coordinated effort involving the spatiotemporal placement of several different tissue components. Morphological defects in this complex process are varied and can occur at any point during septation, accounting for the phenotypic dynamism in VSDs.

Anatomy of Ventricular Septum

Click here to learn more about the anatomy of the ventricular septum.

Diagram of VSD

Ventricular septal defect


Please click here to learn more about the normal ventricular septum anatomy.

Factors Affecting the Pathophysiology of VSD

The primary variable is the size of the defect. As a child grows, the relative size of the defect may decrease and the defect may even close spontaneously in early childhood.

During the first few months of life the PVR decreases, and the magnitude of left-to-right shunt increases. After the first few months the degree of shunting is dependent on the size of the defect.

Presentations in the Adult or Adolescent

a) Small defect without significant left-to-right shunting

b) Large defect with severe pulmonary hypertension and cyanosis due to right-to-left shunt.

c) Large defect with a large left-to-right shunt that has induced secondary infundibular stenosis (tough to differentiate from tetralogy of Fallot).

Small VSDs

A high resistance to flow across the VSD due to the large pressure difference between the two ventricles. There is a small left-to-right shunt (Qp/Qs < 1.5) and a normal ratio of PA to systemic pressures.

There is little or no increase in the pulmonary vascular resistance. A holosystolic murmur is present due to the pressure gradient across the defect. The majority of these defects close during the first three years of life.

Medium-Sized VSDs

There is a moderate left-to-right shunt present (Qp/Qs = 1.5-2.0) that still has some resistance to flow across the defect. There is also volume overload of the LA and the LV and LVH. There may therefore be a mid diastolic mitral murmur and a third heart sound (S3). The ratio of the PA systolic pressure to the systemic pressure is < 5.

The area of the defect is usually less than 1 cm2/m2 of body surface area and is unusual for this group to have a marked increase in PVR. In some cases and depending on the type of VSD, as the child becomes older, the relative size of the defect will decrease.

Large VSDs

There is a large defect on the ventricular septum, > 1 cm2/m2 of BSA, with a large shunt left-to-right (Qp/Qs is > 2), causing volume overload of the LV, which may result in its failure. The defect may approximate the size of the aortic orifice.

The ratio of the PA pressure to the systemic pressure is > 5. Produce the same clinical findings as moderate sized VSD but also pulmonary hypertension.

There is rarely spontaneously closure of the defect, and these patients either die, or progress to adolescence or adulthood with severe pulmonary hypertension or with secondary protective infundibular pulmonary stenosis.

In the group with severe pulmonary hypertension, the left-to-right shunt decreases and the degree of right-to-left shunting increases with accompanying cyanosis (i.e. they develop Eisenmenger's syndrome).

Protective infundibular stenosis may also result in reversal of the shunt, and may be indistinguishable clinically from tetralogy of Fallot.

Gross Pathology

Images courtesy of Professor Peter Anderson DVM PhD and published with permission © PEIR, University of Alabama at Birmingham, Department of Pathology
















References

  1. Anderson RH, Sarwark AE, Spicer DE, Backer CL (2014). "Exercises in anatomy: holes between the ventricles". Multimed Man Cardiothorac Surg. 2014. doi:10.1093/mmcts/mmu026. PMID 25547619.
  2. Anderson RH, Webb S, Brown NA, Lamers W, Moorman A (2003). "Development of the heart: (2) Septation of the atriums and ventricles". Heart. 89 (8): 949–58. PMC 1767797. PMID 12860885.
  3. Schleich JM, Abdulla T, Summers R, Houyel L (2013). "An overview of cardiac morphogenesis". Arch Cardiovasc Dis. 106 (11): 612–23. doi:10.1016/j.acvd.2013.07.001. PMID 24138816.
  4. 4.0 4.1 4.2 Anderson RH, Spicer DE, Brown NA, Mohun TJ (2014). "The development of septation in the four-chambered heart". Anat Rec (Hoboken). 297 (8): 1414–29. doi:10.1002/ar.22949. PMID 24863187.
  5. 5.0 5.1 Gittenberger-de Groot AC, Calkoen EE, Poelmann RE, Bartelings MM, Jongbloed MR (2014). "Morphogenesis and molecular considerations on congenital cardiac septal defects". Ann Med. 46 (8): 640–52. doi:10.3109/07853890.2014.959557. PMID 25307363.

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