Ventricular Septal Defect

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Ventricular Septal Defect

• Deena Abdel_Hadi

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Embryology

• At the 2nd intra-uterine week , when the embryo
  is only 1.5 mm long the heart begins to take
  shape , a functional circulatory system has been
  established by the 4th week the ventricular
  septum is fully developed by the 8th week.
• Consequently any radical alteration of the
  architecture of the heart must occur between the
  2nd 8th weeks of intra-uterine life.
• By about 6 weeks all the principal components
  of the human heart are clearly discernible.

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Embryology

• The common ventricular canal is divided by an
  intra-ventricular septum (septum inferius) which
  start at the 3rd or the beginning of the 4th week
  , grows upward backward toward the common
  atrio-ventricular orifice which it divides into
  the mitral tricuspid valves.

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Embryology

• This septum is muscular is an outgrowth of the
  ventricular wall itself.
• It doesnt reach the floor of the bulbus cordis ,
  an opening in the ventricular septum is left in
  the center high up with a downward convex
  partly from the bulbus cordis.(as mentioned is
  usually completely closed by the 7th or 8th
  intra-uterine week).

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Embryology

• In order for the ventricular septum to divide
  the common atrio-ventricular orifice evenly ,
  this must shift toward the right , failure of
  this orifice to shift result in tricuspid atresia
  an excessive shift gives rise to mitral
  atresia .

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Embryology

• Failure of the bulbar ridges to form the
  membranous part of the septum result in the most
  common forms of V.S.D. .
• Defects of the muscular septum are usually
  ventral high near the aortic orifice only
  rarely do they occur in the neighborhood of the
  apex

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Pathophysiology

• The physical size of the defect is a major, but
  not the only , determinant of the size of the
  left-to-right shunt .
• The shunt magnetite is also determined by the
  level of pulmonary vascular resistance compared
  with systemic vascular resistance.

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Pathophysiology

• When a small communication is present (usually lt
  0.5 cm 2), the defect is called restrictive
  right ventricular pressure is normal .
• The higher pressure in the left ventricle drives
  the shunt left-to right.
• In large non-restrictive defects (usually gt 1.0
  cm2), right left ventricular pressures are
  equalized.

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Pathophysiology

• In these defects, the direction of shunting the
  shunt magnitude are determined by the ratio of
  pulmonary to systemic vascular resistances.
• After birth, in the presence of a large
  V.S.D.,the pulmonary vascular resistance may
  remain higher than normal thus the size of the
  left-to-right shunt maybe limited .
• As pulmonary vascular resistance falls in the 1st
  few weeks after birth because of the normal
  involution of the media of the small pulmonary
  Arteries arterioles,the size of the
  left-to-right shunt increases clinical symptoms
  become apparent.

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Pathophysiology

• When the ratio of pulmonary to systemic
  resistance approaches 11, the shunt becomes
  bi-directional, signs of heart failure abate
  (diminished), the patient becomes cyanotic
  (Eisenmenger physiology).
• Prolonged pulmonary hypertension is prevented by
  early surgical intervention in patients with
  large V.S.D.s

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Pathophysiology

• The magnitude of intracardiac shunts is usually
  described by the ratio of pulmonary to systemic
  blood flow.
• If the left-to-right shunt is small (pulm. to
  syst. flow ratio lt1.751), the cardiac chambers
  will not be appreciably enlarged the pulm.
  Vascular bed will likely be normal.
• If the shunt is large (flow ratio gt2.51), the
  left atrial ventricular volume overloaded
  occur, as well as right ventricular pulm.
  Arterial hypertension.
• The pulm. Arterial trunk, left atrium, left
  ventricle are enlarged because of the large
  volume of pulmonary blood flow.

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Clinical Manifestationssmall defects with
trivial left-to-right shunts NL. Pulm. Art. Pr.

• Asymptomatic.
• Cardiac lesion is usually found via a routine
  physical exam. (harsh ,loud ,blowing,left
  parasternal holosystolic murmer on left lower
  sternal border .
• The systolic murmer maybe not audible via the 1st
  few days(limited left-to-right shunt d.t.higher
  right side pr.

• CXR usually normal .
• ECG usually normal but may suggest LVH
• (RVH suggest pulmonary HTN , large VSD ,or
  associated symptom as pulmonary Stenosis)

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Clinical Manifestationslarge defects with
excessive pulmonary blood flow pulmonary HTN

• Dyspnea , feeding difficulties , poor growth ,
  recurrent pulmonary infections cardiac failure
  in early infancy (cyanosis is usually absent but
  duskiness is noted during infections or crying.
• A palpable parasternal lift , a holosystolic
  murmer , less harsh more blowing d.t. absence
  of a significant pr. Gradient across the defect.

• CXR showed increase broncho-vascular markings
  ,gross cardomegaly with prominence of both
  ventricles , left atrium pulmonary artery,
  frank pulm. edema pleural effusion.
• ECG shows bi-ventricular hypertrophy , P wave
  maybe notched or peaked.

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Diagnosis

• Two-dimensional echocardiogram
• position size of VSD.
• By Doppler examination used to diagnose very
  small muscular septum defect the degree of
  volume overload of the left atrium left
  ventricle.
• Pulsed Doppler calculate the pr. Gradient across
  the defect.this will allow estimation of right
  ventricular pr. help to determine whether the
  patient is at risk for the development of early
  pulmonary vascular disease.
  

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Diagnosis

• Cardiac catheterization
• indicated when clinical evaluation leaves
  uncertainly regarding the size of the shunt or
  when lab. data dont fit well with the clinical
  findings.
• It is useful for detecting the presence of
  associated cardiac defects.

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Prognosis Complications

• (30-50) of small VSDs will close spontaneously ,
  most frequently during the 1st year of life
• the vast majority of defects that close will do
  so before age 4 yr..
• One of the long term risks for these patients is
  that of infective endocarditis.

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Prognosis Complications

• Endocarditis occurs in fewer than 2 of children
  with VSD , is more common in adolescents , is
  rare in children under 2 yr. of age
• it is less common for moderate or large VSD to
  close spontaneously , even defects large enough
  to result in H.F.(manifested in infants as
  F.T.T.) may become smaller rarely will close
  completely.
• Large defects ass. with recurrent chest
  infections C.H.F.

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Treatment(small defects)

• Reassure parents
• allow the child to live a normal life
• surgical repair is not recommended
• protection against infective endocarditis
• follow up screening for pulmonary HTN or pulmonic
  Stenosis indicated by RVH.

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Treatment (large VSD)

• Medical treatment has two aims to control CHF
  to prevent development of pulmonary vascular
  disease.
• Patients show signs of recurrent chest infections
  FTT.
• Pulmonary vascular dse is prevented when surgery
  is performed within the 1st yr. of life.
• Large defects ass. With pulmonary HTN should be
  closed between 6 12 mo. of age.

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Treatment (large VSD)

• Surgical risks are higher for defects in the
  muscular septum , particularly apical defects
  multiple (Swiss-cheese type) defects,they may
  require pulmonary artery binding.
• Catheter occlusion devices are currently being
  tested to close apical muscular VSDs.
• After obliteration of the left-to-right
  shunt,catch-up growth occurs in the majority over
  the next 1-2 yr.
• Systolic ejection murmurs of low intensity may
  persist for months.

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