Ventricular Septal Defect

1

• Ventricular Septal Defect

2
What is the incidence of ventricular septal
defect (VSD) in dogs and cats, compared to other
congenital cardiac defects?

• Dogs 3rd most common congenital cardiac defect
• 5-10 congenital cardiac defects
• may have heredity component
• Cats 1st or 2nd most common congenital cardiac
  defect

3
What are the common locations of the defect?

• Most common location is in membranous septum
  beneath the septal leaflet of the tricuspid valve
  on the right side and the aortic annulus on the
  left
• Occasionally defects occur in infundibular or
  supracrisal region or in muscular septum

4
Describe the pathophysiology associated with VSD.

• Blood flows from high pressure left ventricle ot
  low pressure right ventricle
• Volume of blood shunted determined by size of
  defect and pulmonary vascular resistance
• Left ventricle dilates and hypertrophies as
  result of increased volume
• Pulmonary system tolerates large volume- clinical
  signs not seen until pulmonary flow is more than
  2.5 times systemic flow
• 24 of dogs and cats with VSD have
  pulmonary-to-systmic flow ratio 2.5 1
• Increased pulmonary flow results in increased
  pulmonary vascular resistnace and right
  ventricular hypertrophy
• Pulmonary edema may occur with increased
  pulmonary pressure and flow
• Right to left flow may occu in severe cases
  venous admixture of blood and arterial hypoxemia
• Cyanosis and polycythemia
• Aortic insuffinciency is common secondary
  abnormality result of aortic leaflet into
  infundibular VSD and contributes to left heart
  failure

5
What are 2 factors that determine the volume of
blood shunted?

• Blood flows form high pressure left ventricle to
  low pressure right ventricle
• Volume of blood shunted determined by size of
  defect and pulmonary vascular resistance

6
Which of these is likely to change over time?

• Size of defect ????????

7
Why does it change?

• Because the left ventricle dilates and
  hypertrophies as result of increased volume

8
What are the clinical signs seen with severe VSD?

• Cough
• Dyspnea
• Exercise intolerance
• Stunted growth

9
Why are signs not seen with all patients?

• 25 have CS in the form of a murmur. When the
  pulmonary flow is more than 2.5xs you will see
  CS. If there is equilibration with the left
  ventricle then improvement of CS will be noted.
  The size of the shunt determines the flow of
  blood, in addition to vascular resistence and
  this contributes to whether or not CS will be
  seen.

10
At what volume of shunt flow do clinical signs
develop?

• Clinical signs are not seen until pulmonary flow
  is more than 2.5 times systemic flow

11
Describe the events that lead up to these signs.

• Increased pulmonary flow results in increased
  pulmonary vascular resistnace and right
  ventricular hypertrophy
• Pulmonary edema may occur with increased
  pulmonary pressure and flow

12
What is a common secondary abnormality that may
cause a secondary murmur?

• Aortic insufficiency

13
What is its effect on the progression of disease?

• Result of prolapse of aortic leaflet into
  infundibular VSD ( venturi effect of VSD flow
  loss of support of annulus)
• Contributes to left heart failure

14
Describe primary repair of VSD.

• Dacron or pericardial patch over defect
• Open heart procedure

15
What limits its use in dogs and cats?

• Cats would require a neonatal cardiac bypass
  machine which is expensive and hard to come by

16
What palliative procedure is used in both dogs
and cats?

• Pulmonary artery banding

17
How does it work to relieve clinical signs and
protect the pulmonary vasculature?

• Increase right ventricular systolic pressure and
  thereby decrease shunt flow
• Protects pulmonary vasculature from secondary
  changes
• Reduces volume overload of left heart

18
What are the complications of this procedure?

• Tearing of manin pulmoary artery and hemorrhage
  during surgery
• Fulminant right heart failure in immediate post
  operative period

19
What is the prognosis, with and without
treatment, for mild and severe VSD?

• Small VSD excellent
• Large VSD
• definitive closure excellent
• Pulmonary artery banding good to excellent
• No correction guarded to poor

20
What percentage of dogs and cats with VSD has
clinical signs?

• 75 of dogs and cats with VSD have NO clinical
  signs
• So that leaves 25 that DO have signs yes I am
  captain obvious today!!!

21

• Surgical Diseases of Mediastinum

22
List 4 types of tumors that may occur in the
cranial mediastinum of dogs and cats.

• Lymphatic tumors lymphosarcoma
• Ectopic thyroid/parathyroid tumors
• Chemoreceptor tumors
• Thymoma

23
Which of these is most commonly treated by
surgical removal?

• Thymoma low grade non-invasive tumors

24
Which is not a surgical disease?

• Thymic lymphosarcoma

25
Which is most common in cats?

• Functional thyroid adenoma

26
What is the treatment and prognosis for each type
of tumor?

• Ectopic Thyroid Tumor
• Tx surgical excision in dogs very difficult,
  iodine131 in cats
• Px ??
• Aortic body tumor
• Tx sx excision may be impossible b/c fo
  location and invasive nature
• Pericardectomy if pericaridal effusion is
  clinical problem
• Radiation therapy- difficult location
• Px guarded to poor
• Thymoma
• TXsurgical excision low grade non-invasive
  tumors
• Adjunctive radiation therapy, esp if tumor cannot
  be completely removed
• Survival of 3 years w/out tx
• Px benign non-invasive good
• If paraneoplastic syndrome is present guarded

27
What are the clinical signs associated with mass
lesions of the cranial mediastinum?

• Dyspnea
• Cough
• Dysphagia
• Pleural effusion
• Precaval syndrome

28
What diagnostic tests are used with all types of
tumors?

• ?????
• Thoracic radiographs
• Cytologic evaluation of pleural fluid
• Fine needle aspirate of mediastinal mass
• Paraneoplastic syndrome hypercalcemia

29
What diagnostic tests are used with thymic
lymphosarcoma?

• Thymic lymphosarcoma
• Thoracic radiographs
• Cytologic evaluation of pleural fluid
• Fine needle aspirate of mediastinal mass
• Paraneoplastic syndrome hypercalcemia

30
What diagnostic tests are used with ectopic
thyroid tumors?

• Must differentiate form other mass lesions in
  cranial mediastinum
• Serum chemistry and thyroid hormone levels may be
  suggestive
• Radioisotope thyroid scan very helpful

31
What diagnostic tests are used with thymoma?

• Clinical signs
• Radiographs/ultrasound or mediatinal mass
• Cytology of pleural fluid
• Fine needle aspirate
• Recognition of paraneoplatic signs

32
Which of these tumors may be associated with a
paraneoplastic syndrome?

• Thymic lymphosarcoma
• Thymoma

33
What are these syndromes?

• Hypercalcemia
• Thymoma
• Myasthenia gravis
• Polymyositis
• Autoimmune disorders
• Other primary non-thymic tumors

34

• Surgical diseases of the pericardium

35
What are 2 causes of pericardial effusion that
are treated by pericardectomy?

• Infection
• Idiopathic

36
How are these conditions differentiated from
other, non-surgical cause of pericardial
effusion?

• Infectious
• Granulomatous
• Fungal
• Ideopathic
• fibrotic

37
What is the typical signalment for each of these
conditions?

• Granulomatous Pericarditis
• Adult hunting dogs
• Organisms Nocardia and Actinomyces
• Idiopathic pericarditis
• Large breed dogs, especially golden retrievers
  and irish setters
• Middle aged and older dogs ( 6 years of age)

38
Why is a median sternotomy preferred for subtotal
pericardectomy?

• Allows you to see the phrenic nerve on both sides

39
Why is this procedure more difficult in the dog
with infectious pericarditis?

• Because you cant see the phrenic nerve
• You may have to trace it back from the diaphragm
  and then approximate where it crosses the
  pericardium

40
Describe postoperative management of these dogs.

• Thoracostomy tube until hydrothorax is resolved
  (
• Monitor blood loss

41
What is the prognosis for each type of
pericarditis?

• Granulomatous fair
• Ideopathic good
• 70-80 return to normal
• Remaining cases have recurrence of effusion, may
  require pleuroperitioneal shunt

42
What is a salvage procedure that can be used for
hydrothorax secondary to recurrent idiopathic
pericarditis?

• Pleuroperitoneal shunt