Pulmonary Thromboembolism

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Pulmonary Thromboembolism

• Emily S. Southward DVM
• University of Missouri Columbia Veterinary
  Medical Teaching Hospital

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Definition

• Pulmonary thromboembolism
• One clot or many clots that form at distant sites
  and lodge in the pulmonary vasculature.
• Pulmonary artery thrombus
• Clots that form in the pulmonary vasculature.
• Clots can partially or fully occlude pulmonary
  vessels.

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Virchows Triad

• Venous stasis.
• Injury or abnormalities to the vessel wall.
• Alterations in coagulation properties.

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Venous Stasis

• Accumlation of activated procoagulants.
• Immobilization
• Inadequate cardiac pump.
• Promotes thrombus formation.

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Vessel Wall Injury

• Acute or chronic injury to vessel endothelium.
• Leads to activation of platelets and clotting
  cascade.
• Promotes thrombus formation.

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Vessel Injury
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Platelet Adhesion
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Aggregation
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Alternations in Coagulation

• Increase in procoagulant factors.
• By trauma to vascular wall or extravascular
  tissues.
• Releases tissue thromboplastin and phospholipid.
• Leads to formation of prothrombin activator.
• Prothrombin ? Thrombin

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Alterations in Coagulation

• Decrease in anticoagulant factors.
• Thrombomodulin
• Antithrombin III
• Heparin
• Alpha2-Marcoglobulin
• Plasmin
• Leads to hypercoagulable state by formation of
  thrombin.

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Thrombosis Formation

• Platelet nidus at site of injury.
• Growth by aggregation of platelets and fibrin.
• Activation of clotting cascade.
• Larger growth to a red fibrin thrombus.
• Thrombus fractures and embolizes to other areas
  of the body.

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Predisposing Factors or Diseases for Development
of PTE

• Hypercoagulable state
• Nephrotic syndrome
• Immobilization
• Amyloidosis
• Early DIC
• Hyperadrenocorticism
• Capillary fragility
• Activation of clotting cascade.

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Predisposing Factors or Diseases for Development
of PTE

• Hypercoagulable state
• Capillary fragility
• Diabetes Mellitus
• Immunemediated hemolyitc anemia
• Sepsis
• Hyperadrenocorticism
• Activation of clotting cascade.

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Predisposing Factors or Diseases for Development
of PTE

• Hypercoagulable state
• Capillary fragility
• Activation of clotting cascade.
• Sepsis
• Pneumonia/pyothorax
• Heartworm disease
• Surgery
• Bacterial endocarditis
• Neoplasia

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Consequences of PTE

• Respiratory.
• Increased alveolar dead space.
• Hyperventilation.
• Hypoxemia.
• Ventilation/perfusion inequality.
• Intrapulmonary shunts.

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Normal Alveolus
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Increased Alveolar Dead Space
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Hypoxemia

• Results from ventilation-perfusion inequality,
  physiologic shunting and increased dead space.

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Intrapulmonary Shunts

• Blood that has not been to areas of ventilated
  lung and enters systemic circulation without gas
  exchange taking place.
• Poorly oxygenated blood enters the arterial
  system lowering the PaO2.
• Not responsive to oxygen therapy.

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Ventilation/Perfusion Inequality

• V/Q inequality occurs when distribution of blood
  is altered to the alveoli.
• O2 increase in the alveoli and CO2 decreases.

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Hemodynamic Changes

• Increase in pulmonary vascular resistance.
• Increased afterload to the right heart.
• Can lead to circulatory collapse and shock.

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Clinical Signs

• Not pathognomonic.
• Dyspnea.
• Tachypnea.
• Hemoptysis.
• Tachycardia.
• Hypoxemia.
• Sudden death.

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Diagnosis

• CBC/Biochemistry results reflect primary disease
  process.
• Hypoxemia common but 10 of patients are normal.
• Thoracic radiographs can be normal and
  inconclusive.

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• LaRue MJ and Murtaugh RJ. Pulmonary
  Thromboembolism in Dogs47 cases (1986-87). J
  Amer Vet Med Assoc. 1990 Nov. 15197(1)1368-1372.
  
• Johnson LR et al. Pulmonary Thromboembolism in 29
  dogs1985-1995 J Vet Intern Med. 1999
  Jul13(4)338-345.
• Flükiger MA and Gomez JA. Radiographic Findings
  in Dogs with Spontaneous Pulmonary Thrombosis or
  Embolism. Veterinary Radiology, Vol.25,No.3
  124-131.

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Advanced Diagnostics

• Pulmonary scintigraphy
• Pulmonary angiography.

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Pulmonary Scintigraphy

• Noninvasive
• Aids in diagnosis of PTE but not definitive.
• Two types- ventilation and perfusion scans.

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Perfusion Scan

• Performed first.
• Normal study rules out PTE.
• Radionuclide-labelled, macroaggregated albumin in
  peripheral vein.

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Ventilation Scan

• Inhaled radioactive inert gas-senon-133 or
  technetium-99m.
• Patient under general anesthesia.
• Normal in PTE.

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Ventilation/Perfusion Combo

• With PTE the ventilation scan would be normal and
  the perfusion scan abnormal.
• Suggestive of PTE.F
• Picture from WWW.bschsys.org/DiagnositcImaging/nuc
  md/htm

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Normal Human Perfusion Scan
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Abnormal Human Perfusion Scan
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Pulmonary Angiography

• Performed if definitive diagnosis or exclusion of
  PTE is required.
• Requires sedation or general anesthesia.
• Greater risks.
• Intraluminal filling defect and sharp cutoff are
  diagnostic for PTE.

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Pulmonary Embolus

• Human lung.
• Arrow indicates abrupt termination of a pulmonary
  artery.
• Www.brighamrad.Harvard.edu/cases/bwh/images.

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Treatment

• Oxygen therapy.
• Heparinization 200-300 units/kg subcutaneously
  every 8 hours.
• Streptokinase or TPA.
• Mechanical ventilation.
• Long term- warfarin therapy.

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Monitoring

• Clotting times- want to maintain PTT at 1.5-2.5
  times normal or and ACT at 1.2-1.4 times normal.
• Serial arterial blood gas analysis.
• Respiratory rate.
• Central venous pressure.
• All other basic monitoring.

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Complications Of Therapy

• Hemorrhage most common.
• Not predictable.
• Protamine therapy indicated with hemorrhage due
  to heparin.
• Vitamin K or fresh-frozen plasma in warfarin
  therapy.

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Prognosis

• Guarded.
• Improves with early detection and treatment.
• Improves each day the patient survives.
• At risk for more emboli.

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UMC VMTH Cases

• Three in data base.
• Sadie
• Magnum
• Koko

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Sadie Bailey

• 8-year-old FS mixed breed dog.
• Presented for weight loss, anemia, and anorexia.
• Weak and lethargic on presentation
• Hemoabdomen, thrombocytopenia, and neutrophilia
  with left shift.
• Developed severe dyspnea and ventricular
  tachycardia.

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Sadies Thoracic Films
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Sadies Thoracic Films
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Sadies Necropsy

• Hepatocellular carcinoma
• Adrenocortical hyperplasia
• Pulmonary thrombois most lobar branches
  effected.
• Renal infarction.

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Magnum Meeks

• 8-year-old MC doberman pinscher
• Presented for dyspnea of two days duration.
• Protein losing nephropathy.

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Magnums Thoracic Films
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Magnums Thoracic Films
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Koko Westerhoff

• 12-year-old FS dachshund.
• Presented for lethargy, anorexia, tachypnea, and
  possible CHF.
• History includes diabetes mellitus, IVDD and
  cataracts.
• PE- Increased BV lung sounds, mild crackles,
  tachycardia, and left systolic murmur.

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Kokos Thoracic Films
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Kokos Thoracic Films
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Kokos Pefusion Scintigraphy
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Kokos Pefusion Scintigraphy
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Kokos Necropsy

• Muliple small thrombi in the pulmonary
  vasculature.
• Cardiomegaly

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Thanks

• Dr. Mann
• Dr. Dodam
• Dr. Lattimer
• Dr. Kunz

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Questions?