Pulmonary
Thromboembolism
Emily S. Southward DVM
University of Missouri – Columbia
Veterinary Medical Teaching
Hospital
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.
Virchow’s Triad
 Venous
stasis.
 Injury or abnormalities to the vessel
wall.
 Alterations in coagulation properties.
Venous Stasis
 Accumlation
of activated
procoagulants.
– Immobilization
– Inadequate cardiac pump.
 Promotes
thrombus formation.
Vessel Wall Injury
 Acute
or chronic injury to vessel
endothelium.
 Leads to activation of platelets and
clotting cascade.
 Promotes thrombus formation.
Vessel Injury
Platelet Adhesion
Aggregation
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
Alterations in Coagulation
 Decrease
in anticoagulant factors.
– Thrombomodulin
– Antithrombin III
– Heparin
– Alpha2-Marcoglobulin
– Plasmin
 Leads
to hypercoagulable state by
formation of thrombin.
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.
Predisposing Factors or Diseases
for Development of PTE
 Hypercoagulable
state
– Nephrotic syndrome
– Immobilization
– Amyloidosis
– Early DIC
– Hyperadrenocorticism
 Capillary
fragility
 Activation of clotting cascade.
Predisposing Factors or Diseases
for Development of PTE
 Hypercoagulable
 Capillary
fragility
state
– Diabetes Mellitus
– Immune–mediated hemolyitc anemia
– Sepsis
– Hyperadrenocorticism
 Activation
of clotting cascade.
Predisposing Factors or Diseases
for Development of PTE
 Hypercoagulable
 Capillary
state
fragility
 Activation of clotting cascade.
– Sepsis
– Pneumonia/pyothorax
– Heartworm disease
– Surgery
– Bacterial endocarditis
– Neoplasia
Consequences of PTE
 Respiratory.
– Increased alveolar dead space.
– Hyperventilation.
– Hypoxemia.
– Ventilation/perfusion inequality.
– Intrapulmonary shunts.
Normal Alveolus
Increased Alveolar Dead Space
Hypoxemia
 Results
from ventilationperfusion inequality, physiologic
shunting and increased dead
space.
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.
Ventilation/Perfusion Inequality
 V/Q
inequality occurs when
distribution of blood is altered to the
alveoli.
 O2 increase in the alveoli and CO2
decreases.
Hemodynamic Changes
 Increase
in pulmonary vascular
resistance.
 Increased afterload to the right
heart.
 Can lead to circulatory collapse and
shock.
Clinical Signs
 Not
pathognomonic.
– Dyspnea.
– Tachypnea.
– Hemoptysis.
– Tachycardia.
– Hypoxemia.
– Sudden death.
Diagnosis
 CBC/Biochemistry
results reflect
primary disease process.
 Hypoxemia common but 10% of
patients are normal.
 Thoracic radiographs can be normal
and inconclusive.



LaRue MJ and Murtaugh RJ. Pulmonary
Thromboembolism in Dogs:47 cases (1986-87). J
Amer Vet Med Assoc. 1990 Nov. 15;197(1):13681372.
Johnson LR et al. Pulmonary Thromboembolism
in 29 dogs:1985-1995 J Vet Intern Med. 1999
Jul;13(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.
Advanced Diagnostics
 Pulmonary
scintigraphy
 Pulmonary angiography.
Pulmonary Scintigraphy
 Noninvasive
 Aids
in diagnosis of PTE but not
definitive.
 Two types- ventilation and perfusion
scans.
Perfusion Scan
Performed first.
 Normal study rules
out PTE.
 Radionuclidelabelled,
macroaggregated
albumin in
peripheral vein.

Ventilation Scan
Inhaled radioactive
inert gas-senon133 or technetium99m.
 Patient under
general anesthesia.
 Normal in PTE.

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/nucmd
/htm
Normal Human Perfusion Scan
Abnormal Human Perfusion
Scan
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.
Pulmonary Embolus
Human lung.
 Arrow indicates
abrupt termination
of a pulmonary
artery.


Www.brighamrad.Harvard.edu/cases/b
wh/images.
Treatment
 Oxygen
therapy.
 Heparinization 200-300 units/kg
subcutaneously every 8 hours.
 Streptokinase or TPA.
 Mechanical ventilation.
 Long term- warfarin therapy.
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.
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.
Prognosis
 Guarded.
 Improves
with early detection and
treatment.
 Improves each day the patient
survives.
 At risk for more emboli.
UMC VMTH Cases
 Three
in data base.
– Sadie
– Magnum
– Koko
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.
Sadie’s Thoracic Films
Sadie’s Thoracic Films
Sadie’s Necropsy
 Hepatocellular
carcinoma
 Adrenocortical hyperplasia
 Pulmonary thrombois – most lobar
branches effected.
 Renal infarction.
Magnum Meeks
 8-year-old
MC doberman pinscher
 Presented for dyspnea of two days
duration.
 Protein losing nephropathy.
Magnum’s Thoracic Films
Magnum’s Thoracic Films
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.
Koko’s Thoracic Films
Koko’s Thoracic Films
Koko’s Pefusion Scintigraphy
Koko’s Pefusion Scintigraphy
Koko’s Necropsy
 Muliple
small thrombi in the
pulmonary vasculature.
 Cardiomegaly
Thanks
 Dr.
Mann
 Dr. Dodam
 Dr. Lattimer
 Dr. Kunz
Questions?