Ventricular failure + myocardial infarction Flashcards
(29 cards)
What is myocardial infarction?
Myocardial cell death due to prolonged ischemia
Myocardial infarction leads to damage in the heart muscle due to lack of blood flow.
What is a primary predisposing factor for myocardial infarction in people?
Coronary artery disease
This condition is rare in animals.
What is a significant protective feature of dogs regarding coronary artery disease?
Extensive epicardial collateral network of coronaries
This network reduces the risk of coronary artery disease in dogs.
What are the primary predisposing factors for myocardial infarction in veterinary patients?
Diseases causing a hypercoagulable state
These factors are more common in veterinary medicine compared to coronary artery disease.
What were risk factors for myocardial infarction described by Liu et al. (1987) regarding dogs with atherosclerosis? What were clinical signs?
- Hypothyroidism
- Hyperlipidemia
- Hypercholesterolemia
Clinical signs: GI, weakness, dyspnea, anorexia, general malaise
They exhibited clinical signs like GI issues, weakness, dyspnea, anorexia, and general malaise.
What did Driehuys et al. (1998) report about causes of myocardial infarction in dogs and cats?
- Primary CV disease: 22%
- Primary renal disease: 22%
- IMHA treated with steroids: 16%
This study highlights various underlying health issues related to myocardial infarction.
How does the endothelium in health prevent thrombus formation?
Contains anticoagulant factors that maintain normal blood flow and organ perfusion
The endothelium acts as a barrier and is crucial for vascular health.
What components make up the glycocalyx?
- Glycosaminoglycans (GAGs)
- Proteoglycans
- Glycoproteins
The glycocalyx is essential for endothelial function and interaction with blood components.
What are some anticoagulants that bind to the glycocalyx?
- Heparin cofactor II
- Thrombomodulin
- Tissue factor pathway inhibitor (TFPI)
These anticoagulants help regulate blood coagulation and maintain vascular homeostasis.
What happens during endothelial injury?
- Transitions to a prothrombotic state
- Decreased synthesis of GAG
- activation of endothelial cells –> release of ultra large multimers of vWF –> platelet aggregation + thrombus formation
- release of procoagulant substrances (TF, microparticles) into circulation
- platelet activation + transformation –> shuffle negatively charged phospholipids to surface –> catalyst for clot formation
- decrease in endogenous anticoagulants (antithrombin, protein C, TFPI)
Endothelial injury increases the risk of thrombosis and myocardial infarction.
What is Virchow’s triad?
- Endothelial dysfunction
- Hypercoagulability
- Altered blood flow
These factors collectively increase the risk of thrombotic events such as myocardial infarction.
Name 7 causes for a hypercoagulable state and predisposition to myocardial infarction
- Neoplasia
- Sepsis
- Endocrine disorders
- PLE
- PLN
- Renal disease
- Glucocorticoids
What is released into circulation due to damage of cardiac myocytes? When does this increase after injury? When does it peak? How long can it be elevated?
Troponin
2-4hr after injury
peak: 18-24hr after onset
up to 14d
Troponin levels are used to assess myocardial injury.
How should cardiac troponins be measured in suspected MI cases?
Measured on admission + 3-6 hours later
A rise and/or fall with at least one value above the 99th percentile URL is required for diagnosis.
What are the normal troponin ranges for dogs (Stratus CS analyzer by Siemens)?
Dogs: <0.03-0.07 ng/ml
Elevated levels indicate myocardial injury.
What is the primary difference in troponin levels between CHF and myocardial infarction?
CHF: lower steady elevations
MI: spike
This distinction is crucial for diagnosis.
How does CK-MB behave in response to acute myocardial injury?
rises early and returns to baseline within 48 hours
It can also indicate damage to skeletal muscle, lungs, or spleen.
What is required for wall motion abnormalities to be present in echocardiography?
> 20% of myocardial wall must be affected
This threshold is crucial for diagnosing significant abnormalities.
What imaging modalities are used in people for heart conditions?
Radionuclide imaging
cardiac MRI
CT angiography
These modalities provide additional information beyond echocardiography.
What does ST elevation on an ECG suggest?
Coronary artery occlusion
= ST-elevation myocardial infarction (STEMI)
It indicates ST-elevation myocardial infarction (STEMI).
What ECG changes were observed in dogs with myocardial infarction?
Transient deep and negative T waves
These changes were noted in cases secondary to snake envenomation, sepsis, and SIRS.
What may be seen on echocardiography that can be suggestive of myocardial infarction (in combination with other changes)?
Hyperechoic foci within the myocardium
What disease have been described to be associated with myocardial infarction?
Sepsis
SIRS
Snake envenomation
Describe the 2 phases of troponin release from cardiomyocytes
Acute: cytosolic pool release
Sustained: slower release of bound troponin
