Ischaemia and Vascular Techniques Quiz

Study Notes

Ischaemia

The severity of effects depends on the artery affected, the rate of occlusion, the health of collateral vessels, and the overall health of the patient.
Subclavian artery has better collateral circulation than the popliteal artery.
Acute ischaemia is more dangerous than chronic ischaemia because there is insufficient time for collateral vessels to open.
Patients with myocardial insufficiency or severe anaemia are more vulnerable to the effects of ischaemia.

Vascular Laboratory Techniques

Doppler ultrasound is non-invasive, painless, portable, and inexpensive.
Computed tomography angiography (CTA) involves injecting contrast material through a vein, making it less invasive than catheter angiography.
Magnetic resonance angiography (MRA) uses hydrogen atoms present in the body to create images, requiring no contrast injection.
Digital subtraction arteriography (DSA) visualizes the arterial tree without arterial cannulation, avoiding potential complications.
Direct arteriography is an invasive procedure used for endovascular procedures.
- Direct femoral arteriography involves direct puncture of the femoral artery and injection of contrast material.
- Trans-femoral aortography uses a cannula inserted into the femoral artery to guide a catheter to the desired location for contrast injection.
- Trans-axillary aortography is used when the distal aorta is occluded.
- Translumbar aortography is no longer a common practice.

Arterial Embolism

Embolism is the movement of a substance through the circulation.
Cardiac emboli account for 80-90% of cases and often result from:
- Atrial fibrillation: The leading cause, leading to stasis and thrombus formation in the left atrium.
- Myocardial infarction: Leading to mural thrombosis formation.
- Less common causes: Left ventricular aneurysm, endocarditis associated with rheumatic or congenital heart diseases.
Non-cardiac emboli (about 20%) can originate from extensive atherosclerotic lesions or aneurysms in major arteries like the aortic arch or descending thoracic aorta.

Sites of Arterial Embolism

Common Femoral Artery bifurcation (40%)
Aortic bifurcation (saddle embolus)
Popliteal Artery bifurcation
Brachial Artery bifurcation
Common Carotid Artery bifurcation

Acute Arterial Thrombosis

Atherosclerotic obstruction: The most frequent cause, with acute thrombotic occlusion developing on top of atherosclerotic narrowing.
Pump failure: A sudden decline in cardiac output can lead to acute limb ischaemia in individuals with pre-existing peripheral vascular disease.
Hypercoagulable states: Can contribute to arterial occlusion, particularly in smaller arteries.
Febrile illness: Or gastroenteritis, especially in children, can cause hemoconcentration leading to thrombosis.
Acute graft thrombosis: May occur early due to technical factors or later due to progression of the underlying disease.
Inadvertent intra-arterial injection: Can happen in drug users, causing vasospasm followed by thrombosis.

Sequelae of Acute Arterial Obstruction

Propagation of the thrombus: Widespread distal intravascular thrombosis takes place after circulatory arrest.
Associated venous thrombosis: Resulting from sluggish flow and ischaemic injury to the intima of the affected veins.
Compartment syndrome: Ischaemic muscles swell, exacerbating ischaemia. After revascularization, further oedema can occur, hindering circulation. Early fasciotomy can help prevent this.
Systemic and metabolic sequelae: Muscle ischaemia leads to various systemic and metabolic complications.

Description

Test your knowledge on ischaemia, its effects, and various vascular laboratory techniques. This quiz covers important concepts related to collateral circulation, the impact of acute versus chronic ischaemia, and non-invasive imaging methods. Enhance your understanding of vascular health and diagnostics.