Peripheral artery disease Flashcards
What do we mean with peripheral artery disease? What are the major causes?
Peripheral artery disease is the presence of a flow-liming lesion in an artery that provide blood supply to the limb. The major causes of such arterial stenosis or occlusion are atherosclerosis, thromboembolism, and vasculitis.
What is Poiseuille flow equation? Talk it!
Poiseuille flow equation:
Q= (πPr^4)/8ηL
The change in radius in stenosis has the greatest impact on flow. Poiseuille flow equation also indicated that higher flow rates correspond to greater pressure drops across the stenosis. As the flow velocity increases across a stenotic vessel, the blood turbulence result in a loss of kinetic energy. The result is a decline in perfusion pressure distal to the stenosis.
Why do Peripheral atherosclerotic vascular disease have a reduction in exercise capacity?
In PAD (during exercise), the obstructed arteries can’t response to the vasodilating stimuli, thereby limiting flow increases. In addition, dysfunctional atherosclerotic endothelium doesn’t release normal amount of vasodilating substance. The physical properties of as stenosis and the reduced vasodilator activity imposed by diseased endothelium prevent adequate blood flow from reaching distal tissues and contribute to ischemia. Another reason for the reduction in exercise capacity is changes in muscle structure and function. Denervation and dropout of muscle fiber. The loss of fibers can explain the reduced muscle strength and atrophy that occur in PAD patient. Viable muscle fibers in the affected limbs may show abnormalities of mitochondrial oxidative metabolism.
What are the clinical presentation of Peripheral atherosclerotic vascular disease? Which groups of people are at high risk?
PAD may affect the aorta or the iliac, femoral, popliteal and tibioperoneal arteries. Patient develop (claudication) buttock, thigh, or calf discomfort precipitated by walking and relieved by rest. Patients may experience pain at rest, usually affecting the feet or toes. The chronically reduced blood flow in this case predisposes the extremity to ulceration, infection, and skin necrosis. Patients who smoke or have diabetes mellitus are at high risk.
How to diagnos a patient with Peripheral atherosclerotic vascular disease?
Physical examination revels loss of pulses distal to the stenotic segment. Bruits (swishing sounds) may be audible in the abdomen or over iliac, femoral or subclavian arterial stenosis. In patient with chronic severe ischemia, the lack of blood perfusion results in muscle atrophy, pallor, cyanotic discoloration, hair loss, and gangrene and necrosis of the foot and digits.
Which test are used to evaluate Peripheral atherosclerotic vascular disease?
Test to evaluate PAD:
- Measuring ankle-brachial index using blood pressure cuff and a Doppler to detect blood flow.
- Limb segmental pressure measurements – using pneumatic cuffs placed along the extremity
- Pulse volume recording – graphical measurement of volume changes in segments of the extremity with each pulse.
- Duplex ultrasonography – noninvasive method to visualize and assess the extent of atrial stenosis and the corresponding reduction in blood flow.
What are the treatment available for Peripheral atherosclerotic vascular disease?
Antiplatelet therapy and risk factor modification are important to reduce the likelihood of coronary event. Platelet inhibitors, such as aspirin and clopidogrel, reduce cardiovascular morbidity and mortality in patient with PAD.
Supportive care of the feet to prevent trauma or restriction of blood flow. Exercise improves endurance in part by increasing metabolic efficiency in the skeletal muscle of the leg.
Cilostazol is a selective phosphodiesterase inhibitor that increase cyclic adenosine monophosphate and has vasodilator and platelet-inhibiting properties; it improves exercise capacity in patient with PAD.
Pentoxifylline which improves the deformability of red and white blood cells and may improve claudication symptoms in some patients.
What is acute arterial occlusion?
Acute atrial occlusion is caused either by embolization from a cardiac or proximal vascular site or by thrombus formation in situ.
What is the major origin of emboli in acute arterial occlusion?
The origin of arterial emboli is often the heart, usually resulting from disorders involving intracardiac stasis of flow. Emboli may also originate from thrombus or atheromatous material overlying a segment of the aorta. Primary arterial thrombus formation may appear at site of endothelial damage or atherosclerotic stenosis, or within bypass grafts.
What are the common symptoms of acute arterial occlusion?
Common symptoms for reduction in blood supply include pain, pallor, paralysis, paresthesia, and pulselessness (“5 Ps”).
What are the common treatment of acute arterial occlusion?
Treatment include heparin (followed by oral warfarin) to prevent propagation of the clot and to reduce the likelihood of additional embolic events. A revascularization procedure is indicated if limb viability is at risk.
What is vasculitic syndrome? How does it result?
Vasculitis (vessel wall inflammation) result from immune reactions directed at the vessel wall. Immune complexes activate the complement cascade with subsequent release of chemoattractant and anaphylatoxins that direct neutrophil migration to the vessel wall and increase vascular permeability. Neutrophils injure the vessel by releasing lysosomal contents and producing toxic oxygen-derived free radicals. In cell mediated immune reactions, T lymphocytes bind to vascular antigens and release lymphokines that attract lymphocytes and macrophages to the vessel wall. These inflammatory processes can cause end-organ ischemia through vascular necrosis or local thrombosis.
What is tekayasu arteritis? Target organ Symptoms Diagnosis Treatment
Targets the aorta and its major branches. 80-90% of affected persons are women between 10 and 40. Takayasu arteritis is a cause of aortic aneurysm or aortic dissection.
Symptoms – patients present with systemic complaints such as malaise and fever; focal symptoms are related to inflammation of the affected vessel and include cerebrovascular ischemia (brachiocephalic or carotid artery involvement), myocardial ischemia (coronary artery), arm claudication (brachiocephalic or subclavian artery), or hypertension (renal artery). The carotid and limb pulses are diminished or absent in 85% of patients at the time of diagnosis.
Diagnosis – Histologically, there is a continuous or patchy granulomatous inflammation with lymphocytes, histiocytes, and multinucleated giant cells, resulting in intimal proliferation, disruption of the elastic lamina, and fibrosis. Antiendothelial antibodies may play a role in the disease.
Treatment – Steroid and cytotoxic drugs may reduce vascular inflammation and alleviate symptoms of Takayasu arteritis. Surgical bypass of obstructed vessels may be helpful in severe cases.
What is Giant cell arteritis? Target organ Symptoms Diagnosis Treatment
Giant cell arteritis is a chronic vasculitis of medium-large size arteries (cranial vessel and aortic branches). Most of the patient are over 50 and females. It may be associated with polymyalgia rheumatica (inflammatory condition).
Histologically – the affected vessels include lymphocytes and macrophage infiltration, intimal fibrosis, and focal necrosis, with granulomas containing multinucleated giant cells.
Symptoms – depend on the distribution of affected arteries and may include diminished temporal pulses, prominent headache (temporal artery involvement), or facial pain and caudation of the jaw while chewing (facial artery involvement).
Diagnosis – serum markers of inflammation are elevated in patients. Ultrasound examination can support the diagnosis by demonstrating a hypoechoic halo around the involved arterial lumen with vessel stenosis and/or occlusion.
Treatment – high-dose systemic steroids
What is vasospasm: raynaud phenomenon? When does it occur?
Raynaud phenomenon is a vasospastic disease (vasoconstriction that inhibit blood flow) of the digital arteries that occurs in people when exposed to cool temperatures and emotional stress.
- Primary Raynaud phenomenon – when the condition occurs as an isolated disorder. Patients are mostly women between the ages of 20 and 40.
- Secondary Raynaud phenomenon – when it appears as a component of other conditions (such as connective tissue disease and arterial occlusive disorders).
In healthy vessels, cooling stimulated sympathetic nervous system, resulting in local discharge of noradrenalin. In the fingers and toes, only vasocontricting α receptors are present; other regional circulation has both constrictor and dilator adrenergic responses. However, in Raynaud phenomenon, cold exposure induces severe vasoconstriction.
Treatment of Raynaud phenomenon involves avoiding cold environments, dressing in warm clothes, and wearing insulated gloves or footwear.
