Uncommon Cardiac Mechanisms In Stroke

Similarly emboli arising from the aorta are composed of different substances. White platelet-fibrin thrombi form in crevices and irregular surfaces. These white clots activate the coagulation cascade and promote red thrombi to form on their surface. Red thrombi often form within ulcers or regions of plaque rupture. Red and white thrombi often break off and reach the brain. Large protuberant and mobile plaques often contain red thrombi. Cholesterol crystals within aortic plaques or other complex plaque constituents themselves can travel to the brain. Calcium may also be a component of aortogenic emboli.

Artery-to-artery emboli have the same basic components as those that arise from the aorta: calcium, cholesterol fragments, red and white clots, and so forth. Occasionally air, fat, and foreign materials enter the bloodstream and embolize to the brain and other viscera.

TREATMENT

Selection of treatment for acute embolic brain ischemia should consider the nature of the embolic material. Thrombolytic drugs, such as recombinant tissue plasminogen activator (rt-PA) can lyse red clots but are ineffective against white clots. Glycoprotein IIB/IIIA inhibitors that are active against platelet-fibrin bridges can potentially lyse white clots. These treatments are likely to be ineffective against calcium, cholesterol crystals, tumor fragments, infective agents, and foreign matter. Mechanical methods of retrieving emboli can snare different materials.

Similarly, prophylaxis against re-embolization (secondary prevention) must consider the nature of the embolic material. The most effective prophylaxes against embolism in patients with infective endocarditis are antibacterial and antifungal agents.

Secondary prevention also depends on the nature of the donor sources. Atrial fibrillation might respond to antiarrhythmics or cardiac conduction pathway ablation procedures. Intra-atrial septal abnormalities and defects can be repaired. Ventricular aneurysms can be resected. Abnormal valves can be repaired or replaced by prosthetic valves. Cardiac tumors can be removed. Surgeons have operated on protruding aortic atheromas, and in the future these lesions might be attacked by endovascular techniques. Arterial lesions are often repaired surgically or using endovascular technology in the form of angioplasty and/or stenting.

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