Cardiac Causes of Stroke

Stroke or "brain attack" is caused by an interruption of blood flow to brain tissue. This can happen when a blood vessel tears or clots in the brain. A tear can cause bleeding or hemorrhage and this type of stoke accounts for approximately one-third of strokes. The majority of strokes are caused by clotting of the vessel. The clot can originate within the brain's circulation and travel a short distance where it causes an occlusion. This is related to plaque buildup in the artery walls. Another source of clot that can travel to the brain is the heart. A stroke is a true medical emergency. When symptoms begin, it is imperative to call 911. Treatment with clot dissolving drugs must be administered within 3 hours of the onset of symptoms to provide benefit with and acceptable risk of bleeding. Not every patient is eligible to receive this treatment. After a stroke the focus shifts to prevention of another stroke.

If the source of stroke is defined as the heart the treatment of choice depends on the presumed cause of the stroke. Cardiac causes of stoke include embolism from atrial fibrillation or left ventricular mural thrombus. Embolus from lesions on valves or cardiac tumors, and embolus via congenital heart defects.

If a patient has atrial fibrillation, treatment with warfarin is considered the best choice for many. Some patients require treatment with aspirin because the risk of bleeding is high. Multiple clinical trials have shown that warfarin is superior to aspirin in patients with afib and diabetes, high blood pressure, poor heart function, previous stroke and age greater than 75.

After a large heart attack damaged muscle can't pump effectively. The allows blood to pool and coagulate at the apex of the heart. Left ventricular mural thrombus requires treatment with warfarin to reduce the chance of stroke. In many patients with a large heart attack warfarin is given prophylactically to reduce the risk of cardiac embolic stroke once damage is detected and poor contractile function is detected.

Cardiac tumors are very rare. Left atrial myxoma can cause stroke as fragments of the tumor fly off and go to the brain. This is detected by cardiac echo. Open heart surgery is required to remove the tumor. Some patients present with difficulty breathing when lying flat or on their side because the tumor obstructs the blood flow out of the upper heart chamber.

Heart valve disorders can cause stroke if infected by bacteria. At times a very calcified or congenitally abnormal valve becomes infected after a brief systemic infection. The bacteria cause a "vegetation" to form which is the source of embolic material. If stroke is present or the valve is seriously damaged, it must be surgically replaced.

Paradoxical embolic stroke is a stroke caused by a clot that travels from the right side of the heart to brain by passing through a hole in the heart. The clot is presumed to have originated in the veins and blood flow should normally take it to the lung where small clots would typically cause no problem. If a communication is present between the two upper chambers of the heart this can give a small clot access to the brain. In many cases where a person has a stroke with no identified cause (called a cryptogenic stroke) a small hole in the heart is identified. This defect in the upper chamber of the heart is often a patent foramen ovale (PFO). At times the defect may be a larger atrial septal defect (ASD). PFO is seen up to 60 percent of patients with cryptogenic stroke. In fact, up to 25 percent of the population has a PFO. Treatment of stroke in patients with a PFO is controversial. Right now studies are underway to determine if warfarin, aspirin or closing the hole via the leg veins is best in this patient population. There is currently no FDA approved devices to close a PFO. Closing a PFO with "off-label" devices is a common practice. I currently recommend that all patients with a PFO and a first stroke opt for participation in a clinical trial until more evidence is available. For those who are not eligible for clinical trials device, closure should then be considered.