Approaches to Stroke Risk Reduction
Stroke risk reduction hinges upon targeting a variety of known risk factors such as high blood pressure, elevated cholesterol, and insulin resistance, as well as improving dietary and lifestyle habits. However, one of conventional medicine’s most powerful ischemic stroke risk-reduction strategies is to mitigate the likelihood of blood clots using anticoagulants and antiplatelet medications. It is critical to understand that these medications reduce ischemic stroke risk, but increase hemorrhagic stroke risk. Hemorrhagic stroke risk reduction strategies primarily focus on reducing blood pressure, rather than avoiding clotting (Brott 2000; van der Worp 2007; Davis 2012; Bronner 1995; Brisman 2006).
Warfarin (Coumadin®), an anticoagulant, has been associated with a 64% reduction in ischemic stroke risk (Lip 2012). Warfarin reduces blood clotting by antagonizing the effects of vitamin K (Siguret 2008). However, warfarin can interact with other drugs, and people taking warfarin require constant monitoring to protect against excessive bleeding.
Recently approved oral anticoagulant drugs are now available to treat blood clots after orthopedic surgeries and may reduce stroke risk is some populations (Boehringer Ingelheim Pharmaceuticals 2012; Mannucci 2011; Ru San 2012). Dabigatran (Pradaxa®), which is a direct thrombin inhibitor, and rivaroxaban (Xarelto™), which inhibits an enzyme involved in coagulation called factor Xa, are examples of anticoagulants that have recently been approved for human use.
These newer therapies may have significant benefits over warfarin, which interferes with vitamin K metabolism. First, they both inhibit clotting factors that do not depend on vitamin K, so they are less sensitive to fluctuations of dietary vitamin K intake. Dabigatran does not exhibit major interactions with foods or other medications (Steffel 2011). Unlike warfarin, people taking these medications do not need regular blood testing to monitor coagulation (Thethi 2011). In clinical trials, both treatments were at least as effective as warfarin for reducing stroke risk in patients with atrial fibrillation, and preventing/treating deep vein thrombosis, with a reduced risk of bleeding (Connolly 2009; Schulman 2009; Eriksson 2008). For more information see the Blood Clot Prevention protocol.
Advantages of Pradaxa® vs. warfarin include:
- Rapid onset of action
- Predictable, consistent anticoagulant effects
- Low potential for drug-drug interaction
- No requirement for anticoagulant blood test monitoring
- Preliminary efficacy and safety advantages vs. warfarin based on initial head-to-head, hard-endpoint data
- No need to maintain low vitamin K levels. Insufficient vitamin K promotes arterial calcification.
Disadvantages of Pradaxa® vs. warfarin include:
- No antidote for reversal of over anti-coagulation effect. When too much warfarin is given and the patient's INR indicates they are at risk for a major bleed (or are pathologically bleeding), vitamin K can be injected to immediately reverse warfarin's anti-coagulant effect. If too much Pradaxa® is taken, there is no immediate antidote.
- No long-term safety data on Pradaxa® (the case with virtually all newly approved drugs)
- More expensive than warfarin
Anti-platelet medications. Platelets are cell fragments in the blood involved in clot formation. Anti-platelet drugs make these cell fragments less sticky and less likely to clot. The most frequently used anti-platelet medication is aspirin. Aggrenox®, combination of low-dose aspirin and the anti-platelet drug dipyridamole, may be prescribed instead (Norrving 2006). Other alternatives include clopidogrel (Plavix®) or ticlopidine (Ticlid®) (Merck Manual 2007; Forbes 1998; Aw 2012; Murray 1994).
Left atrial appendage occlusion. For some patients with atrial fibrillation and who cannot take anti-coagulants or other blood-thinners, a surgical procedure called left atrial appendage occlusion has been shown to inhibit clot formation and decrease stroke risk (Holmes 2009; Lopez-Minguez 2012). The left atrial appendage is a muscular pouch that serves as a reservoir for one of the chambers of the heart (left atrium). In the presence of arrhythmia, blood in the appendage is prone to clotting (Alli 2012).