Lone atrial fibrillation (LAF), that is atrial fibrillation without underlying structural heart disease, is not a life-threatening disorder and is not associated with fatal arrhythmias such as ventricular fibrillation. It is also generally agreed that LAF, on its own, is not associated with an increased risk of ischemic stroke (stroke caused by a blood clot). However, if LAF is combined with one or more established risk factors for stroke (hypertension, diabetes, heart failure, heart disease, etc.) then the stroke risk is very real and measures are needed to ensure adequate protection.
The standard medical approach to stroke prevention is pretty well confined to prescribing either aspirin or warfarin. Aspirin, as we shall see, has a negative benefit/risk ratio in preventing a first stroke. The net benefit of warfarin therapy can be substantial when underlying heart disease or a history of stroke or heart attack is present. However, when no additional risk factors for stroke are present, then warfarin therapy is not beneficial and may even be detrimental. Despite this recognized fact, warfarin is often prescribed routinely to AF patients who are unlikely to benefit from it.
There are indeed many myths and misconceptions surrounding stroke prevention in LAF. It is my hope that this book will help dispel most of them.
An ischemic stroke occurs when a blood vessel that supplies the brain is blocked and impairs blood flow. The resulting lack of oxygen (ischemia) causes brain cells and tissues to start dying within minutes. There are two types of ischemic stroke – thrombotic and embolic. A thrombotic stroke is caused by the development of a thrombus (blood clot) in the arteries supplying blood to the brain whereas an embolic stroke is caused by a blood clot that forms elsewhere in the body and then travels through the bloodstream to the brain. A cardioembolic stroke is an embolic stroke caused by a clot formed in the heart – often in the left atrial appendage.
The majority of ischemic strokes occurring in the general population are thrombotic in nature; however, when it comes to strokes related to atrial fibrillation they are more likely to be cardioembolic in nature.
Thrombotic and cardioembolic strokes share many risk factors including hypertension, diabetes, heart failure and coronary artery disease. This means that stroke prevention measures known to work in the general population are likely to also benefit atrial fibrillation patients. Thus the whole realm of proven natural stroke prevention agents opens up for the afibber to consider – and what a treasure trove this is! Several natural antithrombotics have been found to be superior to both aspirin and warfarin and have none of their adverse effects.
Selecting a stroke prevention program is, nevertheless, intensely personal and entails making important choices that every afibber needs to make early in their “career”. There is no easy way to go about making these choices; a great deal of research and soul-searching is required. This, hopefully, is where my book will help.
The first edition of Thrombosis and Stroke Prevention not only provided in-depth discussions of both natural and pharmaceutical stroke prevention agents, it also covered in detail the underlying causes and mechanism of thrombosis (blood clot formation) and stroke. Blood clot formation is a very complex process involving platelet aggregation, coagulation and fibrinolysis. In order to rationally select a stroke prevention program, it is necessary to have at least a rudimentary understanding of the mechanisms and factors involved in these three stages of the thrombosis process. The first two chapters of the book are designed to provide this understanding. Chapters 3 and 4 deal with natural and pharmaceutical antithrombotics and chapter 5 provides detailed questionnaires and tables for estimating stroke risk. Chapter 6 compares the effectiveness of all the agents discussed in previous chapters with some surprising results.
The second edition of Thrombosis and Stroke Prevention updated the information presented in the first edition and added a chapter on how to live with warfarin and one providing details on warfarin interactions with other drugs and herbs.
This third edition adds new information about stroke risk factors and schemes for estimating stroke and bleeding risk. It also provides an update of the latest research concerning natural and pharmaceutical antithrombotics and includes a separate chapter covering the pros and cons of the new oral anticoagulants. Finally, it adds a chapter discussing stroke prevention based on occluding (closing off) the left atrial appendage where the vast majority of cardioembolic clots are generated.
This book would not have been possible without the whole-hearted support of my wife Judi who was instrumental in seeing it come to fruition. Without her word processing skills, editing advice, and encouragement I couldn’t have accomplished it. Jackie Burgess, Patrick Chambers, MD, Norman Fisher, MD, Sadja Greenwood, MD, Martin Klughaupt, MD, FACC, and Frank McCabe also deserve my special, heartfelt thanks for taking the time to thoroughly review and comment on the first edition of Thrombosis and Stroke Prevention.
Hans R. Larsen