Survey Results � Part VII
Since publishing part V of the survey results we have received an additional 24 completed questionnaires giving a total sample size of 99. Twenty respondents have chronic LAF, 35 have the vagal variety, 24 the adrenergic variety, and the remaining 20 a mixture of vagal and adrenergic. The additional 24 sets of data means that we should be able to draw more valid conclusions than with just the original 75 sets. So I decided to re-evaluate all variables using all available data.
Severity of Episodes
There is a strong, statistically significant correlation between time spent in afib and the number of episodes experienced over the six-month survey period (r=0.4567 p=0.0001). Adrenergic afibbers had an average of 11 episodes in six months (range: 0-90), vagal 16 episodes (range: 0-150), and those with the mixed variety 30 episodes (range: 0-180).
There is also a statistically significant correlation between total time spent in afib and the average duration of individual episodes (r=0.2547 p=0.02). The average episode lasted 10 hours for the mixed group (range: 0.1-48 hrs), 13 hours for the vagal group (range: 0.1-168 hrs), and 17 hours for the adrenergic group (range: 0.1-72 hrs).
Effect of Age
The average age of vagal afibbers was 49 years, adrenergic 53 years, mixed 54 years, and chronic 59 years. The age difference between vagal and chronic afibbers was statistically significant (p=0.003). The age difference between vagal and adrenergic afibbers was not statistically significant nor was the difference between vagal and mixed afibbers. Thus it would appear that the vagal variety is associated with a younger age while the chronic variety is associated with an older age.
Effect of Gender
Women with LAF (at least those that responded to the survey) were older than men with LAF. The average age for women was 61 years while that of men was 51 years. This difference was statistically significant (p=0.001).
Effect of Years of LAF
Effect of Aspirin
Effect of Digoxin
There was also a statistically significant difference (p=0.04) between the proportion of women (50%) and men (18%) who had been prescribed digoxin. This could, at least partially, explain why more women than men fell into the chronic LAF category (32% versus 18%).
Effect of Amalgam Fillings
There was also a clear linear relationship between time spent in fibrillation and the number of fillings (r=0.4173 p=0.002). An afibber with 0 fillings could expect to spend 35 hours in afib while someone with 8 fillings could expect 140 hours and someone with 20 fillings could expect an average 300 hours in afib over a six-month period. Afibbers with amalgam fillings also tended to have more episodes (20) and of longer duration (15 hours) than afibbers without (13 episodes of average duration of 9 hours). These differences were, however, not statistically significant.
The findings that afibbers with amalgams have more severe episodes than those without support the contention that at least part of the inflammatory response underlying LAF is caused by oxidative stress or electrical instability generated by the presence of mercury in the heart tissue.
Effect of Dissimilar Metals in the Mouth
An attempt to at least partially account for this bias was made by just considering the 18 respondents who did not have any amalgam fillings. In this case, fish oil supplementation appeared to be beneficial. Fish oil users had only 8 episodes and spent only 24 hours in fibrillation while non-users had 16 episodes and spent 40 hours in fibrillation. Adjusting for age and gender should further improve the picture.
Fish oil users were also significantly more likely to be supplementing with magnesium (76% as compared to only 33% among non-users). The effect of this confounding was eliminated by just considering non- magnesium users. In this group 21% took fish oil while 79% did not. The users of fish oil (average age of 54 years) had an average of 8 episodes and spent 89 hours in fibrillation. The non-users (average age of 45 years) had an average of 16 episodes and spent 106 hours in fibrillation.
Due to the significant confounding of the data it is difficult to draw a firm conclusion as to whether or not fish oils affect the severity of LAF. Nevertheless, considering the excellent stroke protection afforded by fish oils it is probably fair to say that they are overall beneficial to lone afibbers.
Effect of Magnesium Supplementation
Effect of Digestive Problems
Effect of Physical Fitness
Comparison of the Best and the Worst
All members (100%) of the worst group had amalgam fillings (an average of 15 fillings each) while only 43% of the best group did (an average of 2 fillings each). This again points to the crucial role of amalgam fillings as a major cause of LAF.
Perhaps the most intriguing finding is that the members of the best group were almost twice as likely to have digestive problems than were the members of the worst group (79% versus 50%). I have no explanation for this, but it is consistent with the findings of the entire survey.
Stroke Prevention in LAF
Stroke (cerebral infarction, cerebrovascular event) is the third leading cause of death in the United States. It strikes about half a million Americans and kills upwards of 150,000 every year. A stroke involves a sudden interruption of blood flow to the brain. This interruption can be caused by a blood clot (thrombus) that lodges in a small artery in the brain (ischemic stroke) or by the rupture of an artery wall (hemorrhagic stroke). An ischemic stroke is sometimes referred to as a �heart attack of the brain�. The interrupted blood flow results in brain cells being starved of oxygen; if the interruption last more than 4 or 5 minutes the cells will die and irreversible damage will occur. If the cells that die are the ones that control your speech or your left arm then these functions will become impaired. If enough cells die (massive stroke) then so will you.
The risk of a stroke increases with age; it is estimated that 5% of the population over 65 years of age will suffer a stroke. A prior stroke, heart disease, diabetes, hypertension, atrial fibrillation, high homocysteine levels, and a bacterial infection of the lining of the heart cavity (endocarditis) are significant risk factors. Major surgery accounts for a large number of ischemic strokes. It is estimated that as many as 25,000 people suffer a stroke every year as a sequel to coronary bypass surgery[1-5].
Stroke and Atrial Fibrillation
The stroke risk in patients with non-rheumatic atrial fibrillation has been evaluated in at least 5 major randomized clinical trials designed to evaluate the effects of aspirin and warfarin in stroke prevention. Without treatment the annual stroke incidence in patients under 65 and no risk factors is 1%. This is equivalent to the annual incidence in the general population. In other words, afibbers under 65 years of age with no other risk factors do not have an increased risk of stroke. The incidence of stroke, even with no other risk factors, does however increase with age; it is estimated at 4.3% between the ages of 65 and 75 years and 3.5% above age 75. Having one or more risk factors (hypertension, diabetes, prior stroke or heart attack, angina or congestive heart failure) materially increases the risk to 4.9% under age 65, 5.7% between the ages of 65 and 75 years, and 8.1% above age 75[6,7].
Investigators at the National Registry of Atrial Fibrillation have recently devised a new scheme for predicting stroke risk. This system, CHADS2, assigns a score of 0 to atrial fibrillation patients with no additional risk factors. One point is added for the presence of congestive heart failure, hypertension, age 75 years or older, and diabetes (1 point for each) and 2 points for a history of stroke or TIA (transient ischemic attack). Thus an 80-year-old patient (+1) with hypertension (+1) and a prior stroke (+2) would have a CHADS2 score of 4. The investigators have correlated the CHADS2 score with the actual annual incidence of stroke observed in a large study involving 1733 atrial fibrillation patients. Patients with a score of 0 had a stroke rate of 1.2%, which is equivalent to that found in the general population of the same age. Patients with a score of 1 had a rate of 2.8%, those with a score of 2 a rate of 3.6%, and those with a score of 3 a rate of 6.4%.
So what does with mean? Of most importance to lone afibbers is the conclusion that afibbers under 75 years of age with no additional risk factors have an incidence of stroke equal to that of the general population.
Stroke and Lone Atrial Fibrillation (LAF)
So why should lone afibbers under 75 years of age with no additional risk factors worry unduly about an increased stroke risk? They probably should not, but many cardiologists and physicians obviously do.
LAF and Anticoagulation
Platelet Therapy (Aspirin)
Aspirin is not innocuous. It can cause serious bleeding in the gastrointestinal tract and can aggravate existing ulcers. The estimated death rate from gastrointestinal (GI) bleeding is 12%. Researchers at Oxford University have released the results of a very large study aimed at establishing the magnitude of aspirin-related bleeding incidents. They carefully studied the results of 24 major randomized clinical trials involving almost 66,000 participants. They conclude that when treated for a year 2.47% of aspirin users develop GI bleeding as compared to 1.42% among placebo users. Put in terms of the 50 million American now taking aspirin this means that the excess incidence of GI bleeding attributable to aspirin would be 525,000 and the excess mortality would be 63,000 every year. The researchers also investigated whether lower dosages of aspirin would be safer. They found that they were not. The incidence of GI bleeding among low-dose aspirin users was 2.30% compared with 1.45% for placebo users. Somewhat surprisingly, the study also found that enterically-coated or otherwise modified formulations were no safer than standard aspirin. The increase in GI bleeding among users of modified formulations was 93% as compared to 68% for all aspirin users and 59% for low-dose users. The researchers conclude that patients and their physicians need to consider the trade-off between the benefits and harms of long-term aspirin use. Dr. Martin Tramer of the Geneva University Hospitals in Switzerland wholeheartedly agrees with this conclusion and adds, �It may be more appropriate for some people to eat an apple rather than an aspirin a day.�[11,12]
So while taking a daily aspirin may help protect against heart attacks and strokes (particularly the second incident) its use is definitely not without risk. An alternative approach, which you may wish to discuss with your physician, is to take an aspirin at the start and end of an afib episode and for a week or so after if the episode is a long one (greater than 24 hours). The protective effect of aspirin lasts for about a week. This suggested approach assumes, of course, that you can actually feel when you have an episode.
Anticoagulation with Warfarin (Coumadin)
At least 5 major trials have investigated the effectiveness of warfarin in prevention of stroke in patients with atrial fibrillation. The majority of participants in all of these trials had underlying heart disease and some had suffered strokes or heart attacks prior to the trials. Pooling all of the results shows that anticoagulation with warfarin to an INR (International Normalized Ratio) of between 2.0 and 4.0 resulted in a reduction in stroke risk of 64%. This means that if one�s stroke risk without warfarin was say 2.8% (the risk for a 70-year-old afibber with hypertension) then one could reduce this to about 1.0% (actual trial results showed a decrease to 1.7% only so the 64% may be overstated in some cases).
Because warfarin thins the blood to the point where it is difficult for the body to stop even a very minor internal bleeding incident major bleeding and hemorrhagic stroke are very real risks of warfarin therapy especially among older people. The second Stroke Prevention in Atrial Fibrillation (SPAF-II) study found that while warfarin therapy lowered ischemic stroke risk by 3.6% it also increased the risk of major bleeding by 4.2% in patients over 75 years of age.
Another very important consideration when evaluating the results of clinical trials of warfarin is the fact that INR control in daily practice is rarely as good as that obtained in a strictly controlled clinical trial. A study of 2376 patients receiving warfarin reported an incidence of life-threatening or fatal hemorrhage (bleeding) of 3.38% per year in those over 80 years. This excess risk of treatment exceeded the reduction in the rate of major disabling or fatal ischemic strokes resulting from the warfarin therapy.
Some researchers feel that the bleeding problem and the deaths resulting from it makes the benefit/risk ratio for warfarin therapy somewhat dubious. A review by the prestigious Cochrane Institute concluded, �the margin between benefit and harm for warfarin prophylaxis in patients with chronic non-valvular atrial fibrillation is uncomfortably thin. The low absolute risk reductions observed in trials would likely be overwhelmed in less controlled settings by problems associated with the use of warfarin.�
Just recently British researchers concluded that although anticoagulation with warfarin is more effective than antiplatelet therapy with aspirin, �major bleeding was more common in patients receiving anticoagulation, and the evidence to support long term anticoagulation is weak.�
Another problem with warfarin is that it can interact with many common medications, herbs and even foods. This can lead to higher or lower INR values with a concomitant increased bleeding risk or decreased stroke protection[17,18]. The interaction with Tylenol (acetaminophen, Paracetamol) is particularly serious and can raise the INR to 6.0 or higher, a serious bleeding risk[19,20]. To add insult to injury, warfarin also increases the risk of osteoporosis and fractures of the spine and ribs. A recent study at the Mayo Clinic found that women who had been taking warfarin for a year or more had a 5.5 times greater risk of having a spinal fracture and a 3.4 times greater risk of a rib fracture.
So all in all, aspirin and especially warfarin are not really that great a choice for stroke protection in lone afibbers � particularly as most of us don�t even need additional stroke protection. So how can we protect ourselves? Fortunately, there are many highly effective alternative methods for minimizing your risk of stroke whether you are an afibber or not.
Alternative Methods of Stroke Protection
There are numerous alternative ways of obtaining stroke protection equal to or better than that afforded by aspirin and warfarin � and without the side effects. These methods have not been evaluated specifically in atrial fibrillation patients, but since lone afibbers with no additional risk factors have no greater stroke risk than the general population it would seem reasonable that the benefits would be the same.
After adjusting for age, smoking and other cardiovascular risk factors the researchers concluded that women who ate fish once a week lowered their risk of having a stroke of any kind by 22% and those who consumed fish 5 or more times per week reduced their risk by 52%. They ascribe the protective effect of fish consumption to the commensurate intake of fish oils (omega-3 fatty acids). They estimate that women whose intake of fish oils is 0.5 gram/day or more have a 30% lower risk of suffering a stroke than do women whose intake is below 0.1 gram/day. There was no evidence that women with a high fish or fish oil consumption have an increased risk of hemorrhagic stroke. The researchers believe that the protective effects of fish oils are due to their ability to inhibit platelet aggregation, lower blood viscosity, suppress the formation of leukotrienes, reduce fibrinogen levels, and reduce blood pressure levels and insulin resistance. They also note that the beneficial effects of fish consumption were substantially more pronounced among women who did not take aspirin on a regular basis.
Fish oil can be a double-edged sword though. Some fish like swordfish, tuna, shark, king mackerel, and red snapper can have mercury levels exceeding the current US standard of 1.0 ppm. Many more species exceed the New Zealand limit of 0.5 ppm. Salmon usually has very low levels of mercury. If you plan on supplementing with fish oil it is a good idea to ask the manufacturer to certify the maximum level of mercury found in their product and obtain a statement that they use molecular distillation to remove impurities from their product. I asked Pronova, a major Norwegian producer of fish oils, for certification. They stated that their fish oils are molecular distilled and are certified to contain less than 0.1 ppm of mercury (10 times lower than the allowable limit). The actual mercury content of their products is even lower at 0.01 ppm or less. Pronova oils are used in the manufacture of such brands as Coromega, Omacor and Pikasol.
Lifestyle and Diet
Habitual tea drinking provides strong protection against suffering a stroke. This is the major finding of a study published by the Dutch National Institute of Public Health and Environmental Protection. An analysis of dietary data showed that men who consumed more than 4.7 cups of tea per day had a 69% lower risk of having a stroke than did men who drank 2.6 cups per day or less. The Dutch researchers believe that the protective effect of black tea is due to its high content of flavonoids (mainly quercetin). They calculate that en with a daily flavonoids intake of 28.6 mg or more have a 73% lower risk of suffering a stroke than do men with a lower intake (less than 18.3 mg/day). The researchers have previously reported that a high intake of flavonoids also protects elderly men against coronary heart disease. A high intake of beta-carotene from vegetables and the consumption of solid fruits (e.g. apples) also showed some association with a lower stroke risk, but not enough to be statistically significant.
This is it for this edition of The AFIB Report. In the next issue we will carry on with our review of supplements of particular benefit for lone afibbers.
The AFIB REPORT is published monthly by Hans R. Larsen MSc ChE
1320 Point Street Victoria, BC, Canada V8S 1A5
Phone: (250) 384-2524
E-mail: [email protected]
Copyright © 2002 by Hans R. Larsen
The AFIB REPORT does not provide medical advice. Do not attempt self-diagnosis or self-medication
based on our reports.