Findings from LAFS III � Part 2
In this issue we continue the tabulation of the answers to the questions contained in the May 2002 LAF survey.
16. Do you suffer from acid reflux or have you ever been diagnosed with GERD
(gastroesophageal reflux disease)?
18. Have you noticed any correlation between episodes and a flare-up of GERD or a bowel
19. Have you ever taken tranquillizers (valium, ativan, xanax, etc.) for an extended period of
20. Do you feel more upbeat on a sunny day (high barometric pressure) than on a rainy day
(low barometric pressure)?
22. Have you had your tonsils removed?
There was a significant correlation between present age (and age at diagnosis) and the likelihood of having had a tonsillectomy. Older people were more likely to have had one than were younger people indicating that the practice is becoming much less prevalent.
23. Do you consider yourself sedentary, somewhat active or highly active and in strong
24. Do you or did you in the past engage in strenuous physical activity for extended periods
(longer than 40 minutes at a time)?
25. Do you regularly supplement with vitamin E (alpha-tocopherol)?
27. Do you regularly supplement with beta-carotene?
29. When your heart beat is irregular which pattern would best describe it?
30. Has anyone else in your close family (parents, grandparents, siblings) been diagnosed
The estimated overall prevalence of all cardiac arrhythmias in the United States is about 1% with atrial fibrillation accounting for about half of this[4,5]. Cardiac arrhythmias are generally more common among older people. With only 1% of the general population having arrhythmia is it odd that 43% of the survey respondents had a close relative with arrhythmia? This question can really only be answered definitely by comparing the rate of arrhythmia among close relatives of a group of lone afibbers with the rate in a group of age- and sex-matched controls. Too major a project for my limited resources.
Nevertheless, it is possible to get some idea about the likelihood of a genetic connection. Although we afibbers tend to be an odd bunch, it is probably safe to assume that we each had two biological parents?! This means that there were 23 cases among the 202 parents included in the survey or a rate of 11% - in other words, considerably higher than the 1% that would have been expected. This finding does not prove that LAF can be inherited, but it certainly supports the possibility.
The genetic connection is also supported by work done by Dr. Ramon Brugada and his colleagues at the Baylor College of Medicine and the University of Barcelona. These researchers located three families in Spain in which 21 of 49 family members had lone atrial fibrillation. They mapped their genes and concluded that in these families a mutation in a specific chromosome region (10q22-q24) was the cause of their atrial fibrillation. Dr. Maurits Allessie, MD of the University of Maastricht in the Netherlands makes several very interesting observations concerning these findings:
Dr. Allessie concludes, "The anatomical and electrophysiologic features of the atria are such that there is only a narrow margin of safety between normal sinus rhythm and chronic atrial fibrillation." Our survey findings of a possible genetic connection and the fascinating discoveries of Dr. Brugada and colleagues together with Dr. Allessie's profound observations certainly provide much food for thought and will hopefully be followed up by additional research.
This concludes our evaluation of the LAFS III results for this issue. We will complete the evaluation in the October issue.
LAF: The Diagnosis
Atrial fibrillation comes in three flavours � paroxysmal, persistent, and permanent. Paroxysmal AF converts to normal sinus rhythm (NSR) on its own and episodes last less than 7 days (most less than 24 hours); persistent AF episodes usually last more than 7 days, but cardioversion is effective in conversion to NSR; permanent AF is permanent and does not respond to cardioversion. The term "chronic" refers to the fact that AF, with some exceptions, is not an acute disorder, but rather a long-term one. It is estimated that more than 2 million Americans suffer from paroxysmal or persistent AF. The incidence of AF is less than 1% in people under the age of 60 years, but increases to more than 6% in people over the age of 80 years[1,2].
Causes of atrial fibrillation
AF can also occur on a transient (acute) basis after heart surgery or in the aftermath of a heart attack. If none of the above conditions are present then the AF is classified as lone atrial fibrillation (LAF). It is estimated that from 12-30% of all cases of AF are of the lone variety.
Essential (idiopathic, primary) hypertension, electrolyte imbalances, thyrotoxicosis (hyperthyroidism), hypoglycemia, acute infections, alcohol intoxication (binge drinking), pheochromocytoma, and certain pharmaceutical drugs can also cause AF episodes.
Hypoglycemia (low blood sugar) may be quite common among lone afibbers. Our surveys revealed that almost 50% of respondents have medically diagnosed hypoglycemia or symptoms of hypoglycemia. The disorder is diagnosed through a 3-hour or, better yet, a 6-hour glucose tolerance test. If the fasting glucose level is below 50 mg/dL (2.8 mmol/L) or if the glucose level falls below the fasting level 4 to 6 hours after a meal then hypoglycemia is present. However, the actual blood glucose level that causes hypoglycemic conditions can vary considerably between individuals. Hypoglycemia can be controlled by religiously avoiding foods with a high glycemic index (sugar, white and whole grain bread, bananas, raisins, potatoes, rice, and wheat cereal) and by eating frequent small meals throughout the day. Alcohol should be avoided and the intake of dietary fiber increased. A daily multivitamin (and mineral) capsule is very important and a minimum intake of 200-400 micrograms/day of chromium is also recommended.
Pheochromocytoma is not likely to be the underlying cause for most afibbers as it is a rare disease. It is found in about 0.1% of people diagnosed with hypertension. It involves a tumour, most often in the adrenal gland, that periodically releases large amounts of norepinephrine (noradrenaline) and epinephrine (adrenaline) into the blood stream. One of the characteristic features of pheochromocytoma is a feeling of impending doom just prior to the afib episode. Hypertension resistant to normal therapy, headaches, and excessive sweating are other common symptoms. Pheochromocytoma is treated surgically by removal of the tumour.
If no heart abnormalities or any of the above mentioned possible afib triggers are present then the condition is labelled as idiopathic (of no known cause) or primary atrial fibrillation.
The first thing your doctor is likely to do at the initial visit either during or after the first episode is to enquire about any history of stroke or TIAs (transient ischemic attacks), feel your pulse, and measure your blood pressure. An irregular pulse would indicate the presence of an arrhythmia such as atrial fibrillation. A blood pressure above 140/90 mm Hg would raise the suspicion of hypertension (high blood pressure), but this measurement certainly needs to be confirmed on several other occasions before the diagnosis of hypertension is made. During this first visit you are likely to be highly nervous which could increase blood pressure significantly. Or if you are still in afib an abnormally low blood pressure may be found.
The doctor will also want to listen to your heart with a stethoscope (auscultation). By listening carefully to the noises the heart makes when it pumps they will be able to detect problems with the heart valves such as mitral valve prolapse, mitral valve stenosis, and regurgitation. By listening to the lungs pulmonary edema may be detected. Finally an eye examination is usually performed to check for signs of hypertension or atherosclerosis showing up in the small arteries feeding the eye.
Since palpitations can also be a feature in anxiety (panic) attacks and anemia tests for these conditions may also be warranted. The next phase of the evaluation is designed to check for specific heart problems.
Treadmill exercise test
If no underlying heart abnormalities or other disease conditions have been found which can explain the atrial fibrillation then the cardiologist, at this point, should be able to make the diagnosis of lone or idiopathic atrial fibrillation. Of course, this assumes that the presence of other arrhythmias (atrial flutter, supraventricular tachycardia, ventricular arrhythmias) has already been ruled out.
Advanced (and rarely needed) tests
Injection of radioactive tracers and subsequent imaging with a gamma camera (nuclear medicine techniques) can provide further information about heart structure and blood flow and is particularly useful in determining left ventricular ejection fraction. In combination with exercise testing nuclear medicine techniques are also useful for detecting coronary artery disease or for confirming that a heart attack has taken place.
Invasive tests such as cardiac catheterization and angiography are usually not required in diagnosing lone atrial fibrillation. An electrophysiological study may be useful in determining whether atrial flutter or paroxysmal supraventricular tachycardia is involved as predisposing arrhythmias and is also required if ablation therapy is contemplated.
Need for stroke prevention
It is not clear whether patients with paroxysmal AF episodes that terminate on their own need anticoagulation. Whether to prescribe warfarin or not must be decided on an individual basis. General guidelines are:
* Risk factors are heart failure, hypertension, left ventricular ejection fraction of less than 0.35, diabetes, coronary artery disease, thyrotoxicosis, rheumatic heart disease (mitral stenosis), prosthetic heart valves, prior stroke, heart attack or transient ischemic attack (TIA), and a persistent atrial thrombus (blood clot).
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. Please consult your health-care provider if you wish to follow up on the information presented.