EPIDEMIOLOGY AND PATHOPHYSIOLOGY
“Atrial fibrillation is common among older adults. In developed countries, the number of patients with atrial fibrillation is likely to increase during the next 50 years, due to the growing proportion of elderly individuals” (Go, 2001).
Atrial Fibrillation is a result of the abnormal beating of the heart which involves the right and left atrium of the heart. In this disease, the two upper chambers produce abnormal rhythms brought about by the disorganized electrical impulses from the sinoatrial node. Normally, the heart would contract in a regular beat because of the electric impulses. In the case of Atrial Fibrillation (commonly called AF), it happens otherwise, which results to abnormal contraction of the cardiac muscles.
The risk of having AF increases as an individual reaches an old age. It is most common in people aging in their eighties. There are two identified types of AF- one is paroxysmal atrial fibrillation which happens when an individual suffers from the AF rhythm and normal heartbeat alternates spontaneously. The other type which occurs for a longer period of time which is indicated by the occurrences of AF heartbeats without reversing to the normal heartbeat is called chronic atrial fibrillation (Levy, 2000).
Atrial Fibrillation affects millions of victims around the globe. It serves as one of the leading causes of stroke because the inconsistent and irregular beats may result to blood stagnation and clots which may be further sent to the brain.
It is also a type of silent killer since it is an asymptomatic disease. Meaning, it does not explicitly show its occurrence to the individual. However, a person who would suffer from AF may also feel some degrees of palpitation and chest pain before the attack occurs.
Treatment of atrial fibrillation focuses primarily on lessening or slowing the heart rate of the victim and reverting it into its normal heartbeat. The most common categories of drugs which may successfully help in treating this disease are the Calcium Channel Blockers.
SIGN AND SYMPTOMSAND DIAGNOSIS
Atrial Fibrillation may be diagnosed with symptoms such as palpitations, exercise intolerance, angina and other disorders related to the rapid rate of heart beat of an individual. Because of its asymptomatic nature, AF is better diagnosed early with routine exercises and electrocardiography.
When an electrocardiogram is used, patients with Atrial Fibrillation manifest the following characteristics: absence of p-waves, unorganized electrical impulses which makes the cardiac muscles contract, and lastly, the irregularity of intervals of heartbeat because of its being unorganized.
Atrial Fibrillation is has several causes and the following are the most common causes. First is the mitral stenosis wherein the mitral valve of the heart narrows and constricts which makes the flow of the blood irregular in manner. Another is mitral regurgitation wherein the blood flows in an opposite from its intended flow.
Coronary Artery Disease is also considered a factor for having Atrial Fibrillation since in the former disease, the arteries becomes narrow because of the deposited fats and other substances in the arterial walls which makes the blood flow very abnormal. Having a heart surgery may also increase the risk of having this disease since the heart is a sensitive organ and its tangibility makes it sensitive to minute changes in its environment and structure. Because of this, there may be irregularities and complications which may lead to atrial fibrillation.
The reason why the chance of having atrial fibrillation increases with age is because having high blood pressure is one of the major causes of this disease. Sicne high blood pressure is most common as an individual advances his or her age, the chance of having AF also increases in the same manner. The excessive amount of pressure exerted by the blood against the arteries may cause irregularities in the heart beat of an individual.
Another most common cause of AF is pericarditis. Pericarditis is the inflammation of the sac which contains the heart and vessels which is called the pericardium. Since the pericardium encloses and connects the heart and portion of the blood vessels, its inflammation may hamper the electric signals sent for the proper function and contraction of the cardiac muscles.
Treatment of Atrial Fibrillation is aimed at promote the stability of the heart especially in sending and carrying out the electrical impulses for contraction. Controlling and regulating the rate and Rhythm control treatment is the attaining of a normal and regular beat called the sinus rhythm of the heart. There are basically two types of rhythm control treatment, one is the electrical cardioversion and the other is the chemical cardioversion. As the term suggests, electrical method involves the use of electric shocks and impulses to restore the normal heart rhythm to its normal beat. In the chemical method, drugs are being used such as procainamide, ibulitide and the like.
However, one risk of treatment using cardioversions is the chance of embolism of the blood clots which may be present in the previously fibrillated arteries. This is the reason why complete anticoagulation is done first before engaging in this kind of treatment. Rate of relapse is at fifty per cent that is why religious taking of anti-arrhythmic medications is needed for prolonging stability.
Rate control treatment is use to normalized the heartbeat in to “60 to 100 beats/minute”. In rate control cardioversion, the use of medications such as beta-blockers, cardioglycosides and calcium channel blockers (includes verapamil and diltiazem) are involved. These drugs slow down the generation of impulses from the atria. However, out of these drugs, only amiodarone and dofetilide are generally accepted by the FDA. Others including verapamil and diltiazem are not approved for use. They are not considered safe by others for the reason that although they contain blockers which can be of great help, they would lead to ventricular tachycardia which would further lead to fatal conditions and even death.
CALCIUM CHANNEL BLOCKERS
Calcium channel blockers are drugs which have an effect to the excitatory state of some cells in the body and most commonly used for the myocardium. These blockers slow down the electrical conductivity of the heart. They also slow down the heart rate by blocking the number of electrical impulses that pass through the AV node into the ventricular chambers. The negative chronotropic effect of these calcium channel blockers is one reason it is commonly used for patients with uncontrollable heart rate and rhythms because it slows down the cardiac muscles. There are two main divisions of calcium channel blockers: the dihydropyridines and the nondihydropyridines. Verapamil and Diltiazem belong to the latter division of calcium channel blockers.
Verapamil is an anti-hypertensive, anti-arrhythmic and anti-anginal medication which blocks the trans-membrane influx of calcium ions in the cardiac muscles thus slowing down the impulses to be received by the heart. More than 90% of verapamil is being absorbed. Because of this the elimination half-life of the drug and its bioavailability is also high.
Verapamil should not be taken by AF patients because they are contraindicated. In the same manner it is also contraindicated with MI patients (myocardial infarction), atrial flutter, hypotension and many others. In a study conducted, out of almost 5000 individuals who took Isoptin, a brand of verapamil it was recorded that there are at least 37.1% of patients who suffered from adverse reactions (Long, 2005).
Diltiazem is another kind of calcium channel blocker which is used in treatment of circulatory system disorders such as angina pectoris, hypertension and arrhythmia. Being a vasodilator, it serves to increase the blood flow in a certain vessel which usually causes the diseases and disorders stated earlier. It is also used as a medication for decreasing the heart rate of persons with atrial fibrillation.
The dosage of these calcium channel blockers should be given more attention because the amount that a patient should take should be individualized. It is needed because of the great risk it poses to the patients, who may suffer from hypotension. When taken in excessive amounts, the patient may experience cardiovascular effects such as hypotension, potentially fatal dysrhythmmias, and nervous system related effects such as seizures, coma, metabolic acidosis and the like.
ADENOSINE AS TREATMENT FOR AF
Although not considered as a calcium channel blocker, the use of adenosine in treating atrial fibrillation has also been a controversy in the world of pharmacology. It was observed in several studies that the use of adenosine further increased the chances of a person with a heart disease to develop AF. Adenosine’s indirect effect on the atrial tissue further initiates the occurrence of AF. Although adenosine may be safe to patients with paroxysmal supraventricular tachycardia- another disease related to arrhythmias, its use against AF does otherwise.
There have been findings however that Adenosine induced atrial fibrillation is just a case to case basis and is not true to all patients. Adenosine could also treat AF and other heart ailments provided that the dosage is right, the method is effective and the period of treatment is in a timely and accurate manner.
ADVERSE REACTIONS OF CALCIUM CHANNEL BLOCKERS
When the dosages taken are just in the minimal threshold and only intended for therapeutic intentions, there is a very low risk for having adverse effects. However, as the age of the patient advances, the chances of adverse effects become exaggerated. The most common effects happen in the circulatory and nervous system which results from the medicine’s vasodilatory actions.
Cronin and Reid (2006) stated that Verapamil and Diltiazem can sometimes trigger or worsen the heart failure of an individual. The chances are even greater for person with kidney and liver diseases. Because of this, the usage of these drugs is being put into the limelight of medical experts and those concerned authorities such as the FDA.
Atrial Fibrillation is already an increasing threat which exposes the patients, especially those older in age, in great risk of experiencing worse conditions than their diagnosed diseases. The wide use of calcium channel blockers most especially Verapamil and Diltiazem is a challenge for medical professionals and pharmaceutical industries.
It is not an undeniable truth that verapamil and Diltiazem are indeed effective drugs against AF, however, extreme care and focus should be exerted not just by the health care providers but even the patients themselves. Its effectiveness is unanimous however its reliability and safety is still in question by many. Resolution regarding these issues is in dire need for everyone especially the patients because life and death situations are being dealt with at all times and at all costs.
- Cronin, Collin and Reid, Nancy. (2006). Medical Review: Retrieved 5 2007 from <http://health.yahoo.com/ency/healthwise/hw160070>
- Go AS, Hylek EM, Phillips KA, Chang Y, Henault LE, Selby JV, Singer DE (2001). “Prevalence of diagnosed atrial fibrillation in adults: national implications for rhythm management and stroke prevention: the AnTicoagulation and Risk Factors in Atrial Fibrillation (ATRIA) Study”. JAMA 285 (18): 2370-5
- Levy S (2000). “Classification system of atrial fibrillation”. Curr Opin Cardiol 15 (1): 54-7.
- Long, Phillip W. (2005). Internet Mental Health. Retrieved 4 July 2007 from <http://www.mentalhealth.com/drug/p30-i03.html>
- Prystowsky EN (2000). “Management of atrial fibrillation: therapeutic options and clinical decisions”. Am J Cardiol 85 (10A): 3D-11D.
- (2006). Calcium Channel Blockers. RxCC Rx Care Canada Inc. Retrieved 4 July 2007 from <http://www.rxcarecanada.com/Calcium%20Channel%20Blockers.asp>