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Antiarrhythmics are a class of medications that suppress abnormal heart rhythms, which are called cardiac arrhythmias. These medications help treat arrhythmias such as ventricular fibrillation, ventricular tachycardia and atrial fibrillation. There are several types of antiarrhythmic agents, including beta blockers and ion channel blockers. Each of these works in a slightly different way.
Cardiac arrhythmias occur when the heart generates abnormal electrical impulses. They can cause symptoms such as an irregular or fast heartbeat, heart palpitations, dizziness, fainting, shortness of breath and chest pain. Antiarrhythmic medications work by slowing down electrical impulses that are generated in the heart. This allows the heart’s rhythm to normalize.
Arrhythmias are diagnosed with a test called an electrocardiogram. In this test, electrodes are placed over the chest and used to detect electrical impulses generated by the heart. Diagnosis of different types of arrhythmia is made on the basis of interpretation of the pattern of electrical activity. Once diagnosis has been made, a patient will work with his or her doctor to determine the most suitable antiarrhythmic therapy. Often, a patient might try two or three different medications before settling on the most effective option. While a patient is trying out different drugs, he or she might wear a Holter monitor, a portable device that records electrical impulses from the heart so that the effects of the medication can be evaluated.
There are four classes of antiarrhythmic agents. Class I agents are sodium channel blockers and reduce the passage of sodium ions through cellular sodium channels. Class III agents are potassium channel blockers, and Class IV agents are calcium channel blockers. All three of these medication classes work by altering the electrical impulses generated by the heart. Each drug affects a different ion, so they have different effects on the heart and can treat different types of arrhythmia.
Class II agents are beta blockers, and they work differently from the ion channel blockers. Beta blocker medications block the effects of hormones called catecholamines. These hormones play a role in the stress response and can contribute to heart arrhythmias. Beta blockers reduce the ability of catecholamines to affect the heart rate and increase blood pressure, and they therefore can treat hypertension as well as arrhythmias.
Antiarrhythmic drugs can cause a range of side effects. Possible effects include allergic reaction, cough, appetite loss, constipation or diarrhea, blurred vision, shortness of breath, dizziness, fainting, chest pain, abnormally fast or slow heartbeat and swelling of the legs or feet. Anyone experiencing any of these symptoms should notify his or her doctor as soon as possible.