Arrhythmias, cardiac drug therapy

An arrhythmia may occur as a result of heart disease or from a disorder that affects cardiovascular function. Conditions such as emotional stress, hypoxia, and electrolyte imbalance also may trigger an arrhythmia An electrocardiogram (ECG) provides a record of the electrical activity of the heart. Careful interpretation of the ECG along with a thorough physical assessment is necessary to determine the cause and type of arrhythmia The goal of antiarrhythmic drug therapy is to restore normal cardiac function and to prevent life-threatening arrhythmias. 

Normal cardiac contraction depends on the conduction of electrical impulses through the myocardium in a highly coordinated fashion. Any abnormality of the initiation or propagation of the impulse is referred to as an arrhythmia. These disorders are the most common clinical problem encountered by a cardiologist. There is a wide range of types of arrhythmias with multiple etiologies and a variety of symptoms. In this section, two types of cardiac tachyarrhythmias are discussed. The most common treatment for these conditions is drug therapy. 

Clinicians should consider the precipitating cause of the cardiac arrest, such as MI, electrolyte imbalance, or primary arrhythmia. Prearrest status should be carefully reviewed, particularly if the patient was receiving drug therapy. 

Contraindications for antipsychotic therapy are few they may include Parkinson s disease, hepatic failure, hypotension, bone marrow depression, or use of CNS depressants. Overdoses of antipsychotics are rarely fatal, except for thioridazine, which is associated with major ventricular arrhythmias, cardiac conduction block, and sudden death. For other agents gastric lavage should be attempted even if several hours have elapsed since the drug was taken, because gastrointestinal motility is decreased and the tablets may still be in the stomach. Moreover, activated charcoal effectively binds most of these drugs and can be followed by a saline cathartic. The hypotension often responds to fluid replacement or pressor agents such as norepinephrine. 

Patients who tolerate hypotension poorly should avoid second-generation ai-adrenergic antagonists. This includes patients with poorly controlled angina, serious cardiac arrhythmias, patients with reduced circulating volume, and patients on multiple antihypertensives. These patients are candidates for tamsulosin or finasteride, if drug therapy is deemed necessary. Whether extended-release alfuzosin is also a good choice remains to be elucidated in controlled comparison trials with tamsulosin. 

There are many disorders of the cardiovascular system and blood. Common cardiovascular disorders are cardiac failure, ischaemic heart disease, arrhythmias and hypertension. Although these conditions cannot be cured by drug therapy, there are many drugs available to help control them. Cardiac glycosides are useful in cardiac failure and arrhythmias because they improve myocardial contractility and slow conduction through the heart. 

Prophylactic antiarrhythmic drug use does not improve total survival. The Cardiac Arrhythmia Suppression Trial (CAST) (125), based on the supposition that frequent PVCs after myocardial infarction are associated with increased risk of sudden death, evaluated the long-term benefits of antiarrhythmic drug therapy for those patients with > lOPVCs/h after myocardial infarction. After PVC suppression was shown to occur on the antiarrhythmic drug, patients were randomized to the antiarrhythmic drug showing apparent benefit (Class... 

The answer is a. (Hardman, p 224.) Epinephrine is the drug of choice to relieve the symptoms of an acute, systemic, immediate hypersensitivity reaction to an allergen (anaphylactic shock). Subcutaneous administration of a 1 1000 solution of epinephrine rapidly relieves itching and urticaria, and this may save the life of the patient when laryngeal edema and bronchospasm threaten suffocation and severe hypotension and cardiac arrhythmias become life-endangering. Norepinephrine, isoproterenol, and atropine are ineffective therapies Angioedema is responsive to antihis-... 

Optimal therapy of cardiac arrhythmias requires documentation, accurate diagnosis, and modification of precipitating causes, and if indicated, proper selection and use of antiarrhythmic drugs. These drugs are classified according to their effects on the action potential of cardiac cells and their presumed mechanism of action. 

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