Abnormal electrical conduction or automaticity changes heart rate and rhythm in cardiac arrhythmias, also called cardiac dysrhythmias. Cardiac dysrhythmia is technically more correct, as arrhythmia would imply that there is "no rhythm," but this term is not used frequently.
Arrhythmias vary in severity, from those that are mild, asymptomatic, and require no treatment (such as sinus arrhythmia, in which the heart rate increases and decreases with respirations) to catastrophic ventricular fibrillation, which necessitates immediate resuscitation.
Arrhythmias are generally classified according to their origin (ventricular or supraventricular). Their effect on cardiac output and blood pressure, partially influenced by the site of origin, determines their clinical significance.
Arrhythmias may be congenital or they may result from one of several factors, including myocardial ischemia, myocardial infarction, and organic heart disease. Drug toxicity or degeneration of the conductive tissue necessary to maintain normal heart rhythm (sick sinus syndrome) sometimes can also precipitate arrhythmias.
Signs and symptoms
Most arrhythmia does not result in symptoms, but people may experience anxiety , lightheadedness, dizziness, fainting, unusual awareness of the heartbeat, and sensations of fluttering or pounding in the chest.
Cardiac dysrhythmias are often first detected by simple but nonspecific means: auscultation of the heartbeat with a stethoscope , or feeling for peripheral pulses . These cannot usually diagnose specific dysrhythmias, but can give a general indication of the heart rate and whether it is regular or irregular. Not all the electrical impulses of the heart produce audible or palpable beats; in many cardiac arrhythmias, the premature or abnormal beats do not produce an effective pumping action and are experienced as "skipped" beats.
The simplest specific diagnostic test for assessment of heart rhythm is the electrocardiogram (abbreviated ECG or EKG ). A Holter monitor is an ECG recorded over a 24-hour period, to detect dysrhythmias that may happen briefly and unpredictably throughout the day.
Types of cardiac arrhythmias
Following are the different types of cardiac arrhythmias:
Treatment for cardiac arrhythmia
The pharmacological treatments consist of agents that interfere with sodium, pottasium, and calcium pump systems, which are used by the heart to control heart rate. These agents tend to result in longer times between each impulse, by prolonging repolarisation (the heart cells pump Na+ across their membranes during a contraction, and then pump Na+ back in ready for another contraction, this is called repolarisation).
Surgery: Can correct certain types of arrhythmias. For example, arrhythmias caused by coronary artery disease may be controlled by bypass surgery. When an cardiac arrhythmia is causes by a certain area of the heart, sometimes that part of the heart can be destroyed or removed.
Electrical "shock" (defibrillation or cardioversion), the implantation of a temporary pacemaker to interrupt the arrhythmia, or antiarrhythmic drugs may be used.
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