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|Section2= |Section3= }} Celivarone is an experimental drug being tested for use in pharmacological anti-arrhythmic therapy.(1) Cardiac arrhythmia is any abnormality in the electrical activity of the heart. Arrhythmias range from mild to severe, sometimes causing symptoms like palpitations, dizziness, fainting, and even death(2). They can manifest as slow (bradycardia) or fast (tachycardia) heart rate, and may have a regular or irregular rhythm(2). == Molecular causes of cardiac arrhythmias == The causes of cardiac arrhythmias are numerous, from structural changes in the conduction system (the sinoatrial and atrioventricular nodes, or His-Purkinje system) and cardiac muscle(2), to mutations in genes coding for ion channels of the heart. Movement of ions, particularly Na+, Ca2+ and K+, causes depolarizations of cell membranes in node cells, which are then transmitted to cardiac muscle cells to induce contraction. After depolarization, the ions are moved back to their original locations, leading to repolarization of the membrane and relaxation(3). Disruptions in ion flow affect the heart’s ability to contract by altering the resting membrane potential, affecting the cell’s ability to conduct or transmit an action potential (AP), or by affecting the rate or force of contraction(3). The specific molecular changes involved in arrhythmias depend on the nature of the problem. Ion channel mutations can alter protein conformation, and so change the amount of current flowing through these channels. Due to changes in amino acids and binding domains, mutations may also affect the ability of these channels to respond to physiological changes in cardiac demand(4). Mutations resulting in loss of function of K+ channels can result in delayed repolarization of the cardiac muscle cells. Similarly, gain of function of Na+ and Ca2+ channels results in delayed repolarization, and Ca2+ overload causing increased Ca2+ binding to cardiac troponin C, more actin-myosin interactions and causing an increased contractility, respectively(3). Mutations cause many arrhythmic conditions, including Atrial Fibrillation(AF), Atrial Flutter(AFl), and Ventricular Fibrillation(VF) (5-8). Arrhythmias can also be induced by altered activity of the vagus nerve and activation of β1 adrenergic receptors(9). 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Celivarone」の詳細全文を読む スポンサード リンク
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