Ventricular Toxicity

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Amiodarone and Ocular Toxicity An arrhythmia is a problem associated with the electrical activity of the heart resulting in a heartrate that can be too fast (tachycardia) or too slow (bradycardia). Arrhythmias are generally categorized as ventricular or supraventricular.1 Ventricular arrhythmias are a condition in which extra heartbeats originate from the lower chambers of the heart and can be classified as ventricular tachycardia, ventricular fibrillation, or premature ventricular contractions. Supraventricular arrhythmias originate in the upper chambers of the heart and can be less serious than ventricular arrhythmias. Both types of arrhythmia can cause shortness of breath, chest tightness, dizziness, or syncope. The National Institute…show more content…
It is estimated that the incidence of optic neuropathy in patients treated with amiodarone is 1.76% compared to only a 0.3% incidence of optic neuropathy developing in those not treated with amiodarone.12 The exact pathophysiology of optic neuropathy caused by amiodarone is unknown, but it is postulated that damage is caused by drug induced lipidosis.9, 10 Amiodarone is a triiodated benzofuran derivative; it is a cationic amphophilic drug possessing closely spaced hydrophilic and hydrophobic groups that allow the drug to enter lysosomes and bind irreversibly to polar lipids.11 The resulting complexes accumulate in the lysosomes as lamellar inclusion bodies which phospholipases cannot catalyze, resulting in mechanical damage to optic nerve axons via blockage of axoplasmic flow.7, 11,12 This may lead to the optic edema observed in many patients that persists for months after the medication is discontinued due to the drug’s long half-life.12 Another theory is that oxidative damage is the culprit. When amiodarone is reduced, iodine is cleaved from the molecule which generated oxygen-free radicals. Amidoarone generated free radicals can cause an increase in cellular lipid peroxidation and drug-lipid…show more content…
Macaluso et al reviewed 73 cases of amiodarone induced optic neuropathy and concluded that onset is insidious, usually bilateral, and characterized by disc swelling that stabilizes after drug discontinuation.10
Although there are multiple reports of optic neuropathy caused by amiodarone, a major challenge is discerning whether the optic neuropathy has a direct causal relationship with amiodarone use or is due to other factors that increase ones risk in developing NAION. NAION is the most common cause of vision loss in individuals over
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