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Most patients with drug-induced QT prolongation are asymptomatic and are diagnosed solely by EKG in association with a history of using medications known to cause QT prolongation. [7] A minority of patients are symptomatic and typically present with one or more signs of arrhythmia, such as lightheadedness, syncope, or palpitations. [7]
Long QT syndrome; ECG showing typical pattern of inherited Long QT syndrome (LQT1). A QT interval of >480 ms is considered abnormally long. Specialty: Cardiology: Symptoms: Fainting, hearing loss, seizures [1] Complications: Sudden death [1] Causes: Genetic, certain medications, low blood potassium, low blood calcium, heart failure [2] Risk factors
Class Ia drugs prolong the action potential and has an intermediate effect on the 0 phase of depolarization. Increase QT interval; Prevent paroxysmal recurrent atrial fibrillation triggered by vagal overactivity; Treat ventricular arrhythmia; Treat Wolff-Parkinson-White syndrome (procainamide with caution) Ib Lidocaine; Mexiletine; Phenytoin ...
Long QT syndrome, or LQTS, is when somebody’s QT interval is longer than normal, which should typically be less than half of a cardiac cycle. In fact, for a heart rate of 60 beats per minute, the QT interval’s generally considered to be abnormally long when it’s greater than 440 milliseconds in males or 460 milliseconds in females.
Potassium channel blockers exhibit reverse use-dependent prolongation of the action potential duration. Reverse use dependence is the effect where the efficacy of the drug is reduced after repeated use of the tissue. [11] This contrasts with (ordinary) use dependence, where the efficacy of the drug is increased after repeated use of the tissue.
It is of particular use when treating arrhythmias caused by long QT syndrome. [4] The LQT3 form of long QT syndrome is amenable to treatment with mexiletine as this form is caused by defective sodium channels that continue to release a sustained current rather than fully inactivating, however other forms of long QT syndrome can also be treated ...
Long QT syndrome, the most common form of cardiac channelopathy, is characterized by prolonged ventricular repolarization, predisposing to a high risk of ventricular tachyarrhythmias (e.g., torsade de pointes), syncope, and sudden cardiac death.
A long list of factors that can generate a Brugada ECG pattern have been described, including certain medications, electrolyte disturbances such as a decrease in the levels of potassium in the blood, and a reduction in blood supply to key areas of the heart, specifically the right ventricular outflow tract. [8]