Although it is difficult to predict which individuals will be affected from<unk><unk>  long<unk>  syndrome, there are general risk factors that can be associated with the use of certain medications. Generally, as the dose of a<unk>  increases, the risk of<unk><unk>  increases as well. In addition, factors such as rapid infusion, concurrent use of more than one<unk>  known to prolong<unk>  interval, diuretic treatment, electrolyte derangements (hypokalemia, hypomagnesemia, or hypocalcemia), advanced age, bradyarrhythmias, and female sex have all been shown to be risk factors for developing<unk> . TdP has been shown to occur up to three times more often in female patients compared with males, likely as a result of post-pubertal hormonal influence on cardiac ion channels. The<unk> c interval is longer in females, as well as having a stronger response to IKr-blocking agents. In males, the presence of testosterone upregulates IKr channels and therefore decreases<unk>  interval. Stated otherwise, estrogens prolong the<unk>  interval, while androgens shorten it and decrease the response to IKr-blocking agents. Structural heart disease, such as heart failure, myocardial infarction, and left ventricular hypertrophy, are also risk factors. Diuretic-induced hypokalemia and/or hypomagnesemia taken for heart failure can<unk> proarrthymia. The ischemia that results from myocardial infarctions also<unk><unk><unk> .<unk> s that cause<unk><unk>  The main groups of<unk> s that can cause<unk><unk>  are antiarrythmic medications, psychiatric medications, and antibiotics. Other<unk> s include antivirals and antifungals. Antiarrhythmic agents Source: * Class IA * Class IA antiarrhythymic<unk> s work by blocking sodium and potassium channels. Blocking sodium channels tend to shorten the action potential duration, while blocking potassium channels prolongs the action potential. When the<unk>  concentration is at a low to normal concentration, the potassium channel blocking activity takes precedence over the sodium channel blocking activity * Disopyramide * Procainamide * Propafenone * Quinidine * Because of the predominance of the potassium blocking activity, TdP is seen more frequently with therapeutic levels of quinidine. Sodium blocking activity is dominant with subtherapeutic levels, which does not lead to<unk><unk>  and TdP. * Class III * Class III antiarrhythmic<unk> s are potassium channel blockers that cause<unk><unk>  and are associated with TdP. * Amiodarone * Amiodarone works in many ways. It blocks sodium, potassium, and calcium channels, as well as alpha and beta adrenergic receptors. Because of its multiple actions, amiodarone causes<unk><unk>  but TdP is rarely observed. * Dofetilide * Ibutilide * Ibutilide differs from other class III antiarrhythmic agents in that it activates the slow, delayed inward sodium channels rather than inhibiting outward potassium channels. * Sotalol * Sotalol has beta-blocking activity. Approximately 2 to 7 percent of patients taking at least 320 mg/day experience proarrhythmia, most often in the form of TdP. The risks and effects are dose-dependent. Psychiatric medications Psychiatric medications include antipsychotics and antidepressants that have been shown to lengthen the<unk>  interval and<unk> TdP, especially when given intravenously or in higher concentrations. * Typical antipsychotics * Chlorpromazine * Haloperidol * Haloperidol functions by blocking the KCNH2 channel, the same pathway that other<unk> -inducing LQTS block. Patients taking haloperidol are at a higher risk if they also have electrolyte abnormalities (such as hypokalemia and/or hypomagnesemia), congenital LQTS, cardiac abnormalities, hypothyroidism, or if they are concurrently taking other medications known to lengthen the<unk>  interval. * Thioridazine * Atypical antipsychotics * Quetiapine * Overdoses on quetiapine cause<unk><unk>  in patients with cardiac risks. * Risperidone * Mild<unk><unk>  can be caused by risperidone but there are no specific<unk>  warnings associated with this. * Ziprasidone * SSRIs * An ECG is recommended before patients are prescribed SSRI agents citalopram and escitalopram if the prescribed dose is above 40 mg or 20 mg per day, respectively. * Fluoxetine * Paroxetine * Sertraline * SNRIs * Venlafaxine * Tricyclic antidepressants * Amitriptyline * Desipramine * Doxepin * Imipramine Antibiotics Source: * Macrolides * Azithromycin * Clarithromycin * Erythromycin * When taken independently, erythromycin has been shown to cause both<unk><unk>  and TdP. Erythromycin works inhibiting the CYP3A protein. Patients who have low CYP3A activity and are also concurrently taking other medications such as disopyramide, which can lead to<unk><unk>  and TdP. * Fluoroquinolones * Ciprofloxacin * Levofloxacin * Moxifloxacin Other agents * Chloroquine * Cisapride * Foscarnet * Hydroxychloroquine * Ketoconazole * Methadone * Octreotide * Tacrolimus * Tamoxifen
Drug-induced QT prolongation
Benign early repolarization
Catecholaminergic polymorphic ventricular tachycardia
Tachycardia-induced cardiomyopathy
Sudden arrhythmic death syndrome
Toxic anterior segment syndrome
Pre-excitation syndrome
Long QT syndrome