Acquired Long QT Syndrome in Critically Ill Patients
Mohsen Talaat Mohammed;
Abstract
The QT interval represents the duration of the action potential (activation; depolarization and recovery; repolarization) of the ventricular myocardium. Prolonged recovery (delayed repolarization) from electrical excitation increases the likelihood of dispersing refractoriness, when some parts of myocardium might be refractory to subsequent depolarization.
LQTS is a disorder affecting myocardial repolarization characterized by a prolongation of the QT interval on electrocardiograms beyond the normal limits, with a propensity to ventricular tachyarrhythmias which may lead to syncope, cardiac arrest, or sudden death. LQTS can be congenital or acquired. The acquired form of LQTS is more common than the congenital form.
Three potassium currents (IK1, IKs, and IKr) are believed to be responsible for the majority of ventricular repolarization. Prolongation of action potential can result from an increase in inward current (e.g., through sodium or calcium channels) or a decrease in outward current (e.g., through potassium channels). Myocardial repolarization is primarily mediated by efflux of potassium ions. Prolonged repolarization can cause early afterdepolarizations (EADs) due to activation of inward depolarizing currents, L-type calcium channels or sodium calcium exchange current, that appear as depolarizing oscillations in membrane voltage during phases 2 and 3 of the action potential. Early after-depolarization (EAD) that reaches threshold voltage can cause a ventricular extrasystole preceded by a long QT interval on the surface ECG.
The of guidelines for the management of patients with LQTS, as suggested by the American College of Cardiology, the American Heart Association, and the European Society of Cardiology, in collaboration with the European Heart Rhythm Association and the Heart Rhythm Society, summarizes: (1) no participation in competitive sports for patients with the diagnosis established by means of genetic testing only (2) ß-blockers should be given to patients who have QTc-interval prolongation (>460 ms in women and >440 ms in men) and are recommended (class IIa) for patients with a normal QTc interval (3) an implantable cardioverter-defibrillator (ICD) should be used in survivors of cardiac arrest and is recommended (class IIa) for patients with syncope while receiving ß-blockers; ICD therapy can be considered (class IIb) for primary prevention in patients with characteristics that suggest high risk (including LQT2, LQT3, and QTc interval >500 ms).
LQTS is a disorder affecting myocardial repolarization characterized by a prolongation of the QT interval on electrocardiograms beyond the normal limits, with a propensity to ventricular tachyarrhythmias which may lead to syncope, cardiac arrest, or sudden death. LQTS can be congenital or acquired. The acquired form of LQTS is more common than the congenital form.
Three potassium currents (IK1, IKs, and IKr) are believed to be responsible for the majority of ventricular repolarization. Prolongation of action potential can result from an increase in inward current (e.g., through sodium or calcium channels) or a decrease in outward current (e.g., through potassium channels). Myocardial repolarization is primarily mediated by efflux of potassium ions. Prolonged repolarization can cause early afterdepolarizations (EADs) due to activation of inward depolarizing currents, L-type calcium channels or sodium calcium exchange current, that appear as depolarizing oscillations in membrane voltage during phases 2 and 3 of the action potential. Early after-depolarization (EAD) that reaches threshold voltage can cause a ventricular extrasystole preceded by a long QT interval on the surface ECG.
The of guidelines for the management of patients with LQTS, as suggested by the American College of Cardiology, the American Heart Association, and the European Society of Cardiology, in collaboration with the European Heart Rhythm Association and the Heart Rhythm Society, summarizes: (1) no participation in competitive sports for patients with the diagnosis established by means of genetic testing only (2) ß-blockers should be given to patients who have QTc-interval prolongation (>460 ms in women and >440 ms in men) and are recommended (class IIa) for patients with a normal QTc interval (3) an implantable cardioverter-defibrillator (ICD) should be used in survivors of cardiac arrest and is recommended (class IIa) for patients with syncope while receiving ß-blockers; ICD therapy can be considered (class IIb) for primary prevention in patients with characteristics that suggest high risk (including LQT2, LQT3, and QTc interval >500 ms).
Other data
| Title | Acquired Long QT Syndrome in Critically Ill Patients | Other Titles | متلازمة استطالة فترةQTالمكتسبة في مرضى الحالات الحرجة | Authors | Mohsen Talaat Mohammed | Issue Date | 2014 |
Recommend this item
Similar Items from Core Recommender Database
Items in Ain Shams Scholar are protected by copyright, with all rights reserved, unless otherwise indicated.