Long QT syndromes and torsade de pointes

In the long QT syndromes (LQTS), malfunction of ion channels impairs ventri cular repolarisation and triggers a characteristic ventricular tachyarrhyth mia: torsade de pointes. Symptoms in the LQTS (syncope or cardiac arrest) a re caused by this arrhythmia. In congenital LQTS, mutations in the genes en coding for ion chanels cause this channel malfunction. Six genotypes (LQT1 to LQT6) have been identified, and attempts are being made to correlate dif ferent mutations with clinical signs and specific therapy. In acquired LQTS , channel malfunction is caused by metabolic abnormalities or drugs. The li st of drugs that may impair ion-channel function expands continuously. More over, attributes that increase the risk for drug-induced torsade (eg, femal e sex, recent heart-rate slowing, or hypokalaemia) and electrocardiographic "warning signs" are recognised. Recent data suggest that patients with an acquired LQTS have some underlying predisposition to proarrhythmia. Mutatio ns causing "silent" forms of congenital LQTS, in which the patient remains free of arrhythmias until exposed to drugs that further impair repolarisati on, are now recognised.