Congenital or acquired long QT syndromes
, baseline QT interval >450 ms
It has new content on atrial fibrillation, implantable defibrillators, indications for pacemaker implantation, anticoagulant therapy, long QT syndromes
and other channelopathies, and recently-approved anti-arrhythmia drugs.
Beta-blockers are considered beneficial in long QT syndromes
, the first choice of therapy in patients with congenital long QT (31), reduce the prevalence of cardiac events and syncope (17,32), but there is a lack of prospective, placebo-controlled studies (33).
Long QT syndromes are rare autosomal dominant inherited syndromes affecting approximately 1 in about 2500 individuals, and are produced by more than 400 different mutations (5,6).
Myocardial diseases such as dilated cardiomyopathy and hypertrophic cardiomyopathy along with primary electrical diseases of the heart such as long QT syndrome, Brugada syndrome, idiopathic ventricular fibrillation, etc.
In cases in which no structural heart disease can be identified, arrhythmias resulting from such disorders as the long QT syndromes (LQTSs) are now commonly considered to be likely causes.
Long QT syndromes are diagnosed by surface electrocardiograms, clinical presentation, and family history.
9) Acquired long QT syndrome is most commonly caused by drug administration, typically that of antiarrhythmic drugs such as quinidine.
The most common form of inherited long QT syndrome is the Romano-Ward syndrome, which is transmitted as an autosomal dominant trait.
Mutations in the hminKgene cause long QT syndrome
and suppress IKs function.
Torsade de pointes is a form of polymorphic ventricular tachycardia that occurs in the setting of both congenital and acquired long QT syndrome
T wave morphology was defined as in the congenital Long QT syndrome
(LQTS): 1) "LQT1-like morphology" denoted a long QT interval (QTc interval [greater than or equal to] 450 ms) with broad T waves; 2) "LQT2-like morphology" denoted a long QT interval with double (notched) T waves; and 3) "LQT3-like morphology" denoted a long QT interval with small T waves separated from the (IRS interval by a long isoelectric ST-segment (12, 13).