|
Romano-Ward syndrome (RWS) is an autosomal dominant variant of the long QT syndrome (LQTS, see this term) characterized by syncopal episodes and electrocardiographic abnormalities (QT prolongation, T-wave abnormalities and torsade de pointes (TdP) ventricular tachycardia). The prevalence of RWS is estimated at 1/2,500. Cardiac events occur from infancy through middle age. Most patients develop the symptoms during exercise or in response to stress or emotional disturbances and symptoms rarely occur at rest or during sleep. The syncopal episodes are due to TdP, a polymorphic ventricular tachycardia. TdP often degenerates to ventricular fibrillation and causes cardiac arrest or sudden death. In some patients, cardiac arrest may be the first manifestation of the disease. The electrocardiogram typically shows a prolongation of ventricular repolarization (QTc > 460 ms) and biphasic or notched T-waves in the precordial leads. Beat-to-beat alternation of the T wave (in polarity or amplitude) may be present at rest, but most commonly appears during emotional or physical stress and may precede TdP. The heart rate at rest or during exercise may be slower than normal. RWS may result from mutations in genes encoding subunits of cardiac ion channels (KCNQ1, KCNH2, SCN5A, KCNE1, KCNE2, and SCN4B) or in those encoding proteins interacting with cardiac ion channels (ANK2,CAV3, AKAP9 or SNTA1) and is inherited in an autosomal dominant manner with low penetrance. Thus, the terms LQT1 through LQT6 and LQT9 through LQT12 describe patients affected by genetic variants of RWS, with LQT7 referring to Andersen syndrome and LQT8 referring to Timothy syndrome (see these terms). Diagnosis is based on typical electrocardiographic findings, clinical manifestations and family history. Molecular diagnosis should always be performed in patients with a clinically suspected diagnosis. It should also be performed on affected family members with normal/borderline QT intervals to identify those at risk of sudden death. Prenatal testing may be available for families in which the disease-causing mutation is known. Typical cases are so characteristic that they do not require differential diagnosis. For borderline cases, the following conditions should be considered: catecholaminergic polymorphic ventricular tachycardia (CPVT), hypertrophic cardiomyopathy orthostatic hypotension, Jervell and Lange-Nielsen syndrome and other forms of LQTS, Brugada syndrome (see these terms), as well as vasovagal syncope, ventricular tachycardia, drug-induced LQTS and epilepsy. Beta-adrenergic blockers represent the first choice therapy in symptomatic patients. Whenever syncopal episodes recur despite full-dose beta-blocking therapy, left cardiac sympathetic denervation (LCSD) should be considered and implemented whenever possible. Cardiac pacing is only rarely indicated (e.g. in infants or young children with 2:1 atrioventricular block). Implantable cardioverter defibrillators (ICDs) are always indicated after cardiac arrest, or when requested by the patient, and whenever syncope recurs despite beta-blockade and LCSD. Prophylactic use of beta blockers in asymptomatic children and adults under age 40 years with LQTS (LQT1, LQT2 or LQT3) is indicated. LQTS and its variants are leading causes of sudden cardiac death in young, otherwise healthy, subjects and contribute significantly to sudden infant death syndrome (SIDS). As very effective therapies exist, early diagnosis (neonatal ECG screening) is of crucial importance and permits preventive management. |