cardiovascular disorders
Long QT Interval Syndromes
Symptoms and Signs of Long QT Interval Syndromes
The LQTS are asymptomatic unless TdeP VT occurs, which can cause palpitations, near syncope, or syncope. Some patients experience myoclonic jerks during syncope; they may incorrectly have a diagnosis of epilepsy pursued. Because the ventricular action potential duration decreases with increasing heart rate, TdeP VT is often self-terminating. However, it may degenerate into ventricular fibrillation and cause cardiac arrest and sudden death with a risk that is approximately 5% per year (higher in LQTS2 and LQTS3 than in LQTS-1). 