260x260px Although individuals with<unk>  may not experience any symptoms, the most commonly reported symptoms are blackouts or sudden loss of consciousness, referred to as syncope. These blackouts often occur during exercise or as a response to emotional stress—situations in which chemical messengers known as catecholamines, such as adrenaline, are released within the body. Blackouts may be misinterpreted as being caused by simple faints or epilepsy, often leading to delays in reaching the correct diagnosis. In a third of those affected, the first manifestation of the disease may be cardiac arrest, potentially leading to sudden death. This can occur in very young children, presenting as sudden infant death syndrome or 'cot death'. Approximately 30% of those with<unk>  will have a family member who has experienced blackouts, seizures, or sudden death in response to exercise or stress. In those with<unk> , catecholamine release can lead to an abnormal heart rhythm or arrhythmia known as<unk>  tachycardia. The<unk>  tachycardia may take a characteristic form known as bidirectional<unk>  tachycardia. This form of<unk>  tachycardia occurs relatively infrequently, but if seen is suggestive of an underlying diagnosis of<unk>  or the related condition Andersen-Tawil syndrome. These<unk>  arrhythmias in some cases terminate by themselves, causing a blackout from which the person then recovers. However, if the abnormal heart rhythm continues, it can degenerate into a more dangerous arrhythmia known as<unk>  fibrillation causing a cardiac arrest and, if untreated, sudden death. There are typically very few abnormal signs on clinical examination in persons with<unk> . However, those with<unk>  may develop a less serious heart rhythm disturbance called atrial fibrillation, which can be detected on examination as an irregular pulse. Furthermore, approximately 20% of those with<unk>  have a slow resting heart rate known as a sinus bradycardia.
Catecholaminergic polymorphic ventricular tachycardia
Benign early repolarization
Junctional ectopic tachycardia
Brugada syndrome
Pre-excitation syndrome
Long QT syndrome
Wandering atrial pacemaker
Andersen–Tawil syndrome