- Juvenile onset (HP:0003621): Onset of signs or symptoms of disease between the age of 5 and 15 years. Evidence: PCS. Frequency: 1/5. (PMID:24917665)
- Ventricular fibrillation (HP:0001663): Uncontrolled contractions of muscles fibers in the left ventricle not producing contraction of the left ventricle. Ventricular fibrillation usually begins with a ventricular premature contraction and a short run of rapid ventricular tachycardia degenerating into uncoordinating ventricular fibrillations. Evidence: PCS. Frequency: 2/6. (PMID:24917665;PMID:23388215)
- Bradycardia (HP:0001662): A slower than normal heart rate (in adults, slower than 60 beats per minute). Evidence: PCS. Frequency: 4/6. (PMID:24917665;PMID:23388215)
- Cardiac arrest (HP:0001695): An abrupt loss of heart function. Evidence: PCS. Frequency: 3/6. (PMID:24917665;PMID:23388215)
- Seizure (HP:0001250): A seizure is an intermittent abnormality of nervous system physiology characterized by a transient occurrence of signs and/or symptoms due to abnormal excessive or synchronous neuronal activity in the brain. Evidence: PCS. Frequency: 1/5. (PMID:24917665)
- Left ventricular noncompaction (HP:0030682): Left ventricular noncompaction (LVNC) is defined by 3 markers: prominent left ventricular (LV) trabeculae, deep intertrabecular recesses, and the thin compacted layer. Evidence: PCS. Frequency: 1/5. (PMID:24917665)
- Prolonged QTc interval (HP:0005184): A longer than normal interval (corrected for heart rate) between the Q and T waves in the heart's cycle. Prolonged QTc can cause premature action potentials during late phase depolarizations thereby leading to ventricular arrhythmias and ventricular fibrillations. Evidence: PCS. Frequency: 6/6. (PMID:24917665;PMID:23388215)
- Ventricular bigeminy (HP:0034306): An electrocardiographic finding of a normal QRS followed by a premature ventricular contraction; a rhythmic pairing of normal and atypical beats originating in the ventricles in a 1-1 ratio such that an ectopic ventricular beat follows each regular heartbeat. Evidence: PCS. Frequency: 1/5. (PMID:23388215)
- Polymorphic ventricular tachycardia (HP:0031677): A type of ventricular tachycardia that is characterized by variable QRS complexes within each lead (i.e., QRS complexes may be different from beat to beat). Evidence: PCS. Frequency: 1/5. (PMID:24917665)
- 2:1 atrioventricular block (HP:0034305): A type of second-degree atrioventricular block in which every other P wave is not conducted through the AV node such that only every other P wave is followed by a QRS complex. Evidence: PCS. Frequency: 1/1. (PMID:23388215)
- Childhood onset (HP:0011463): Onset of disease at the age of between 1 and 5 years. Evidence: PCS. Frequency: 3/5. (PMID:24917665)
- Fetal onset (HP:0011461): Onset prior to birth but after 8 weeks of embryonic development (corresponding to a gestational age of 10 weeks). Evidence: IEA. Frequency: 1/1. (PMID:23388215)
- Premature ventricular contraction (HP:0006682): Premature ventricular contractions (PVC) or ventricular extrasystoles are premature contractions of the heart that arise in response to an impulse in the ventricles rather than the normal impulse from the sinoatrial (SA) node. Evidence: PCS. Frequency: 2/5. (PMID:24917665)
- Syncope (HP:0001279): A transient loss of consciousness (i.e., characterized by a rapid onset, a short duration, and a spontaneous and complete recovery) due to cerebral hypoperfusion. Evidence: PCS. Frequency: 4/5. (PMID:24917665)
- Autosomal dominant inheritance (HP:0000006): A mode of inheritance that is observed for traits related to a gene encoded on one of the autosomes (i.e., the human chromosomes 1-22) in which a trait manifests in heterozygotes. In the context of medical genetics, an autosomal dominant disorder is caused when a single copy of the mutant allele is present. Males and females are affected equally, and can both transmit the disorder with a risk of 50% for each child of inheriting the mutant allele. Evidence: PCS. (PMID:23388215)
- Sinus bradycardia (HP:0001688): Bradycardia related to a mean resting sinus rate of less than 50 beats per minute. Evidence: PCS. Frequency: 1/1. (PMID:23388215)
- Neonatal onset (HP:0003623): Onset of signs or symptoms of disease within the first 28 days of life. Evidence: PCS. Frequency: 1/5. (PMID:24917665)
These phenotypes are associated with the disease long QT syndrome 15 (OMIM:616249).