- 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: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:90647)
- Bilateral sensorineural hearing impairment (HP:0008619): A form of sensorineural hearing impairment that affects both ears. Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:90647)
- Profound sensorineural hearing impairment (HP:0011476): Complete loss of hearing related to a sensorineural defect. Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:90647)
- 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: TAS. Frequency: Frequent (HP:0040282). (ORPHA:90647)
- Torsade de pointes (HP:0001664): A type of ventricular tachycardia characterized by polymorphioc QRS complexes that change in amplitue and cycle length, and thus have the appearance of oscillating around the baseline in the EKG. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:90647)
- Loss of consciousness (HP:0007185): Loss of awareness of oneself or one's surroundings, involving (i) a loss of normal motor control is evident as flaccidity or stiffness, either of which can be accompanied by jerking movements, and postural control is lost so that patients fall if they are in an upright position; (ii) normal responsiveness is lost; and (iii) the patient experiences amnesia for the event. Loss of consciousness my be transitory (e.g., syncope) or prolonged. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:90647)
- Arrhythmia (HP:0011675): Any cardiac rhythm other than the normal sinus rhythm. Such a rhythm may be either of sinus or ectopic origin and either regular or irregular. An arrhythmia may be due to a disturbance in impulse formation or conduction or both. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:90647)
- Postexertional symptom exacerbation (HP:0030973): Post-exertional symptom exacerbation (PESE), also referred to as post-exertional malaise (PEM), is defined as the worsening of symptoms that can follow minimal cognitive, physical, emotional, or social activity, or activity that could previously be tolerated. Symptoms typically worsen 12 to 72 hours after activity and can last for days or even weeks, sometimes leading to a relapse. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:90647)
- 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: TAS. Frequency: Occasional (HP:0040283). (ORPHA:90647)
- 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: TAS. Frequency: Occasional (HP:0040283). (ORPHA:90647)
- Iron deficiency anemia (HP:0001891). Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:90647)
These phenotypes are associated with the disease Jervell and Lange-Nielsen syndrome (ORPHA:90647).