The part of the autonomic nervous system originating in the brain stem and the lower part of the spinal cord that, in general, inhibits or opposes the physiological effects of the sympathetic nervous system, as in tending to stimulate digestive secretions, slow the heart, constrict the pupils, and dilate blood vessels.
Paroxysmal supraventricular tachycardia (PSVT) Alternative names PSVT; Supraventricular tachycardia Definition: Paroxysmal supraventricular tachycardia (PSVT) is a rapid heart rate, which occurs from time to time (paroxysmal). PSVT starts with events taking place above the ventricles.
Long QT syndrome (LQTS) is a disorder of the heart's electrical activity. It can cause sudden, uncontrollable, dangerous arrhythmias (ah-RITH-me-ahs) in response to exercise or stress. Arrhythmias are problems with the rate or rhythm of the heartbeat.People who have LQTS also can have arrhythmias for no known reason.he timing of the heart's electrical activity is complex, and the body carefully controls it. Normally the QT interval is about a third of each heartbeat cycle. However, in people who have LQTS, the QT interval lasts longer than normal.