Heart rate over 100 (as high as 240) beats per minute. When it is a normal response to exercise or stress, it is no danger to healthy people, but when it originates elsewhere, it is an arrhythmia. Symptoms include fatigue, faintness, shortness of breath, and feeling the heart thumping. It may subside within minutes or hours with no lasting ill effects, but in serious heart, lung, or circulatory disease it can precede atrial fibrillation or heart attack and demands immediate medical attention. Tachycardias can be treated by an electric shock to the heart, by antiarrhythmic drugs, and by pacemakers
an autosomal dominant inherited heart disorder caused by a mutation in voltage gated ion channels and resulting in arrhythmias. CPVT may cause exercise-induced ventricular arrhythmias and/or syncope occurring during physical activity or acute emotion, but demonstrates no structural problems of the heart. Ventricular tachycardia may self-terminate or degenerate into ventricular fibrillation, causing sudden death without immediate cardiopulmonary resuscitation. The majority of events occur during childhood and more than 60% of affected individuals will have a first episode of syncope or cardiac arrest by age 20