Lown-Ganong-Levine syndrome is part of the preexcitation syndromes cluster, a condition with no definite structural support, manifesting as tachycardia paroxysms and a typical electrocardiogram aspect, with short PR interval, normal QRS complex duration and absent delta wave.
Lown-Ganong-Levine syndrome (LGLS) patients usually have no cardiovascular symptoms between tachycardia crisis. The ailment most often affects men  in their second or third decade of life , but signs may occur at any age and consist of rapid, regular palpitations caused by a heart rate of 200 beats per minute or more. Episodes typically begin and end suddenly, but the latter may also be perceived as gradual because the episode is followed by sinus tachycardia. Diminished cardiac output caused by the fact that diastole duration is diminished leads to lightheadedness and dyspnea. Chest pain is encountered in victims with coronary artery disease (due to the fact that coronary supply is ensured during diastole), hypertrophic cardiomyopathy or structural heart malformations, such as tricuspid atresia, Ebstein’s anomaly, mitral valve prolapse or corrected transposition of great vessels. Atrial fibrillation may be experienced in such cases, but usually, have short duration . During the attack, arterial hypotension may be recorded. In advanced situations, syncope is noticed by ventricular tachycardia or ventricular fibrillation. Patients sometimes present with heart failure symptoms. The episodes may be followed by polyuria.
The frequency of the crisis tends to diminish with the advancement of age. The death risk is low, however, incidences have been recorded . The demise mechanism is arrhythmic and always appears in patients that have experienced arrhythmia episodes before, so sudden death is never the first symptom .
Those who perceive palpitations in the cervical area are more likely to have nodal reentrant tachycardia instead of LGLS . Vagal maneuvers, such as Valsalva or carotid sinus massage may block atrioventricular node conduction and stop the arrhythmia if its technique involves the node, may have no effect or temporarily slow atrioventricular conduction. This clinical response is valuable while trying to establish the process of an paroxysmal tachycardia attack .
LGLS diagnosis is mainly based on electrocardiography (ECG). The criteria include a normal or inverted P wave, a short PR interval less than or equal to 0.12 second (120 ms), with normal QRS complex duration, the absence of a delta wave and presence of clinical complaints consisting of tachycardia episodes. However, QRS complexes may also be wide, if the sufferer has a preexisting or functional right bundle or left bundle branch block. A short PR interval may be seen in ectopic atrial rhythms and atrioventricular junctional rhythms . When a patient describes typical supraventricular arrhythmia but normal sinus rhythm is observed on the electrocardiogram, Holter monitorization or implantable loop recorder are indicated. A Holter monitor is useful when symptoms are observed every day, whereas the other method is employed when crisis appear not as often. Obtaining an electrocardiography documentation is particularly important because it can offer important information about the mechanism of the tachycardia.
Blood tests should include serum thyroid-stimulating hormone electrolytes, calcium, and magnesium level. Further information is provided by vagal maneuvers. A carotid sinus massage can only be performed if the subject has no history of cerebrovascular events, has no carotid bruits and the blood pressure is not decreased. It should be done under blood pressure and ECG monitorization. This maneuver can terminate the episode or induce transient atrioventricular block.
A novel technique is represented by noninvasive cardiac mapping using computed-tomography scan–based three-dimensional electroimaging and 252-lead ECG . When the condition becomes intolerable or when a ventricular arrhythmia is suspected, an invasive electrophysiology study is needed.