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Anderson RH, Becker AE, Brechenmacher C, et al. Ventricular preexcitation. A proposed nomenclature for its substrates. Eur J Cardiol 1975; 3:27. 17. Anderson RH, Becker AE, Brechenmacher C, et al. The human atrioventricular junctional area. A morphological study of the A-V node and bundle. Eur J Cardiol 1975; 3:11. 18. Bharati S, Bauernfiend R, Scheinman M, et al. Congenital abnormalities of the conduction system in two patients with tachyarrhythmias. Circulation 1979; 59:593. https://www.uptodate.com/contents/lown-ganong-levine-syndrome-and-enhanced-atrioventricular-nodal-conduction/print 12/19 7/6/23, 11:14 AM Lown-Ganong-Levine syndrome and enhanced atrioventricular nodal conduction - UpToDate 19. Childers R. The AV node: normal and abnormal physiology. Prog Cardiovasc Dis 1977; 19:361. 20. Prystowsky EN, Pritchett LC, Smith WM, et al. Electrophysiologic assessment of the atrioventricular conduction system after surgical correction of ventricular preexcitation. Circulation 1979; 59:789. 21. Benditt DG, Klein GJ, Kriett JM, et al. Enhanced atrioventricular nodal conduction in man: electrophysiologic effects of pharmacologic autonomic blockade. Circulation 1984; 69:1088. 22. Abella JB, Teixeira OH, Misra KP, Hastreiter AR. Changes of atrioventricular conduction with age in infants and children. Am J Cardiol 1972; 30:876. 23. DuBrow W, Fisher EA, Amaty-Leon G, et al. Comparison of cardiac refractory periods in children and adults. Circulation 1975; 51:485. 24. Meijler FL. Atrioventricular conduction versus heart size from mouse to whale. J Am Coll Cardiol 1985; 5:363. 25. Moro C, Cos o FG. Electrophysiologic study of patients with short P-R interval and normal QRS complex. Eur J Cardiol 1980; 11:81. 26. Josephson ME, Kastor JA. Supraventricular tachycardia in Lown-Ganong-Levine syndrome: atrionodal versus intranodal reentry. Am J Cardiol 1977; 40:521. 27. Moleiro F, Mendoza IJ, Medina-Ravell V, et al. One to one atrioventricular conduction during atrial pacing at rates of 300/minute in absence of Wolff-Parkinson-White Syndrome. Am J Cardiol 1981; 48:789. 28. Denes, P, Wu, et al. Demonstration of dual AV pathways in a patient with the Lown-Ganong- Levine syndrome. Chest 1974; 64:343. 29. Bauernfeind RA, Ayres BF, Wyndham CC, et al. Cycle length in atrioventricular nodal reentrant paroxysmal tachycardia with observations on the Lown-Ganong-Levine syndrome. Am J Cardiol 1980; 45:1148. 30. Ward DE, Camm J. Mechanisms of junctional tachycardias in the Lown-Ganong-Levine syndrome. Am Heart J 1983; 105:169. 31. Gallagher JJ, Pritchett EL, Sealy WC, et al. The preexcitation syndromes. Prog Cardiovasc Dis 1978; 20:285. 32. Wiener I. Syndromes of Lown-Ganong-Levine and enhanced atrioventricular nodal conduction. Am J Cardiol 1983; 52:637. 33. Holmes DR Jr, Hartzler GO, Maloney JD. Concealed retrograde bypass tracts and enhanced atrioventricular nodal conduction. An unusual subset of patients with refractory paroxysmal supraventricular tachycardia. Am J Cardiol 1980; 45:1053. https://www.uptodate.com/contents/lown-ganong-levine-syndrome-and-enhanced-atrioventricular-nodal-conduction/print 13/19 7/6/23, 11:14 AM Lown-Ganong-Levine syndrome and enhanced atrioventricular nodal conduction - UpToDate 34. Fisher JD. Role of electrophysiologic testing in the diagnosis and treatment of patients with known and suspected bradycardias and tachycardias. Prog Cardiovasc Dis 1981; 24:25. 35. Josephson ME. Paroxysmal supraventricular tachycardia: an electrophysiologic approach. Am J Cardiol 1978; 41:1123. 36. Myerburg RJ, Sung RJ, Castellanos A. Ventricular tachycardia and ventricular fibrillation in patients with short P-R intervals and narrow QRS complexes. Pacing Clin Electrophysiol 1979; 2:568. 37. Blanc, JJ, Fontaliran, et al. Electrophysiologic and histopathologic correlation (abstract). Pacing Clin Electrophysiol 1981; 4:A. 38. 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Topic 1000 Version 17.0 https://www.uptodate.com/contents/lown-ganong-levine-syndrome-and-enhanced-atrioventricular-nodal-conduction/print 14/19 7/6/23, 11:14 AM Lown-Ganong-Levine syndrome and enhanced atrioventricular nodal conduction - UpToDate GRAPHICS Types of accessory pathways Diagram of 4 types of abnormal conduction pathways: classic accessory atrioventricular pathway (red), atriofascicular pathway (green), fasciculoventricular pathway (light blue), and nodoventricular pathway (dark blue). The atrioventricular node and His-Purkinje system are represented in yellow. Atrioventricular, atriofascicular, and nodoventricular pathways are capable of supporting atrioventricular reciprocating tachycardias. In contrast, an isolated fasciculoventricular pathway can cause subtle preexcitation but does not support clinical tachycardia. Graphic 138850 Version 1.0 https://www.uptodate.com/contents/lown-ganong-levine-syndrome-and-enhanced-atrioventricular-nodal-conduction/print 15/19 7/6/23, 11:14 AM Lown-Ganong-Levine syndrome and enhanced atrioventricular nodal conduction - UpToDate Lown-Ganong-Levine syndrome The 12 lead ECG of a patient with the Lown-Ganong-Levine syndrome shows a short PR interval of 0.10 second and a normal QRS complex. Graphic 74221 Version 2.0 Sinus rhythm The normal P wave in sinus rhythm is slightly notched since activation of the right atrium precedes that of the left atrium. The P wave is upright in a positive direction in leads I and II. A P wave with a uniform morphology precedes each QRS complex. The rate is between 60 and 100 beats per minute and the cycle length is uniform between sequential P waves and QRS complexes. In addition, the P wave morphology and PR intervals are identical from beat to beat. Graphic 69872 Version 2.0 https://www.uptodate.com/contents/lown-ganong-levine-syndrome-and-enhanced-atrioventricular-nodal-conduction/print 16/19 7/6/23, 11:14 AM Lown-Ganong-Levine syndrome and enhanced atrioventricular nodal conduction - UpToDate Patterns of AV nodal conduction in EAVNC The atrial to His (A-H) interval, which represents atrioventricular (AV) nodal conduction time, is plotted against the pacing cycle length or A1-A2 interval. The normal response is a progressive lengthening of the AH interval with a shorter pacing cycle length (ie, faster heart rate), a phenomenon known as decremental conduction. In patients with enhanced AV nodal conduction (EAVNC), four patterns of response are seen. Type I represents reduced AH interval prolongation in response to atrial pacing; type II shows an initial increase in the AH interval followed by a plateau and then a further increase in the AH interval with faster pacing rates; type III reveals no change in AH interval in response to increasing atrial pacing rates; type IV represents no change in AH interval until the pacing cycle lengths are very short, thereby resulting in marked AH prolongation. Graphic 63880 Version 1.0 https://www.uptodate.com/contents/lown-ganong-levine-syndrome-and-enhanced-atrioventricular-nodal-conduction/print 17/19 7/6/23, 11:14 AM Lown-Ganong-Levine syndrome and enhanced atrioventricular nodal conduction - UpToDate AF in EAVNC The 12 lead ECG during sinus rhythm (panel A) in a patient with enhanced atrioventricular nodal conduction (EAVNC). The ECG shows a normal PR interval and QRS complex without evidence of preexcitation. During atrial fibrillation (AF) (panel B), there is a rapid ventricular response of up to 270 beats/min, a result of EAVNC and a short AV nodal refractory period. Graphic 81361 Version 1.0 https://www.uptodate.com/contents/lown-ganong-levine-syndrome-and-enhanced-atrioventricular-nodal-conduction/print 18/19 7/6/23, 11:14 AM Lown-Ganong-Levine syndrome and enhanced atrioventricular nodal conduction - UpToDate Contributor Disclosures Philip J Podrid, MD, FACC No relevant financial relationship(s) with ineligible companies to disclose. Peter J Zimetbaum, MD Consultant/Advisory Boards: Abbott Medical [Lead extraction]. All of the relevant financial relationships listed have been mitigated. Susan B Yeon, MD, JD, FACC No relevant financial relationship(s) with ineligible companies to disclose. Contributor disclosures are reviewed for conflicts of interest by the editorial group. When found, these are addressed by vetting through a multi-level review process, and through requirements for references to be provided to support the content. Appropriately referenced content is required of all authors and must conform to UpToDate standards of evidence. Conflict of interest policy https://www.uptodate.com/contents/lown-ganong-levine-syndrome-and-enhanced-atrioventricular-nodal-conduction/print 19/19