General principles of asynchronous activation and preexcitation
- Bradley P Knight, MD, FACC
Bradley P Knight, MD, FACC
- Section Editor — Cardiac Arrhythmias
- Professor of Medicine
- Feinberg School of Medicine, Northwestern University
Normal electrical activation of the right and left ventricles during the cardiac cycle follows a precisely defined pattern. After an impulse emerges from the atrioventricular (AV) node, it traverses the His bundle, and propagates down the bundle branches and the fascicles of the bundle branches to the terminal Purkinje fibers and ultimately the ventricular myocardium.
Conduction abnormalities result in asynchronous electrical activation causing asynchronous mechanical activation of the ventricles. This problem can be induced by one of two mechanisms: delayed activation of an area of the ventricles or early activation (preexcitation) of an area of the ventricles.
This topic will present an overview of asynchronous activation and preexcitation. The clinical manifestations of abnormal activation or preexcitation are discussed in detail separately. (See "Right bundle branch block" and "Left bundle branch block" and "Left anterior fascicular block" and "Left posterior fascicular block" and "Atrioventricular reentrant tachycardia (AVRT) associated with an accessory pathway".)
Delayed activation causes asynchronous activation and may be a result of anatomic abnormalities or of physiologic properties of the cardiac tissues. Activation delay may occur between the ventricles or portions of the ventricles (interventricular delay), within the terminal Purkinje fibers and/or ventricular myocardium (intraventricular delay) or between layers of the heart (intramural delay) .
Clinically, conduction delay causing ventricular electrical dyssynchrony is manifest as an abnormal QRS complex on the electrocardiogram (ECG). Specific ECG patterns that are clinically distinguished include right bundle branch block (RBBB), left bundle branch block (LBBB), a prolonged QRS complex without specific features of LBBB or RBBB (usually called "intraventricular conduction delay" or IVCD), left anterior hemiblock, and left posterior hemiblock. While all of these conduction patterns are sometimes referred to collectively as forms of intraventricular conduction delay, the precise location of the conduction disturbance cannot be reliably determined from the surface ECG. In the case of RBBB and LBBB, it is probably more accurate to refer to these entities as forms of "interventricular conduction delay."To continue reading this article, you must log in with your personal, hospital, or group practice subscription. For more information on subscription options, click below on the option that best describes you:
- Auricchio A, Fantoni C, Regoli F, et al. Characterization of left ventricular activation in patients with heart failure and left bundle-branch block. Circulation 2004; 109:1133.
- Durrer D, van Dam RT, Freud GE, et al. Total excitation of the isolated human heart. Circulation 1970; 41:899.
- Van Dam RT, Janse MJ. Activation of the Heart. In: Comprehensive Electrocardiology: Theory and Practice in Health and Disease, MacFarlane P, Veitch Lawrie TD (Eds), Pergamon Press, New York 1980. p.101.
- Kent, AF . Researches on the structure and function of the mammalian heart. J Physiol 1893; 14:233.
- Anderson RH, Becker AE, Brechenmacher C, et al. Ventricular preexcitation. A proposed nomenclature for its substrates. Eur J Cardiol 1975; 3:27.
- Boineau JP, Moore EN. Evidence for propagation of activation across an accessory atrioventricular connection in types A and B pre-excitation. Circulation 1970; 41:375.
- JAMES TN. Morphology of the human atrioventricular node, with remarks pertinent to its electrophysiology. Am Heart J 1961; 62:756.
- MAHAIM I. Kent's fibers and the A-V paraspecific conduction through the upper connections of the bundle of His-Tawara. Am Heart J 1947; 33:651.
- Lev M, Fox SM 3rd, Bharati S, et al. Mahaim and James fibers as a basis for a unique variety of ventricular preexcitation. Am J Cardiol 1975; 36:880.
- Klein GJ, Guiraudon G, Guiraudon C, Yee R. The nodoventricular Mahaim pathway: an endangered concept? Circulation 1994; 90:636.
- Sternick EB, Gerken LM, Vrandecic MO, Wellens HJ. Fasciculoventricular pathways: clinical and electrophysiologic characteristics of a variant of preexcitation. J Cardiovasc Electrophysiol 2003; 14:1057.
- Josephson ME. Clinical Cardiac Electrophysiology: Techniques and Interpretations, 2d ed, Lea & Febiger, Philadelphia 1993.
- LOWN B, GANONG WF, LEVINE SA. The syndrome of short P-R interval, normal QRS complex and paroxysmal rapid heart action. Circulation 1952; 5:693.
- Denes P, Wu D, Amat-y-Leon F, et al. The determinants of atrioventricular nodal re-entrance with premature atrial stimulation in patients with dual A-V nodal pathways. Circulation 1977; 56:253.
- Benditt DG, Pritchett LC, Smith WM, et al. Characteristics of atrioventricular conduction and the spectrum of arrhythmias in lown-ganong-levine syndrome. Circulation 1978; 57:454.
- Bauernfeind RA, Swiryn S, Strasberg B, et al. Analysis of anterograde and retrograde fast pathway properties in patients with dual atrioventricular nodal pathways: observations regarding the pathophysiology of the Lown-Ganong-Levine syndrome. Am J Cardiol 1982; 49:283.
- Zivin A, Morady F. Incessant tachycardia using a concealed atrionodal bypass tract. J Cardiovasc Electrophysiol 1998; 9:191.
- Wellens HJJ. The preexcitation syndrome. In: Electrical Stimulation of the Heart, Wellens HJJ (Ed), University Park Press, Baltimore 1971. p.97.
- Gillette PC, Garson A Jr, Cooley DA, McNamara DG. Prolonged and decremental antegrade conduction properties in right anterior accessory connections: Wide QRS antidromic tachycardia of left bundle branch block pattern without Wolff-Parkinson-White configuration in sinus rhythm. Am Heart J 1982; 103:66.
- Klein GJ, Guiraudon GM, Kerr CR, et al. "Nodoventricular" accessory pathway: evidence for a distinct accessory atrioventricular pathway with atrioventricular node-like properties. J Am Coll Cardiol 1988; 11:1035.
- McClelland JH, Wang X, Beckman KJ, et al. Radiofrequency catheter ablation of right atriofascicular (Mahaim) accessory pathways guided by accessory pathway activation potentials. Circulation 1994; 89:2655.
- Cappato R, Schlüter M, Mont L, Kuck KH. Anatomic, electrical, and mechanical factors affecting bipolar endocardial electrograms. Impact on catheter ablation of manifest left free-wall accessory pathways. Circulation 1994; 90:884.
- Grogin HR, Lee RJ, Kwasman M, et al. Radiofrequency catheter ablation of atriofascicular and nodoventricular Mahaim tracts. Circulation 1994; 90:272.
- Li HG, Klein GJ, Thakur RK, Yee R. Radiofrequency ablation of decremental accessory pathways mimicking "nodoventricular" conduction. Am J Cardiol 1994; 74:829.
- Mantovan R, Verlato R, Corrado D, et al. Orthodromic tachycardia with atrioventricular dissociation: evidence for a nodoventricular (Mahaim) fiber. Pacing Clin Electrophysiol 2000; 23:276.
- Gallagher JJ, Smith WM, Kasell JH, et al. Role of Mahaim fibers in cardiac arrhythmias in man. Circulation 1981; 64:176.
- Ott P, Marcus FI. Familial Mahaim syndrome. Ann Noninvasive Electrocardiol 2001; 6:272.
- Shih HT, Miles WM, Klein LS, et al. Multiple accessory pathways in the permanent form of junctional reciprocating tachycardia. Am J Cardiol 1994; 73:361.
- DELAYED ACTIVATION
- Interventricular conduction delay
- Intraventricular and intramural conduction delay
- Genesis of ECG pattern
- - Magnitude
- - Duration
- General anatomic considerations
- Atrioventricular accessory pathways (connections)
- James fibers (intranodal or atrionodal bypass tract)
- - Lown-Ganong-Levine syndrome
- - Reentrant SVT
- Role of Mahaim fibers
- Classification of arrhythmias associated with accessory pathways
- Preexcited tachycardias