ECG: UNDERSTANDING ACCELERATED CONDUCTION Dr. Krishnendu Maity BHMS [Calcutta] MD (Hom. Repertory) [Pune] Professor & HOD, Dept. of Medicine Teaching Medicine, Materia & Repertory Lal Bahadur Shastri Homœopathic Medical College, Bhopal – 26 (MP) Email: post.krishnendu2010@ymail.com

INTRODUCTION There are 02 types of accelerated conductions from the atrium to the ventricles; viz. Wolff-Parkinson-White (WPW) Syndrome / Pre-excitation Syndrome. Lown-Ganong-Levine (LGL) Syndrome.

WPW SYNDROME Bundle of Kent by-pass the AV node or by Mahaim fibes – which goes from Bundle of His to Ventricular Septum. The pre-excitation of ‘Bundle of Kent’ is called WPW Syndrome. The atrial impulse passes through the normal path of conduction and also through the anterior intra-nodal fibre [Bachmann’s fibre / Bundle of Kent], simultaneously.

CLASSIFICATION OF WPW SYNDROME WPW Syndrome is of 02 types ---- Type A: where excitation travels along Left accessory pathway – giving rise to RVH / RBBB. Type B: where excitation travels along Right lateral accessory pathways – giving rise to LBBB. If it is associated with Cyanotic CHD – Ebstein’s Anomaly is diagnosed.

ECG OF WPW Syndrome Short P-R interval [less than 0.12 sec.]. Wide QRS complex. Appearance of -wave / slurred upstroke of QRS. Normal P-wave axis.

CAUSES OF WPW Syndrome Normal individuals. Myocardial Infarction. Acute Rheumatic Fever. CHD – Ebstein’s Anomaly. Cardiac catheterization / Surgical manipulation of Heart. Hypertrophic Sub-aortic Stenosis. Idiopathic Cardiomyopathy. Thyrotoxicosis.

WPW SYNDROME WITH ATRIAL FIBRILLATION Irregularly irregular, wide complex tachycardia. Impulses from the atria are conducted to the ventricles via either both the AV node and Accessory pathway producing a broad fusion complex. or just AV node producing a narrow complex (without -wave). or just Accessory pathway producing a very broad 'pure' - wave. People who develop this rhythm and have very short R-R intervals are at higher risk of VF.

LGL Syndrome James Accesory Tract / Bundle of James by-pass the upper part of the AV node. The pre-excitation of the ‘Bundle of James’ is called LGL Syndrome. The artrial impulse preferentially passes through the posterior intra-nodal fibre [Thorel’s fibre / Bundle of James] and conducted to His Bundle. Pateints of this syndrome are prone to develop Supra-ventricular arrhythmias, ventricular tachycardia & Ventricular fibrillation.

ECG OF LGL Syndrome Short P-R interval. Normal QRS complex. Normal T-wave. No -wave.

LGL SYNDROME WITH ATRIAL FIBRILLATION Short PR interval [less than 3 small squares]. No -wave.

REFERENCES Das, Dr. P. C. – Textbook of Medicine [Reprint April, 1995; Current Book International]. Ganong, Dr. William F. – Review of Medical Physiology (22ND edition, 2005; McGraw Hill). Mehta, Dr. P. J. – Understanding ECG [Reprint 6TH edition, 2008; The National Book Depot].

THANKS TO ALL ------