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  1. 1. THE ELECTROCARDIOGRAM Professor A. gowri shankar `s unit Presented by Dr. Ramesh unit -2
  2. 2. History <ul><li>Mr . Ranganathan 60/male, </li></ul><ul><li>a known hypertensive – 10yrs. </li></ul><ul><li>not a known DM / CAD. </li></ul><ul><li>no specific complaints. </li></ul>
  4. 4. <ul><li>Standardization and technical features are normal. </li></ul><ul><li>HR – 94/min </li></ul><ul><li>Rhythm – sinus. </li></ul><ul><li>P wave- normal </li></ul><ul><li>PR interval -(180 ms). </li></ul><ul><li>QRS DURATION- (0.13 s) . </li></ul><ul><li>mean QRS electrical axis (-70 to -60 ´ ). </li></ul><ul><li>QRS configuration – rSR pattern in lead V1 & slurring of S wave in V6. </li></ul><ul><li>qR pattern in lead 1 & aVL, `r S`pattern in lead II, III & aVF </li></ul><ul><li>QT interval-normal. </li></ul><ul><li>No abnormal Q waves / ST segment elevation </li></ul>ECG interpretation Name – Mr. Ranganathan, 60/m. Date - 19/6/11
  5. 5. The Electrical System of the Heart AV Node Posterior Inferior Fascicle Anterior Superior Fascicle Septal Depolarization Fibers Purkinjie Fibers Inter- nodal Tracts Bundle of HIS Left Bundle Branch Right Bundle Branch SA Node
  6. 6. <ul><li>RBBB </li></ul><ul><li>The impulse is transmitted normally by left bundle to most of left ventricle </li></ul><ul><li>Impulse to part of interventricular septum and RV delayed, because of cell to cell depolarization </li></ul><ul><li>Slow impulse causes slower depolarization time. </li></ul><ul><li>LAFB </li></ul><ul><li>  Depolarization of left ventricle has to progress from interventricular septum, inferior wall, and posterior wall toward anterior and lateral walls </li></ul><ul><li>Gives rise to unopposed vector pointed superior and leftward </li></ul><ul><li>Changes net axis of ventricles toward left, producing left axis deviation </li></ul><ul><li>Electrical axis of ventricles found in left quadrant of hexaxial system, between –30˚ and –90˚. </li></ul>
  7. 7. <ul><li>A typical RBBB ECG </li></ul><ul><li>wide QRS complexes with a terminal R wave in lead V1 & </li></ul><ul><li>slurred S wave in lead V6. </li></ul>CRITERIA FOR RBBB CRITERIA FOR LAFB <ul><li>The heart rhythm must originate above the ventricles (i.e. SA node, AVnode) to activate the conduction system at the correct point. </li></ul><ul><li>The QRS duration >100 ms (incomplete block) or >120 ms (complete block) [3] </li></ul><ul><li>terminal R wave in lead V1 (e.g. R, rR', rsR', rSR' or qR) </li></ul><ul><li>slurred S wave in leads I and V6 </li></ul><ul><li>Abnormal left axis deviation ( usually bt –45° and –60°) </li></ul><ul><li>qR complex in the lateral limb leads (I and aVL) & rS pattern in the inferior leads (II, III, and aVF) </li></ul><ul><li>Delayed intrinsicoid deflection in lead aVL (> 0.045 s) </li></ul><ul><li>left anterior fascicular block together with right bundle branch block is indicative of ischaemia </li></ul>
  8. 9. Causes of RBBB Causes of LAFB <ul><li>Normal variant. </li></ul><ul><li>Cor pulmunale. </li></ul><ul><li>Pulmonary embolism. </li></ul><ul><li>MI, CMP`S, HHD,CHD </li></ul><ul><li>Mechanical damage. </li></ul><ul><li>Lev`s disease. </li></ul><ul><li>Chronic hypertension </li></ul><ul><li>Aortic stenosis </li></ul><ul><li>Aortic root dilation </li></ul><ul><li>Dilated cardiomyopathy </li></ul><ul><li>Impairment of the cardiac electrical conduction system </li></ul><ul><li>Acute myocardial infarction </li></ul><ul><li>Lung diseases </li></ul><ul><li>Aging </li></ul><ul><li>Degenerative fibrotic disease </li></ul>
  9. 10. Combination of RBBB & LAFH on ECG <ul><li>Slurred S wave in lead I & V 6. </li></ul><ul><li>rabbit ear pattern in V 1 of RBBB w/delayed QRS complex of 0.12 sec or more </li></ul><ul><li>Left axis deviation & rS waves in lead III are typical of LAFB </li></ul>
  10. 11. DISCUSSION <ul><li>LAFB is far more common than LPFB why ? </li></ul><ul><li>The traditional explanations are  </li></ul><ul><li>Anterior fascicle is relatively sub epicardial in location </li></ul><ul><li>It is a  long and thin  structure prone to damage easily </li></ul><ul><li>Exposed to the mechanical   stress of   LVOT </li></ul><ul><li>Anterior fascicle has  only a single blood supply(LAD) </li></ul><ul><li>Clinical Significance of LAFB </li></ul><ul><ul><li>seen in approximately 4% of acute MI </li></ul></ul><ul><ul><li>It is the most common type of intraventricular conduction defect seen in acute anterior MI, and the left anterior descending artery is usually the culprit vessel. </li></ul></ul><ul><ul><li>It can be seen with acute inferior wall MI . </li></ul></ul>