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Heart Block

Heart Block. Garcia, Cholson Banjo E. Heart Blocks. Conduction disturbance Originate from: sinus node AV node bundle branch. Kinds of Blocks. Sinoatrial Block Atrioventricular Block Bundle Branch Block Fascicular Block. Sinoatrial Block.

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Heart Block

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  1. Heart Block Garcia, Cholson Banjo E.

  2. Heart Blocks • Conduction disturbance • Originate from: • sinus node • AV node • bundle branch

  3. Kinds of Blocks • Sinoatrial Block • Atrioventricular Block • Bundle Branch Block • Fascicular Block

  4. Sinoatrial Block • Impaired conduction from the SA node to the atria • No depolarization of the atria • Absence of PQRST complex

  5. Etiology • Increased vagal tone • Inferior wall MI • Age related degeneration • Drugs (digoxin, beta blockers, ccb, class IA-antiarrythmic) • Hyperkalemia • myocarditis

  6. RR interval: irregular (creating a pause, atria is blocked so it never depolarized • PP interval surrounding the pause is commonly multiple of the previous PP interval

  7. Atrioventricular Block • 1st degree AV block • 2nd degree AV block, Type 1 (Mobitz or Wenkebach) • 2nd degree AV block, Type 2 (Mobitz II) • 3rd degree AV block (CHB)

  8. 1st degree AV block • Prolonged conduction between the atria and the ventricles • Partial block within the AV node • Prolongation of the PR interval and preservation of the underlying rhythm

  9. Etiology • Drugs • Increased vagal tone • Hyperkalemia • MI (inferior wall) • Myocarditis • Degeneration of conducting pathways assoc. with aging • Idiopathic cause

  10. PR interval: > 0.20 seconds • Length of PR interval is constant • P wave is followed by a QRS complex

  11. 2nd degree AV block • Mobitz type I or Wenckebach • Intermittent conduction between the atria and ventricle • Found with the AV node

  12. Etiology • Digitalis • Escessive vagal tone • MI (inferior wall) • Ischemic heart disease • Myocarditis • Normal variant

  13. Progressive lengthening of the PR interval until a QRS complex is dropped; P wave appears on time, but no QRS follows • RR interval: irregular owing to drop beats causing the QRS complex to appear clustered together (narrow) • “Grouped Beating” • PP: constant

  14. 2nd degree AV block, Type II • Mobitz type II • Intermittent and sudden loss of conduction between atria and the ventricles • Found below the bundle of his • Can proceed to complete heart block • Ventricular rate tends to be slower and cardiac output diminishes

  15. Etiology • Acute Myocardial Infarction (anterior wall) • Drugs (digitalis, beta blocker, ccb) • Degeneration of electrical conduction system (assoc. with aging)

  16. PR interval: constant or fixed • QRS: wider than normal because of associated conduction block in ventricles • Conduction ratio varies (1:1, 2:1; 3:1) • PP: regular • RR: irregular

  17. 3rd degree AV block • Complete heart block • Complete absence of conduction between atria and ventricles

  18. Etiology • Drug toxicity (digoxin, beta blocker, ccb) • Excessive vagal tone • Acute MI • Age-related Degeneration of electrical conduction system • Myocarditis • Endocarditis • Cardiac Surgery • Congenital origin

  19. Atrial and ventricular rates are different • No relationship between P waves and the QRS complex • P waves appear but no QRS • PP and RR interval: constant

  20. Differentiating AV block • Look for 3 ECG patterns • Look for the RR interval. Regular or irregular? • Look at the P wave. Is there one or more P wave for every QRS • Look at the PR interval. Stay the same or change?

  21. If REGULAR (1st degree or 3rd degree) • Only 1 P wave for every QRS • PR interval stay the same • 1st degree • more than 1 P wave • PR interval changes • 3rd degree

  22. IRREGULAR ( 2nd degree) • PR interval change: 2nd degree AV block, TYPE I • PR interval stay the same: 2nd degree AV Block, TYPE II

  23. Bundle Branch Blocks • Defect in the intraventricular conduction • Supravetricular impulse: from the unblocked branch depolarizes one ventricle • Blocked branch: impluse spread slowly through the ventricular muscle resulting in abnormal depolarization • Hallmark: abnormal wide QRS complex

  24. Right bundle branch block • Conduction Delay in the right bundle branch • Etiology • RVH • Right ventricular strain • ASD • Wolf parkinson -white • Coronary artery disease • Myocarditis • Cardiac contusion • Idiopathic cause

  25. QRS complex: 0.12 or more in width • QRS is wide and positive assumes in lead V1 • rSR: leads V1 and V2 • Wide or Deep I, avL V5 and V6 • Down slopping of ST segment V1 and V2

  26. Left bundle branch block • Etiology • LVH • Cardiomyopathy • HPN • Wolf parkinson -white • Coronary artery disease • Myocarditis

  27. QRS complex: 0.12 or more in width • QRS is negative V1 and V2 • rSR (rabbit ear) in I, avL, V5, V6 • Wide or deep S V1 and V2 • Down slopping of ST segment I, avL, V5, V6

  28. Fasicular Block • Hemiblocks • Disturbed conduction in either the anterior or posterior division, or fasicle, of the left bundle branch

  29. Left Anterior Fasicular Block • Delay in the conduction through the anterior fascicle of the LBB • Anterior fascicle long thin and has a single blood supply, making it vulnerable to block

  30. Etiology • Coronary artery disease • MI • Congenital Heart disease • Cardiac surgery • Aging process • Normal variant

  31. QRS: prolonged (0.08-0.11) • Left axis deviation QRS axis (-45 and -90) • Small q wave and a tall R wave in lead I and avL • Small r wave and deep S wave in lead II, III and avF

  32. Left Posterior Fascicular Block • Delay in the conduction through the posterior fascicle of the LBB • Posterior: short, thick and has double blood supply • Appearance implies large amount of Myocardial injury has occurred

  33. Etiology • Coronary artery disease • MI • Congenital Heart disease • Cardiac surgery

  34. QRS: prolonged (0.08-0.11) • Right axis deviation QRS axis (+90 and +180) • Small q wave and a tall R wave in lead II, III and avF • Small r wave and deep S wave in lead I and avL

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