Heart block

In this ppt, I am going to discuss Heart block

1. Heart block Dr Praveen Gupta 05.12.2017 JIPMER Pondicherry India CLT students class 1

2. Atrioventricular block (heart block) An AV block exists if the atrial impulse is conducted with delay or is not conducted at all to the ventricle when the AV junction is not physiologically refractory During AV block, block can occur in AV node, His bundle, or bundle branches Disturbance of impulse conduction that can be permanent or transient 2 Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine, 10th Edition, Chpater 37, Page no 792-95

3. Classified by severity into three categories F irst-degree heart block, conduction is prolonged but all impulses are conducted Second-degree heart block in two forms, Mobitz type I ( Wenckebach ) and type II Type I heart block is characterized by progressive lengthening of the conduction time until an impulse is not conducted Type II heart block denotes an occasional or repetitive sudden block of conduction of an impulse, without prior measurable lengthening of conduction time. When no impulses are conducted, complete or third-degree block A dvanced or highgrade heart block,indicate blockage of two or more consecutive impulses 3 Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine, 10th Edition, Chpater 37, Page no 792-95

4. First-Degree Atrioventricular Block E very atrial impulse is conducted to the ventricles and a regular ventricular rate PR interval exceeds 0.20 second in adults. PR intervals can exceed the P-P interval, known as skipped P waves Result from a conduction delay in the AV node (A-H interval), in the His-Purkinje system (H-V interval), or at both sites Equally delayed conduction over both bundle branches Intra-atrial conduction delay can result in PR prolongation 4 Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine, 10th Edition, Chpater 37, Page no 792-95

5. First-Degree Atrioventricular Block QRS complex on the scalar ECG is normal, the AV delay in the AV node QRS complex shows a bundle branch block pattern, the conduction delay within the AV node or the His-Purkinje system Acceleration of the atrial rate or enhancement of vagal tone by carotid massage cause first-degree AV nodal block to progress to type I second-degree AV block 5 Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine, 10th Edition, Chpater 37, Page no 792-95

6. Second-Degree Atrioventricular Block Blocking of some atrial impulses conducted to the ventricle N onconducted P wave can be intermittent or frequent, occur at regular or irregular intervals, and be preceded by fixed or lengthening PR intervals Type I second-degree AV block is characterized by progressive PR prolongation culminating in a nonconducted P wave whereas in type II second-degree AV block, the PR interval remains constant before the blocked P wave 6 Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine, 10th Edition, Chpater 37, Page no 792-95

7. 3.2 AV block 7 © 01/12/2017, Department of cardiology, JIPMER, Pondicherry, India

8. Second-Degree Atrioventricular Block AV block is intermittent and repetitive and can block several P waves in a row Mobitz type I and Mobitz type II are applied to the two types of block Wenckebach block refers to type I block only Type I conduction disturbance can be difficultm to recognize. During a typical type I block, the increment in conduction time is greatest in the second beat of the Wenckebach group, and the absolute increase in conduction time decreases progressively over subsequent beats. 8 Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine, 10th Edition, Chpater 37, Page no 792-95

9. 2.1 AV block 9 © 2017, Department of cardiology, JIPMER, Pondicherry, India

10. Characteristics of classic Wenckebach group beats Interval between successive beats progressively decreases, although conduction time increases (but by a decreasing function ) D uration of the pause produced by the nonconducted impulse is less than twice the interval preceding the blocked impulse (which is usually the shortest interval ) C ycle that follows nonconducted beat (beginning the Wenckebach group) is longer than cycle preceding the blocked impulse Typical grouping occurs in < 50 % of patients with a type I Wenckebach AV block 10 Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine, 10th Edition, Chpater 37, Page no 792-95

11. Differentiation of Type I from Type II Atrioventricular Block A 2:1 AV block can be a form of type I or type II AV block If QRS is normal , block likely type I and in AV node, and search for transition of the 2:1 block to a 3:2 block, during which the PR interval lengthens in the second cardiac cycle If bundle branch block is present, block can be in AV node or His- Purkinje 11 Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine, 10th Edition, Chpater 37, Page no 792-95

12. Differentiation of Type I from Type II Atrioventricular Block First-degree and type I second-degree AV block can occur in normal healthy children, and a Wenckebach AV block normal in athletes due to increase in resting vagal tone In patients who have chronic second-degree AV nodal block (proximal to the His bundle) without structural heart disease, the course is relatively benig , whereas in those with structural heart disease, the prognosis is poor. 12 Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine, 10th Edition, Chpater 37, Page no 792-95

13. Third-Degree ( Complete) Atrioventricular Block No atrial activity is conducted to the ventricles A trial pacemaker can be sinus or ectopic (tachycardia, flutter, or fibrillation) or can result from AV junctional focus above the block with retrograde atrial conduction V entricular focus is located just below the region of the block, which can be above or below the His bundle bifurcation. Ventricular pacemaker closer to the His bundle stable and faster escape rate than can those located more distally in the conduction system. 13 Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine, 10th Edition, Chpater 37, Page no 792-95

14. Complete heart block 14 © 01/12/2017, Department of cardiology, JIPMER, Pondicherry, India

15. Third-Degree (Complete) Atrioventricular Block R esult from a block at AV node, bundle of His, Purkinje If block proximal to the His bundle, there will be normal QRS complexes at 40 to 60 beats/minute Intrahisian block poor prognosis Acquired complete AV block occurs most commonly distal to the bundle of His because of trifascicular conduction disturbance. QRS complex is abnormal, and ventricular rate < 40 beats/minute 15 Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine, 10th Edition, Chpater 37, Page no 792-95

16. Third-Degree (Complete) Atrioventricular Block Paroxysmal AV block caused by vagotonic reflexes Surgery , electrolyte disturbances , myoendocarditis , tumors , Chagas disease, rheumatoid nodules, calcific aortic stenosis, myxedema , polymyositis , infiltrative processes (e.g., amyloidosis, sarcoidosis, scleroderma) can produce AV block R apid rates sometimes followed by block (called tachycardia-dependent AV block), which is thought to be due to a phase 3 block (block caused by incomplete action potential recovery), postrepolarization refractoriness, and concealed conduction in the AV node 16 Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine, 10th Edition, Chpater 37, Page no 792-95

17. Third-Degree (Complete) Atrioventricular Block Pause-dependent paroxysmal AV block results in AV block after a pause or during relative bradycardia Referred to as a phase 4 block because it is thought that spontaneous depolarizations during the resting phase of the action potential result in an inability to depolarize, 17 Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine, 10th Edition, Chpater 37, Page no 792-95

18. Third-Degree (Complete) Atrioventricular Block In children AV block is congenital AV block can be an isolated finding or be associated with other lesions Neonatal autoimmune disease, account for most cases of heart block 18 Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine, 10th Edition, Chpater 37, Page no 792-95

19. Third-Degree (Complete) Atrioventricular Block Children are asymptomatic, some children, symptoms requiring pacemake Adams-Stokes attacks can occur H eart rate at rest 50 beats/minute or less correlates with the incidence of syncope Prolonged recovery times of escape foci after rapid pacing , slow heart rates on 24-hour electrocardiographic recordings, and the occurrence of paroxysmal tachycardias may be factors predisposing to the development of symptoms 19 Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine, 10th Edition, Chpater 37, Page no 792-95

20. Clinical Features First-degree AV block, long a to c wave interval in the jugular venous pulse Diminished first heart sound In type I second-degree AV block, the heart rate may increase imperceptibly with gradually diminishing intensity of the first heart sound; widening of the a to c interval, terminated by a pause; and an a wave not followed by a v wave. Intermittent ventricular pauses and a waves in the neck not followed by v waves characterize type II AV block. First heart sound maintains a constant intensity 20 Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine, 10th Edition, Chpater 37, Page no 792-95

21. Clinical Features In complete AV block, the findings are the same as those in AV dissociation Significant clinical manifestations of first- and second-degree AV block usually consist of palpitations or subjective feelings of the heart “missing a beat.” Persistent 2:1 AV block can produce symptoms of chronic bradycardia Complete AV block can be accompanied by signs and symptoms of reduced cardiac output, syncope or presyncope , angina , or palpitations from ventricular tachyarrhythmias 21 Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine, 10th Edition, Chpater 37, Page no 792-95

22. Management Holter or external loop recorders can be useful Longer periods of recording require an implantable loop recorder In patients with presyncope or syncope, one should suspect intermittent infra-His block in those with bundle branch block or an intraventricular conduction defect . An EP study to thoroughly evaluate AV conduction (including infusion of isoproterenol and/or procainamide) may be warranted to make the diagnosis, particularly in those with severe symptoms 22 Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine, 10th Edition, Chpater 37, Page no 792-95

23. Management Drugs cannot be relied on to increase the heart rate Temporary or permanent pacemaker for symptomatic bradyarrhythmias . For short-term therapy, atropine are useful Isoproterenol can be used transiently Symptomatic AV block or high-grade AV block (e.g., infrahisian , type II AV block, third-degree heart block not caused by congenital AV block), permanent pacemaker placement is the treatment of choice. 23 Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine, 10th Edition, Chpater 37, Page no 792-95

24. Thank you 24