tailieunhanh - Ebook Swanton’s cardiology (6/E): Part 2

(BQ) Part 2 book “Swanton’s cardiology” has contents: Disturbances of cardiac rhythm - tachycardias and ablation, infective endocarditis, pericardial disease, the heart in systemic disease, systemic hypertension, pulmonary hypertension and pulmonary embolism, cardiac investigations, and other contents. | CHAPTER 7 7 Disturbances of Cardiac Rhythm: Bradycardias, Pacing, the ICD, Biventricular Pacing for Heart Failure Indications for Temporary Pacing AV Block in Acute MI Complete AV block (Figure ) In inferior infarction, complete AV block usually results from right coronary artery occlusion. The AV nodal artery is a branch of the right coronary artery. Second-degree AV block (Wenckebach type) does not always represent AV nodal artery occlusion because vagal hyperactivity may play a part. A localized, small inferior infarct may thus cause complete AV block. In anterior infarction, complete AV block usually represents massive septal necrosis with additional circumflex artery territory damage. The prognosis in complete AV block is dependent on infarct size and site rather than the block itself. Complete AV block in either type of infarction should be temporarily paced. Second-degree AV Block (Figure ) • Wenckebach (Mobitz type I): incremental increases in PR interval with intermittent complete blocking of the P wave. This is decremental conduction at the AV node level. In inferior infarction it does not necessarily require pacing unless the bradycardia is poorly tolerated by the patient. It may respond to atropine. In anterior infarction, Wenckebach AV block should be temporarily paced. • Mobitz type II AV block: fixed PR interval with sudden failure of conduction of atrial impulse (blocking of the P wave). Often occurs in the presence of a wide QRS because this type of block is usually associated with distal fascicular disease. It carries a high risk of developing complete AV block. It Swanton’s Cardiology: A concise guide to clinical practice Sixth Edition By R. H. Swanton and S. Banerjee © 2008 R H Swanton and S Banerjee. ISBN: 978-1-405-17819-8 310 Bradycardias, Pacing, the ICD, Biventricular Pacing for Heart Failure 311 Figure Second- and third-degree AV block. usually occurs in association with anterior infarction, but should be .

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