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Twelve-Lead Electrocardiography - Part 7

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Độ cao hơn của khối tim xảy ra với nhồi máu cơ tim trước thực hiện một tiên lượng xấu bởi vì họ thường là kết quả của nhồi máu hoại tử rộng rãi với các vách ngăn tâm thất và đóng gói của ông chi nhánh bó. | 100 Chapter 11 The Electrocardiogram and the Clinical Evaluation of Chest Pain Higher degrees of heart block occurring with anterior myocardial infarction carry a bad prognosis because they are usually the result of extensive infarction with necrosis of the ventricular septum and the bundle of His or the bundle branches. Pacing is usually required for these higher degrees of heart block but rarely alters outcome because these patients typically die of pump failure as a consequence of the extensive nature of the infarction. Inferior Wall STEMI Inferior myocardial infarction occurs with occlusion of the right coronary artery. It is commonly associated with a significant vasovagal response characterized by marked sinus bradycardia and hypotension that is usually responsive to atropine and volume expansion. Sinus bradycardia may be further aggravated by a diminution in perfusion to the SA node. AV block when seen with inferior myocardial infarction is typically lower grade first degree or Mobitz type I and is the result of edema of the AV node as opposed to necrosis. Because the level of block is in the AV node even when block advances to third degree there is typically a reliable junctional escape rhythm present. Pacing is not usually required and symptomatic bradycardia can usually be adequately treated with atropine. Pump failure is less often a problem than with anterior myocardial infarction unless the patient has a more extensive than usual right coronary circulation or has lost muscle mass from a previous myocardial infarction. Patients presenting with evidence of inferior myocardial infarction and isolated right heart failure jugular venous distention and hypotension with clear lungs should also have an ECG with V3 and V4 placed in their corresponding positions on the right side of the chest to rule out a right ventricular infarction. Role of Serial ECGs and Continuous ST-Segment Monitoring Earlier in this chapter we discussed how the ECG may be negative in the