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PRINCIPLES OF INTERNAL MEDICINE - PART 5

bình thường chức năng tâm thu thất. Malposition của bộ máy van hai lá, một kết quả của vách ngăn bị bóp méo, thường dẫn đến một số mức độ của trào ngược van hai lá. VII-37. Câu trả lời là B. (226 Chaps., 230) Một làn sóng đồng bằng hoặc bị chậm nét nhỏ trong một chư QRS được mô tả. | VII. Disorders of the Cardiovascular System Answers 155 normal ventricular systolic function. Malposition of the mitral apparatus a result of the distorted septum often leads to some degree of mitral regurgitation. VII-37. The answer is B. Chaps. 226 230 A delta wave or slowed QRS upstroke is depicted. This finding occurs in the Wolff-Parkinson-White syndrome in which accessory Kent bundles result in an apparently short PR interval caused by the l y j issed AV node arid early onset of the QRS complex. Left bundle branch block could result in marked initial delay whereas right bundle branch block results in late delay. Left ventricular hypertrophy causes minor uniform QRS prolongation. Right ventricular infarction has little effect on QRS duration in the absence of right bundle branch block. VII-38. The answer is B. Chap. 226 Alterations in the serum potassium level can dramatically alter the electrocardiogram. Hyperkalemia can produce a progressive evolution of changes in the electrocardiogram which can ultimately lead to ventricular fibrillation and death. The presence of electrocardiographic changes is probably a better measurement of clinically significant potassium toxicity than is the serum potassium level. As the serum potassium begins to rise the T waves across the entire 12-lead ECG begin to peak. This affect can easily be confused with the peaked T waves of an acute myocardial infarction. The difference is that the changes in an infarction are confined to those leads overlying the area of the infarct. In hyperkalemia the changes are widespread. With continued increase in the serum potassium level the PRinterval becomes progressively prolonged and the P waves gradually flatten. Ultimately the QRS complex will widen until it merges with the T wave forming a sine-wave pattern and ventricular fibrillation may eventually develop. Any change in the ECG that is due to hyperkalemia mandates immediate clinical intervention. VII-39. The answer is B. Chap. 239 Acute