Khả năng của thiết bị đặc biệt sau là cần thiết để xác định các tiềm năng điện sau phức hợp QRS. Một kỹ thuật signalaveraging được sử dụng cho mục đích này (Hình 5,16) [25] Thông thường, rất ít khả năng có thể được xác định sau đây | 85 After-Potential Special equipment is needed to identify the electrical potential that follows the QRS complex. A signalaveraging technique is used for this purpose Fig. . 25 Normally very little potential can be identified following the QRS complex. Examples of Normal Electrocardiograms The electrocardiograms shown in Figures through are normal. The mean QRS vector is vertical in Figure intermediate in Figure and horizontal in Figure . Figure The electrocardiogram of a normal tall 37-year-old male with a vertical mean QRS vector. Note that the electrodes at positions V4 V5 and V6 are located near the transitional pathway for the mean QRS vector. Accordingly the QRS complex is nearly diphasic in all of these leads. Note the relationship of the mean initial QRS vector and the mean T vector to the mean QRS vector. I thank Dr. Philip Gainey for providing this electrocardiogram. 86 Figure The electrocardiogram of a normal medium-sized 27-year-old male with an intermediate mean QRS vector. The magnetic resonance images shown in Figures through are of the same subject. Note the relationship of the mean initial QRS vector and the mean T vector to the mean QRS vector. I thank Dr. Mark Lowell for providing this electrocardiogram. 87 Figure The electrocardiogram of a normal heavy-set broad-chested 31-year-old male with a horizontal mean QRS vector. Note the relationship of the mean initial QRS vector and the mean T vector to the mean QRS vector. I thank Dr. Curtis Weaver for providing this electrocardiogram. Comments about the apparently normal electrocardiogram. Considerable heart disease can be present without being revealed by the electrocardiogram. The best example is the patient with severe atherosclerotic heart disease who has been successfully resuscitated from an episode of ventricular fibrillation and has a normal resting electrocardiogram. I also wish to emphasize once again .
