một đề nghị bảo thủ hướng dẫn liên quan Gradient siêu âm Doppler mức độ nghiêm trọng của hẹp động mạch chủ (AS) ở người lớn với sản lượng tim bình thường và nhịp tim bình thường trung bình được thể hiện trong Bảng 53,3. Một đề nghị phân loại mức độ hẹp động mạch chủ được đưa ra | Indications for surgery in aortic valve disease stenosis these patients should be considered as having severe stenosis. Since gradients are frequently measured initially by Doppler ultrasound a suggested conservative guideline for relating Doppler ultrasound gradient to severity of aortic stenosis AS in adults with normal cardiac output and normal average heart rate is shown in Table . A suggested grading of the degree of aortic stenosis is given in Table . Table Doppler ultrasound gradient as an Indicator of severe aortic stenosis AS Peak gradient Mean gradient AS severe 80mmHg 70 mmHg High likely 60-79 mmHg 50-69 mmHg Probable 60 mmHg 50 mmHg Uncertain From Rahimtoola 15 with permission Table Grading of stenosis by aortic valve area AVA Aortic stenosis AVA cm2 AVA index cm2 m2 Mild 1-5 0-9 Moderate 1-1-1-5 0 6-0 9 Severea 1-0 0 6 a Patients with AVAs that are at borderline values between the moderate and severe grades 0 9-1 1 cm2 0 55-0 65cm2 m2 should be individually considered. From Rahimtoola15 with permission Natural history The duration of the asymptomatic period after the development of severe aortic stenosis is uncertain. In a study of asymptomatic patients with varying degrees of severity of aortic stenosis 21 of 143 patients18 with a mean age of 72 years required valve replacement within 3 months of evaluation at a referral center. At 2 years the mortality was 10 and the event rate death valve replacement in the remaining patients was 26 . Moreover it is important to recognize that most patients in this study had only moderate aortic stenosis. In another study of 123 asymptomatic adults 7 also with varying grades of severity of aortic stenosis aged 63 16 years only the actuarial probability of death or aortic valve surgery is provided. It was 7 5 at 1 year 38 8 at 3 years and 74 10 at 5 years. The event rate at 2 years for aortic jet velocity by Doppler ultrasound of 4-0 m s peak gradient by Doppler ultrasound 64 mmHg was 79 18 for a .
