血管内超声基础知识阜外医院 钱杰,南方会2008,血管内超声基础知识,一、血管内超声基础 二、血管内超声和冠脉造影的关系 三、主要适应症 四、什么是VH,南方会2008,Rotating Element,Drive Shaft,Multi-element Array,There are two types of imaging systems: Mechanical (rotating transducer) and Electronic Array,南方会2008,High frequency sound waves echo off vessel walls and are sent back to system,System electronics process the signal,南方会2008,Intimal disease (plaque) is dense and will appear white Media is made of homogeneous smooth muscle cells and does not reflect ultrasound (appears dark) Adventitia has sheets of collagen that reflect a lot of ultrasound (appears white),南方会2008,南方会2008,Calcium,Bright echoes (brighter than the adventitia) Obstructs the penetration of ultrasound (acoustic shadowing) only the leading edge is detected and thickness cannot be determined. Results in reverberations - the oscillation of ultrasound between transducer and calcium causing repeating arcs,南方会2008,Calcium is quantified by measuring the “arc” it encompasses Calcium is classified by its location within the plaque Superficial calcium is closer to the lumen than to the adventitia Deep calcium is closer to the adventitia than to the lumen,南方会2008,Fibrotic Plaque,As bright or brighter than the adventitia (hyperechoic) Majority of atherosclerotic lesions are fibrotic Very dense, fibrous plaques may cause so much acoustic shadowing that they could be misclassified as calcified,南方会2008,Soft Plaque,Not as bright as the adventitia (hypoechoic) “Soft” refers to the low echogenicity, generally due to high lipid content in a mostly cellular lesion. Reduced echodensity may also be due to: necrotic zone within plaque intramural hemorrhage thrombus,南方会2008,Vulnerable Plaque,Fibrous Cap,Lipid Core,南方会2008,Mixed Plaque,南方会2008,0,1,4mm,Example of Thrombus,南方会2008,Basic Measurements (I),External elastic membrane (EEM) cross sectional area (CSA) = total arterial CSA = media area tracing the boundary between the dark media and the bright adventitia (i.e., the apparent outer edge of the media stripe) Lumen CSA Max and min lumen diameters Stent CSA Max and min stent diameters Plaque+media (P+M) CSA = EEM - Lumen CSA in non-stented lesions = EEM - stent CSA in stented lesions Intimal hyperplasia CSA = Stent - Lumen CSA,南方会2008,Basic Measurements (II),Eccentricity = maximum/minimum P+M thickness Plaque Burden (=cross-sectional narrowing or %plaque area) = P+M/EEM CSA Remodeling Index = Lesion/Reference EEM CSA Area Stenosis = (Reference - Lesion)/Reference Lumen CSA Arc of calcium Lesion lengths measured using motorized transducer pullback, ideally at 0.5 mm/sec,南方会2008,Non-stented artery,南方会2008,Stented Artery,南方会2008,Proximal Reference,Lesion Site,Distal Reference,EEM,Lumen,P+M,Max P+M Thickness,Min P+M Thickness,Ca+,南方会2008,Proximal Reference,Lesion Site,Distal Reference,EEM CSA = 20.4 Lumen CSA = 9.7 Max lumen diam = 3.7 MLD = 3.1 P+M CSA = 10.7 Eccentricity = 1.0/0.3 Plaque burden = 0.52 Arc of Ca = 60,EEM CSA = 21.6 Lumen CSA = 4.5 Max lumen diam = 32.8 MLD = 2.3 P+M CSA = 17.1 Eccentricity = 3.0/0.1 Plaque burden = 0.79,EEM CSA = 13.3 Lumen CSA = 8.9 Max lumen diam = 3.6 MLD = 3.0 P+M CSA = 4.4 Eccentricity = 0.6/0.2 Plaque burden = 0.33,Average Reference EEM CSA = 16.9 Remodeling Index = 1.3 Average Reference Lumen CSA = 9.3 Area Stenosis = 52%,南方会2008,In-Stent Restenosis,In-stent intimal hyperplasia (IH) often appears with a very low echogenicity Could be less echogenic than the blood speckle Appropriate system settings are critical to visualize IH (do not “black out” center),南方会2008,血管内超声基础知识,一、血管内超声基础 二、血管内超声和冠脉造影的关系 三、主要适应症 四、什么是VH,南方会2008,Limitations of Coronary Angiography,Focal Disease,50% Lesion,50% Lesion,Diffuse Disease,Angiogram Silhouette,南方会2008,Angiographically Silent Disease,In 884 native coronary arteries, the plaque burden in the angiographically “normal” reference segment was 5113%,Mintz GS, et al. J Am Coll Cardiol 1995;25:1479-1485,南方会2008,Coronary Remodeling Hypothesis,Compenatory Expansion Maintains Consistant Lumen,Expansion Overcome: Lumen Narrows,Normal Vessel,Minimal CAD,Moderate CAD,Severe CAD,南方会2008,Proximal reference,Lesion,Distal reference,Intermediate,remodeling,Negative,remodeling,Positive,remodeling,Nishioka. JACC 1996; 27:1571-1576,Dicotomous Classification of Remodeling,南方会2008,Irregular Plaque / Irregular Lumen,A,Cross-section,RAO View,LAO View,B,C,南方会2008,IVUS EEM CSA = 22.7mm2 Lumen CSA = 16.6mm2 Mean lumen diameter = 4.6mm,QCA 9F guiding catheter Reference diameter = 3.12mm,南方会2008,血管内超声基础知识,一、血管内超声基础 二、血管内超声和冠脉造影的关系 三、主要适应症 四、什么是VH,南方会2008,Validation of IVUS Assessment of Ischemia Producing Stenosis (Doppler FloWire and SPECT),Diagnostic accuracy = 92%. Abizaid et al, AJC 1998;82:42-8,Diagnostic accuracy = 93%. Nishioka et al, JACC 1999;33:1870-8,南方会2008,IVUS Criteria for a Significant Stenosis,Based on the studies comparing IVUS to flow wire, pressure wire, or SPECT thallium and based on studies with clinical outcome - most feel that a lumen area less than 4.0 mm2 in a proximal epicardial artery excluding the Left Main is a flow limiting stenosis,