Coronary Thrombus Grading SystemsTh

Coronary Thrombus Grading Systems

Thrombus grading scales are essential tools used for qualification and quantification of the thrombus burden. They provide a platform for clinical assessment and subsequently effect management decisions prior to and during interventions. The widely used TIMI thrombus grading scale was originally created by the TIMI study group investigators.[24] The introduction of this universal classification reflected a growing recognition among cardiologists that the yield of thrombolytic therapy for evolving AMI was defined by different size and burden of intracoronary thrombi. Altogether, the TIMI classification relies on the angiographic assessment of the presence of thrombus and its relative size, utilizing a simple score ranging from grade 0 (no thrombus), to grade 5 (very large thrombus content that completely occludes vessel flow; ).


Box 1. The TIMI thrombus scale.




•Grade 0: no angiographic evidence of thrombus


•Grade 1: angiographic features suggestive of thrombus

◦Decreased contrast density


◦Haziness of contrast


◦Irregular lesion contour


◦A smooth convex meniscus at the site of a total occlusion


◦Suggestive, but not firmly diagnostic of thrombus




•Grade 2: definite thrombus present in multiple angiographic projections

◦Marked irregular lesion contour with a significant filling defect – the thrombus' greatest dimension is 1/2 to 2 vessel diameters




•Grade 5: definite complete thrombotic occlusion of a vessel

◦A convex margin that stains with contrast, persisting for several cardiac cycles





TIMI: Thrombolysis in myocardial infarction.
Data taken from [24].

While this classification is user friendly and universally accepted, the accuracy of the highest level, grade 5, is subject to interpretation challenges. With its hallmark characteristic of TIMI 0 flow, the ischemic vessel containing grade 5 thrombus is totally occluded. Consequently, the histological relationship between the underlying plaque burden and thrombus content is unknown, yet this grade supposedly represents the highest thrombus load. Notably, such assumptions may be erroneous and, in fact, lead to faulty decisions concerning the potential of percutaneous revascularization to open the occluded vessel. Thus, in order to overcome the abovementioned limitation of TIMI grade 5, an important modification was recently introduced by the Thoraxcenter (Rotterdam, The Netherlands) investigators.[25] Focusing on this specific grade, they added a much needed critical step to the reclassification that significantly improves the determination of the correct load of the underlying thrombus (). Their method utilizes either a guide wire or a 1.5 mm balloon for crossing and recanalization of the target thrombus. This intervention re-establishes a certain degree of antegrade coronary flow to the extent that the exposed underlying thrombus can undergo restratification into either a small thrombus burden (grade 1–3) or a large thrombus burden (grade 4) with treatment ensuing accordingly (Figure 2). In most instances a stratified small-grade thrombus can be managed with an aspiration catheter followed by implantation of a thrombus-capturing stent or with pharmacologic agents.[26] The larger size clot requires a dedicated mechanical thrombectomy device for removal. Options for the task vary from rheolytic thrombectomy to X-Sizer or excimer laser[27,28] and subsequent stenting, preferably, again, with a thrombus-capturing stent.[29] The merit of the new reclassification extends beyond the original application for AMI, and this method can be used in all encounters of grade 5 thrombus in patients with ischemic coronary syndromes.


Box 2. Restratification of thrombolysis in myocardial infarction grade 5 thrombus.




•Angiographic detection of a grade 5 TIMI thrombus leads to further exploration of the occlusive thrombotic content. Either a PCI guide wire, or a small balloon, is advanced across the thrombotic total occlusion. Crossing the thrombus results in restoration of antegrade flow in the treated vessel. Consequently, the ensuing coronary angiogram enables restratification of the underlying residual thrombus as follows:

◦No residual thrombus – grade 0


◦Small residual thrombus – grade 1–3


◦Large residual thrombus – grade 4





PCI: Percutaneous coronary intervention; TIMI: Thrombolysis in myocardial infarction.
Data taken from [25].





Figure 2.

Thrombolysis in myocardial infarction grade 5 thrombus in the circumflex artery.
(A) Coronary angiogram demonstrating a target vessel containing a large thrombus burden. This angiogram was obtained pre-application of Siano's restratification of grade 5. (B) Restratification of the thrombolysis in myocardial infarction grade 5 thrombus following guide wire crossing of the thrombus. As the guide wire recanalized the thrombotic occlusion antegrade flow was established demonstrating a low residual thrombus burden. The restratification in this case enabled a decision to continue with direct stenting. (C) Final agiographic view post-adjunct stenting.



Another practical grading classification was introduced by Niccoli et al. (). Recognizing the fact that the differentiation between TIMI grades 1–3 can be challenging (Figure 3 & 4) and subject to observer bias, they proposed a simple bi-level categorization whereby only 2 thrombus grades are used: a low grade is assigned to the abovementioned TIMI grades 1–3 and a high grade corresponds to TIMI grades 4–5.[20] Of note, the bi-level system is also useful in assessment of thrombus within old saphenous vein grafts (Figure 5 & 6). In another recent development, Aleong et al. innovatively combined edge detection and video densitometry-based quantitative coronary angiography for enhanced quantitative assessment of thrombus presence. Their early experience with this method suggests that it accurately quantifies the thrombus volume.[30]


Box 3. The bi-level thrombolysis in myocardial infarction thrombus grading scale.




•Low thrombus content corresponds to TIMI thrombus grades 1–3


•High thrombus content corresponds to TIMI thrombus grades 4–5



TIMI: Thrombolysis in myocardial infarction.
Data taken from [20].





Figure 3.

Thrombolysis in myocardial infarction thrombus grade 1.
The angiographic features are suggestive of thrombus.







Figure 4.

Thrombolysis In myocardial infarction thrombus grade 2.
The thrombus accompanies an eccentric middle right coronary artery lesion.







Figure 5.

Bi-level grading classification: a low thrombus grade in a saphenous vein graft.







Figure 6.

Bi-level grading classification: a high thrombus grade in a saphenous vein graft.



Altogether, the usefulness and merit of the contemporary thrombus grading classifications are widely accepted (). However, certain limitations should be recognized as well: sole reliance on visual assessment, underestimation of thrombus presence and size, as compared with the more accurate tools, such as coronary angioscopy, ultrasound and optical coherent tomography; inability to differentiate between types of thrombus; inability to define the thrombotic content of chronic total occlusions and the lack of either quantitative or qualitative assessment of the underlying plaque burden.


Box 4. The merit of contemporary thrombus classifications.




•Assist the determination of an appropriate course of management for patients with acute or chronic coronary thrombotic ischemic syndromes.


•Provide reliable and universal assessment of thrombotic lesions.


•Enable correlation between thrombus burden to corresponding clinical events and outcomes.


•Effect treatment decisions during diagnostic angiograms and interventions.


•Constitute a practical method for comparison of thrombus presence, location and size with previous diagnostic angiograms and interventions.



Thrombus Grading Scales in Other Vascular Beds

In addition to the available coronary thrombus grading scales, other clot scoring systems are used in varying locations of the vascular bed. For example, neurologists and neuroradiologists use a CT angiography-based clot burden score as an important determinant of clinical and radiologic outcomes in stroke patients.[31] The clot burden score constitutes a scoring system that defines the extent of the thrombus present in the proximal anterior circulation and is scored on a scale of 0–10. A score of 10 is normal, implying absence of a clot, while a score of 0 represents complete, multisegment thrombotic vessel occlusion. Interestingly, the location of the thrombus is taken into consideration in this classification; for example, two points are subtracted from the idyllic score of 10 if the thrombus is found in each of the supraclinoid internal carotid artery, the proximal or distal part of the middle cerebral artery trunk. With the identification of thrombus, a score of 1 is subtracted from the top score of 10 if the thrombus is located in the infraclinoid internal carotid artery, the anterior cerebral artery and for each affected middle cerebral segment M2 branch. Another angiographic thrombus classification utilized for patients with acute ischemic stroke is based on the method proposed by Qureshi et al., which created a 5-point scale, essentially constituting a modification of one of the earliest TIMI scales in use.[32,33] In a recent development, Barreto et al. developed modified criteria for a simpler thrombus scaling system aiming to improve certain limitations of the traditional scoring method.[34] According to their angiographic and clinical experience, an inherit difficulty in distinguishing between two of the grades representing low thrombus burden, grade 2 ver

Kết quả (Việt) 1:

Coronary Thrombus Grading SystemsThrombus grading scales are essential tools used for qualification and quantification of the thrombus burden. They provide a platform for clinical assessment and subsequently effect management decisions prior to and during interventions. The widely used TIMI thrombus grading scale was originally created by the TIMI study group investigators.[24] The introduction of this universal classification reflected a growing recognition among cardiologists that the yield of thrombolytic therapy for evolving AMI was defined by different size and burden of intracoronary thrombi. Altogether, the TIMI classification relies on the angiographic assessment of the presence of thrombus and its relative size, utilizing a simple score ranging from grade 0 (no thrombus), to grade 5 (very large thrombus content that completely occludes vessel flow; ).Box 1. The TIMI thrombus scale.•Grade 0: no angiographic evidence of thrombus•Grade 1: angiographic features suggestive of thrombus ◦Decreased contrast density◦Haziness of contrast◦Irregular lesion contour◦A smooth convex meniscus at the site of a total occlusion◦Suggestive, but not firmly diagnostic of thrombus•Grade 2: definite thrombus present in multiple angiographic projections ◦Marked irregular lesion contour with a significant filling defect – the thrombus' greatest dimension is <1/2 vessel diameter•Grade 3: definite thrombus appears in multiple angiographic views ◦Greatest dimension from >1/2 to <2 vessel diameters•Grade 4: definite large size thrombus present ◦Greatest dimension >2 vessel diameters•Grade 5: definite complete thrombotic occlusion of a vessel ◦A convex margin that stains with contrast, persisting for several cardiac cycles TIMI: Thrombolysis in myocardial infarction. Data taken from [24].While this classification is user friendly and universally accepted, the accuracy of the highest level, grade 5, is subject to interpretation challenges. With its hallmark characteristic of TIMI 0 flow, the ischemic vessel containing grade 5 thrombus is totally occluded. Consequently, the histological relationship between the underlying plaque burden and thrombus content is unknown, yet this grade supposedly represents the highest thrombus load. Notably, such assumptions may be erroneous and, in fact, lead to faulty decisions concerning the potential of percutaneous revascularization to open the occluded vessel. Thus, in order to overcome the abovementioned limitation of TIMI grade 5, an important modification was recently introduced by the Thoraxcenter (Rotterdam, The Netherlands) investigators.[25] Focusing on this specific grade, they added a much needed critical step to the reclassification that significantly improves the determination of the correct load of the underlying thrombus (). Their method utilizes either a guide wire or a 1.5 mm balloon for crossing and recanalization of the target thrombus. This intervention re-establishes a certain degree of antegrade coronary flow to the extent that the exposed underlying thrombus can undergo restratification into either a small thrombus burden (grade 1–3) or a large thrombus burden (grade 4) with treatment ensuing accordingly (Figure 2). In most instances a stratified small-grade thrombus can be managed with an aspiration catheter followed by implantation of a thrombus-capturing stent or with pharmacologic agents.[26] The larger size clot requires a dedicated mechanical thrombectomy device for removal. Options for the task vary from rheolytic thrombectomy to X-Sizer or excimer laser[27,28] and subsequent stenting, preferably, again, with a thrombus-capturing stent.[29] The merit of the new reclassification extends beyond the original application for AMI, and this method can be used in all encounters of grade 5 thrombus in patients with ischemic coronary syndromes.Box 2. Restratification of thrombolysis in myocardial infarction grade 5 thrombus.•Angiographic detection of a grade 5 TIMI thrombus leads to further exploration of the occlusive thrombotic content. Either a PCI guide wire, or a small balloon, is advanced across the thrombotic total occlusion. Crossing the thrombus results in restoration of antegrade flow in the treated vessel. Consequently, the ensuing coronary angiogram enables restratification of the underlying residual thrombus as follows: ◦No residual thrombus – grade 0◦Small residual thrombus – grade 1–3◦Large residual thrombus – grade 4 PCI: Percutaneous coronary intervention; TIMI: Thrombolysis in myocardial infarction. Data taken from [25].Figure 2. Thrombolysis in myocardial infarction grade 5 thrombus in the circumflex artery.(A) Coronary angiogram demonstrating a target vessel containing a large thrombus burden. This angiogram was obtained pre-application of Siano's restratification of grade 5. (B) Restratification of the thrombolysis in myocardial infarction grade 5 thrombus following guide wire crossing of the thrombus. As the guide wire recanalized the thrombotic occlusion antegrade flow was established demonstrating a low residual thrombus burden. The restratification in this case enabled a decision to continue with direct stenting. (C) Final agiographic view post-adjunct stenting.Another practical grading classification was introduced by Niccoli et al. (). Recognizing the fact that the differentiation between TIMI grades 1–3 can be challenging (Figure 3 & 4) and subject to observer bias, they proposed a simple bi-level categorization whereby only 2 thrombus grades are used: a low grade is assigned to the abovementioned TIMI grades 1–3 and a high grade corresponds to TIMI grades 4–5.[20] Of note, the bi-level system is also useful in assessment of thrombus within old saphenous vein grafts (Figure 5 & 6). In another recent development, Aleong et al. innovatively combined edge detection and video densitometry-based quantitative coronary angiography for enhanced quantitative assessment of thrombus presence. Their early experience with this method suggests that it accurately quantifies the thrombus volume.[30]

Box 3. The bi-level thrombolysis in myocardial infarction thrombus grading scale.




•Low thrombus content corresponds to TIMI thrombus grades 1–3


•High thrombus content corresponds to TIMI thrombus grades 4–5



TIMI: Thrombolysis in myocardial infarction.
Data taken from [20].





Figure 3.

Thrombolysis in myocardial infarction thrombus grade 1.
The angiographic features are suggestive of thrombus.







Figure 4.

Thrombolysis In myocardial infarction thrombus grade 2.
The thrombus accompanies an eccentric middle right coronary artery lesion.







Figure 5.

Bi-level grading classification: a low thrombus grade in a saphenous vein graft.







Figure 6.

Bi-level grading classification: a high thrombus grade in a saphenous vein graft.



Altogether, the usefulness and merit of the contemporary thrombus grading classifications are widely accepted (). However, certain limitations should be recognized as well: sole reliance on visual assessment, underestimation of thrombus presence and size, as compared with the more accurate tools, such as coronary angioscopy, ultrasound and optical coherent tomography; inability to differentiate between types of thrombus; inability to define the thrombotic content of chronic total occlusions and the lack of either quantitative or qualitative assessment of the underlying plaque burden.


Box 4. The merit of contemporary thrombus classifications.




•Assist the determination of an appropriate course of management for patients with acute or chronic coronary thrombotic ischemic syndromes.


•Provide reliable and universal assessment of thrombotic lesions.


•Enable correlation between thrombus burden to corresponding clinical events and outcomes.


•Effect treatment decisions during diagnostic angiograms and interventions.


•Constitute a practical method for comparison of thrombus presence, location and size with previous diagnostic angiograms and interventions.



Thrombus Grading Scales in Other Vascular Beds

In addition to the available coronary thrombus grading scales, other clot scoring systems are used in varying locations of the vascular bed. For example, neurologists and neuroradiologists use a CT angiography-based clot burden score as an important determinant of clinical and radiologic outcomes in stroke patients.[31] The clot burden score constitutes a scoring system that defines the extent of the thrombus present in the proximal anterior circulation and is scored on a scale of 0–10. A score of 10 is normal, implying absence of a clot, while a score of 0 represents complete, multisegment thrombotic vessel occlusion. Interestingly, the location of the thrombus is taken into consideration in this classification; for example, two points are subtracted from the idyllic score of 10 if the thrombus is found in each of the supraclinoid internal carotid artery, the proximal or distal part of the middle cerebral artery trunk. With the identification of thrombus, a score of 1 is subtracted from the top score of 10 if the thrombus is located in the infraclinoid internal carotid artery, the anterior cerebral artery and for each affected middle cerebral segment M2 branch. Another angiographic thrombus classification utilized for patients with acute ischemic stroke is based on the method proposed by Qureshi et al., which created a 5-point scale, essentially constituting a modification of one of the earliest TIMI scales in use.[32,33] In a recent development, Barreto et al. developed modified criteria for a simpler thrombus scaling system aiming to improve certain limitations of the traditional scoring method.[34] According to their angiographic and clinical experience, an inherit difficulty in distinguishing between two of the grades representing low thrombus burden, grade 2 ver