It is a fashionable topic in cath meetings and workshops to discuss about thrombus loaded coronary arteries. Still visualizing a thrombus in coronary angiogram is never a mean task ! It needs lots of visual acuity and imagination to recognise intra coronary thrombus.
- A lesion which looks fresh with multiple layers of irregularity within the lumen is often assumed to be thrombus.
- An intra luminal filling defect is the most often used “criteria to suspect” a thrombus
Thrombus vs plaque ?
Both are radiolucent . But a thrombus or a plaque coated with dye will make it radio opaque. The radio opacity of a thrombus is determined by extent of dye coating , the thickness of the dye layer, obliqueness to the x-ray beam . A thrombus plaque interface can have two different planes of densities.
Theoretically dye can not encircle a plaque in its entire circumference as it will be attached to vessel wall (Unless circumferential dissection is present ) Hence , dye can not coat a plaque fully , at best it can give an appearance of eccentric filing defect with over hanging edges . While a thrombus can manifest with a complete filling defect
Thrombus vs dissection
This is still more complex . Both can have a filling defect .A flap is a line like filling defect To complicate the issues further, both thrombus and dissection occur together in the same spot .
How confidently one can identify a thrombus in coronary angiogram ?
During acute MI there is no difficulty in identifying it , as every acute obstruction must contain some thrombus* . Some interventionists have special ocular sense to detect thrombus. Few others rely on their intuition rather than solid evidence.
Sucking out a thrombus during primary angioplasty has now become standard concept and is indeed feasible in most situations. It is obvious we have a task on hand to identify thrombus correctly and quickly during primary PCI /UA .
Blind suction, even though rewarding should be avoided. Caution is required as blind suction pulls a plaque with force !
A plaque debri with a thrombus, a dissected flap all can combine together to produce a complex “masala” of coronary lesion especially after a difficult guidewire cross . This is refereed to as a battered coronary artery .These are the lesions which are prone for recurrent acute or sub acute thrombosis even if the lesion is stented properly.
During primary PCI thrombus coated dissected plaque is just tucked and opposed behind the gentle stent struts.The thin layers of thrombus between stent struts and the vessel wall is missed , 100 out of 100 times by coronary angiogram . (IVUS very good in detecting this) .Because of this risk , Intensive anti -coagulation in complex PCI becomes mandatory
* Diagnosing thrombus in a chronic lesion is much . . .much difficult !
What are specific modalities available to confirm thrombus
IVUS, Angioscopy, OCT are hi tech tools to identify intra coronary thrombus .(Which i feel have little practical value in real emergency situations)
Thrombus may be a key finding in acute coronary syndrome (Of course the contribution of fissure, injured , plaques to the lesion can never be underestimated . ) Still , we have no simple , accurate method to identify it ( Forget quantifying it) . Lots of assumption , guess work and gut feeling is at play in the cath lab .
We expect better online , real time tools to improve out tentativeness inside the coronary artery .