![]() Grade 0 (No perfusion): There is no antegrade flow beyond the point of occlusion. Originally used following thrombolysis, now universally used for all angiogram (Is it appropriate ?) TIMI Grading The most popular form of reporting coronary blood flow across a stenosis is TIMI grading. * This has created the concept of flow limiting lesions and non flow limiting lesion. It is well known, coronary blood flow goes on smoothly, uninterrupted until very late stages of obstruction. I s it possible, for an obstruction to have little impact on the blood flow ? Fortunately ,”yes”, the physics of fluid dynamics is patient friendly. ![]() Read also Glagovian phenomenon – A form of intra stenotic coronary artery dilatationĬoronary arterial obstruction is considered, dangerous because it obstructs the coronary blood flow. If the distal instent stenosis occur (even if it is minor ! ) it can induce a cycle of post stenotic eversion of normal segment and risk of edge effect or stent thrombosis is more. The post stenotic segment has a potential to misbehave in the period following PCI. Significance in interventional cardiology There is a possibility it occurs only in genetically susceptible individuals. Not every one goes for post stenotic dilatation. Is there a anatomical defect in post stenotic dilatation ? (Opposite of what is expected in Bernoulli effect ?) This somehow has an effect on the distending pressure and the adjacent vessel wall gets radially stressed and begins to dilate. At this point, the rate of increment in velocity of peaks. This pressure drop recovers beyond a certain distance. There is a definite ,sudden pressure drop distal to the obstruction. What determines the post stenotic dilatation ? Coronary ectasia is also a possibility but since it is related to site of obstruction the former is likely. Here is a patient with a tight LAD lesion with a significantly dilated segment located immediately beyond the obstruction.This can be considered as a post stenotic dilatation. It is more common in large vessels than small ones. It may not be linked to newtons law but it is observed in many. In vascular hemodynamics whenever there is a an obstruction, there tend to be a dilatation of the same blood vessel somewhere distally. Newtons third law of motion says for every action there is an equal and opposite reaction. Let me post our experience during PCI shortly. I feel so, but my colleague Dr Gnanavelu strongly differs ! ![]() (We can’t get a stent just like that unless it is a real emergency. He is posted for elective PCI this week-end. Since he had significant angina there were no debates regarding management. **Note further : This hemodynamic principle may not apply in acute occlusion as in STEMI, where acute obstruction often has a linear relationship with the quantum of blood flow.īy the way what happened to the above patient ? * The garden hose analogy is a gross simplification of complex factors that determine coronary blood flow.But it effectively clarifies a point ie coronary blood flow is least dependent on coronary stenosis (until very late stages) This is based on Bernoulli principle and is akin to how a garden hose pipe can simply increase the velocity by tightening the nozzle.* The distal vascular bed drops its resistance drastically once it senses the problem in proximal segment. Realise there is no simple relation between the degree of obstruction and degree of blood flow impediment.It can be linear, curvilinear, or even inverse depending upon the evolution and timing of obstruction, number of lesions, presence or absence of collateral support, finally and most importantly the integrity of microvascular bed. This is what is happening to this man with a stable angina and perfectly normal micro vascular bed.ĭo not get fooled by the lay man’s logic. If it is normal even a hair-line patency can profusely perfuse the distal myocardial segment. The distal flow beyond an obstruction is not primarily dependent on degree of obstruction but the status of the distal vascular bed. An almost invisible antegrade channel doing a exemplary job !
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