In this video from our Coronary Angiography Essentials course, you'll learn how to treat acute no-reflow, understand why some cases are difficult to manage, and gain a deeper appreciation of coronary microcirculation and why it's such a crucial aspect of the cardiovascular system.
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Coronary angiography is one of the key diagnostic procedures in cardiology. If you work in internal medicine, you’ve probably taken care of many patients with coronary artery disease who’ve had percutaneous coronary interventions, stents, or bypass procedures. This course teaches you how to do a basic assessment of the coronary angiogram so you can take the best possible care of these patients.
[00:00:00] So let's try and highlight the importance of the microcirculation by looking at a real case of acute no-reflow. In this case, one can see a right coronary angiogram, in a patient presenting with an acute coronary syndrome. We'll discuss the specific anatomy in detail in subsequent chapters, so don't worry about that just yet. In this right coronary artery, you can see a
[00:00:30] very tight narrowing or stenosis in the proximal vessel, highlighted on the screen now. The right coronary artery has also been wired for the angioplasty procedure. It's quite difficult to see the angioplasty wire but if you look before the contrast fills the vessel, it's more apparent. You can also see the more radiopaque tip of the wire in the distal right coronary vessel. The tight stenosis is being treated by a technique known as direct stenting.
[00:01:00] That basically just means that a stent is being implanted, without first stretching or dilating the lesion with the balloon. The stent balloon is filled with a dilute radiographic contrast, so that it's visible on fluoroscopy and you can see it, here, between the two markers, as shown. This is also done from a safety perspective. As, if this balloon were to rupture, then just contrast would go down the artery rather than air,
[00:01:30] which can be fatal. After the balloon has been deflated, you can see two things. The first thing is that the narrowing at the proximal vessel is now very much better. It's been highlighted on the diagram, here. What you may notice, however, is that flow into the distal right coronary artery is already very slow or reduced. Maybe it's worth just having a look back at that original image, that we looked at. Even with the tight narrowing, proximally,
[00:02:00] flow in the distal right coronary artery looks fairly normal. In the following image, you can see a different projection of the same artery. Look at the position of the distal angioplasty wire in the artery, which is now being highlighted. This will give you a reference point, as it's in the same position in the artery as it was in the previous image. You can hopefully appreciate now that the flow in the artery has almost completely stopped in
[00:02:30] the mid-vessel. Here, it's being highlighted again for you to see when the contrast flows. You can see the proximal part of the artery, which was previously stented, is widely open. Here it is up here. We know from the first image that there was no obstruction in the artery further down the vessel. This phenomenon is known as acute no-reflow. It's where the epicardial vessel appears open but there doesn't appear to be
[00:03:00] any distal runoff, of contrast, into the microcirculation. It's a very complex phenomenon. But it's thought to occur as a combination of thrombus embolization from that proximal lesion, which transiently blocks up some of the small vessels in the microcirculation but also some spasm of the microcirculation, which is thought to be due to prostaglandin and prostacyclin release, from proximal balloon injury.
[00:03:30] So what do we do about this phenomenon? Well, the treatment of acute no-reflow is to deliver a pharmacological agent, via a small microcatheter placed as distally as we can in the artery, to reverse this microvascular spasm. There's little point in delivering drugs to the proximal coronary artery, in the absence of flow, they're not really going to reach their target of the microcirculation. Some agents that we use in the cath lab, for this reversal of
[00:04:00] spasm are adenosine, verapamil or sodium nitroprusside. In addition to these, oral antiplatelet agents such as aspirin, clopidogrel, prasugrel, ticagrelor. In addition to these, oral antiplatelet agents such as oral aspirin, clopidogrel, prasugrel, ticagrelor. A more potent intravenous glycoprotein inhibitors such as tirofiban, eptifibatide, abciximab,
[00:04:30] are also used in many acute syndrome cases, to reduce the chance of thrombus formation and propagation. You'll hopefully be able to see now, at the end of the case, following this distal delivery of adenosine, there's no evidence of any major residual epicardial coronary artery disease. Acute no-reflow is often associated with ST elevation on a 12-lead ECG, in association with chest pain for the patient. This is often short-lived
[00:05:00] and resolves fully. In cases with higher thrombus burden such as in the context of an ST-elevation myocardial infarction, acute no-reflow phenomena can be profound and can be very difficult to manage even with modern adjunctive pharmacotherapy. It’s often seen if the artery is over dilated or repeatedly dilated, and this should be avoided, if at all possible, in patients with acute coronary syndromes.