 Welcome back to part 3 of ACS. In this section we'll talk about how to make the diagnosis using non-ECG modalities. They're separated into imaging and blood work. For imaging we have chest x-ray, bedside ultrasound, and CT. Let's start with that. The purpose of imaging is really to exclude other diseases that give patient chest pain. Let's start with the chest x-ray. Remember our goal here is to exclude other diagnosis. What do you think of this chest x-ray? The patient was complaining of left-sided chest pain. Do you see any abnormality on the chest x-ray? You can see here the lung is only partially inflated. And this area looks much darker than the other side. What is this diagnosis? This is a left-sided pneumothorax. What about this chest x-ray? What do you see? You can see bilateral infiltrate in the lungs, consistent with the picture of pneumonia. What about this chest x-ray? What do you think? You may notice the wide medial stynum on this chest x-ray, leading you to be suspicious of aortic dissection. Next, we'll talk about bedside ultrasound. What other causes can be excluded by bedside ultrasound? Let's take a look at this still image. The chambers of the heart are labeled. The black space in the pericardium represent pericardioefusion. On the bedside ultrasound, you might also be able to see a right ventricle dilatation in the case of a PE. For CT, the other diagnosis we will be entertaining include aortic dissection and PE. Next, we'll discuss blood work. We will draw routine tests such as CBC, lights and creatinine. In terms of the CBC, we want to make sure that the hemoglobin is not low, since patients can have symptoms based on anemia. Electrolytes and creatinine are a good baseline function. It may also affect the way we decide on our treatment later on. The more specific tests for acute coronary syndrome are cardiac enzymes. These are specific blood tests that will increase if there has been myocardioef. Some more specific to the heart cells than others. They include the following, myoglobin, CKMB and troponin I and troponin T. Out of all these markers, the last two are the one they're most used, with the troponin I being the most sensitive. Troponin takes a few hours for it to be released into the bloodstream. It will peak in a day or two and it will take about two weeks for it to return to baseline. The important thing is that it takes a few hours for these troponin to show up in the bloodstream. It can be something like this graph. So you can see here it takes at least three hours, if not up to twelve hours, for the blood test to show up in the bloodstream in a detectable level. And by twelve hours, the cardiac markers should all be in the bloodstream. Let's say the patient present at two hours. You know that even if he did have an event at two hours, his cardiac enzymes would still not be in the detectable level. Now we can still use an ECG to help us to make a real-time diagnosis, but if we want to rely on our troponin, two hours is too early. As we draw the blood a little later after the patient's symptoms have started, you can see that our sensitivity has now gone up. It's more likely for it to be picked up on the blood test now. Different institutions will use different time frames for this delayed enzyme. Most people choose either six or eight hours after the event. However, it can be based on the sensitivity of the troponin assay that you're using. So it's best to check with your team. It's important to know what we're trying to rule out. A delayed negative troponin means there has not been a myocardial infarction. It is unable to rule out angina, since there has not been any infarction. And as we just discussed, an early negative troponin does not even rule out MI, since it's simply too early. In summary, we talk about using imaging and blood work to finish our diagnosis for ACS. We know that imaging is really used to rule out other diagnosis. We talked about using troponin as the diagnosis for MI, but it has to be done at least six to eight hours after the event, depending on the sensitivity of your assay. We hope you find this helpful. Thank you for watching.