Virchow's Triad – Thrombotic Disorders

by Richard Mitchell, MD, PhD

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    00:01 Okay, let's talk now on the flip side.

    00:04 We've talked about bleeding disorders.

    00:06 Let's turn to thrombotic disorders or hypercoagulability, also, called, “Thrombophilia,” meaning, “Loving tooth thrombose.” What leads to a thrombus? This is a very important concept, again, Virchow, our good German pathologist, who was kind of the father of pathology.

    00:25 Identified kind of a triad, the things that will contribute to driving thrombosis.

    00:32 And there are three components to it hence the triad.

    00:35 Number one is probably going to be endothelial injury and that makes a lot of sense because endothelium is going to be really, really important, in terms of driving, both coagulation, but also, anticoagulation.

    00:47 And if the endothelium is not happy, you're going to have a tendency to be more pro-thrombotic.

    00:52 So, endothelium is one angle of the triangle of the Virchow’s triad.

    01:00 Another one, is “Stasis” or “Turbulence,” so, basically, abnormal flow.

    01:04 If you have blood sitting around for a period of time, you will get stochastic activation of coagulation factors and you'll form a clot.

    01:11 If you have turbulence, that's actually on the backside of turbulence, you'll have eddy currents, so that you will have focal areas of stasis.

    01:20 So, abnormal flow, non-laminar flow, is also going to be something that will lead into thrombosis.

    01:27 And the final component of the triad is, “Hypercoagulability.” And this is much more than kind of a general concept, there are a number of things that we'll talk about shortly, that lead to a greater tendency to have thrombosis.

    01:42 You make more coagulation factors, you make less anticoagulation factors, you activate coagulation inappropriately, all of these things will contribute to thrombosis.

    01:55 Now, it's not just those three things in isolation, but they all crosstalk with one another.

    02:00 So, endothelial injury, actually, because it's important for driving both, coagulation and anticoagulation, will lead to hypercoagulability.

    02:08 An endothelial injury, clearly will lead to areas of stasis or turbulence.

    02:13 And stasis or turbulence in turn will impact endothelial integrity, so, all these things crosstalk.

    02:21 But in general, when we have a thrombus, one or more of Virchow’s triad has been in play.

    02:29 So, endothelial injury, is going to be a major driver for arterial thrombi and it's mostly platelet-driven.

    02:37 Keep in mind, as we talk about clotting that occurs anywhere in the vascular system, if there's a lot of flow, it's going to be very hard for coagulation factors alone to drive a thrombus, because they're going to be diluted, they're going to be driven downstream very quickly.

    02:54 So, in the arterial circulation, if a thrombus occurs, it's usually because we've had endothelial injury and we've recruited platelets that can stick quite firmly, quite avidly to the underlying von Willebrand factor for example.

    03:09 So, arterial thrombi, tend to be due to endothelial injury and are platelet-driven.

    03:15 Conversely, where there's stasis, now we can have local activation of the coagulation factors and so, in venous thrombi, it's usually coagulation factor driven, not so much by platelets.

    03:29 So, we don't have endothelial loss, we don't have exposure or underlying von Willebrand factor and so the venous thrombosis tends to be driven by coagulation factors.

    03:44 Thromboembolism, let's just kind of look at a couple examples, three examples to be exact.

    03:48 So, here we have a pulmonary embolus, the big inverted y-shaped white thing up top, is a pulmonary artery, that branches into the right and left pulmonary arteries and that defect in the whiteness, is a pulmonary embolization.

    04:08 This occurred, almost certainly because of relative stasis, in the lower extremity veins and that could have been due to a variety of things, including just inactivity and then that thrombus that formed there, in the venous circulation, breaks free, goes through the heart and impacts in the pulmonary circulation.

    04:31 So, that's a pulmonary embolism or a thromboembolism.

    04:35 Now, we're on the arterial side.

    04:37 So, that large circle near the top with the white defect.

    04:42 That white defect is in fact the normal flow, we’ve put in a radio opaque dye, so that, we can see where the lumen is and there's a vast darker area around that.

    04:53 That is an abdominal aortic aneurysm and the darker area, that is excluding the dye, is a big thrombus.

    05:01 And it's occurring there, because we have abnormal flow, we have a dilated aorta, so, we can have relative areas of stasis and in that setting we are now getting a thrombus that forms.

    05:15 We can also have, in the right ventricular chamber here, a thrombus indicated by the arrow that is forming, as a result of endothelial dysfunction.

    05:24 So, we now have abnormal anticoagulation, regulatory effects occurring and we're getting a thrombus that's formed.

    05:35 So, we have the three different components of Virchow’s triad.

    05:39 On the pulmonary embolism, that's forming due to stasis.

    05:42 We have abnormal flow in our aortic aneurysm.

    05:46 And we've got abnormal endothelium and so all of these will be leading to thromboembolism.

    About the Lecture

    The lecture Virchow's Triad – Thrombotic Disorders by Richard Mitchell, MD, PhD is from the course Hemostasis.

    Included Quiz Questions

    1. Arterial thrombi
    2. Venous thrombi
    3. Stasis of blood flow
    4. Turbulent blood flow
    5. Hypercoagulation
    1. It activates the coagulation factors.
    2. It damages the underlying endothelium.
    3. It enables platelet aggregation.
    4. It causes platelet adhesion.
    5. It damages the collagen.
    1. Sitting for long hours
    2. Swimming every week
    3. Cycling in the hills
    4. Walking on the beach
    5. Lifting heavy weights

    Author of lecture Virchow's Triad – Thrombotic Disorders

     Richard Mitchell, MD, PhD

    Richard Mitchell, MD, PhD

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