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Venous Diseases – Disambiguation

by Joseph Alpert, MD
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    00:01 Welcome back to Vascular Medicine - The Advanced Venues.

    00:05 We are going to discuss today venous diseases. We’ve been talking a lot about arterial diseases up to this point. Now we’re going to look at the second component of the cardiovascular system: the venous diseases.

    00:18 We’re going to start with a definition of the various kinds of venous diseases. It turns out that, just as in the arterial disease, thrombosis – or the development of a blood clot –can develop in patients in the veins just as they can in the artery. And just as in the artery, pieces of the blood clot can break off and go elsewhere in the circulation and cause mischief. The same thing can happen in the venous system.

    00:48 In the venous system, when a blood clot forms and breaks off it goes to the lung and is known as pulmonary embolism.

    00:58 What often leads to clot in the veins is an inflammatory process called deep venous thrombosis or DVT. And that inflammation in the wall of the vein – and we’ll talk about the reasons why that can happen – results in a blood clot forming. The blood clot can get bigger and bigger and bigger, pieces can embolize and result in pulmonary embolism. If enough blood clot gets into the lung, you can have enough obstruction of blood flow through the lung that the patient may develop shock – the subject of the last lecture.

    01:37 So, often this disease is called venous thromboembolism because there’s clots in the leg and there’s clots embolising to the lung. And that’s often abbreviated as VTE.

    01:50 Remember what a thrombus is. A thrombus is a solid mass of platelets and / or fibrin that has formed locally in a vessel. It’s a blood clot. And it forms when the clotting mechanism is activated.

    02:07 Thrombosis is actually obstruction of a blood vessel by a thrombus. And, of course, when that happens in the arterial system, nourishing blood fails to get to a blood vessel. In the venous system, that doesn’t happen because we have so many reserve veins. Blood usually goes around the area where there’s a thrombus or thrombosis. However, when pieces break off and embolize to the lung, that causes real trouble.

    02:35 The most common form of embolism, much more common than arterial embolism, is venous thromboembolism.

    02:43 And the commonest form of venous thromboembolism results from deep venous thrombosis.

    02:48 And there’s a whole variety of illnesses that increase people’s risk for developing thrombosis in the veins. For example, long periods of bed rest; or long periods of travel in an aeroplane where you’re seated with your legs down; or cancer increases the clotting ability of the blood and can result in that; pregnancy. A whole variety of conditions can lead to either increased clotting tendency or injury to the vein. For example, a fracture, a trauma can injure the vein and lead to deep venous thrombosis. And, again, a piece of the clot breaks off, goes up to the lung and that can cause lots of trouble.

    03:32 Occasionally, for example in some forms of trauma, you can have fat or air that embolizes or even little bits of an atherosclerotic plaque that can embolize. But in fact the vast majority of embolism on the venous side is blood clot. And it’s a blood clot that results from deep venous thrombosis.

    03:55 When the embolus lodges downstream, it often lodges in the narrowest area. And so in the lung the thrombus will travel until it finds a small enough blood vessel that it gets stuck and then, of course, it causes obstruction of blood flow through that area of the lung.

    04:18 Let’s just review the venous-side events that relate to thrombosis once more.

    04:25 Deep venous thrombosis is due to a thrombus – a blood clot – that forms within a deep vein. We can also have superficial venous thrombosis but that’s usually just a transient irritation and not as serious as the deep venous thrombosis.

    04:43 Deep venous thrombosis often involves a substantial amount of clot so that, when it embolizes, it causes significant obstruction in the lung circulation.

    04:54 The source of these emboli in the legs – we’re going to talk about some more subsequently in this talk – but it usually starts in the veins of the calf and then extends up into the veins of the thigh.

    05:09 When the blood clot breaks off and travels to the lung as pulmonary embolism, if it blocks a major artery of the lung, that can cause immediate shock or decreased blood pressure in the patient.

    05:25 But often these clots are small. They get out into the periphery and it’s only with repeated episodes of embolisation of clot to the lung that significant obstruction of the pulmonary circuit occurs.

    05:39 The condition with deep venous thrombosis plus pulmonary embolism is often called venous thromboembolism or VTE. And it’s obstruction in the vein caused by a thrombus. But then pieces break free and are carried away with the blood flow into the lung. And if there’s enough of the pulmonary circulation that’s obstructed, as I said the patient can develop very serious illness including shock and this can be fatal.

    06:09 Just to compare a little bit about what happens with thrombosis in the arterial and the venous system: Deep venous thrombosis can be asymptomatic. It can resolve without any problems but, when a blood clot breaks off and travels to the lung as pulmonary embolism then, as I’ve said, the patient can have a very serious illness.

    06:32 On the arterial side, the major problems relating to thrombosis are either myocardial infarction or unstable angina.

    06:39 With myocardial infarction, the thrombosis completely occludes the artery and cuts off blood flow beyond.

    06:45 With unstable angina, often the atherosclerotic plaque plus some overlying thrombus doesn’t completely occlude the artery so the patient has chest pain at rest that comes and goes or pain that’s easily provoked when they do the most minimal exertion.

    07:03 Again just to show you the difference between what happens when there’s a clot on the venous side versus a clot on the arterial side.

    07:12 Venous side: DVT, pulmonary embolism, arterial-side myocardial infarction, unstable angina.

    07:21 Now it turns out that, as in hypertension, DVT is often silent. And even pulmonary embolism can be silent. In fact, as you can see from this pyramid, the vast majority of patients have silent DVT or silent PE. And often it resolves without any therapy.

    07:42 In a smaller percentage of patients, the DVT and the pulmonary embolism can be symptomatic.

    07:47 And in a very small amount, it’s fatal.

    07:50 So of course what we would like to do is identify the DVT or the PE when it’s silent and when the amount of pulmonary embolism has been very small so that we can prevent progression up the pyramid to the point where the obstruction causes symptoms or even is potentially fatal.

    08:11 I mentioned before, where does deep venous thrombosis commonly develop? It commonly develops in the popliteal or superficial femoral veins – that is just below the knee and just above the knee. And that clot there, particularly the ones in the popliteal veins, can be quite small and may never embolize or, if they embolize, they may not cause much trouble. But as the clot develops – and what happens is it can of course continue to build – it may extend up into the common femoral vein and even into the iliac vein.

    08:52 At that point, we’re dealing with a large volume of blood clot. If that large amount of clot breaks off and goes to the lung, we could see either fatal pulmonary embolism or shock.

    09:07 You’ll notice that only a small percentage of clots are found in the popliteal vein alone, more in the superficial femoral vein. 42% in popliteal vein, both veins. Again only a small percentage in the common femoral but a substantial number get into the iliac and inferior vena cava – 35%. And those are the most dangerous ones.

    09:30 We would like to discover the clots when they’re just down in the popliteal vein or in the superficial femoral, not when they develop in large volume up in the inferior vena cava or the iliac vein where, if they embolise, could be fatal.

    09:46 Again, the consequences of venous thromboembolism are clear. There can be fatality if the pulmonary circulation is markedly occluded. This can happen suddenly. There can be acute mortality.

    10:01 There can be recurrence. So the patient may have an episode of pulmonary embolism. He’s sick, gets better, goes home from the hospital. Once they’ve had one episode, they’re at high risk for another episode. And often that’s because they develop recurrent thrombophlebitis.

    10:15 They have a tendency to develop this inflammatory clotting disorder in the veins and then, of course, for pieces of it to break off.

    10:24 Sometimes the veins get completely occluded with the clot and then they can cause something I will talk about later called post-thrombotic syndrome in which the patient experiences chronic swelling of the leg. And even ulcers and really a very, very unpleasant sequence of events can occur with a lot of clotting in the venous system.

    10:53 The definition of thrombophlebitis is of course the presence of thrombus in a vein. It’s almost always accompanied by an inflammatory process in the vein wall. As I’ve said before, it can affect superficial veins when it’s usually not very serious and often as a result of some minor trauma. And it can be treated with just some local heat and maybe some aspirin or ibuprofen. When it gets in the deep veins, that’s when there’s a much greater potential for pulmonary embolism. As we said, pulmonary embolism can be fatal. And there are a whole variety of risk factors for developing thrombophlebitis: long periods of bed rest, long airplane trips, cancer, heart failure, severe lung disease… A lot of these place patients at higher risk for developing thrombophlebitis and pulmonary embolism.

    11:47 I mentioned before the post-thrombotic syndrome. This is a very serious complication of venous thrombosis. It’s a long-term complication of deep venous thrombosis. What happens is you occlude enough of the veins in the lower leg so that it is difficult for blood arriving in the muscles and skin of the leg to get out of the leg. So you have pooling of blood there, you have increased pressure from standing, from gravity. This results in much more fluid getting out of the capillaries that can be resorbed. So you have swelling. And then with all of this swelling, it actually impairs arterial flow from getting into the tissues and you may have necrosis – or death of tissues – and development of an ulcer as you can see from the picture here.

    12:39 A number of symptoms are related to the post-thrombotic syndrome: there can be pain or heaviness in the leg; itching or tingling; as I’ve already mentioned, edema swelling; development of severe varicose veins; brownish or reddish skin discoloration from red blood cells being deposited in the skin. And, of course, the worst complication is ulcers. And even, occasionally, the ulcer gets infected and this could lead to amputation. So the post-thrombotic syndrome can be very, very severe.

    13:13 So, in summary, in this first lecture on the venous system, we’ve talked about the most common and potentially serious illness from the venous system, which is that which occurs when a thrombus or blood clot – a solid mass of platelets and fibrin – forms locally in the vein and often is associated with activation of a clotting mechanism that increases the size of the blood clot.

    13:42 It’s not uncommon for these clots to form in the veins of the legs, much more common than in the arms, where they block blood flow. Pieces of these clots can break off and travel to the lung circulation where they cut off blood flow to a portion of the lung – that’s pulmonary embolism. We’re already talked about it. Patients can be very sick with pulmonary embolism or it can even be fatal. And we’ll be talking more about therapy as we go along and talk more about pulmonary embolism in a subsequent lecture. The therapy is, of course, blood thinners or blood-clot dissolvers to help resolve the clots that are already in the lung.


    About the Lecture

    The lecture Venous Diseases – Disambiguation by Joseph Alpert, MD is from the course Venous Diseases. It contains the following chapters:

    • Venous diseases - Overview
    • Thrombosis examples
    • Consequences of venous thromboembolism
    • Venous diseases - Summary

    Included Quiz Questions

    1. Pulmonary embolism is rarely fatal
    2. Deep venous thrombosis occurs commonly in hospitalized patients who undergo surgery
    3. Pulmonary embolism is a complication of deep venous thrombosis
    4. Most episodes of deep venous thrombosis occur in the veins of the leg
    1. The development of leukemia
    2. Increased risk of death
    3. The development of post phlebitic leg syndrome
    4. The development of recurrent venous thromboembolism

    Author of lecture Venous Diseases – Disambiguation

     Joseph Alpert, MD

    Joseph Alpert, MD


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