Health Help:
Veins and blood clots


We learn more about VTE, a potentially deadly yet mostly preventable medical condition, from Dr Herman Sung-Yu Liu. He’s a specialist in haematology and haematological oncology at Hong Kong’s Premier Medical Centre.


What is VTE, or venous thromboembolism? Is it the same thing as deep vein thrombosis?

Venous thromboembolism is a clot inside a vein. There are three types; the first one is superficial vein thrombosis, which is easily resolved and seldom needs treatment. The second one is deep vein thrombosis – we call it DVT. The third one is pulmonary embolism, or PE in short; This involves a clot inside the pulmonary vessel.

It’s important to treat DVT and PE as soon as possible because of their potential fatal complications.

What are some of the symptoms of VTE? Is there one “classic” symptom or tell-tale sign?

With DVT, the usual signs will be pain, swelling and redness; usually in the leg. It’s also unilateral, which means that the symptoms present on one side.

With PE, the patient can experience chest pain, palpitations or shortage of breath.

What are the risk factors of developing VTE?

The risk factors can be multifactorial. In particular, we use the term “Virchow’s triad” to refer to the following three categories of factors that can contribute to thrombosis:

#1 Hypercoagulability: This simply means that the blood can easily form clots. The condition can occur in patients with cancer, for example, or in those who are taking contraceptive pills or suffering from dehydration.

# Vessel injury: This is where there has been some kind of trauma to the vessels – for example, from an indwelling catheter, which is commonly used in cancer patients.

# Stasis: This third category refers to when the blood flow is sluggish. This can occur, for example, from sitting in an awkward position on a long-haul flight, from immobility after an operation, or if the patient has had a stroke.

Apart from Virchow’s triad, other factors include the congenital inherited blood clotting disorder known as FactorV Leiden, which is quite common in Caucasians.

Are particular groups of people more susceptible to VTE?

Nowadays, because we are facing an ageing population, more patients will have cancers, which brings with it an increasing incidence of venous thromboembolism.

Is it true that expats can be at risk because of their tendency to take lots of long-haul international flights – at least, in “normal” times?

Yes, this is very true. In an article published 20 years ago in the New England Journal of Medicine, a study of the registry of the Charles de Gaulle Airport in Paris showed that the incidence of VTE is directly related to the distance a passenger has travelled. “Long-haul” was defined as more than 5,000 kilometre – or roughly around eight hours of flying time.

What can our readers do to avoid VTE?

When you’re on a plane, try to mobilise yourself, try to drink more water, stay well hydrated and avoid alcohol.


If a person is unlucky enough to develop VTE, what are some treatment options?

The treatment options are mainly medical, including the use of three different types of drugs. The most common is DOAC, or direct oral anticoagulants. These new anticoagulants are given orally, and they’re good in that they have a very fast onset, they don’t need close monitoring and the bleeding tendency is lower compared to older medication.

The second type of medication is the conventional warfarin, which has been in use for more than half a century. But the drawback is the patient is required to undertake dietary control and also frequent blood monitoring.

The third treatment involves the use of low molecular weight heparin, which is administered via a daily injection. The problem is that most patients don’t like daily injections, so it tends to be given to patients who aren’t able to tolerate DOAC or warfarin and is mainly limited to patients with cancer.

What’s the prognosis for someone recovering from VTE?

It depends on whether there are any associated risk factors; for example, if the thrombosis is associated with an operation or with long-haul flying, usually the patient will respond very well; they’ll likely need only a finite period of treatment, rather than any life-long treatment.

On the other hand, if the condition is related to congenitally inherited thrombophilia or if there is a concurrent active cancer, the patient will probably need life-long treatment.

The most commonly encountered complication is what’s known as post- thrombotic syndrome, or PTS. This is due to the damage of the valves inside the veins. These valves are used to pump blood in the right direction back to the heart. If they are damaged, you’ll have symptoms such as swelling, pigmentation, pain or even some superficial ulcers.

On a personal note, what led you to your interest in this type of medicine?

When I was in medical school, I was always told that venous thromboembolism rarely existed in the local Chinese population. But when I started to practice, I noticed there were a lot of new cases, day in and day out.

In fact, a survey from back in 2001 showed that VTE isn’t uncommon in Chinese. Indeed, we have calculated that there are about 16 new cases per 100,000 per year; now, while this is only about 20 percent of the prevalence you find in Western countries, it’s still quite a lot.

Nationalities aside, the reality is that there are many VTE cases in Hong Kong. Ours is a multinational city, with a lot of foreigners, and an airport that is generally very busy; as such, we see cases day in and day out.



This article first appeared in the Autumn 2021 issue of Expat Living magazine