Treating venous disease

Access:

The right IJV is the ‘universal gateway’ and can be used for access even in the presence of iliofemoral DVT. Make sure that there is a contemporary ultrasound to document the site and extent of thrombus. Placing a catheter through a thrombosed vein is likely to result in iatrogenic pulmonary embolism (PE)!

Catheterization:

From the jugular route, use a Cobra catheter and 3-mm J-guidewire to carefully negotiate through the right atrium to the IVC.

Assessment is required for three reasons:

• To demonstrate the patency of the IVC, assess its size and any angulation

• To confirm conventional anatomy, i.e. single IVC

• To document the position of the renal veins.

Tip

In practice most patients will have had a contrast-enhanced computed tomography (CECT), which demonstrates the anatomy and IVC size, leaving you only needing to establish the position of the renal veins.

If digital subtraction angiography (DSA) is required it is usually sufficient to perform a simple IVC injection through a pigtail catheter placed just above the confluence of the iliac veins. An initial gentle hand injection will ensure that there is no thrombus adjacent to the catheter; perform a more vigorous injection to demonstrate the entire IVC. The position of the renal veins is usually apparent because of streaming of unopacified blood ( Fig. 51.1 ). If the renal veins cannot be identified, use a Cobra catheter to engage them and perform selective hand injections to demonstrate their position.

Tip

Use the patient's spine as a reference for the position of the renal veins.

Once the position of the renal veins has been established, do not move the table or the image intensifier.

Alarm

If you did not measure it on the CT scan, do not forget to measure the diameter of the infra-renal IVC. Most IVC filters can only be used within a specified range of IVC diameters; if the filter is too small, the first place it will lodge is the tricuspid valve!

Positioning the filter:

There are two sites to place an IVC filter, and the position is determined from the cavogram.

• Infrarenal: this is the optimal site; if the filter causes IVC thrombosis, the renal veins will be spared. Conical filters should be placed with the filter apex at the level of the renal veins; the high flow promotes dissolution of thrombus trapped or formed within the filter.

• Suprarenal: in the presence of infrarenal thrombus, a filter can be sited between the renal and hepatic veins. In this position, filter thrombosis can lead to renal vein thrombosis and renal infarction.

Deploying the filter:

Each type of filter is deployed differently and there may even be differences for a single type of filter, depending on whether the jugular or femoral route is used. Read the instructions carefully before use; if you do not understand them, seek help! It is traditional, but unnecessary, to perform a completion venogram to demonstrate the position of the filter; a single-shot image will suffice. If you must do this, consider injecting through the sheath and take great care if you pass a pigtail catheter or J-wire through the filter as they might become entangled!

Alarm

If there is no contraindication, the patient should be anticoagulated while the filter is in situ, to minimize the chance of filter thrombosis.

Filter removal:

There is no absolute consensus on the length of time a filter can be left in place before removal is attempted. Longer dwell times are associated with greater complications and the filter should be removed as soon as it is no longer clinically required. Always perform a cavogram ( Fig. 51.2 ) to see if there is any residual thrombus either in the filter or which would threaten significant PE. If there is <1 cm ³ of thrombus in the filter, it can be removed. Most removable filters have a hook at their apex, this is snared from the jugular vein. The snare must be placed at the top of the hook; the snare is held in place and the sheath advanced over it to close the filter ( Fig. 51.2 ). There is almost always thrombus/tissue on the filter struts ( Fig. 51.3 ).

Alarm

If there is difficulty STOP! DO NOT USE FORCE. Accept that it may not be possible to remove the filter. It is better to leave a permanent filter than cause an IVC laceration.

If filter retrieval is difficult it is often worth stopping and obtaining a CT of the abdomen.

Access site thrombosis:

Femoral vein thrombosis was particularly common with early devices but is only seen in 2–3% of patients with smaller contemporary devices.

IVC perforation:

Filter struts may perforate the caval wall ( Fig. 51.1 ); this is rarely clinically significant but may make the filter irretrievable. Caval strut perforation is common and is best assessed on CT.

Incorrect deployment:

There are four forms of incorrect deployment:

• Malposition in relation to the renal veins

• Incorrect filter sizing. At worst, this will result in fatal embolization of the filter. More commonly, it results in tilting or incorrect opening

• Conical filters can be tilted; this may reduce filter effectiveness

• The filter may open incorrectly so that the struts are not evenly distributed or appear not to reach the IVC wall. This may impair filter function. If you have any doubt, perform a limited CT to clarify the situation ( Fig. 51.4 ).

  

If you have placed a permanent filter, you are stuck, whereas a removable filter can be repositioned. If there is severe misalignment, a second filter may have to be placed above the first.

Tip

Try to deploy the filter in a straight portion of the IVC; it is more likely to be effective and much easier to remove.