Vascular surgery is a special area of surgery. It differs greatly from general surgical procedures in terms of methods, techniques, and equipment. Alexis Carrel developed the techniques of vascular suturing, and received the Nobel Prize for his work in 1912. The discovery of heparin was fundamentally important in surgeries involving the exclusion of blood vessels from circulation, due to its ability to prevent intraoperative thrombosis. What we now call vascular surgery began in the middle of the 20th century, and has been constantly developing ever since.
Vascular incision and suturing techniques
Transverse arteriotomy
The blood vessel is opened perpendicular to its longitudinal axis with a vascular scalpel, without complete transectio. It requires relatively intact vascular walls, and the absence of significant stenosis near the incision. The latter is important, because the degree of stenosis may increase during suturing if there are nearby plaques that severely obstruct the lumen. This may even lead to thrombosis at the affected site. The closure is made with monofilament suture, either simple running or interrupted sutures are used to close the incision. For small-caliber arteries and in the case of children, interrupted sutures are preferred. This technique is suitable for thrombectomy and embolectomy, for both arteries and veins.
Longitudinal arteriotomy
This technique is used if the vascular wall is thick, coated with plaques that significantly decrease the lumen, or if the lesion affects a longer segment or any side branches. A vascular scalpel is used to incise the blood vessel parallel to its longitudinal axis at the desired length. In these cases, longitudinal incision allows for a wide opening in order to repair localized pathologies. There are two possible suturing methods. If the lumen is consistently wide, monofilament material may be used to close the incision using direct running suture, without any additional material. This is a quick and safe method, provided the lumen remains sufficiently wide. Generally speaking, if the lumen is around 5 mm in diameter, the technique is safe to use. If the direct suture would likely result in a narrowed lumen, patch angioplasty is used instead. The patch may be from autogenous vein, bovine material (modified bovine-sourced carotid tissue), synthetic graft, or homograft. It is cut to the correct size, and, starting from one end, stitched around using monofilament suture. It is used in local thromboendarterectomy and bypass surgery.
Transverse transsection
The blood vessel is completely transected, so that the continuity of the vascular wall is interrupted between the stumps. This method is used if the goal is to anastomose the blood vessel end-to-end to itself or to a vascular graft. It is most commonly used in case of injuries and aneurysm surgery. The artery is either
anastomosed end-to-end to itself using simple running suture with monofilament material, or, if the ends remain unsuitable after the procedure, the missing segment is bypassed with some type of vascular graft interposition.
Desobliteration (removing obstacles from the blood vessel). Bypasses
Embolectomy
Embolectomy is the emergency removal of emboli which are blocking blood circulation. Embolization occurs when a thrombus breaks off from the heart or other segment of the circulatory system, and then obstructs a blood vessel distant from its origin. The blood vessel is incised transversely, and a balloon catheter (Fogarty catheter) is inserted in proximal – distal direction. The balloon is inflated, and then the catheter is slowly withdrawn. The embolus is carefully removed along with the newly formed thrombus. This maneuver is repeated until the balloon is no longer able to remove any more thrombi/emboli. The arteriotomy is closed transversely using monofilament suture with the techniques described above.
Thrombectomy
This procedure is most commonly used for clearing previously implanted grafts (usually at the distal anastomosis) when these become occluded. The incision is usually longitudinal, since in case of arterial thrombosis the blood clot forms in the diseased, stenotic vascular segment, and the plaques causing the stenosis must also be removed. If necessary, local open desobliteration is performed. Thrombectomy is insufficient if the thrombosis forms in the patient’s native vessels. In these cases, the desobliteration or bypassing of the affected vascular segment is required.
Thromboendarterectomy (TEA)
This is one of the most common type of vascular surgeries. Its goal is to remove both the thrombus and its cause by clearing the plaque from the vascular wall. The blood vessel is incised longitudinally, and then a layer is formed on a portion of the vascular wall with the help of a small spatula. Following this, the plaque is detached from the remaining layer of the vascular wall in a circular direction. The pathological section is then removed. Ideally, if the layer had been appropriately prepared, the result is a smooth, even internal surface. The plaque often continues in the segment beyond the bifurcation of the blood vessel. In this case, the plaque is cut sharply, and the downstream edge is tacked using Kunlin’s technique. The transverse edge is closed using monofilament material, with either running or interrupted suture to avoid dissection. The suture must completely penetrate the vascular wall, in order to avoid dissection.
Semi-closed (closed) thromboendarterectomy
The blood vessel is incised longitudinally, and a circular layer is formed in the above-described manner described above. Along this layer, a thin, dull instrument is guided downstream to continuously detach the circular layer up to the proximal end of the obstructing plaque causing the stenosis. This is usually the bifurcation of the common iliac artery, as the method is most often performed on this segment. Once we have ensured that the column of plaque is mobile, it is introduced into the ring-stripper, and carefully pushed up to the bifurcation. Here, the plaque cylinder is cut below the bifurcation with a looped wire threaded into the stripper. The instrument is withdrawn and the cylinder is removed. If the maneuver was successful, a spray of heavy inflow signifies this. If the operation was insufficient, intraoperative angiography is performed. If necessary, the blood vessel is dilated and/ or stented.
Eversion endarterectomy
This method is most often used for the desobliteration of the internal carotid artery.
The artery is explored. Following the clamping, the artery is transected, and and the vessel wall is everted (turning inside out). The outer layer of the blood vessel, which includes the adventitia and part of the media, is held with forceps and gently lifted away from the plaque.
The plaque core is developed circumferentially and held firmly with the forceps. As the plaque is being extracted from the artery, the adventitia is retracted backward, and the artery is pushed forward from within, causing the plaque to protrude and be separated from the outer arterial media and adventitia. It is then transected when an appropriate endpoint is reached.
This technique requires mobilization of a good segment of the proximal artery to allow eversion.
This technique used mainly in arteries without branches (internal carotid, external iliac, short segment of superficial or common femoral artery)
Bypass, interposition
If an occlusion is detected in a vascular segment, and it is unsuitable for desobliteration or if it is contraindicated due to the expected poor outcome, a form of bypassing may be performed to treat the occlusion. In these cases, the stenotic/ occluded vascular segment remains in place, and the bypass is anastomosed onto the healthy segments. This may be autogenous vein graft (most often the great saphenous vein), other homologous blood vessel, or synthetic graft. If autologous (great saphenous vein) or heterologous (donor vein or artery) blood vessels are used, the first step is the ligation of its side branches. Due to the presence of venous valves, vein grafts must be implanted in a reverse position, so that the valves would not inhibit blood flow; that is, the direction of the flow is from the direction of the thinner, originally distal, end. Anastomosis is performed either end-to-end or end-to-side, irrespective of the material of the graft. If anastomosed end-to-end, the involved artery is incised transversely, and the graft is circularly anastomosed onto the artery with monofilament suture. From a hemodynamic perspective, this solution is ideal. The other option is the end-to-side anastomosis, when a longitudinal arteriotomy is performed on the artery, and the graft is anastomosed onto this.
If the diseased segment is resected, and a graft is anastomosed end-to-end, it is termed an interposition (usually performed in the case of aneurysm or vascular injury).
However, if the detached blood vessel is anastomosed to a different nearby blood vessel, it is referred to as transposition.
Vascular graft materials
If biological material is implanted into a biological organism with therapeutic intent, it is referred to as transplantation.
Autologous grafts (autograft)
In this case, the patient’s own blood vessel (usually a vein) is used during bypass. Autogenous vascular grafts remain unobstructed for the longest in time, and resist infection the most effectively. Both the great or small saphenous vein may be used, as well as the cephalic vein, or even the femoral vein. Arterial segments can also be used either as a patch or as a shorter interposition. For example, previously occluded segments of the superficial femoral artery may be used after desobliteration.
Homologous grafts (homograft, allograft)
In this case, human blood vessels are used, which, after a special freezing process, may be stored for long time at ‑110°C (in a homograft bank). Any artery may be used from the aorta to the popliteal artery, along with veins from the vena cava to the popliteal veins and the previously mentioned superficial veins. These materials have a worse rate of remaining unobstructed, and are less resistant against infections than autologous blood vessels. However, in case of infection, homologous implants have better results against infection than synthetic grafts. Rejection does not occur. In this case, the genotype does not matter.
Heterologous grafts (xenograft)
Transplantation between different species is called heterologous. In (human) vascular surgery, the most commonly used xenografts come from cattle (bovine graft).
Synthetic vascular grafts
The disadvantage of these synthetic blood vessels compared to biological material is that they are less resistant against infections. If an infection is present in the bloodstream, microbes may accumulate and proliferate on the graft. This may lead to the occlusion of the graft, the failure of the anastomosis, pulsing hematoma, and, ultimately, fatal hemorrhaging. There are two basic materials in this group: Dacron and polytetrafluorethylene (PTFE or teflon). Synthetic blood vessels may be woven or knitted from Dacron strands, while PTFE grafts are molded. A mix of graft material and stent yields stentgrafts (Figure 6). When the bypass runs over joints, the synthetic grafts may break, which leads to occlusion. In order to prevent this,the prostheses are externally reinforced with rings or synthetic coils, making them more resistant to bending and breaking. There are grafts that are impregnated with antibiotics and silver nitrate. These may resist infections better, but so far, the results are mostly convincing in the area of prevention of infections. If an infection is already present, the safest option is to use biological grafts.