Transcatheter aortic valve implantation (TAVI) and endovascular aortic repair (EVAR) are increasingly being used as therapeutic options for patients with severe aortic stenosis ineligible for surgery and with aortic aneurysm with suitable anatomical features. Despite encouraging results from randomised studies and registries regarding the pursuit of endovascular treatment in selected patients, these procedures may be associated with severe complications, especially related to the vascular route of access.1–8 In this article we review the incidence and cause of vascular access complications associated with TAVI and EVAR and their management and prevention.
The Problem
The devices currently available for valvular replacement (Edwards SAPIEN system; Edwards Lifesciences, CA, US; and CoreValve® revalving system; Medtronic, MN, US) and aneurysm repair (Talent™; Medtronic; Excluder® and TAG, Gore; AZ, US) share the requirement of a large sheath to be delivered via the common femoral artery (CFA). The Edwards-Sapien valve is available in two sizes, 23 and 26mm, requiring an external delivery sheath calibre of 24 French (Fr) (external diameter 7.7mm) and 28Fr (external diameter 9mm), respectively. Notably, the newest Edwards-Sapien NovaFlex systems can undergo delivery via an 18Fr sheath (external diameter 6.5mm). Similarly, both the 26 and 29mm CoreValve protheses require an 18Fr introducer sheath. Introducer sheaths for endoprothesis to treat aortic aneurysms vary from 14Fr for abdominal devices up to 24Fr for thoracic devices.
The reported rate of vascular complications varies widely depending on the definition of major vascular complications (MVC) and different levels of experience between operators and centres. Early experience with larger delivery sheaths (>18Fr) demonstrated a relatively high incidence of MVC (from 8 to 16%), with a negative impact on survival.4,8 By contrast, smaller delivery systems demonstrated a lower incidence of MVC (2–13%), contributing to better outcome of these patients compared with those in whom larger delivery systems were utilised.1,7 However, it should be noted that the incidence of MVC in both TAVI and EVAR procedures has been remarkably reduced with the increasing experience of operators.2,8 Interestingly, the need for blood transfusions remains high in all series. A recently published review of percutaneous EVAR studies confirmed the low incidence of vascular complications (4.4%), which was similar to rates of open EVAR.9
Vascular Complications – What Should I Fear?
Dissection and perforation of the ilio-femoral arteries are the most important vascular complications during the TAVI and EVAR procedures. Both may occur as a consequence of excessively traumatic sheath insertion. Non-occlusive, limited, retrograde arterial dissection is usually benign and, once antegrade flow is restored, conservative management allows spontaneous healing. More extensive arterial dissection with flow impairment needs endovascular treatment with a stent or, less commonly, surgical repair.
More dramatic, with life-threatening consequences, is vessel perforation associated with retroperitoneal haemorrhage (see Figure 1). This insidious complication is heralded by sudden and often unexplained hypotension, which must be investigated immediately. As other important causes, such as pericardial tamponade following a TAVI procedure, may lead to acute and severe hypotension, prompt exclusion of these complications is of pivotal importance. Additionally, a high level of suspicion is required because when the sheath is large enough to be occlusive, bleeding might become evident only after removal. Time is critical due to the high volume of blood loss through the ruptured iliac artery. Immediate volume expansion and bleeding control by placement of a highly compliant occlusion balloon proximally to the area of suspected perforation provides time for definitive management, either surgical or endovascular. Special attention must be paid when sheath withdrawal meets some resistance: this could mean adherence between endothelium and sheath, which is unusual but possible with large and occlusive sheaths. Forcing sheath removal in the presence of adherence to iliofemoral arteries carries the risk of complete vessel avulsion with subsequent catastrophic haemorrhage. Smaller sheaths, periodic sheath rotation and early removal can minimise this risk. When this phenomenon is suspected, pre-emptive placement of an occlusion balloon before further sheath removal attempts and preparation for possible surgical repair is prudent (see Figure 2).
During all phases of delivery and sheath device manipulation, a high level of attention is required. Abortion of the procedure should be considered if sheath progression finds major resistance (unusual movement of arterial calcification on fluoroscopy during sheath advancement or removal). If this is the case, an alternative access site (subclavian or transapical in TAVI procedures) should be considered. As an alternative, in the presence of severly unsuitable femoro-iliac anatomy, reconstruction of the ilio-femoral artery axis with stents or endografts can be a feasible solution.10
Finally, potential failure of the vascular closure device – used in the vast majority of cases for access-site closure in both TAVI and EVAR procedures – may lead to bleeding of varying severity, from that needing prolonged manual compression to complete surgical reparation (see below). Stenosis and occlusion of the artery might also be a consequence of vascular closure device failure: in this case a balloon angioplasty is usually enough to restore patency of the vessel (see Figures 3 and 4).
Although very rare, infection of the site of puncture has also been described, drawing attention to the requirement for meticulous preparation and sterilisation of the access site.11
Avoiding Vascular Complications
Patient Selection
The first step in avoiding MVC is the extremely careful selection of patients, with particular attention to ilio-femoral anatomy. Once the decision for TAVI or EVAR procedure has been made, the next step is the detailed bilateral imaging of the femoral and iliac arteries. Ideally, non-tortuous vessels with minimal calcification would be the best scenario for patients undergoing TAVI or EVAR. By protocol, the minimal luminal diameters of both the iliac artery and CFA, the degree of vessel wall calcification and the vessel angulation must be carefully assessed. Healthy, compliant vessels should be >6mm to accommodate 18Fr sheaths, >7mm for 22Fr sheaths and >8mm for 24Fr sheaths. When vessels are calcified or angulated, the minimal vessel diameter must be larger (at least 1mm or more of the values reported previously) in order to accommodate such a large sheath more easily. Transfemoral access should be avoided in the following cases:
- previous aorto-femoral bypass;
- bulky aortic atherosclerosis (severe atheroma with mobile element >5mm);
- a minimal luminal diameter smaller than the external diameter of the introducer sheath;
- severe vessel angulations (minimal angle <40°); and
- circumferential and extensive vascular calcifications.
Non-invasive computed tomography (CT) angiography scan or invasive iliac angiography using a graded pigtail catheter provide more reliable vessel imaging. Sixty-four-slice CT is performed with 90ml of iodinated medium contrast injected at a rate of 3ml per second with an axial field of view of 50cm and a longitudinal coverage of the entire aorta and ilio-femoral arteries, and is considered to be the gold standard method for the quantitative assessment of femoro-iliac artery diameter. Femoro-iliac angiography should be performed at the same time as coronary angiography screening, with 20ml of iodinated contrast injected into the infra-renal aorta to study the contralateral to the selected site of main access via the femoro-iliac axis, and 10ml selectively in the ipsilateral common iliac artery (see Figure 5).
Vessel Puncture and Closure
Identifying the correct site where the vessel can be safely accessed is a critical point. The correct site is the midline of the anterior arterial wall of the CFA in a disease-free area (see Figure 6). When a suture-based closure device is used in TAVI and EVAR, a high puncture site is associated with increased risk of haemorrhage and retroperitoneal bleeding after patient mobilisation due to inguinal ligament fibre incorporation into the sutures of the closure device, leading to late failure of the latter (see Figure 1). Both superficial femoral artery and posterior/lateral arterial wall puncture have been shown to be associated with increased bleeding risk and arteriovenous fistula formation. Intraoperative ultrasound- or fluoroscopy-guided puncture improve success rate and reduce lowering complications, especially during the initial phase of the learning curve.
The routine utilisation of an adequate closure device (Prostar® XL; Abbott) allowed the development of the complete percutaneous approach in EVAR, initially performed with surgical exposure of the CFA (open EVAR). The so-called ‘pre-closure’ technique consists of placement of one (for sheaths up to 18Fr) or two (for even larger sheaths) Prostar XL closure devices within the vessel before introducer insertion. The first Prostar XL is advanced into the CFA until pulsatile blood flow is observed through the marker lumen, indicating that the sutures and needles are in the correct position. All four needles carrying sutures are then deployed. The sutures are removed and loosely secured with haemostats on the drapes around the access site. A second Prostar XL device is then deployed at 45° to the previous device. At the end of the procedure the Prostar’s sutures (still ‘half-tied’) are knotted and closed simultaneously with sheath removal.
A recent review of studies regarding percutaneous access for EVAR showed that this strategy is safe and effective, with a 90% procedural success rate and an acceptable complication rate (4.8%). Time to haemostasis and time to patient mobilisation, hospital length of stay and blood loss have been reduced in comparison with open EVAR with surgical exposure of the CFA (CFA ‘cut-down’ technique).
A Wire to Survive – The Cross-over Technique
Recently, Sharp et al.12 proposed a simple way to approach the problem of accurate CFA puncture in an effort to minimise the risk of MVCs. After detailed angiographic imaging of the iliaco-femoral arterial axis, operators might define the main CFA, i.e. the artery that will receive/accommodate the larger sheath. The cross-over technique allows safe and accurate puncture of the main CFA under fluoroscopic guidance, and safe removal of the sheath due to the presence of a wire in the main CFA. The contralateral CFA should be cannulated with a 40cm braided 7Fr sheath and the aortic bifurcation should be crossed towards the main CFA, generally using a pigtail catheter. Through the pigtail catheter a 0.025-inch wire (e.g. SV5; Boston Scientific) should be advanced and left in the main CFA; selective angiography is performed to indicate the exact anatomy of the artery, the midline of the vessel, the side branches and, more importantly, the areas of tortuosity and heavy calcification that must be avoided during the puncture. When the exact site of puncture has been identified, if possible, the pigtail catheter can be advanced at the middle of the CFA, providing an exceptional marker for CFA puncture. Once the correct position of the catheter is angiographically confirmed, the distal, rounded tip of the pigtail catheter can serve as the ideal marker for accurate CFA puncture: just puncture directly at the centre of the pigtail’s rounded tip. Alternatively, the main CFA is punctured and cannulated under fluoroscopic guidance using the wire as a landmark. The above-described pre-closure technique is now applied. The skin overlying the artery is then incised (1cm incision) and a blunt dissection is used to create a track down onto the artery. A 7Fr dilator followed by a 10Fr dilator and sheath is then inserted into the CFA. Sequential increasing of sheath size avoids excessive trauma to the vessel, while giving the artery enough time to adapt its diameter to the sheath’s large size. In most TAVI cases, the aortic valvuloplasty balloon requires sheath upsizing up to 14Fr as a first step. Following valvuloplasty, a second upsizing step from 14Fr up to 18, 22 or 24Fr is needed depending on the size of the prosthetic valve selected.
After the valve is deployed, the prosthetic valve delivery system is removed and the large introducer sheath remains at the junction of the distal aorta and contralateral CFA. At this point, the cross-over of aortic bifurcation is repeated with the pigtail catheter and a 0.025-inch wire (e.g. SV5; Boston Scientific) placed in the main CFA. Notably, the wire should be guided into the introducer sheath in the main CFA in order to avoid the possibility of exiting a possibly ruptured vessel beneath the sheath.
Withdrawal of the large sheath starts with multiple steps: first, 10mm retraction followed by subsequent angiography to ensure iliac patency and absence of any damage. Before a further 20–30mm of retraction, a semi-compliant peripheral angioplasty balloon is placed proximally to the sheath via the cross-over pathway to provide immediate haemostasis in case of iliac rupture. A second angiography is then performed to promptly exclude possible rupture at the level of the iliac arteries – a catastrophic complication that could easily lead to massive and potentially lethal haemorrhage. In that case, immediate inflation of the proximal balloon ensures haemostasis and gives time to evaluate the adequate therapeutic approach, either surgical or endovascular, without risking haemodynamic compromise. Another check should be performed after a further 20–30mm retraction of the sheath for evaluation of the external iliac artery. If the vessel is intact, the operator could start managing the closure of the site of arterial access. The knots of Prostar sutures are ‘half-tied’ externally to allow more rapid deployment. Before final removal of the sheath, keeping the angioplasty balloon inflated in the external iliac or, alternatively, some external manual compression reduces or blocks the flow to the puncture site, helping operators to fully remove the sheath and tie up the Prostar knots without major bleeding. A little extravasation can occur at this point, mainly because the closure device’s suture knots may be too tight or too loose, resulting in a small hole in the artery’s wall. This does not necessarily mean failure of the Prostar device, as usually successful closure can be achieved within the next couple of minutes. Having the 0.025-inch wire placed in the superficial femoral artery, a gentle inflation of the balloon at very low pressure at the site of the puncture would facilitate more rapid haemostasis, as it can gently stretch the vessel and tighten the Prostar sutures.
In a relatively low number of cases, the Prostar closure device may fail, leading to significant blood extravasation. Repeated balloon inflations for a prolonged period of time (>10 minutes) could lead to successful bleeding control and eventually closure of the access site. Definite Prostar failure should be considered if two 10-minute inflations of the balloon fail to stop extravasation and in this case urgent surgical repair is indicated (see Figure 7). However, as described above, with the balloon inflated in the proximal part of the CFA, surgical repair can be easily achieved without hurry, with the bloodless surgical field providing the opportunity for an optimal result. Otherwise, once haemostasis is achieved, the sutures are cut and the skin incision closed at a later time using surgical adhesive strips (Steri-Strips). It is better to keep the incision trauma open for a while to ensure immediate identification of a delayed blood leak or local haematoma. Finally, if a stenosis of the CFA at the site of the Prostar sutures is evident, a prolonged (at least five minutes) low-pressure inflation of the balloon could positively remodel the artery. The contralateral femoral access could be closed either manually or with a closure device. In our catheter laboratory we use a modified version of the cross-over technique, as shown in Figure 8.
In EVAR procedures the technique should be the same, except for the use of a larger introducer sheath, which is also needed in the contralateral artery; this means that the cross-over technique could be used for the main CFA access, and careful removal and closure with the pre-closure technique of the smaller sheath should be undertaken. However, theoretically, a third access (e.g. radial or brachial) could be used before ending the procedure, placing a guidewire and a balloon in the contralateral CFA as previously described.
Conclusion
Vascular access is one of the leading complicationss of the TAVI and EVAR procedures, and can have severe consequences. The continuous growth of operator experience together with the evolving technology of the devices and refinement of the procedural techniques as described in this article will reduce dramatically the incidence of MVC.