Angulation and tortuosity

Editors-In-Chief: C. Michael Gibson, M.D., Alexandra Almonacid M.D., and Jeffrey J. Popma M.D.; Associate Editors-in-Chief: Duane Pinto, M.D., Brian C. Bigelow, M.D.

Overview
Severe vessel tortuosity and the presence of eccentric angulated lesions have long been identified as significant predictors of percutaneous coronary intervention (PCI) failure, as well as worse clinical outcomes. Challenges in the treatment of angulated lesions and lesions in tortuous segments includes difficulty in delivering the interventional equipment and the increased risk of vessel dissection and vessel perforation.

Angiography
A highly curved or tortuous vessel segment may result in substantial foreshortening of the artery. The length of the stenosis should therefore be assessed in the most unforeshortened projection so that the appropriate length of stents and balloons can be selected.

Guiding Catheter Selection
When choosing a guiding catheter, it is important to select the appropriate guiding catheter based upon the vessel location, takeoff, and size so that coaxial alignment and support are maximized.

"Deep seating" the guide or selective coronary intubation may provide improved support to deliver guidewires, balloons, or stents in a tortuous and angulated vessel. However, this aggressive strategy is associated with an increased risk of vessel injury. If using this technique, a guide with side holes helps to maintain perfusion. If a guide catheter with side holes is used, intracoronary pharmacotherapy may not be delivered at high concentrations.

There are specific guiding catheters that may be selected so that coaxial alignment may be optimized. For instance, larger guiding catheters (7 or 8 French) offer improved support. Additionally, the material composition of the catheter is also important, as the material affects torque control, kink resistance, risk of vessel trauma, and stiffness. Different catheters can also be used depending on whether you are working with the left or right system. Extra backup (XB) guiding catheters in the left coronary system, and Ampltaz left (AL) guiding catheters in the right coronary system, can provide improved support. However, these catheters can increase the risk of guide trauma to the proximal vessel, so extra care must be taken. If the operator is unable to pass the wire word the angioplasty equipment, then consideration should be made to switch to a guide catheter system that provides greater support. The operator should also confirm that the guiding catheter is in coaxial alignment with the lumen of the artery to improve the delivery of guidewires and equipment. This is particularly true in the right coronary artery. Switching to the 45° RAO view can help in determining the anterior posterior angulation of the guide catheter.

A long femoral sheath can straighten iliac tortuosity and improve guiding catheter support.

Shaping the Wire
In severely angulated arteries, sometimes both a primary bend and a secondary bend to the cornary guidewire are required. The primary bend should approximate the shape of the lesion while the secondary bend should approximate the shape of the artery in the tortuous segment.

Initial Guidewire Selection
A flexible "workhorse" wire with a floppy tip can be used to initially cross the lesion. It is important to remember that a stiff guidewire in a very tortuous vessel may frequently lead to "vessel pleating" and pseudo-lesions.

Conventional 0.014-inch guidewires are often sufficient when treating angulated and tortuous lesions, but other options may offer distinct advantages. For instance, stiffer-tip guidewires (wires in which the core of the wire goes all the way to the tip of the guidewire) offer a greater ability to manipulate the tip, while tapered-tip guidewires may be useful if the wire prolapses away from the lesion. Although stiff wires are better able to track balloons to lesions than flexible wires, they may handle poorly and be more likely to result in adverse events. Since extra-support wires have a stiffer shaft, they may help straighten tortuosity and ease movement. However, extra-support wires can also increase the likelihood of "vessel pleating" and "pseudo-lesions".

Switching to a Stiffer Wire after Crossing with the Flexible Wire
It is possible to first cross the lesion with a flexible workhorse wire and then exchange it for a heavy-duty wire through a balloon lumen. This can be accomplished in an over-the-wire (OTW) system or an intracoronary catheter such as an Ultrafuse or Transit catheter. OTW balloon systems push and track more easily than monorail systems and enable guidewires to be exchanged.

Utilization of Balloons to Improve Wire Passage
Placement of a blocking balloon inflated at low pressures can help deflect a guidewire into the appropriate segment or branch. Long balloons (30-40 mm) help straighten angulation proximal to the lesion to facilitate passage of the guidewire.

Directable Tip Guidewires
There are new directable-tip guidewires and catheters that are of assistance in angulated lesions in tortuous vessel segments. The Seer-It device manufactured by Cordis Corporation and a catheter that allows for the tip to be flexed named The Venture Catheter manufactured by St. Jude Medical Incorporated are new technologies that may be of use.

Use of the "Buddy Wire" Technique
In some circumstances, the addition of a second guidewire across the stenosis, commonly referred to as a “buddy wire,” will aid in the delivery of the device. The second wire often straightens the vessel allows for easier delivery of the device or stent. If a buddy wire is used, a wire of different stiffness and lubricity from the original wire is usually chosen. Care should be taken to remove the body wire before deploying the stent or activating an atherectomy device. Furthermore, concerns regarding wire entrapment and microembolization of wire coating should be considered. These topics are actively being researched, but to date, they have not proven to be significant clinical problems.

Over the Wire Versus Monorail Balloons
Monorail catheters, also known as rapid-exchange catheters, were designed to allow an easier exchange of catheters by a single operator. They consist of a short catheter shaft that contains two lumens; one is used for balloon inflation and extends through the whole length of the catheter, and the second houses the guidewire and only runs through a portion of the shaft. While monorail catheters have advantages, including enhanced visualization and low-profile balloons, one of their major limitations includes poor performance in severely stenotic and angulated lesions. Therefore, over the wire system (OTW) balloons may offer an advantage in tortuous and angulated vessel segments.

Fixed Wire Balloon Catheters
Fixed balloon catheters, which have distal flexible steering tips with the balloon mounted on a central hollow wire, may deliver more easily across tortuous vessels or stenosis, but also cannot recross the lesion without first removing the system. Furthermore, steerable catheters, such as the Venture catheter, may allow for improved direction of the wire into extremely angulated side branches.

Delivery of Stents in Angulated in Tortuous Lesions
If OTW systems fail, then lower profile monorail and fixed wire systems, such as the SVELTE stent in some countries. Also, shorter stents are easier to deliver than longer stents, and newer bare metal stents, such as those made of a chromium cobalt alloy, may be easier to deliver than older generation stents. Furthermore, newer drug eluting stents (DES), such as Xience/Promus or Endeavor, have smaller strut profiles and may also be easier to deliver, in comparison to first generation DES. A Wiggle wire can be used to facilitate the passage of a balloon or stent in tortuous segment by optimizing the coaxial push.

Additional Techniques to Improve the Passage of Wires and Balloons across Angulated Segments
Having the patient take a deep breath in and hold it can straighten a vessel segment and can improve both wire and device passage. In some rare instances having the patient completely exhale and hold it can also improve wire and device passage.

Complications
In general, high procedural success (>85%) and low complication rates (<3%) have been reported. However, these assessments of outcomes are limited by variable definitions of angulation and tortuosity. More specifically, angulation >60 degrees is associated with an increased risk of failure. Also, rotational atherectomy of lesions >45 degrees should be avoided, as they are have lower success rates and an increased risk of dissection and mortality. Stenting of highly angulated lesions may be associated with higher restenosis rates at the points of angulation. There may also be an increased risk of stent fracture in these lesions.

There is an increased risk of subintimal passage of the guidewire in highly angulated vessel segments. A 1:1 torque response, easy advancement of equipment, and the absence of distal wire kinking suggest a safe intraluminal position. The position of the wire can be confirmed by advancing a small balloon distally in performing a distal injection.

Coronary Artery Bypass Grafting
Patients with severely angulated or tortuous lesions that supply large areas of the myocardium should be considered for coronary artery bypass graft (CABG) surgery, especially if multivessel disease is present and percutaneous revascularization is deemed high risk or unsuccessful.

Future Considerations
The degree of angulation at bifurcation lesions, which is a possible independent predictor of percutaneous coronary intervention (PCI) outcome, can be assessed with three-dimensional quantitative coronary angiography. The feasibility of this analysis is currently being investigated.

Furthermore, it is suggested that PCI affects the distal bifurcation angle (between the LAD and LCx). Both the proximal (between the left main (LM) and circumflex branch of left coronary artery (LCx)) and distal bifurcation angles are affected by motion during the cardiac cycle.