Steering catheters ( otherwise known as usher catheters ) are the conduit tube by which transdermal coronary intercessions ( PCIs ) are performed. Choosing an appropriate guiding catheter is a calculated action undertaken upon the mark vas at the oncoming of PCI and a misreckoning at this measure may be puting the phase for an unsuccessful PCI effort. In the worst-case but non uncommon scenario, unsuitably choosing an aggressively-curved guiding catheter may bring on a major complication such as ostial coronary dissection within seconds of cannulating the mark vas! On the other manus, stableness of the chosen usher catheter throughout the instance is paramount to any successful PCI effort.
Apart from supplying entree to the ostium of the mark vas for bringing of interventional devices, steering catheters serve three other maps. As with coronary angiography, contrast is selectively delivered to the coronary arteria intubated ; nevertheless, opacification is greater than with diagnostic catheters in position of the larger internal lms and hence better profiles the coronary lesion ( s ) , sometimes motivating a alteration in PCI scheme when the lesion ( s ) appear more/less terrible than indicated in the original diagnostic angiogram.
Third, the guiding catheter provides mechanical support to let transition of the interventional kit to and past the coronary lesion ( s ) with subsequent deployment of balloons/stents at the lesion site. The support provided by a guiding catheter can be described as either active or inactive. Passive support is due to a guiding catheter ‘s built-in stiffness, conformance to the aortal root curvature and grade of co-axial alliance of the distal tip within the intubated coronary arteria. When utilizing a guiding catheter in a inactive manner, extra use is by and large non required for advancement/deployment of interventional devices. If inactive support is unequal, so active support can be achieved either by pull stringsing the guiding catheter so that the aortal root provides “ backup ” or by deep sub-selective promotion of the guiding catheter into the coronary vas.
Finally, appraisal of coronary arterial force per unit area at the tip of the guiding catheter is possible since the fluid-filled lms is in continuity ( in between contrast injections ) with a manifold connected to an external force per unit area transducer, as with diagnostic coronary angiography.
23.2.1 Design characteristics of steering catheters
A battalion of factors need to be considered in steering catheter design. These include catheter size ( maximizing internal diameter whilst understating wall diameter ) , radial strength ( to minimise “ crimping ” ) , understating internal frictional opposition, columnar and torsional strength ( to maximize “ pushability ” and “ torquability ” ) , overall flexibleness and radiodensity. The chief difference in map between diagnostic versus steering catheters is the latter ‘s demand for supplying support and transition for interventional devices hence the difference in design characteristics as summarized in Table 23.2.1.
There may be a tradeoff in order to accomplish the coveted balance of features. For a given external diameter, increasing lms diameter can merely be achieved by cut downing wall thickness, yet overall properties may be preserved by using different wall stuff and building as claimed by makers of different trade names of steering catheters. More flexible catheters should be safer to pull strings into active battle yet a stiffer catheter should supply better inactive support and potentially rid of the demand for active support. Therefore a design via media frequently utilized is to plan the distal part of the guiding catheter to be softer and more flexible while retaining strength and stiffness in the chief proximal part of the catheter.
Table 23.2.1 Comparison of diagnostic versus steering coronary catheters
Scope of sizes available: 4F –
Scope of sizes available: 5F –
Wall constructed in two-layers
Wall constructed in 3 beds by and large
Thicker wall diameter yet less radial strength
Thinner wall diameter yet greater radial strength
Smaller internal diameter/narrower lms
Larger internal diameter/wider lms
Lesser transmittal of rotational torsion
Greater transmittal of rotational torsion
No radiopaque tip marker
Radiopaque tip marker nowadays
Angulated primary ( most distal ) curve
More unfastened primary ( most distal ) curve
23.2.2 Size of steering catheter
Choice of steering catheter size is by and large determined by the size/profile of interventional devices anticipated to be used during the process ( e.g. straightforward PCI balloons/stents would non ask as big a guiding catheter internal lms as PCI affecting “ snoging balloon ” technique or rotational atherectomy ) . In maintaining with all vascular devices, size is described in footings of external diameter whereby 1 French ( Fr ) = 0.33cm. In general, straightforward PCI is conducted utilizing 6Fr steering catheters whereas the more complicated processs described may necessitate 7Fr or 8Fr catheters undertaken normally via the transfemoral path.
However, progressively transradial entree is being utilised for PCI as it has less associated vascular complications ( e.g. puncture site or retroperitoneal bleeding ) , allows for earlier patient mobilization post-procedure and has overall better patient satisfaction ( mentions! ) as compared to transfemoral entree. Disadvantages of transradial PCI tend to associate to the restriction of steering catheter size imposed upon by the radial arteria ‘s smaller diameter as compared to the femoral arteria, particularly if the smaller quality consequences in inability to finish the whole process via this path due to radial arteria cramp ; nevertheless, with transradial entree there is seldom any post-procedure complication of any clinical effect including early/late thrombosis of the radial arteria ( up to 5 % incidence- mention ) .
Until late the size of steering catheter could at most be equal to that of the entree sheath size i.e. if it is merely possible to infix a 5Fr sheath into a little quality radial arteria so a 5Fr guiding catheter would be the largest to suit such a sheath. A modern option has been the coming of “ sheathless ” steering catheters, whereby as the name suggests a guiding catheter may be inserted without a vascular entree sheath. Sheathless steering catheters with an outer diameter about 1.5F size smaller than the corresponding radial arteria sheath overcomes this restriction with a high success rate ( mention ) .
Regardless of entree path complications, the chief advantages of utilizing as little a guiding catheter as possible to finish a successful PCI include less possible for occlusive cannulation of the mark vessel ostium but deeper cannulation if increased active usher support is required. Conversely smaller Fr steering catheters provide less inactive support and sometimes may necessitate the added complexness of upsizing to a larger diameter if more bulky interventional devices become necessary during the PCI, which is particularly non ideal in the emergency/ bail-out scene.
23.2.3 Shape of steering catheter
Steering catheters are available in a assortment of pre-formed forms designed to conform to specific aortal arch/root and coronary anatomy. As shown in Figure 23.2.1 ( figure needed ) , a guiding catheter can be described in footings of the constellation of its primary, secondary and ( if nowadays ) third curves. By convention, the numerical value assigned to each catheter is a measuring of the distance between the primary and secondary curves of the catheter, where a higher figure denotes a more unfastened constellation.
The most normally used diagnostic catheters for coronary angiography are the Judkins left and right constellation catheters, and their guiding catheter opposite numbers are every bit popular for PCI ( see Figure 23.2.2, figure needed ) . Judkins catheters are available in a scope of sizes, from 3cm to 6cm. As alluded to in Table 22.214.171.124, a Judkins steering catheter has a shortened distal tip and more unfastened primary curve as compared to a Judkins diagnostic catheter, a design characteristic which improves the coaxal relationship of the tip of the guiding catheter within the coronary ostium and hence reduces the potency for coronary injury.
Other popular steering catheter forms include the Amplatz constellations, which provide a greater grade of inactive support when seated, but tend to prosecute the coronary vas more sharply than their Judkins opposite numbers with consequent increased hazard of doing coronary/aortic dissection. However in patients with a superior coronary beginning in peculiar, Amplatz catheters frequently provide more coaxal coronary battle and better support due to their conformance to the aortal root curvature ( see Figure 23.2.3, figure needed ) .
In general, the interventionalist ‘s attack is to take a guiding catheter form appropriate to the anatomy to accomplish battle in the most coaxal mode, and rely upon inactive support for the promotion of interventional devices. However, when handling Type C lesions ( e.g. terrible calcific strictures, drawn-out lesions in Byzantine vass, or chronic entire occlusions ) , steering catheter use to make active support may be required as antecedently alluded to. With the steering catheter already engaged, the method to accomplish active support by deep subselective battle is to force the catheter tip over an undeployed angioplasty balloon in the proximal vas or “ pull ” it in over the guidewire when the angioplasty balloon is inflated. Prior to this tactic, it is of import to foremost estimate the orientation of the guiding catheter tip within the proximal vas section: in the instance of the RCA, this is normally best visualised in the right front tooth oblique ( RAO ) projection with clockwise rotary motion of the guiding catheter being normally needed to accomplish coaxal alliance.
Alternatively if a Judkins-type catheter is unmoved, so use of the guiding catheter into a form that conforms to the aortal root is another method of active battle termed “ Amplatzing ” . This alteration in constellation can be induced with both Judkins left and right guiding catheters. In the instance of the Judkins left steering catheter, the tactic is performed by progressing the guiding catheter over a deployed angioplasty balloon whilst using counterclockwise torsion, with coincident abjuration of the balloon catheter: the steering catheter tip should so prolapse upward into the left mainstem while the secondary curve becomes dead set into the left coronary cusp, presuming an Amplatz-like form. ( ? illustration )
Potential acute complications of both methods of active battle include intimal injury doing coronary dissection and/or occlusion of the arteria. A ulterior complication thought to be related to steering catheter tip injury is rapid patterned advance of coronary stricture, which has been described with left mainstem disease.
23.2.4 Other assortments of steering catheter
Some conventional guiding catheters have a fluctuation available with a side-hole at the tip to let extra transition of blood to the intubated coronary arteria, when there is deemed to be deficient infinite between the outer wall of the guiding catheter and the interior lms of the intubated coronary to let for equal coronary perfusion. One disadvantage of side-holes is the little decrease in vessel opacification during contrast injections due to some of the contrast get awaying via the side-holes. The chief disadvantage is that there may still be unequal end-bed coronary perfusion but yet the visual aspect of a normal force per unit area following derived from side-hole flow, and hence many interventionalists do non comprehend that benefit is derived from the usage of side-hole catheters.
“ Mother-and-child ” steering catheters
Aggressive guiding catheter support and other angioplasty techniques may neglect to negociate transition of interventional devices to the mark lesion in complex coronary anatomy. A recent development to overcome this challenge has been the coming of “ mother-and-child ” steering catheters. It basically involves telescoping a specifically designed longer length but smaller sized ( “ kid ” e.g. 5F ) guiding catheter into a larger sized ( “ female parent ” e.g. 6F ) criterion steering catheter so that the tip of the “ kid ” catheter protrudes beyond the “ female parent ” catheter and efficaciously deeply intubates the mark vas to let bringing of a stent.
The Heartrail IIA® ( Terumo, Japan ) is one such system, utilizing the mark vessel itself to supply the excess backup support required for stent bringing. The absence of a primary curve and the flexibleness of its tip permit the “ kid ” catheter to stay coaxal within the mark vas, taking to cut down the hazard of catheter-induced coronary dissection. The Guideliner A® ( Vascular Solutions Inc, Minneapolis, USA ) is a fluctuation upon the subject: it is a “ kid ” catheter extension delivered through a standard guiding catheter on a monorail. It comprises a flexible 20 centimeter consecutive extension ( internal diameter about one Fr size smaller than the guiding catheter ) connected to a stainless-steel push tubing, with a “ neckband ” that can be deployed through the bing Y-adapter for rapid exchange bringing. The extension comprises an interior Teflon ( PTFE: Polytetrafluoroethylene ) liner, surrounded by a stainless-steel spiral ( to impartsflexibility and strength ) and an outer bed of PebaxA® polymer. The quoted internal lms diameters of both systems are shown in Table 23.2.2. The smallest “ kid ” catheter available is a 4 Fr Kiwami A® ST01 “ kid ” catheter developed by Terumo which is lower profile, has a more flexible shaft and an extra hydrophilic surfacing leting for easier deep battle.
Table 23.2.2 Comparison of internal diameter for HeartrailA® and GuidelinerA® “ kid ” catheters
HeartrailA® internal diameter
GuidelinerA® internal diameter
Apart from hazard of coronary dissection from deep battle, a possible increased complication of the “ mother-and-child ” systems is air embolism- this can happen when the “ kid ” catheter is wedged against the vas wall. Methods to avoid air intercalation in this context include careful attending to the force per unit area following displayed and look intoing there is backflow of blood from the manifold ‘s Y-connector after stent deployment.
Tornus guiding catheter
? talk about normal coronary arteria origin/angles
( will speak about dilated aortal root/ascending aorta when depicting different JL sizes for LCA guide caths )
23.2.5 Steering catheter choice schemes
Choice of an appropriate guiding catheter for any interventional process is of paramount importance to the successful completion of the instance without complications. Apart from the issue of size as discussed above, pick of an appropriate assortment of steering catheter is based upon
diagnostic catheter used for the original diagnostic angiogram
path of entree ( radial V femoral )
size and form of the go uping aorta and aortal arch
mark vas features
mark lesion features
type of interventional devices planned for the process ( e.g. rotational atherectomy )
It is ever utile to reexamine the features of the original diagnostic catheter in footings of whether its form and size provided good stableness and orientation during the diagnostic angiogram. Generally-speaking, if for illustration a JL4 diagnostic catheter appeared to be an appropriate tantrum, so A? Fr size smaller guiding catheter ( i.e. JL3.5 ) would supply a corresponding tantrum. However, if path of entree has changed between diagnostic and interventional processs ( e.g. from radial to femoral or vice-versa ) so this equation will non keep true and a given form may supply unequal support for device deployment compared to the minimum support required for selective coronary angiography, asking choice of a more aggressive guiding catheter. At any rate, the influence of size and curvature of the go uping aorta/aortic arch upon the behavior of the diagnostic catheter should assist foretell the behavior of a likewise shaped steering catheter.
For a given mark vas, the presence/absence of important atheroma and geometrical orientation of the proximal coronary section is a major factor finding the pick of steering catheter, as is the presence/absence of important vessel calcification. Target lesion variables necessitating to be taken into history include figure of lesions to handle, lesion badness ( particularly chronic Vs acute nature of any occlusion ) , lesion length, location of lesions to be treated ( particularly if side-branches require protection or intervention with “ snoging balloon ” techniques ) and vessel tortuousness proximal to the mark lesion ( s ) . In general, intervention of coronary chronic sum occlusions requires a guiding catheter with good backup/support whereas for rotational atherectomy it is more of import for the guiding catheter to be coaxal than provide good backup.
The undermentioned subdivisions endeavour to sketch these considerations in choosing and pull stringsing steering catheters for left and right coronary arterias, vein transplants and internal mammary transplants.
Left coronary arteria