Ostial lesions





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Ostial lesions are lesions located within 3–5 mm of the vessel origin .


There are two types of ostial lesions: (1) aorto-ostial lesions, and (2) branch ostial lesions ( Fig. 15.1 ) .



  • 1.

    Aorto-ostial lesions: involve the ostia of the right coronary artery, left main, and aorto-coronary bypass grafts (both saphenous vein grafts and arterial grafts, such as left internal mammary artery grafts [LIMA]).


  • 2.

    Branch ostial lesions: involve the ostia of branches of the coronary vessels, such as left anterior descending artery LAD), ramus, and circumflex (branches of the left main), diagonals (branches of the LAD), obtuse marginals (branches of the circumflex) the posterior descending and posterolateral (branches of the right coronary artery [RCA] in right dominant coronary circulation and of the circumflex in left dominant coronary circulation), and ostial lesions of Y-grafts (graft attached to another graft, such as free right internal mammary artery [RIMA] attached to LIMA).




Figure 15.1


Types of ostial lesions: aorto-ostial ( yellow ) and branch ostial ( green ).



Aorto-ostial lesions



Planning


Aorto-ostial lesions can be challenging to engage and severe ischemia can occur upon engagement. It is best to have a guidewire preloaded within the guide catheter before attempting to engage, so that the wire can be immediately advanced into the coronary artery upon engagement, allowing subsequent guide disengagement to prevent ischemia (“hit and run”). Alternatively, the wire can be advanced into the vessel with non-selective guide engagement, minimizing the risk of ischemia and ostial trauma.


Aorto-ostial lesions can be fibrotic, calcified, rigid, and prone to recoil. As a result, they can be challenging to dilate, sometimes requiring atherectomy.



Monitoring


Pressure dampening is common when treating aorto-ostial lesions, requiring constant attention to the guide pressure waveform ( Section 5.6 ).



Medications


Medications are administered as described in Chapter 3 , Medications. No special medications are required for treatment of aorto-ostial lesions.



Access





  • Arterial access is obtained as described in Chapter 4 , Access.



  • Radial or femoral access are both acceptable for aorto-ostial lesion stenting. In highly complex cases femoral access and large (i.e., 7 or 8 French) guide catheters may provide better support, but are more likely to cause pressure dampening upon engagement.




Engagement


A common challenge associated with aorto-ostial lesion PCI is pressure dampening upon engagement ( Fig. 15.2 ), that may lead to ischemia and hemodynamic compromise .




Figure 15.2


Pressure dampening upon engagement of a coronary artery that has an aorto-ostial lesion.


Other causes of pressure dampening (such as intracatheter thrombus or debris, catheter kinking, non-coaxial alignment, or transducer malfunction) should be considered and excluded as discussed in Chapter 5 , Coronary and Graft Engagement, Section 5.6 , Step 6.


Prevention of pressure dampening:




  • Use small (such as 6 French) guide catheters.



  • Avoid deep guide engagement.



  • Use guide catheters with side holes ( Section 30.2.5 ). However, side-hole guides may provide a false sense of security, as pressure dampening and ischemia may not be appreciated. They should not be used in an unprotected left main coronary artery, given the large area at risk of ischemia, but can be used in the right coronary artery, bypass grafts, and a protected left main coronary artery. Similarly, they should not be used in the right coronary artery if it is the donor vessel to a totally occluded vessel in the left system. Disadvantages of side-hole guide catheters include contrast exit though the side holes that may hinder visualization of the lesion, and lead to use of larger contrast volume for completing the PCI.



  • Use of the Ostial Pro device ( Section 30.13.1 ) for keeping the guide catheter outside the ostium.



  • Place a second guidewire through the guide catheter into the aortic root (“floating wire”) to keep the guide catheter off the coronary ostium ( Fig. 15.3 ).




    Figure 15.3


    The floating wire technique for aorto-ostial stenting. While treating an aorto-ostial and proximal right coronary artery lesion (panel A) a second floating guidewire ( arrows , panel B) was inserted in the aorta, serving as a marker of the ostium guiding stenting implantation (panel C). After postdilation of the ostium by withdrawing the stent balloon (panel D) a nice final result was achieved (panel E). Intravascular ultrasound confirmed that the RCA ostium was covered with stent struts protruding into the aorta ( arrows , panel F).



  • Use a small guide catheter extension to engage the coronary artery and “back out” the guide catheter.



Solutions:




  • A guidewire should be inserted and advanced to the tip of the guide catheter prior to engagement, to facilitate immediate wiring upon engagement, as described under “Planning”. Use of extra support guidewires (such as Grand Slam, Iron Man, Wiggle, etc.) can facilitate guide engagement and disengagement as well as coaxial alignment.



  • Use smaller (such as 6 French) guide catheters as larger guide catheters are more likely to cause pressure dampening upon engagement.



  • Less aggressive guide catheters, such as a JR4 (and sometimes IM catheters for shepherd’s crook RCA) are preferred for isolated aorto-ostial disease, as they are easier to intermittently engage and disengage. These catheters, however, may not provide enough support for more diffusely diseased or tortuous vessels compared with more aggressive guide catheters, such as AL shapes.



  • Avoid contrast injections while pressure is dampened to minimize the risk of coronary ostial dissection that can propagate down the coronary artery or in the ascending aorta.



  • Intermittently disengage the guide catheter to alleviate ischemia. Disengagement is best done by torquing the guide to a noncoaxial position as opposed to pulling it back, as the latter may lead to loss of distal wire position.



  • Place a second guidewire through the guide catheter into the aortic root (“floating wire”) to keep the guide catheter off the coronary ostium.


    Contrast injection while pressure is dampened can lead to aorto-coronary dissection.


    Aorto-coronary dissection :


    Prevention:




    • Use small guide catheters.



    • Avoid deep guide engagement.



    • Use gentle manual injection—avoid automated injectors or use a gentle injection preset.



    • Avoid injection while pressure is dampened.



    • If possible, wire the vessel prior to contrast injection.



    • Use a small guide catheter extension to engage the coronary artery, keeping the guide catheter outside the ostium.


      Solutions:



    • Maintain guidewire position within the target vessel.



    • STOP INJECTING contrast.



    • If vessel needs wiring, confirm intraluminal position with IVUS (without contrast injections).



    • Stent vessel ostium to seal entry into the dissection flap.




Guide engagement in patients with protruding stents in the aorta .


Engaging vessels with prior aorto-ostial stenting can be difficult due to protruding stent struts, and may result in stent deformation. Sometimes, it can also be challenging to engage the guide catheter in a coaxial manner. In such cases, the vessel can often be wired with the guide catheter disengaged (and ideally knuckling the wire to avoid wire advancement through stent struts), followed by guide engagement over the wire. In the RCA, wiring through previously deployed aorto-ostial stents is easier with a JR4 guide catheter. If a more supportive guide shape is needed, guide exchange can be performed using a microcatheter and a 300 cm supportive guidewire ( Chapter 5 : Coronary and Graft Engagement, Section 5.7 , Step 7).



Angiography


Performing coronary angiography is described in detail in Chapter 6 , Coronary Angiography.




  • Nitroglycerin should be administered before angiography to exclude coronary spasm.



  • For aorto-ostial lesions with severe dampening upon engagement, nonselective angiography can reduce the risk of dissection, but may provide suboptimal quality images.



  • The “independent-hand” technique for holding the guide catheter ( Fig. 15.4 ) can significantly facilitate all steps of aorto-ostial lesion stenting.




    Figure 15.4


    The “independent-hand” technique. The left hand advances and withdraws the guide catheter while the right hand advances or withdraws the balloon or stent or other equipment.



  • Multiple angiographic acquisitions should be avoided to minimize the risk of aorto-ostial lesion dissection; intravascular imaging can help determine the presence and severity of aorto-ostial lesions and response to treatment.



  • If the contrast is not allowed to clear the coronary artery after injection, ventricular fibrillation or ventricular tachycardia may occur. Failure of the contrast to clear is likely due to occlusion of the ostium from the catheter. The catheter should be disengaged, to allow contrast clearance.



  • Determining the optimal view to define the true ostium is essential to avoid geographic miss during stenting. If a patient has a prior coronary CT angiography, the optimal angle can be noted prior to the procedure. In general, the following projections offer the least foreshortening of the ostium:




    • RCA: steep LAO +/− caudal.



    • Left main: LAO caudal and LAO cranial.



    • Right-sided SVGs: LAO.



    • Left-sided SVGs: RAO.



    • LIMA and RIMA: AP with shallow cranial.





Determining culprit lesion(s)


If the severity of an aorto-ostial lesion is questionable, nitroglycerin should be administered to exclude spasm and coronary physiology (or intravascular imaging for ostial left main lesions) should be used ( Section 15.1.13 ). Because of the slanted nature of coronary takeoffs, two-dimensional IVUS area measurements should be interpreted with care in aorto-ostial lesions, especially when making therapeutic decisions about the left main.



Wiring


Performing coronary wiring is described in detail in Chapter 8 , Wiring.


Tips and tricks :



  • 1.

    The guidewire should be advanced to the tip of the guide catheter prior to engagement, to facilitate immediate wiring upon engagement.


  • 2.

    In difficult to wire vessels, a hydrophilic-coated or polymer-jacketed guidewire can be advanced through a microcatheter to the distal vessel and then exchanged for a safer guidewire. Wiring should be done with great caution to minimize the risk of subintimal tracking and acute vessel closure.


  • 3.

    Once the vessel is wired, the original guidewire can be exchanged for a supportive guidewire (such as Iron Man, Grand Slam, Mailman, and Wiggle, Section 30.7.4 ) which can facilitate engagement and disengagement of the guide catheter.




Lesion preparation


Lesion preparation is described in detail in Chapter 9 , Lesion Preparation.


Aorto-ostial lesions are often resistant to dilatation and prone to recoil due to the greater thickness of muscular and elastic tissue in the aortic wall. These lesions are also often heavily calcified and “balloon undilatable” ( Section 23.2 ), hence excellent preparation is important prior to stenting.


Balloon angioplasty: Balloons should be placed partially into the vessel and partially into the aorta to ensure adequate lesion preparation. Noncompliant and longer balloons (such as 30 mm long) are useful. Use of plaque modification balloons (Angiosculpt, Chocolate, and cutting balloon, Section 30.9.3 ) can facilitate lesion expansion and prevent excessive balloon movement.




  • Challenges



    • 1.

      Watermelon seeding (excessive movement of the balloon either distally into the vessel or proximally into the aorta).




      • Prevention:




        • Slow balloon inflation (1 atm increase at a time, while observing the balloon position with gentle retraction of the balloon catheter).



        • Use a buddy wire.



        • Use a plaque modification balloon (such as Angiosculpt, Chocolate, and cutting balloon, Section 30.9.3 ).



        • Use longer balloons (such as 30 mm long balloons).



        • Use a winged balloon.



        • Use intravascular lithotripsy (Section 29.9.8) or the very-high-pressure SIS OPN balloon ( Sections 30.9.7 and 23.2.10 ).




      • Treatment:




        • Same as for prevention above.




    • 2.

      Balloon undilatable lesions (discussed in detail in Section 23.2 )




      • Prevention:




        • Ensure full balloon expansion prior to placing stent. The balloon should be sized 1:1 with the target vessel.



        • Intravascular imaging to ensure complete lesion expansion.




      • Treatment:




        • As outlined in the balloon undilatable algorithm ( Section 23.2 ).






Atherectomy : Atherectomy ( Chapter 19 : Calcification) can be very useful in severely calcified balloon undilatable aorto-ostial lesions. Both rotational ( Section 30.10.1 ) and orbital ( Section 30.10.2 ) atherectomy can be used.


Rotational atherectomy should ideally be done using the Rotawire extra support. Placing the guide catheter coaxial to the artery is important to decrease the risk of perforation or aortic dissection and facilitate maximal debulking of the lesion. Often, the burr needs to be activated at the end of the guide catheter with tension off the burr to prevent it from “jumping” through the lesion that could increase the risk of burr entrapment. Larger burr sizes may be required to achieve sufficient aorto-ostial lesion modification.


Orbital atherectomy of aorto-ostial lesions can be challenging, as activation of the device that is not engaged into the vessel ostium can result in unconstrained device orbit that could cause vessel injury and/or perforation . If the atherectomy crown can cross the lesion (sometimes with the help of GlideAssist), the crown should be advanced distal to the lesion and the aorto-ostial lesion treated while withdrawing the crown . If the aorto-ostial lesion is too severe for the crown to cross, make sure the guide catheter is coaxial and place the nose cone of the device into the ostium keeping the crown 5 mm from the lesion. This will constrain the orbit and allow the lesion to be treated in a more controlled manner .


Intracoronary lithotripsy (Section 3.9.8) is another emerging option for dilating heavily calcified and hard to expand aorto-ostial lesions.



Stenting


When there are distal lesions in addition to the aorto-ostial lesion, the more distal lesions should ideally be stented first, as advancing equipment through an ostial stent may result in stent deformation and/or equipment loss.


Aorto-ostial lesion stenting—step-by-step :


Baseline : The aorto-ostial lesion is pretreated and guide catheter is engaged ( Fig. 15.5 ).


Feb 4, 2021 | Posted by in CARDIOLOGY | Comments Off on Ostial lesions
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