Bypass grafts—prior CABG patients





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PCI in patients with prior coronary artery bypass graft surgery (CABG) can be challenging in many ways:



  • 1.

    In addition to the native coronary arteries, bypass grafts need to be engaged, visualized, and sometimes treated.


  • 2.

    Native coronary artery lesions are often quite challenging (bypass grafting accelerates native coronary atherosclerosis), and


  • 3.

    Prior CABG patients have higher baseline risk, as they are often old and have multiple comorbidities .



Due to the need to engage and visualize the bypass grafts (and the often high complexity of treated lesions) angiography and PCI in prior CABG patients requires longer procedural and fluoroscopy time, higher radiation dose, and larger volume of contrast . As a result (and also because of often decreased baseline renal function), the risk of contrast-induced acute kidney injury and possibly hemodialysis is increased in prior CABG patients.


Even though coronary perforations were previously considered “innocent” complications in prior CABG patients due to pericardial adhesions preventing formation of a pericardial effusion and tamponade, it is now appreciated that they can be lethal events. Coronary perforation in prior CABG patients can lead to loculated hematomas resulting in cardiac chamber compromise and hemodynamic collapse (dry tamponade) . Such loculated effusions may require surgery or computed tomography–guided drainage for treatment. Prompt identification and treatment of coronary or graft perforation is, therefore, critical in prior CABG patients .


Some of the current recommendations for catheterization and PCI in prior CABG patients are summarized in Fig. 18.1 .




Figure 18.1


Overview of recommendations about cardiac catheterization and PCI in prior CABG patients.

Reproduced with permission from Xenogiannis I, Tajti P, Hall AB, et al. Update on cardiac catheterization in patients with prior coronary artery bypass graft surgery. JACC Cardiovasc Interv 2019;12:1635–49. Copyright Elsevier.



Planning



CABG anatomy


The goal of diagnostic angiography in the post-CABG patient is to visualize the native coronary arteries and all bypass grafts in the safest and most expeditious way. Detailed and meticulous preparation of the angiographer is key and includes:



  • 1.

    Review of the surgical report;


  • 2.

    Review of any prior coronary angiograms, including pre- and post-CABG angiograms; and


  • 3.

    Review of ancillary imaging studies, especially coronary computed tomography angiography .



Obtaining the CABG surgical report and reviewing prior coronary angiograms is key for optimal coronary and bypass graft angiography and can save time, contrast, radiation dose, and reduce the number of catheters needed for engaging the grafts . In non-urgent cases it may be best to delay angiography to allow time for obtaining the CABG report. It is important to review the operative report if at all possible instead of relying on what has been thought to be the post-surgical anatomy, as mistakes are frequently made and details can be “lost in translation.”


Review of prior angiograms can help determine the location of the bypass graft proximal anastomoses and the catheters that were successful in engaging them. In addition, review of prior chest computed tomograms, even if not geared toward cardiac evaluation, can be very helpful. Thinner slice reconstruction (i.e., ≤1 mm) is enough to identify the CABG anatomy, that is, the origin and number of bypass grafts. Although dedicated coronary computed tomography angiography has been shown to be an excellent method to determine the anatomy of the native coronary arteries, location and patency of bypass grafts, visualization of distal native vessels and graft anastomoses can sometimes be hindered by the presence of calcification and surgical clips .



Review of comorbidities and pre-procedural optimization


Prior CABG patients often have multiple noncardiac comorbidities that could impact performance of the procedure, such as chronic kidney disease and peripheral arterial disease. Risk scores can be used to estimate each patient’s risk for contrast-induced acute kidney injury : in high-risk patients meticulous attention should be given to pre-procedural hydration, using isoosmolar contrast media, and limiting contrast volume to less than 3.7× the estimated glomerular filtration rate (GFR) through careful preprocedural planning and contrast saving devices.


Prior CABG patients often experience congestive heart failure; in non-emergent cases, cardiac catheterization may be best deferred in patients who appear to be volume overloaded to allow hemodynamic optimization. This process can often be guided by right heart catheterization. In prior CABG patients with severe peripheral arterial disease access site selection may be difficult and could be facilitated by preprocedure CT angiography.



Monitoring


Monitoring is performed as described in Chapter 2 : Monitoring. Careful monitoring is especially important in prior CABG patients given their higher baseline risk and often complex coronary anatomy.



Medications


Intragraft vasodilators (such as adenosine , nitroprusside , nicardipine , and verapamil ) can be administered both before and after saphenous vein graft (SVG) PCI to prevent or treat no reflow by causing vasodilation and facilitating passage of debris and/or chemical mediators liberated. Nicardipine (100–300 mcg intragraft) is often preferred due to prolonged duration of action and less hypotensive effect and is often administered both before and after PCI, especially if slow flow or no reflow occurs.


In contrast, platelet glycoprotein IIb/IIIa receptor inhibitors can cause harm during SVG intervention and should not be used routinely in SVG PCI .



Access


Engagement of arterial grafts and SVGs for angiography and/or PCI ( Section 5.7 ) can be performed using either femoral or radial approach, however femoral access is generally preferred as it is associated with shorter time, fewer catheters and lower contrast and radiation dose .


If radial access is selected, the left radial artery should be used in most cases to facilitate engagement of the left internal mammary artery (LIMA) and the other bypass grafts. If left radial access is not feasible, the right radial artery can be used, but LIMA engagement can be challenging. Use of a Simmons catheter ( Fig. 18.2 ) can facilitate LIMA engagement via right radial access, whereas the Bartorelli-Cozzi catheter ( Fig. 18.3 ) can facilitate LIMA engagement via left radial access. When graft engagement is challenging using radial access, early conversion to femoral access should be considered . In patients with bilateral IMA grafts upfront femoral access is preferred.




Figure 18.2


Use of a Simmons catheter to engage the LIMA (panel A), a saphenous vein graft to the right coronary artery (panel B) and a saphenous vein graft to a diagonal (panel C) via right radial access.

Courtesy of Dr. Abdul Hakeem.



Figure 18.3


The Bartorelli-Cozzi catheter (Cordis) can be used to perform selective LIMA angiography via left radial access.

Courtesy of Dr. Jaikirshan Khatri.



Engagement



Native coronary arteries


Engagement of native coronary arteries is performed as described in Chapter 5 : Coronary and Graft Engagement.



Saphenous vein grafts


Knowledge of the coronary and bypass graft anatomy facilitates selective graft engagement. The usual location of bypass grafts is shown in Fig. 18.4 .




  • Graft markers can help graft engagement, but are only used in a minority (approximately 10%) of CABG patients . The most commonly used catheter for engaging bypass grafts ( Section 5.7 ) is the multipurpose for right coronary artery grafts, and the Amplatz left (AL) 1 or left coronary bypass (LCB) for left-sided grafts. Often, both right and left grafts can be engaged using a Judkins right (JR) 4 catheter, hence many operators will try this catheter first immediately after right coronary artery angiography in an attempt to save time and equipment cost.



  • If the CABG anatomy is unknown, attempts to engage grafts should be continued until sources of coronary flow to all myocardial territories are identified. Bilateral subclavian artery angiography can help determine whether one or both IMAs were utilized as grafts. The presence of surgical clips along the IMA can help determine if it was used by the surgeon or not. In case of challenging graft engagement, aortography can be performed (usually administering 60 mL of contrast at a rate of 20 cc/sec) while performing cineangiography in the left anterior oblique projection.



  • If graft intervention is needed, obtaining adequate guide catheter support is critical. This can be accomplished by using large guide catheters (such as 7 or 8 French), supportive guide catheter shapes (such as Amplatz left for left-sided grafts), deep guide intubation, or use of a guide catheter extension .




Figure 18.4


Usual location of aorto-coronary bypass grafts. CX , circumflex; Dx , diagonal; LAD , left anterior descending artery; OM , obtuse marginal; RCA , right coronary artery; SVG , saphenous vein graft.



Arterial grafts





  • Radial grafts are engaged as described for SVGs. Nitroglycerin administration is important, as radial grafts are very prone to spasm.



  • Internal mammary artery grafts are usually engaged using the internal mammary (IM) catheter, or the modified internal mammary artery catheter (IM-VB1, named after Victor Behar) that has a shape that is similar to the proximal two-thirds of the curve of a standard pigtail catheter ( Fig. 18.5 ). Alternatively, in the absence of specialized catheters, a pigtail catheter can be used with a coronary wire or by cutting a small part of its tip .




    Figure 18.5


    The IM-VB1 diagnostic ( top ) and guide ( bottom ) catheters.

    Reproduced with permission from Warner JJ, Gehrig TR, Behar VS. The VB-1 catheter: an improved catheter for difficult-to-engage internal mammary artery grafts. Catheter Cardiovasc Interv 2003;59:361–5.



  • Deep guide intubation and use of guide catheter extensions may lead to IMA dissection and/or perforation.




Angiography



Native coronary arteries


Angiography of native coronary arteries in prior CABG patients is performed as described in Chapter 6 : Coronary Angiography. Given the high prevalence of CTOs in prior CABG patients , long cine runs without panning can be useful in determining the presence and course of collateral circulation, as described in Chapter 21 : Chronic Total Occlusions.



Saphenous vein grafts


Optimal graft engagement is critical for obtaining excellent quality diagnostic images of the bypass grafts (and the native coronary arteries) in prior CABG patients. Prolonged cineangiography runs can be useful for clarifying distal coronary filling, especially in patients with long grafts supplying a large myocardial territory.



Arterial grafts


In patients with IMA grafts, nonselective angiography of the proximal subclavian artery should be performed before selective angiography of the left or right IMA to identify subclavian lesions that could lead to subclavian steal . If subclavian angiography is not performed, careful attention should be paid to the arterial pressure waveform in the subclavian artery as compared with that of the central aorta. Subclavian steal is a rare cause of recurrent cardiac ischemia and vertebrobasilar insufficiency, such as vertigo, in patients with previous CABG when an IMA graft has been used . It is caused by significant stenosis of the ipsilateral subclavian artery and should be suspected in patients with >20 mmHg difference in systolic pressure between their arms.



Selecting target lesion(s)


PCI in prior CABG patients may be performed in native coronary arteries or in saphenous vein or arterial bypass grafts.



Native coronary arteries


In general native coronary artery PCI is preferred over SVG PCI in prior CABG patients, given lower periprocedural risk and better long-term outcomes. However, native coronary artery lesions in prior CABG patients can be challenging to treat, for example due to severe calcification or because they are chronic total occlusions.



Saphenous vein grafts


There are several treatment options in patients presenting with saphenous vein graft lesions ( Fig. 18.6 ).




Figure 18.6


Revascularization options in prior CABG patients presenting with SVG lesions.

Reproduced with permission from Xenogiannis I, Tajti P, Hall AB, et al. Update on cardiac catheterization in patients with prior coronary artery bypass graft surgery. JACC Cardiovasc Interv 2019;12:1635–49. Copyright Elsevier.


In patients presenting with SVG lesions revascularization is usually performed with PCI because redo CABG carries high risk. In few patients, however, especially those who do not have a LIMA-LAD graft and in whom a LIMA-LAD graft is feasible, redo CABG may be an option.


Otherwise, if the native coronary artery supplied by the SVG can be easily treated with PCI, PCI of the native coronary artery is preferred. If however, PCI of the native coronary artery is challenging (for example the native coronary artery lesion is a complex CTO), and PCI of the SVG appears to be simple, PCI of the SVG is performed instead.


When SVG PCI fails or in patients with recurrent SVG failure, recanalization of the native coronary artery CTO can be performed instead, at experienced centers.



Acute SVG occlusions


Acute saphenous vein graft (SVG) thrombosis is challenging to treat due to large thrombus burden, diffuse SVG degeneration, and high recurrent SVG failure rates . Aggressive use of thrombectomy and EPDs is often required to restore luminal patency, but even if acute recanalization is achieved, long-term SVG patency is low .


Alternative revascularization approaches, such as ad hoc or staged PCI of the bypassed native coronary artery may provide better outcomes , but these can be challenging procedures, requiring dedicated equipment and expertise.



Chronic SVG occlusions


Because of high restenosis risk, SVG CTOs should generally not be recanalized (class III indication, level of evidence C) , unless no other treatment options exist. Occluded SVGs can be used, however, for retrograde crossing of the corresponding native coronary artery if the occlusion morphology is favorable.



Arterial grafts





  • PCI of arterial grafts, especially the IMA grafts, is much less common than SVG PCI. The two main reasons are the higher rates of IMA patency as compared with SVGs and the more frequent performance of redo CABG in cases of IMA failure. Redo CABG is usually avoided in patients with a patent IMA graft to the LAD .



  • PCI through IMA grafts should be avoided, given high risk of ischemia and complications, such as pseudolesion formation after wiring (see Section 18.8 ) and dissection.



  • Despite the aforementioned limitations, PCI to IMA lesions has been associated with higher rates of restoration of TIMI-flow 3 and lower rates of periprocedural complications compared with SVG PCI. IMA anastomotic lesions sometimes respond to low-pressure balloon dilatation while proximal and mid-segment of IMA graft are stented in most cases.



  • In patients with IMA grafts, the proximal subclavian artery should be evaluated, as severe lesions in this location could lead to coronary ischemia, and even acute coronary syndromes . Subclavian artery stenting can be an effective treatment in such cases.




Wiring



Native coronary arteries


Wiring of native coronary arteries is performed as discussed in Chapter 8 : Wiring. If wiring of a native coronary artery lesion is performed via a bypass graft, the distance from the guide tip to the lesion can be very long, sometimes not allowing equipment to reach the target lesion .


Potential solutions include:



  • 1.

    Short guide catheters


  • 2.

    Deep guide catheter intubation into the target vessel.


  • 3.

    Use of long (300 cm) guidewires


  • 4.

    Long-shaft balloon and stents




Saphenous vein grafts



Embolic protection devices in saphenous vein grafts


Embolic protection devices should be used in SVG PCI, if technically feasible, to reduce the risk of distal embolization. Two embolic protection devices are currently available in the US, the Filterwire (Boston Scientific) and the Spider (Medtronic) . Both require a distal landing zone for deployment, hence they cannot be used in distal anastomotic lesions (unless the filter is deployed in the native coronary artery). The Filterwire is advanced (collapsed within the delivery sheath) through the target lesion, whereas the Spider is advanced over a standard 0.014 in. guidewire that is first advanced through the lesion.



Filterwire ( Section 30.8.1 )


Filterwire use: step-by-step.



Step 1: Determine that use of Filterwire is feasible





  • Criteria :



    • 1.

      De novo SVG lesion (in-stent restenotic SVG lesions have low risk for embolization and do not require use of an embolic protection device).


    • 2.

      Reference SVG diameter at the planned filter loop deployment site is between 2.25 and 5.5 mm.


    • 3.

      Adequate landing zone (25 mm for the Filterwire EZ 2.25–3.5 mm device and 30 mm for the Filterwire EZ 3.5–5.5 mm device)




  • Challenges



    • 1.

      Short landing zone



    In patients with short landing zone, the filter loop could potentially be deployed within the native coronary artery supplied by the SVG, although this will offer only partial protection.




Step 2: Preparation of the Filterwire



Feb 4, 2021 | Posted by in CARDIOLOGY | Comments Off on Bypass grafts—prior CABG patients
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