|Year : 2021 | Volume
| Issue : 2 | Page : 8-14
Intravascular ultrasound-guided zero-contrast percutaneous coronary intervention: The next frontier in coronary interventions
N Prathap Kumar, V Blessvin Jino, R Manu, J Stalin Roy, Sandheep G Villoth
Meditrina Hospital, Kollam, Kerala, India
|Date of Web Publication||14-Feb-2022|
Dr. N Prathap Kumar
Meditrina Hospital, Kollam, Kerala.
Source of Support: None, Conflict of Interest: None
Chronic kidney disease (CKD), diabetes mellitus, older age, acute coronary syndrome, and cardiogenic shock are the common predisposing factors for contrast-induced acute kidney injury (CI-AKI) after percutaneous coronary intervention (PCI). Apart from intravenous normal saline administration, other measures to prevent CI-AKI have not been consistently beneficial. More recently, intravascular ultrasound (IVUS)-guided zero-contrast PCI has emerged as an important method to prevent CI-AKI in experienced centers. Technical expertise in complex PCI and meticulous analysis of IVUS are required for this procedure. In this review, the authors have described the basic details of the steps involved in this technique. The authors believe that clinical implementation of this technique has the potential for mortality benefit in patients who are at high risk of CI-AKI.
Keywords: Contrast-induced AKI, intravascular ultrasound, zero-contrast PCI
|How to cite this article:|
Prathap Kumar N, Blessvin Jino V, Manu R, Stalin Roy J, Villoth SG. Intravascular ultrasound-guided zero-contrast percutaneous coronary intervention: The next frontier in coronary interventions. KERALA HEART J 2021;10:8-14
|How to cite this URL:|
Prathap Kumar N, Blessvin Jino V, Manu R, Stalin Roy J, Villoth SG. Intravascular ultrasound-guided zero-contrast percutaneous coronary intervention: The next frontier in coronary interventions. KERALA HEART J [serial online] 2021 [cited 2022 Sep 25];10:8-14. Available from: http://www.csikhj.com/text.asp?2021/10/2/8/337619
| Introduction|| |
Contrast-induced acute kidney injury (CI-AKI) is the third most common cause of hospital-acquired acute kidney injury (AKI), after decreased renal perfusion and nephrotoxic medications. Currently, the most accepted definition of CI-AKI is the Kidney Disease Improving Global Outcomes (KDIGO) definition: a rise in serum creatinine by ≥0.3 mg/dL within 48 h after contrast exposure or an increase to ≥ 50% within 7 days. According to NCDR cath PCI registry, the overall incidence of CI-AKI in patients undergoing percutaneous coronary interventions is 7.1%. CI-AKI can become life-threatening, though most of the patients recover from this rise in creatinine. CI-AKI is associated with increased both short-term and long-term mortality rates. Out of all the risk factors associated with CI-AKI, ST-elevation myocardial infarction (STEMI), cardiogenic shock, and eGFR< 30 mL/min/1.73 m2 are the most important factors in terms of the risk for dialysis.
Although robust data to support a dose–toxicity relationship are lacking for intravenous iodinated contrast administration, the incidence of CI-AKI in patients undergoing PCI is related to the dose of contrast media. Hence, the dose of iodinated contrast should be reduced during PCI to prevent CI-AKI, regardless of their baseline predicted risk. Low osmolality contrast media (LOCM) are less nephrotoxic than high osmolality contrast media (HOCM) in patients with underlying renal insufficiency. But this advantage is not seen with iso-osmolality contrast media (IOCM) in comparison to LOCM. Since iodinated contrast is water-soluble, volume expansion with isotonic crystalloids enhances elimination of contrast via urine, and it has been shown to be effective in many studies, particularly when guided by left ventricular end-diastolic pressure (LVEDP). No adjunctive pharmaceutical agent (N-acetylcysteine, trimetazidine, ascorbic acid, aminophylline, fenoldopam, etc.) has been demonstrated to prevent CI-AKI consistently. Currently, intravenous isotonic crystalloid administration and reduction in contrast volume are the two consistent ways to prevent CI-AKI. Moreover, intracoronary contrast administration in patients with underlying moderate-severe left ventricular systolic dysfunction may lead to pulmonary edema, as contrast media-related hyperosmolality and functional hypocalcemia depress the myocardial contractility. Hence, iodinated contrast media should be reduced or avoided entirely, if possible, to reduce the abovementioned adverse events.
In patients undergoing coronary interventions, limiting the total contrast volume using the formula, maximum dose = 5 mL × (body weight in kg)/(serum creatinine in mg/dL), has been shown to reduce the incidence of CI-AKI. Alternatively, the ratio of volume of contrast to creatinine clearance (CV/CrCl) <3.7 has been shown to reduce CI-AKI. Ultra-low contrast PCI (CV/CrCl<1) reduces CI-AKI risk significantly when compared with low contrast PCI (CV/CrCl: 1–3). The usage of intravascular ultrasound (IVUS) to minimize CI-AKI has been validated in few studies. Finally, few case series have reported the feasibility and outcome of “zero-contrast PCI” in advanced CKD patients, using IVUS guidance without any contrast at all., The most promising approach to prevent CI-AKI in patients requiring PCI is to perform IVUS-guided zero-contrast PCI.
Zero-contrast PCI: step by step
Patient selection and preparation
There are no universally accepted criteria for selecting patients for zero-contrast PCI, and it is the treating heart team’s decision to choose the best possible method of revascularization. We follow a simplified criterion at our institution to select patients who require zero-contrast PCI for better clinical outcomes. When a patient needs PCI as per the standard guidelines, we consider zero-contrast PCI if they have any of the following:
- eGFR<30 mL/min/1.73 m2 (stage 4 and 5 CKD);
- eGFR 30–45 mL/min/1.73 m2(stage 3b CKD) and
- Age ≥75 years or
- Left ventricular ejection fraction (LVEF) <30%.
Although CKD patients who are not on maintenance dialysis are benefited most, zero-contrast PCI is also useful in patients who are already on hemodialysis as it preserves the residual renal function. Residual renal function is an important predictor of long-term quality of life in CKD patients. BMC2 risk score is a reliable tool to predict CI-AKI in patients undergoing PCI. It can be calculated before PCI, and an online calculator is available. Predicted risk of <1%, 1-7% and, >7% are considered as low risk, intermediate risk, and high risk, respectively. Patients with predicted risk >7% may also be offered zero-contrast PCI.
Even when zero-contrast PCI is planned, all patients require adequate hydration with isotonic saline before procedure as per local institutional protocol. POSEIDON trial showed that LVEDP-based intravenous fluid administration prevents CI-AKI effectively. All patients need to undergo routine baseline ECG and echocardiographic examination before procedure. This is important to compare and identify any new change during procedure.
Although both radial and femoral accesses are feasible for zero-contrast PCI, femoral access allows preservation of the radial arteries for future dialysis. Moreover, larger sized catheters can be used (>7 F) in femoral approach, which give better support and larger lumen for multiple wires and IVUS runs. Many CKD patients have heavily calcified vessels, which often need rotational atherectomy for lesion preparation. Hence, femoral access is preferred by many operators.
Baseline coronary angiogram using minimal contrast (total contrast volume in mL <eGFR—ultra-low contrast volume) is mandatory for all cases to know the underlying anatomy. Though higher frames are preferred by some, we generally use 15 frames/s acquisition. For left system, RAO caudal and AP/RAO cranial projections are sufficient in most cases. For right system, LAO cranial is the preferred projection. 5F catheter with smaller sized syringes (5–10 mL) are preferred to minimize contrast use. Catheters without side holes should be used always. Biplane angiography reduces the contrast usage much. Similarly, diluted contrast can help in many cases, and higher acquisition rates may improve the image quality when diluted contrast is used. Unnecessary contrast puffing in between catheter engagement should be avoided. There is no specific time limit recommended between coronary angiogram and zero-contrast PCI, although few case series have done it with an average interval of 5–8 days. Most LOCM have half-life of 2 h and hence it takes approximately 20 h for the contrast to be eliminated in patients with normal renal function. It is proposed by some to give at least 24 h interval in-between two doses of contrast, but this is not endorsed by the ACR Committee on contrast media. Moreover, in patients with underlying renal dysfunction, this interval may Vary. Hence, personalized decision-making should be done before proceeding to the next procedure, considering the urgency of revascularization. However, we generally do PCI on ad-hoc basis in most cases, except when the coronary angiogram has been done in another center because of the unreliability of the volume of contrast used.
Catheter engagement and wiring the vessel
Before inserting the guidewires into the guiding catheter, contrast in the guiding catheter should be removed by back-bleeding or by aspiration. This step is needed in cases in which guiding catheter is taken for coronary angiogram. Calcified vessels allow visualization of arterial course and facilitate easier catheter engagement in many cases [Figure 1]. Even in non-calcified vessels, catheter engagement poses little challenge for experienced operators. Once catheter engagement is done, it can be confirmed by inserting the guidewire into the coronary. Although ECG repolarization changes on saline injection into coronaries have been described as a method of confirmation of catheter engagement, earlier one is an easier method.
|Figure 1: (a) Arrow points to the calcium at the RCA ostium which was used as a marker to engage the guiding catheter in LAO view. (b) Guidewire was inserted into the RCA and engagement was confirmed|
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It is essential to have previous coronary angiographic views as roadmap, as further steps such as guidewire crossing, lesion preparation, and stent deployment need the roadmap to identify the vessel course, lesion area, and landing zones (LZ). Hence, it is advisable to use the same fluoroscopic projections like coronary angiogram in all the steps.
After catheter engagement and lesion crossing, the main operating wire may be parked as distal as possible. If possible, creating a loop in the distal tip of the guidewire is preferred, as the looped wire usually courses along the main vessel and also it is atraumatic most of the time. Following this, additional guidewires (preferably hydrophilic) should be inserted into the major branches of the main vessel (marker wires) and this should be done in the same fluoroscopic projection like the angiogram [Figure 2]. For left anterior descending artery (LAD) stenting, left circumflex artery (LCX), major septal artery, and at least one major diagonal are wired whenever possible. Similarly, for LCX stenting, at least one OM and LAD are wired and for right coronary artery (RCA) stenting, conus branch, right ventricular (RV) branch, posterior descending branch (RPDA), and postero-lateral branch (RPLB) are the preferred side branches to be wired. Importantly in aorto-ostial stenting, one wire is placed in the aorta to mark the vessel ostium [Figure 3]. The number of marker wires and the branches to be wired are selected according to the lesion and the discretion of the operator. Metallic silhouette is created to identify the proximal and distal landing zones easily and to position the stent correctly in the landing zones. Meticulous attention should be given while inserting multiple wires to prevent wire wrap, as these marker wires need to be in place till stent deployment.
|Figure 2: (a) RAO caudal view showing significant disease in LCX, OM, and LAD. (b) Metallic silhouette created by wiring two branches of OM and distal LCX. (c) Stent positioned using the marker wires|
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|Figure 3: (a) LAO cranial view showing the wire over the aorta to mark the RCA ostium and ostial positioning of stent. Note the loop created in the wire at RPDA. (b) Stent positioned in LAD according to the marker wires at septal, diagonal, and LCX|
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Another method (“marking wire” technique) using double Y connector is also described in the literature. But we prefer “metallic silhouette” method as it is an easier method and it allows us to identify proximal and distal landing zones clearly, which are described below.
“Pre-IVUS” run and lesion preparation
Once metallic silhouette is created, “pre-IVUS” run should be done. Sometimes, lesions are hard to be crossed by the IVUS probe and pre-dilatation may be needed. The operator experience is needed for pre-dilatation before IVUS run, as sub-intimal tracking of wire is possible in complex cases. Most experienced operators can identify this by tactile sensation. It is advisable to use smaller sized balloons like 1.25–1.5 mm, to pre-dilate before IVUS. Then IVUS probe should be inserted as distal as possible, as angiographically normal areas may have significant disease on IVUS. Commercially available IVUS imaging systems have 100–150 mm pullback length, which is sufficient for most cases. During initial IVUS run, it is essential to confirm the wire position in true lumen first. Then minimal luminal area, proximal and distal reference vessel diameters, lesion length, and calcium arc and length are measured along with identification of proximal and distal landing zones [Figure 4]. During IVUS pullback whenever good landing zones are seen, “cine” store should be done, which can guide the stent placement.
|Figure 4: (a) IVUS image showing lesion length measurement from ostium of LAD to distal landing zone. In the IVUS picture, we can see the wire in the LCX which is relatively free of disease. (b) Length measurements when two stents are planned, particularly when there is gross size discrepancy between proximal and distal landing zones|
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Lesion preparation is done as per the operator’s discretion. In general, calcium arc >180° and >5 mm length requires plaque modification with rotational atherectomy.
Repeat IVUS and stent sizing
Whenever possible, repeat IVUS run after initial lesion preparation is needed. This is to identify the dissection extent, if any, and to assess the adequacy of lesion preparation and to confirm the lesion length again, which guides in appropriate stent selection. Conventionally, stent size is selected according to the distal reference vessel diameter and the length is selected according to the IVUS measured length. In tortuous vessels, it is important to keep in mind that IVUS-measured proximal LZ- distal LZ length may be different from the actual length because of wire bias. Additionally, when two stents are selected, stent overlap length should be considered and in aorto-ostial stenting, stent protrusion into the aorta should be considered while selecting stent length. During IVUS analysis, length between distal landing zone and the distal-most marker wire and length between proximal landing zone and the proximal-most marker wire should be measured clearly. This helps in positioning the stent fluoroscopically. Additionally, some fluoroscopic markers such as catheter tip, vessel calcium, rib margin, diaphragm margin, etc. in a particular projection may aid in positioning the stent correctly. But stent positioning based on the marker wires is probably the best method. In cases in which two stents are required, repeat IVUS may be done after the first stent deployment, whenever possible. This is to select the second stent length more accurately, which is measured from the first stent edge to the proximal/distal landing zones. In our experience, we have found that there is a small difference in the “second” stent length, when it is selected as per the repeat IVUS measurements after the “first” stent deployment. So we prefer to do repeat IVUS after first stenting to confirm the second stent length. “Stent boost”/“clear stent” technologies can help us to position the second stent fluoroscopically.
Post-IVUS and stent optimisation
After stenting, IVUS run is done to identify the adequacy of stent expansion, malapposition, edge dissection, minimal stent area (MSA), and ostial coverage in cases in which vessel ostium is planned to be covered. Stent optimization is done as per operator’s discretion, and final IVUS run is done to confirm the optimization. Finally, MSA >80% of average reference lumen area, or MSA >5.5 mm2 in non-LMCA and >8 mm2 in LMCA without significant edge dissection or malapposition, without using contrast, is considered as technically successful procedure. Final angiographic TIMI flow is a strong predictor of long-term outcome after PCI and it cannot be graded in IVUS. The long-term outcome of this zero-contrast PCI still is not known and it needs further large studies.
Though complication management is common to all PCI procedures, meticulous attention is warranted during “zero-contrast PCI.” Any new onset or worsening angina, hypotension, and fresh ECG changes should alert the operating team about the possible complications. Whenever hypotension occurs during procedure, echocardiography should be done immediately to rule out vessel perforation. Check angiogram with minimal contrast may be used whenever complications are suspected. Even after successful completion of the procedure, serial echocardiography is needed to identify distal wire perforation. As many CKD patients have complex coronary anatomy, aggressive preparation of the vessel and optimization of stent are needed and complications should be expected always by the operating team. Final check coronary angiogram is advised by many operators, although it is not mandatory. Before commencing the procedure, there should be a “shared decision-making” between the heart team and the patient regarding this final check angiogram. This helps to avoid legal problems.
| Conclusion|| |
Coronary artery disease is the leading cause of death in patients with CKD. Though revascularization improves the short-term and long-term outcome in these high-risk patients, it is often not performed in most centers, in fear of CI-AKI and the risk of dialysis requirement. “IVUS-guided zero-contrast PCI” is a promising method to prevent CI-AKI and dialysis requirement in these patients. Moreover, very elderly patients and patients with underlying severe LV systolic dysfunction who are at very high risk of CI-AKI can also be treated using this novel method. Technical expertise in complex PCI and IVUS image interpretation is extremely important for this procedure. Widespread availability of intracoronary imaging, better knowledge in image analysis, and advancements in technology may help us to fulfill the large unmet needs in the revascularization of these patients.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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