Synergistic Coronary Artery Calcium Modification With Combined Atherectomy and Intravascular Lithotripsy

Abstract

Background. Severe coronary artery calcification (CAC) remains challenging during percutaneous coronary intervention (PCI) and often requires 1 or more advanced calcium modification tools. Objectives. We describe the combination use of rotational (RA) or orbital atherectomy (OA), with intravascular lithotripsy (IVL), termed rotatripsy and orbital-tripsy, respectively, for modifying CAC prior to stent implantation during PCI. Methods. We performed a retrospective analysis of patients treated with rotatripsy or orbital-tripsy at our center between July 2019 and March 2022. The primary efficacy endpoint was procedural success (successful stent implantation, <30% residual stenosis visually, Thrombolysis in Myocardial Infarction 3 flow; absence of types C to F dissection/perforation or loss of side branch ≥2.0mm visually) without in-hospital major adverse cardiovascular event (MACE, defined as cardiovascular death, myocardial infarction [MI], target-vessel revascularization). Results. A total of 25 patients (14 rotatripsy and 11 orbital-tripsy) were included in our study. The mean age was 72.2 ± 7.6 years and 76% were men. PCI was guided by intravascular imaging in 24 patients (96%). All cases were treated with either RA or OA before utilization of IVL. Procedural success was achieved in 22 cases (88%) with 1 sidebranch loss without periprocedural MI (4%) and 2 in-patient deaths (8%) unrelated to the procedure (1 intracerebral hemorrhage and 1 cardiac arrest). Conclusion. We describe efficacious use of both rotatripsy and orbital-tripsy to modify severe CAC during PCI in a real-world setting. Intravascular imaging can guide appropriate use of these devices to complement each other to modify severe CAC to achieve optimal outcomes.

J INVASIVE CARDIOL 2023;35(3):E128-E135. Epub 2023 January 13.

Key words: coronary artery calcification, intravascular lithotripsy, orbital atherectomy, percutaneous coronary intervention, rotational atherectomy

Recent evidence has shown that the development of coronary artery calcification (CAC) is an active process reflective of systemic inflammatory status, typically seen in patients with diabetes mellitus, metabolic syndrome, or chronic kidney disease.^1,2 CAC is highly prevalent in patients with coronary artery disease (CAD), and usually implies the presence of CAD irrespective of other risk factors or symptoms.³ During percutaneous coronary intervention (PCI), the presence of CAC is associated with adverse outcomes such as in-stent thrombosis or restenosis.^4,5 It also adds to procedural complexity of PCI, often requiring specialized tools to modify the calcium during lesion preparation, facilitating the delivery and optimal expansion of drug-eluting stents.^6,7

CAC modification tools can be broadly divided into balloon-based and atherectomy-based therapies. Coronary intravascular lithotripsy (IVL) is a balloon-based catheter system that delivers circumferential acoustic waves which selectively fractures intimal and medial calcium layers. Principles of IVL in modifying CAC has been previously well described, and its use has shown a high procedural success rate, with low rates of major adverse events up to 12 months.^8-11

The combination of rotational atherectomy (RA) and IVL, commonly termed “rotatripsy,” has been described in case reports and series as a successful approach in modifying CAC.^12-15 RA is often used in these cases to debulk superficial CAC, before delivering the IVL balloon for additional lesion preparation. Yarusi et al reported a single-center series of 8 patients treated with combination orbital atherectomy (OA) and off-label use of the peripheral IVL system for CAC modification.¹⁶ We present the largest single-center experience of both “rotatripsy” and “orbital-tripsy,” with specific case examples using intravascular imaging to highlight the synergism of these tools.

Methods

In this retrospective analysis at a tertiary teaching hospital (Prince of Wales Hospital, Chinese University of Hong Kong), consecutive patients who were treated with combination atherectomy (RA or OA) and IVL between July 2019 and March 2022 were included.

Following coronary angiography showing significant CAC and decision to proceed with PCI at the discretion of the interventional cardiologist, intravascular imaging was performed. Optical coherence tomography (OCT) was performed with the Dragonfly Optis system (Abbott Vascular) and optical frequency domain imaging (OFDI) with the FastView catheter connected to the Lunawave system (Terumo). Intravascular ultrasound (IVUS) was performed with the Altaview catheter connected to the VISICUBE system (Terumo). If the imaging catheter could not cross the lesion, upfront RA or OA was performed to modify the CAC before prestent intravascular imaging was performed. The decision to use IVL following RA or OA was made intraprocedurally by the operator, based on intravascular imaging findings, or inadequate lesion preparation.

RA was performed with the Rotablator or Rotapro system (Boston Scientific) and OA was performed with the Diamondback 360 Coronary OA System (Cardiovascular Systems, Inc). IVL was performed with the C² catheter (Shockwave Medical, Inc) and pulses were delivered at 4 atm in all patients. The total number of pulses used was at the operator’s discretion.

Baseline demographics and procedural details were collected retrospectively from the electronic patient database.  Lesions assessed by OCT/OFDI were scored 0-4 according to the calcium score described by Fujino et al,¹⁷ with 2 points for maximum calcium angle >180°, 1 point for maximum thickness >0.5 mm, and 1 point for length >5 mm. Lesions assessed by IVUS were scored 0-4 according to the calcium score described by Zhang et al,¹⁸ with 1 point for calcium >270° in ≥5 mm, 1 point for 360° calcium, 1 point for calcified nodule, and 1 point for vessel diameter <3.5 mm. Due to shadowing at the site of maximum calcification, the closest slice with a visible vessel wall was used to determine the vessel diameter.

The primary efficacy endpoint was procedural success (successful stent implantation, <30% residual stenosis visually, Thrombolysis in Myocardial Infarction 3 flow; absence of types C to F dissection/perforation, or loss of side branch ≥2.0 mm visually) without in-hospital major adverse cardiovascular event (MACE, defined as cardiovascular death, myocardial infarction [MI], and target-vessel revascularization).

This retrospective study was approved by the Joint Chinese University of Hong Kong–New Territories East Cluster Clinical Research Ethics Committee.

Results

Baseline patient and procedural characteristics. Between July 2019 and March 2022, a total of 25 patients underwent combined atherectomy and IVL during their PCI. RA and OA were used in 14 patients (56%) and 11 patients (44%), respectively. Baseline demographics are shown in Table 1. Cardiovascular risk factors were highly prevalent, and 19 patients (76%) were men. PCI was performed for stable ischemic heart disease in 19 patients (76%) and acute coronary syndrome in 6 patients (24%). The left anterior descending (LAD) coronary artery was the most common target vessel, in 16 patients (64%), followed by right coronary artery (RCA) in 7 patients (28%) and left circumflex artery (LCX) in 2 patients (8%).

Procedural characteristics and outcomes are summarized in Table 2. Rotatripsy or orbital-tripsy was performed in de novo calcified lesions in all cases. Three patients (12%) required mechanical circulatory support-assisted PCI (2 Impella [Abiomed, Inc] and 1 extracorporeal membrane oxygenation [ECMO]). The patient who had ECMO-supported PCI had concurrent severe aortic stenosis requiring transcatheter aortic valve implantation. PCI was guided by intravascular imaging in nearly all cases (n = 24; 96%).

The primary efficacy endpoint was achieved in 22 patients (88%). The single case of angiographic complication was a loss of diagonal branch after stent deployment in the LAD. However, this did not result in cardiac enzyme rise or periprocedural MI. The in-hospital MACE rate in our cohort was 8%. One patient died from an intracerebral hemorrhage while on triple-antithrombotic therapy due to concurrent atrial fibrillation, while another patient with underlying severe ischemic cardiomyopathy died from a cardiac arrest 3 days after PCI.

Rotatripsy. Individual procedural characteristics and intravascular imaging findings of the 14 patients who underwent rotatripsy are summarized in Table 3. PCI was guided by OFDI/OCT in 8 patients, IVUS in 5 patients, and angiography alone in 1 patient. The intravascular imaging catheter was able to cross the lesion for baseline assessment before RA in 3 out of 13 patients (23%). Of the lesions assessed by OCT/OFDI, 7 out of 8 (88%) had an OCT calcium score of 4, while 4 out of 5 (80%) assessed by IVUS had an IVUS calcium score ≥2. All 8 patients assessed with OCT/OFDI had maximum calcium thickness >0.5 mm. A calcified nodule was identified in 3 of the 13 lesions (23%) assessed by intravascular imaging. Nine patients (64%) had dilation with non-compliant balloons after RA and prior to IVL. Four patients (29%) had dilation with non-compliant balloons after IVL, 1 of which was a scoring balloon. Rotatripsy patient #10 died from an intracerebral hemorrhage and patient #14 died from a cardiac arrest as an inpatient following PCI.

Rotatripsy patient #7. A 68-year-old man with hypertension, type 2 diabetes mellitus, and dyslipidemia underwent elective PCI for progressive angina. He was found to have severely calcified diffuse disease in the proximal to mid LAD (Figure 1A). The OCT catheter was unable to pass the lesion for baseline assessment, therefore, upfront RA was performed with a 1.5-mm burr at 180,000 rpm. Several runs were performed successfully and baseline OCT was then acquired, showing concentric 360° calcification, with a maximum calcium thickness of 1.09 mm (Figure 1B). Although RA allowed enough lumen gain to pass the OCT catheter, the imaging showed minimal modification to the thick concentric calcification. Predilation with a 2.75 x 15-mm non-compliant balloon did not open well, therefore, a 2.5 x 12-mm IVL balloon was used to deliver 80 pulses of lithotripsy. Following stenting and balloon postdilation, final OCT showed good stent expansion with deep calcium cracks created by the lithotripsy (Figure 1C). Final angiographic result is shown in Figure 1D.

Rotatripsy patient #10. A 76-year-old man with hypertension and end-stage kidney disease underwent staged PCI to his calcified RCA following an anterior ST-segment-elevation MI (Figure 2A). After small balloons were unable to pass the mid RCA to predilate the distal vessel, the workhorse guidewire was exchanged for a RotaWire Floppy (Boston Scientific), with multiple runs using a 1.5-mm burr at 180,000-200,000 rpm across the mid RCA. The lesion was further predilated with a 2.0 x 15-mm non-compliant balloon to facilitate IVUS assessment. This showed concentric 360° calcification in the mid RCA with a minimal lumen area (MLA) of 3.5 mm² (Figure 2B) and a calcified nodule in the proximal RCA (Figure 2C). A 3.0 x 12-mm IVL balloon was used to deliver 50 pulses of lithotripsy, followed by further predilation with a 3.0 x 15-mm non-compliant balloon. Final IVUS following stenting and balloon optimization showed a minimal stent area (MSA) of 6.7 mm², with a stent expansion of 94% (Figures 2D and 2E). Final angiographic result is shown in Figure 2F.

Orbital-tripsy. Individual and procedural characteristics of the 11 patients who underwent orbital-tripsy are shown in Table 4. All patients had OCT/OFDI-guided PCI and the imaging catheter was able to pass the lesion for baseline assessment prior to OA in 6 out of 11 patients (55%). All lesions had an OCT calcium score of 4, with 360° concentric calcification seen in 5 patients (45%). The mean maximum calcium thickness was 0.99 ± 0.15 mm and a calcified nodule was identified in 4 patients (36%). Two patients (18%) had dilation with non-compliant balloons after OA and prior to IVL, while 5 patients (45%) had dilation with non-compliant balloons after IVL.

Orbital-tripsy patient #4. A 69-year-old man underwent a staged procedure to a calcified mid to distal LAD after primary PCI to his proximal LAD for an anterior ST-segment-elevation MI (Figure 3A). Past medical history was also significant for hypertension, type 2 diabetes mellitus, and dyslipidemia. The OCT catheter was unable to cross the lesion for baseline assessment, therefore, the workhorse guidewire was switched for a ViperWire Advance for OA using multiple low- (80,000 rpm) and high-speed (120,000 rpm) runs, taking care to start beyond the recently placed proximal LAD stent. OCT then showed a calcium arc of 260°, MLA of 2.25 mm², and maximum calcium thickness of 0.91 mm at the most calcified segment (Figure 3B). A 2.5 x 12-mm IVL balloon was then used in this segment to further prepare the lesion, with a repeat OCT run showing the MLA increased to 4.94 mm² and new fractures in the calcium (Figure 3C). Dissections penetrating both intimal and medial layers can be seen post IVL distal to the most calcified segment (Figure 3D). Following stenting and balloon optimization, the final OCT run showed an MSA of 6.36 mm² (Figure 3E). Final angiographic result is shown in Figure 3F.    

Orbital-tripsy patient #8. A 78-year-old woman with hypertension and type 2 diabetes mellitus underwent an elective coronary angiography following an abnormal computed tomography coronary angiography. The baseline angiogram showed a calcified proximal to mid LAD (Figure 4A). Baseline OFDI was acquired and showed eccentric calcification in the mid LAD (Figure 4B)and concentric calcification in the proximal LAD (Figure 4C), with maximal thickness of 0.92 mm. The workhorse wire was switched out for the ViperWire Advance to perform multiple low- (80,000 rpm) and high-speed (120,000 rpm) OA runs in the calcified segment, followed by another OFDI run to assess the calcium modification. A classic “snowman” appearance was seen in the eccentrically calcified mid LAD, a common finding after OA (Figure 4D). This unique appearance is due to the bidirectional ability of OA to ablate calcification. In the mid LAD, forward OA runs typically bias the crown toward the outer curve (diagonal side) whereas backward OA runs bias toward the inner curve (septal side). In this case, the eccentric calcification was on the inner curve, therefore, preferential ablation in this segment was achieved by predominantly backward OA runs, then advancing the crown beyond the lesion with GlideAssist mode between each run. The concentric calcification in the proximal LAD remained minimally modified by OA, therefore, a 3.0 x 12-mm IVL balloon was chosen to modify this segment. However, predilation with a 2.5 x 15-mm non-compliant balloon was required to deliver the IVL balloon, with post-stent OFDI showing calcium fractures (Figure 4E). Final angiographic result is shown in Figure 4F.

Discussion

Our study demonstrates the synergistic use of both RA and OA with IVL in heavily calcified coronary stenoses with good procedural success rates. Both IVUS and OCT/OFDI are more sensitive than coronary angiography in detecting coronary calcification and enhance procedural planning ability during PCI.¹⁹ IVUS- and OCT-based calcium scores have been utilized to quantify coronary calcification and to guide choice of calcium modification tool. An OCT calcium score of 4 was associated with stent under-expansion of 78% vs 96% (P<.01) for scores of 0 to 3.¹⁷ In our cohort, 17 of 18 lesions (94%) assessed with OCT/OFDI had a calcium score of 4. An IVUS calcium score of ≥2 is predictive of stent under-expansion (stent expansion <70%) and requires adjunctive calcium modification before stent implantation.¹⁸ In our cohort, 4 of 5 lesions (80%) assessed with IVUS had a calcium score of ≥2. The high proportion of lesions with OCT or IVUS calcium scores that predicted stent under-expansion in our study necessitated the use of multiple calcium modification tools to achieve optimal stent outcomes.

In our practice, as with many existing decision algorithms for treating calcified stenoses, upfront atherectomy is utilized if the intravascular imaging catheter is unable to cross the lesion in the presence of moderate to heavy angiographic calcification, which occurred in 15 out of 24 cases (63%).^1,20-22 Although atherectomy can be utilized to safely bail out cases where balloons do not adequately expand, upfront use of either RA or OA is preferable when there is an absence of significant balloon-induced dissection.²³ The choice between RA and OA is dependent on several factors. First, RA has a front-drilling action, which may be preferable when the calcified stenosis limits crossing of small balloons or microcatheters. Second, OA may be more favorable in large vessels or long lesions, as the 1.25-mm crown is effective in vessel diameters of 2.5-4.0 mm. Therefore, OA can debulk calcium in variable vessel sizes without the need to upsize the burr like RA, which may be limited by the size of guide catheter used.²⁴ Third, the authors believe individual operator preference and experience is an important factor when choosing between RA and OA.

IVL has the unique ability to create fractures in both superficial and deep calcium layers.⁹ All of the lesions assessed with OCT/OFDI in our study had a maximum calcium thickness of >0.5 mm. In our experience, the decision to use IVL following atherectomy was either due to the presence of thick circumferential calcium on intravascular imaging that may not be adequately modified by atherectomy, or inadequate expansion of non-compliant balloons following RA or OA. The current iteration of IVL is the C² catheter, which is compatible with 6-Fr guides, with the balloon measuring 2.5-4.0 mm in diameter and 12 mm in length. The crossing profile of the IVL balloon is comparable to other commercially available cutting or sculpting balloons and bulkier than scoring balloons (Table 5).²⁵ Although the IVL balloon can be delivered using various techniques such as buddy wires, buddy balloons, and guide extension catheters, upfront calcium debulking with RA or OA is often required in the most severely stenosed lesions before IVL delivery, as with the examples presented herein.

Interestingly, the death due to cardiac arrest (rotatripsy patient #14) was the only case where PCI was guided by angiography alone. Although the number of patients is too small to draw any conclusions, the use of intravascular imaging in the setting of severe CAC is paramount to assess lesion preparation and optimize stent expansion. Our study contributes to the growing body of evidence describing successful use of rotatripsy and orbital-tripsy. Understanding the mechanism of action of each device as well as their limitations allows operators to maximize procedural and clinical success when tackling severe CAC during PCI.

Study limitations. This is a single-center, retrospective study that has inherent limitations due to a small study population. First, the choice between RA or OA, the use of non-compliant balloons before and after IVL, and the mode of intravascular imaging were all at the discretion of the operator. Second, the OCT- and IVUS-based calcium scores were validated in lesions that have not been treated with atherectomy. However, the intravascular imaging catheter was unable to pass the lesion before atherectomy in 63% of cases, reflecting the reality of real-world management of severe CAC during PCI. Finally, the intravascular imaging was assessed retrospectively; therefore, inconsistencies in image timing and quality did not allow for sequential reporting of MLA, MSA, or stent expansion.

Conclusion

This is the largest single-center study demonstrating combined use of RA or OA with IVL—termed rotatripsy and orbital-tripsy, respectively—in preparing severely calcified lesions during PCI. We have highlighted the severity of CAC and mechanisms of action of the devices using intravascular imaging. The combination use of atherectomy followed by IVL was demonstrated to be efficacious and to have acceptable procedural outcomes.

Acknowledgments. Dr Wong is supported by the New Zealand Heart Foundation during his overseas fellowship.

Affiliations and Disclosures

From the Division of Cardiology, Department of Medicine and Therapeutics, Prince of Wales Hospital, Chinese University of Hong Kong, Hong Kong SAR, China.

Disclosure: The authors have completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. Dr Wu reports research funding from OrbusNeich, Asahi Intecc, Abiomed; consulting honoraria from Boston Scientific, Abbott Vascular; board of directors for APCTO Club. The remaining authors report no conflicts of interest regarding the content herein.

The authors report that patient consent was provided for publication of the images used herein.

Manuscript accepted September 23, 2022.

Address for correspondence: Bernard Wong, MD, Division of Cardiology, Department of Medicine and Therapeutics, Prince of Wales Hospital, Chinese University of Hong Kong, Hong Kong SAR, China. Email: bernardwong@hotmail.co.nz

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