Evaluation of the Safety and Efficacy of the Novel Svelte Acrobat Integrated Delivery System via Radial Approach With 5 Fr Catheters

Abstract: Purpose. To evaluate the safety and efficacy of the Svelte Acrobat integrated delivery system (IDS) via radial approach with 5 Fr catheters. The direct stenting (DS) system enables easy delivery, deployment, and postdilatation of a cobalt-chromium stent. Methods. Patients with coronary artery disease (CAD) were prospectively enrolled at three centers to undergo percutaneous coronary intervention with DS via radial approach using 5 Fr catheters. The primary endpoint was IDS success, which was defined as DS without postdilatation and final stenosis <20% with Thrombolysis in Myocardial Infarction (TIMI)-3 flow. Results. Fifty consecutive patients with 55 lesions were included. The procedure success rate was 98%. The device could not cross the lesion in 2 cases, so DS success was 96%. Fifty lesions met the primary study objective; thus, IDS success rate was 91%. The procedure duration was 21 ± 9 minutes, fluoroscopy time was 7.3 ± 4.7 minutes, and contrast volume per vessel was 103 ± 33 cm3. The final residual stenosis, by quantitative coronary angiography, was 3.4 ± 4%. The reduced need for additional catheters resulted in a 20% procedural cost reduction. There were no bleeding or vascular complications. At 8 months, the event-free survival rate was 84%. Conclusions. DS using the Svelte Acrobat IDS via radial approach with low-profile catheters is safe and efficacious in select coronary artery disease patients, and its use is associated with potential procedural cost savings. 

 J INVASIVE CARDIOL 2015;27(12):E312-E318. Epub 2015 August 25.

Key words: direct stenting, acute coronary syndrome

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In the last decade, direct stenting (DS) has become a feasible and safe technique because of improvements in stents and delivery systems. Several randomized trials and other studies compared DS with stenting after balloon predilation,^1-6 and DS was associated with shorter procedure time, less radiation exposure, and lower procedural costs.^7,8 However, DS is only performed in 30%-60% of all percutaneous coronary interventions (PCIs) because of coronary complexity and the relative stiffness of the metallic stents.

After PCI, especially in cases of acute coronary syndrome (ACS), the incidence of hemorrhagic complications is associated with a higher mortality.^9,10 Compared with femoral access, the radial approach resulted in a lower incidence of bleeding and vascular complications.^11,12 Therefore, DS via radial approach may be favorable in PCI. 

The Svelte Acrobat (Svelte Medical Systems) integrated delivery system (IDS) is a new, bare-metal, thin-strut, ultra-flexible, cobalt-chromium stent mounted on a fixed-wire platform. It is indicated for PCI with DS approach, given that its low profile is compatible with 5 Fr catheters, which do not compromise target vessel opacification during the procedure.¹³ Our objective was to evaluate the safety and efficacy of the Svelte Acrobat IDS via radial approach using low-profile guiding catheters for coronary catheterization.

Methods 

Patient selection. This prospective, multicenter, non-randomized, single-arm study evaluated coronary artery disease (CAD) patients who were candidates for elective PCI with the Svelte Acrobat IDS via radial approach with 5 Fr guiding catheters. Inclusion criteria were: ≥18 years old; diagnosis of stable angina (Canadian Cardiovascular Society class 1, 2, 3, or 4), silent ischemia, or unstable angina (Braunwald class 1-3 and B-C); presence of a primary coronary lesion with a reference diameter of 2-3 mm and a target lesion with stenosis of 50%-99% (visual analysis) with ≤20 mm extension; and agreement to participate in the study and provide informed consent (prior to procedure) after the overall risks, goals, and nature of the trial were explained.

The exclusion criteria were: refusal or inability to sign the written informed consent form; reverse Allen’s test; pregnant women; clinical presentation of acute myocardial infarction (<72 hours); candidacy for primary angioplasty; cardiogenic shock (<90 mm Hg systolic pressure for >30 minutes and not responsive to fluids); serum creatinine >2.0 mg/dL; history of bleeding diathesis or coagulopathy or inability to accept blood transfusions; known hypersensitivity or contraindication to heparin, aspirin, or clopidogrel; terminal illness associated with limited life expectancy (<1 year); left ventricular ejection fraction ≤30%; in-stent restenosis; target lesion ≥50% in the unprotected left main artery; target lesion in bifurcation (secondary branches with a diameter of ≥2.5 mm); excessive calcification requiring ablative techniques prior to stent implantation; stent previously deployed <10 mm from the target lesion; previous PCI <6 months prior or scheduled within the next 30 days. 

The study protocol was approved by an independent ethics committee at each participating research-related institution in accordance with the Declaration of Helsinki for Human Research. All patients read and signed the informed consent.

The stent system. The Svelte Acrobat IDS is a balloon-expandable 605 cobalt-chromium metallic alloy stent with strut thickness of 81 µm, which is premounted on a single-lumen fixed delivery catheter and secured to a guidewire (0.012˝ and 22 mm long), constituting a single integrated system for coronary stent delivery (Figure 1). The Svelte Acrobat IDS has a working length of 145 cm and includes two proximal shaft markers at 90 cm and 100 cm. Proximal and distal radiopaque markers mounted under the balloon indicate both the working length of the balloon and the stent under fluoroscopy. The stent is highly flexible, with a crimped cross-sectional area one-half that of the currently available commercial stents.¹³ Low-compliant balloon material and balloon control bands superimposed on the tips of the balloon were designed to control expansion and limit vessel contact with multiple inflations, while facilitating balloon re-wrapping after stent deployment. An integrated torquing device located on the proximal shaft of the IDS beneath the inflation connector port could be loosened and positioned along the proximal shaft to facilitate steerability. Alternatively, the catheter could be rotated using the connector wings. The wire tip is a small, atraumatic (0.012˝) flexible coil, minimizing vessel contact with a 22 mm length that provides effective device position (Figure 2).¹³ Overall, stents were available in 2.5-3.5 mm diameters, and 13, 18, and 23 mm lengths.

Procedure and follow-up. Patients were assessed clinically and were pretreated with aspirin and clopidogrel according to standard guidelines. PCI was primarily performed with 5 Fr catheters via radial access. In comparison to 6 Fr catheters, the use of 5 Fr catheters in non-coaxial cannulation may compromise back-up support and result in more fluoroscopy time. Therefore, careful selection of the best catheter to achieve coaxial alignment with the target coronary artery was done in all cases in order to improve back-up support during PCI, even with deep insertion into coronary arteries, when needed. All patients received a weight-adjusted bolus of heparin and nitroglycerin intravenously immediately before the opacification of the target vessel, which was held in at least two orthogonal views. Then, the Svelte Acrobat IDS was introduced to the target lesion, and the stent was deployed, always with high pressure (>12 atm). If the target vessel had a significant angulation (>45°) or tortuosity (at least one bend >75° in a segment proximal to the target lesion), a more pronounced curve at the distal end of the wire was manually manipulated to facilitate access to the target lesion. If this was not possible, a conventional  guidewire was introduced and standard balloon predilatation was performed. Importantly, appropriate stent sizing to the reference vessel diameter and the lesion length was emphasized in order to achieve optimal stent expansion and full coverage of the lesion. In case of dissection, the operator could implant additional stents; however, it was recommended not to remove the integrated system from the target vessel until crossing into the target vessel with another wire was achieved, thus maintaining access to the distal vessel. The objective was to obtain <20% residual stenosis with DS, and if this was not possible with the Svelte Acrobat IDS, the operator was allowed to use extra guidewires and non-compliant balloons inflated at high pressures. After the procedure, the arterial sheath was immediately removed, and a compressive bandage was applied to the radial artery for 2-4 hours following a specific protocol. In general, hospital discharge was scheduled approximately 24 hours post procedure, and clinical follow-up was performed at 1 and 8 months after the index procedure. At the prescheduled medical visits, patients were noted for all clinical events according to the study protocol. In case of myocardial infarction or objective evidence of myocardial ischemia by altered functional tests, the patient was sent to a new angiographic study.

Endpoints and definitions. The primary endpoint was IDS success via radial approach with 5 Fr catheters, which was defined as DS without requirement of postdilatation with additional balloon catheters and achievement of Thrombolysis in Myocardial Infarction (TIMI)-3 flow and residual stenosis <20% as determined by quantitative coronary angiography (QCA) at the end of the procedure. Secondary endpoints and other variables noted included: (1) successful DS of the target lesion; (2) successful stenting of the target lesion, with or without predilatation; (3) procedure success; (4) stent thrombosis in accordance with Academic Research Consortium (ARC) criteria; (5) the incidence of bleeding; (6) procedural length; (7) fluoroscopy time; (8) the amount of contrast used during procedure; (9) the need for additional materials for procedure success; (10) in-hospital major adverse cardiac event (MACE) rate; and (11) the MACE-free survival rate at 8 months.

Major adverse cardiac event (MACE) was defined as death, non-fatal myocardial infarction, or target-vessel revascularization (TVR). All deaths were considered to be cardiac in origin for the purpose of this investigation, unless non-cardiac etiology was established in an additional examination or during necropsy. Myocardial infarction was defined as the presence of increased enzyme release (creatine kinase [CK] ≥3x the upper limit of normal in the presence of an elevated MB isoenzyme up to 3x the reference value), associated or not with the occurrence of new Q-waves in two or more contiguous electrocardiogram leads. TVR was reported at 30 days and at the 8-month follow-up, and a new target-lesion revascularization (TLR), whether percutaneous or surgical, was performed mainly for the treatment of recurrences. Angiographic binary restenosis was defined as diameter stenosis >50% at the stented segment as determined by QCA analysis. Stent thrombosis was classified as definite, probable, or possible, according to the ARC criteria.¹⁴Bleeding was defined using the Bleeding ARC criteria.¹⁵Stent success was defined as residual stent stenosis <20% of the target lesion (by QCA) and TIMI-3 flow. DS success was defined as stent success without predilation. IDS success was defined as DS success without postdilatation and additional balloon catheters. Procedural success was defined as stent success in the absence of in-hospital MACE. 

Quantitative coronary angiography evaluation. QCAs were obtained in multiple views after the intracoronary injection of nitrates (100-200 µg), unless clinically contraindicated, and included two orthogonal projections. Quantitative analyses including all angiographic parameters reported before and after the procedure, and were performed by an independent core laboratory (Instituto Dante Pazzanese de Cardiologia). The guide catheter filled by contrast was used for calibration via automated edge detection. All QCA analyses were performed offline by experienced operators who were blinded to the procedural data, using a validated and commercially available computerized software (QAngio XA 7.3; Medis Medical Imaging Systems BV).

Analysis of procedural costs. In Brazil, the public health system generally provides reimbursement for one PCI with the following materials: one guiding catheter, one guidewire, one balloon catheter (which can be used for pre- or postdilatation), and one stent. Based on this, we simulated a matched analysis of the PCIs using the Svelte Acrobat IDS in this study with the expected PCIs from the Monorail system, as available in our public health system. 

For this analysis, we excluded issues related to the procedure time and contrast volume as potential additional costs due to unplanned stents to cover edge dissections, given that this could occur using any stent technique. We assumed the same reimbursement for any bare-metal stent.

Statistical analysis. A sample size of 50 patients was deemed sufficient for the initial performance, safety, and efficacy evaluation of the Svelte Acrobat device with a reasonable distribution of clinical and angiographic variables related to the procedure and materials in question. Statistical analysis was performed using Microsoft Office Excel 2007, version 12.0 (Microsoft Corporation). Absolute numbers and percentages were calculated. Discrete variables were expressed as frequencies and percentages, and continuous variables were expressed as mean ± standard deviation. The discrete variables were compared between the groups using Chi-square test, and continuous variables were compared using the Student’s t-test. Differences were considered statistically significant at P<.05. 

Results

Between March and December 2012, we prospectively recruited 50 patients with CAD in 55 target vessels at three sites. Baseline demographic and clinical characteristics are shown in Table 1. Overall, mean age was 58 years and 44% of the patients were women. In addition, there was relatively high prevalence of comorbidities, including diabetes in 36%; as for clinical presentation, unstable angina was found in almost 80% of patients.

All cases were successfully performed via radial approach. Fluoroscopy time was 7.3 ± 4.7 minutes, 1.1 coronary lesions were treated per patient, total procedure length was 21 ± 9 minutes, and the contrast amount used per target vessel was 103 ± 33 cm³. Procedure and angiographic characteristics are presented in Table 2. Most of the vessels had mild calcification (91%), but more than one-half had moderate to severe tortuosity (at least one bend >75° in a segment proximal to the target lesion), indicating that most target lesions had moderate complexity (lesion type B1/B2 = 87% according to the American College of Cardiology/American Heart Association classification). Figure 3 illustrates two successful Svelte Acrobat IDS implantations in complex lesions. The average stent length was 18 ± 2.89 mm, and the ratio of the stent length to the lesion length was 1.42 ± 0.39. All stents were implanted at high pressures (>12 atm), and the maximal balloon inflation pressure after stenting averaged 15.2 ± 2.37 atm. Reference vessel diameter was 2.82 ± 0.42 mm and mean lesion length was 13.95 ± 5.37 mm. The acute lumen gain was 2.00 ± 0.29 mm, and the final residual stenosis was 3.4 ± 4.0%. QCA variables are presented in Table 2. Stents were implanted in 100% of cases, but in 1 case, the final residual stenosis was 21.7%, which was above the definition of success in this study (residual stenosis <20% by QCA), despite use of a non-compliant high-pressure balloon at up to 24 atm. Stent success, by definition, was 98%. Consequently, procedural success was high (98%), and no MACE occurred during hospitalization. In 2 cases, there was need to predilate the lesions due to: (1) severe stenosis located in the distal segment of the right coronary artery; and (2) a tortuous and complex lesion in the right coronary artery (Figure 4). In these cases, the Svelte stent was successfully implanted after predilatation, and overall DS success was 96%. 

Fifty lesions met the primary study objective; thus, IDS success was 91% (Table 3).We had to postdilate 4 lesions with additional non-compliant balloons to achieve minimal residual stenosis. The most relevant complication was 1 dissection of the right coronary artery related to the guiding catheter. In this case, the first IDS was implanted in the distal artery, followed by a second IDS in the proximal vessel covering the dissection with a satisfactory angiographic result. Notably, there was no difficulty introducing the second stent within the low-profile guiding catheter. In 3 additional cases, stent edge dissections were detected and successfully treated with other stents. In these cases, the stent length in relation to the lesion length was straight, and averaged 1.08 mm.