The Mynx® Vascular Closure Device: The Piedmont Heart Institute Experience

The Piedmont Heart Institute is a cardiovascular care center serving patients in the greater Atlanta area. It operates an innovative cardiovascular healthcare delivery model that integrates a continuum of care for patients from primary and secondary prevention to outpatient and inpatient cardiovascular care. The Heart Institute is the first integrated cardiovascular healthcare delivery program affiliated with a community health system in the Atlanta area, and includes physician practices and hospital services, including the Fuqua Heart Center of Atlanta at Piedmont Hospital. The Piedmont Heart Institute also provides cardiovascular services to three other hospitals (Piedmont Fayette Hospital, Fayetteville, GA; Piedmont Mountainside Hospital, Jaspar, GA; Piedmont Newnan Hospital, Newnan, GA) and employs 65 cardiologists who work closely with cardiovascular and vascular surgeons in a synergistic model. Commitment to high-quality patient care at the Institute has meant careful reflection about the options for sealing the arteriotomy after diagnostic and interventional cardiac catheterization procedures. Since the advent of vascular closure devices in the mid-1990s, the published scientific literature has left little doubt that vascular closure devices offer several advantages over manual compression alone, including faster hemostasis and ambulation, increased patient comfort, accelerated time to discharge, and improved patient satisfaction.1-3 While some of this literature has also suggested that earlier generations of closure devices were associated with higher complication rates than manual compression, contemporary analyses of the newer-generation closure devices suggest that such a disparity in complication rates may have been resolved.1, 4-8 Currently, closure devices are employed in about 40%9 of patients, with the majority of patients receiving compression largely due to limitations of traditional closure device technology. For many interventionalists, the rare but serious, even potentially catastrophic, complications associated with traditional closure devices remain a lingering concern. Indeed, infections, femoral artery compromise, arterial laceration, uncontrolled bleeding, device embolism and limb ischemia have all been reported with closure devices.10,11 Such complications, albeit relatively infrequent with the current generation of devices, tend to be more serious (i.e. ischemic or embolic events, infection) than those associated with manual compression (i.e. hematoma, pseudoaneurysm, re-bleed).10-15 Several years ago, many physicians at the Heart Institute abandoned the use of closure devices in favor of manual compression alone. This was based on concern over the infrequent yet very serious complications that can arise with those devices that rely on intra-arterial components. However, the increased patient comfort, limited bedrest and early ambulation with closure devices remained an important consideration. We decided to try a new device called the Mynx Vascular Closure Device (Figure 1) (Access Closure, Inc., Mountain View, CA). Physicians were initially intrigued by the extravascular design because, with no intra-arterial components left behind in the vessel, it should not be prone to ischemic, embolic or infectious complications. It appeared that the Mynx Vascular Closure Device could provide the convenience of groin closure for the patient and catheterization laboratory staff without the risk of potentially catastrophic vascular complications. In this article, we share a retrospective review of our first 10 months using the Mynx device for arteriotomy closure after diagnostic and interventional catheterizations at Piedmont Hospital. An Extravascular Sealant The Mynx device was approved by the U.S. Food and Drug Administration in May 2007 for arteriotomy closure after diagnostic and interventional cardiac catheterization procedures. Hemostasis is achieved by delivering a water-soluble, bio-inert, non-thrombogenic sealant on the shaft of a delivery catheter to the surface of the artery. The catheter is advanced through the existing 6F or 7F sheath used for the catheterization procedure. Apposition of a 6-mm semi-compliant balloon to the anterior arterial wall establishes temporary hemostasis during deployment of the sealant and ensures its extra-arterial placement. As the sealant encounters blood and subcutaneous fluids, they immediately fill the porous structure of the sealant, creating a durable hemostasis, sealing the arteriotomy and tissue tract (Figure 2). The Mynx sealant is made of polyethylene glycol (PEG), a bio-inert polymer with an established safety profile in a broad range of medical applications, including gel caps and cranial sealing. When delivered to the tissue tract, the PEG sealant instantly absorbs blood and fluids from the arteriotomy, creating a hydrated, porous sealant that provides immediate hemostasis by swelling 3 to 4 times its original size. When fully expanded, the sealant is composed of 95% blood and fluids and 5% PEG. The sealant material completely dissipates through hydrolysis within 30 days. Because the PEG monomers generated during hydrolysis are small enough to undergo renal clearance, all traces of the sealant are removed from the body. The extravascular sealant design offers several potential advantages. Closure devices employing collagen-based or metallic technologies to compress, suture, or clip the arteriotomy site, necessitate placement of components within the arterial lumen or wall. Mynx provides an immediate mechanical seal over the arteriotomy and within the tissue tract, achieving hemostasis with placement of the sealant outside of the artery, avoiding compromise of the lumen that may result from components residing within the artery or wall. The tissue-like, resorbable sealant may eliminate factors that can make re-access challenging, such as excessive fibrotic responses. Early experience has shown a marked absence of inflammation and scarring following use of the Mynx device (Figure 3). The absence of sutures or clips also eliminates the need for tugging or cinching during deployment, which can result in trauma to the artery. The comparatively gentle deployment of the extravascular sealant minimizes pain or discomfort for the patient during closure. Additionally, because the rapidly expanding sealant also fills the tissue tract, there is less likelihood of post-procedure oozing and the subsequent utilization of nursing resources and hemostatic pads, as well as potential for delayed ambulation. With delivery of the sealant through the existing 6F or 7F procedural sheath, tract dilation and sheath exchange are not required, which should limit potential for enlargement of the arteriotomy site, infection and inflammation. In one early prospective study of 190 patients undergoing diagnostic or interventional cardiac catheterization at five European centers, the sealant was successfully delivered in 99.5% of patients with no evidence of sealant migration, embolization or intra-arterial deployment.16 Hemostasis was achieved in a median 0.5 minutes with no significant difference observed between diagnostic and interventional patients (0.5 vs. 0.6 minutes). The mean time to ambulation was 2.6 hours. The only major complication was a single case (0.5%) of access-site bleeding requiring blood transfusion. The Piedmont Hospital Experience Historically, vascular access-related complications occur in 0.8% to 1.8% of diagnostic catheterizations and 1.5% to 9% of percutaneous coronary interventions (PCI).17 We decided to retrospectively analyze our experience to understand whether use of a new device would result in a decreased risk of complications for our patients. In the first 10 months using the Mynx device at Piedmont Hospital (October 2007 to July 2008), 761 patients undergoing diagnostic (n=554, 73%) or interventional catheterization (n=207, 27%) primarily with 6F sheaths had their arteriotomies closed with this extravascular closure device. The Mynx device was initially used for closure after diagnostic catheterizations and later used in PCI. Anticoagulation in the PCI population of patients was primarily achieved with bivalirudin (89%), with heparin (8%) and glycoprotein IIb/IIIa inhibitors (3%) administered in a minority of cases. The Mynx device was successfully deployed in 98.7% of cases with few vascular complications. The low major vascular complication rate of 0.67% (n=5) included 1 retroperitoneal bleed, 1 surgical repair, and 3 blood transfusions. The minor vascular complication rate of 0.53% reflects the occurrence of 4 small pseudoaneurysms that resolved without sequelae. As might be expected with a sealant technology applied extra-arterially, these complications were more similar to those seen with manual compression. Outcomes with the Mynx device have been excellent, especially as one considers that this experience incorporates operator learning curves and that catastrophic complications were non-existent. Results are summarized in Table 1. From an operator perspective, the device was easy to deploy, with deployment steps and techniques mastered in the first few procedures. In our practice, angiographic assessment of the femoral anatomy is performed in all cases to identify the arteriotomy location and other important anatomical variances prior to deploying the Mynx device. Following deployment of the sealant, mild to moderate pressure is applied for 2-3 minutes at the arteriotomy site to permit adequate time for the sealant to expand. In this community hospital-based experience, the Mynx device was deployed by more than 15 operators in more than 750 patients during the early experience. It should be noted, of course, that because these procedures were performed at a single center, the outcomes may be vulnerable to the effects of operator-dependent factors that could influence device success and subsequent patient outcomes. Nonetheless, these outcomes reflect real-world experience during the early adoption of a new vascular closure technology in a large catheterization laboratory. Patient Comfort One of the major benefits of the Mynx device is the lack of pain associated with the procedure. From a patient perspective, patients in the Piedmont experience were often unaware that the Mynx device had been placed at the end of the procedure. For some who had prior experience with traditional closure devices, it was surprising that the Mynx device was placed without some degree of pain. In our experience, Mynx has been consistently associated in most patients with absence of pain or only the slightest discomfort for the patient. After Mynx closure, patients need not endure manual compression or the ensuing extended period of bed rest. In our experience, there is very little, if any, oozing, perhaps because the tissue tract is sealed along with the arteriotomy. The device has also proved helpful in hard-to-close, very overweight or obese patients where manual compression is challenging due to difficulty locating the femoral artery and holding pressure. Complex Patients There remain several categories of patients for whom timely hemostasis is a challenge and for whom closure devices with intravascular components are not a suitable option. For example, it is commonplace to avoid closure devices with intravascular components in patients with peripheral vascular disease, particularly those with diffusely diseased vessels, due to the increased risk of ischemic events in this diseased milieu. The extravascular nature of the Mynx device may eliminate the ischemia concern. Similarly, intravascular closure devices are not designed for use in bifurcation anatomy, an environment in which a conformable, extra-arterial sealant may be more suitable. Obese patients represent a group for which an extravascular sealant may offer a solution to difficulties with both accessing the femoral vessels (i.e. no need for sheath exchange) and effectively applying manual pressure to the arteriotomy site for an adequate duration to achieve hemostasis. Case Report A 61-year-old male patient presented at the emergency room with a several-day history of shortness of breath. He reported episodes of paroxysmal nocturnal dyspnea and orthopnea as well as adema. There was no history of coronary artery disease, diabetes, hypertension or prior cardiac testing. The patient was morbidly obese (BMI 37.6 kg/m²) and had a history of hyperlipidemia. Left and right heart catheterization was planned to further evaluate the patient with a new diagnosis of congestive heart failure. Angiography revealed a normal left coronary artery except for an area around the first diagonal and first septal branches, which had a 75-80% narrowing. All other vessels were normal. Severe systolic left ventricular dysfunction was noted. The patient’s ejection fraction was 20-25% and there was moderate pulmonary artery hypertension and marked elevation in filling pressures. Following catheterization, the decision to use the Mynx device was made because of the concern that obtaining hemostasis would be particularly challenging given the patient’s obesity. Femoral angiography was obtained prior to closure to permit assessment of the puncture location and the diameter of the artery at the sheath insertion site (Figure 4). In this case, the location of the access site was at the bifurcation. Closure of the femoral artery following catheterization was achieved with the Mynx device without complication. The patient ambulated without difficulty and there were no subsequent vascular access site complications. Discussion As the prevalence of obesity in the United States increases, more patients from this cohort are presenting to the cath lab for evaluation. Successful compression of the access site in this patient population is particularly challenging due to the difficulty of palpating and compressing the femoral artery, making vascular closure devices appealing, especially with data indicating a significantly lower rate of vascular complications compared with non-obese patients.18 Furthermore, the Mynx device is deployed through the procedural sheath, eliminating the need for a challenging sheath exchange. The integrity of the tract is maintained, permitting unencumbered delivery of the sealant directly on top of the arterial surface. Other devices require a sheath exchange and negotiation of components through a deep tract, increasing the challenge of use in obese patients. Femoral angiography confirmed the sheath insertion site at the bifurcation, exacerbating the challenge of obtaining hemostasis in an obese patient. Bifurcation punctures are associated with an increased risk of vascular complications because vessels are typically smaller than the common femoral artery, leading to greater potential of partial or total obstruction, especially with placement of intraluminal components. The complex angles associated with bifurcation anatomy pose challenges with placement of intra-arterial components while an extra-arterial approach is unconstrained in this regard. Finally, patients undergoing catheterization procedures often have peripheral vascular disease, which may include disease in bifurcation anatomy, further diminishing arterial diameters and blood flow. By design, the Mynx device avoids problems associated with placement of intraluminal components at the bifurcation and in our early clinical experience, outcomes have been favorable. Conclusions Several of our physicians now favor closure with Mynx over manual compression in catheterization procedures using 6F or 7F sheaths. Not only did this technology allay our concerns regarding rare but serious arterial complications, but the extra-arterial design appears to offer clinical versatility in treating patient cohorts not typically considered eligible for intravascular closure devices (femoral artery disease, bifurcation, obesity) and the option for immediate or early re-access. A cost analysis to assess use of the Mynx device compared to manual compression has not been performed to date at our institution and further evaluation of cost data is required to determine the economic impact of Mynx device use. While results from analyses of other closure devices cannot be directly extrapolated to the Mynx device, economic benefits derived from early discharge and reduced complications may supplement the benefits of patient comfort and greater clinical versatility. In this early, real-world experience at the Piedmont Heart Institute, high procedural success and a low incidence of complications have been achieved. Additionally, successful outcomes have been possible in challenging patient subsets, including peripheral vascular disease and obesity. With wider adoption of this technology will come an opportunity to fully evaluate its capabilities in the range of patient cohorts treated in the catheterization laboratory. Acknowledgments The author wishes to thank colleagues Ken Taylor, MD, and Laurie LaRusso, MS, ELS, for contributions to the writing of this article. Disclosures Dr. Brown reports receiving equity from CardioMEMS, Inc; LifeSync Corporation; SurgiVision, Inc.; speaking fees from Abbott Laboratories and Access Closure, Inc.; and research grants from Abbott Laboratories and Volcano Therapeutics, Inc. Dr. Brown has no equity ownership in Access Closure, Inc. Dr. Brown can be contacted at carmen.smith@piedmont.org

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