Catheter-based Devices Research Articles

Open-Chest Device Closure for the Minimally Invasive Management of Atrial Septal Defect in Young Children

We integrated a catheter-based device and minimally invasive surgical techniques for the treatment of atrial septal defect for children younger than 2 years old. Forty-three patients were divided into 3 groups: group A underwent open-chest device closure with a right lateral thoracotomy (n = 12), group B underwent open-heart repair with a right lateral thoracotomy and cardiopulmonary bypass (n = 11), and group C underwent open-heart repair with a median thoracotomy and cardiopulmonary bypass (n = 20). Group A had the lowest weight (9.25 +/- 1.3 kg) and smallest defect size (10.25 +/- 3.9 mm). In group A, 2 patients had to be transitioned to open-heart repair after unsuccessful occlusion. Compared with the open-heart groups, the device group had a shorter total operation time (111 +/- 39 minutes), required the minimum amount of blood products (39 +/- 38 mL), and had a smaller amount of pleural drainage in the first 12 hours after the procedure (29 +/- 12 mL). All patients were discharged. The right ventricular end-diastolic diameter reduced significantly after the repair; furthermore, there was no difference in the size of reduction. However, the device group had the highest medical costs (30,639 +/- 3831 Chinese yuan). During the follow-up, there were no occluder-related complications observed in Group A, and there were no residual shunts or arrhythmia observed in the groups. The open-chest device closure was safely performed as a supplement for percutaneous treatment for young children.

A Percutaneous Catheter‐Based System for the Measurement of Potential Gradients Applicable to the Study of Transthoracic Defibrillation

The local electric (E) field or potential gradient produced by a shock reliably predicts VF termination. In this study we evaluated a multiple electrode, catheter-based device for closed-chest 3D measurements of E field from transthoracic defibrillation shocks. Catheters with multiple electrodes on the tip were placed in intracardiac locations in anesthetized swine. An empirically derived calibration matrix and custom microprocessor was used to transform simultaneously measured voltages into orthogonal E field vector components. E fields produced in six intracardiac locations by 30 and 300 J shocks were compared in eight animals. Correlations were determined for measured current and E field at various shock strengths at two different transthoracic impedances in five additional animals. VF was induced in 12 animals and E field measured during defibrillation attempts. The E field measurements resulting for 30 J transthoracic shocks were not significantly different among different intracardiac sites. At 300 J, however, significant differences were observed between sites with the greatest intensities recorded in the coronary sinus and right ventricle. Within animals, the variability of the measurement at each site was small, ranging from 2.8 +/- 1.6% to 5.7 +/- 4.5%. Significant correlations (P < 0.001) between measured E field and peak current were observed at native impedance (34 +/- 4 Omega, r = 0.81) and at adjusted impedance (76 +/- 4 Omega, r = 0.78) with transthoracic shocks of 200, 300, and 360 J. In VF studies, the probability of defibrillation was closely fit by a sigmoidal dose response curve in the coronary sinus E field with an approximate threshold of 4.7 V/cm with 50% defibrillation success at 9.3 V/cm. The measured intracardiac E field variability within animals and at a specific site was small, exhibiting a median value of 5.1%, contrasted to median variabilities across animals of 5-11% suggesting the capacity of this measurement system to provide subject specific information on the distribution of E fields. The measured E field magnitudes across animals in the coronary sinus were linearly correlated with applied shock current with a very strong linear relation to effective shock voltage observed in vitro in a saline tank. When evaluated as a predictor of shock success, the observed values were consistent with previously reported critical fields. This technique may be of value in evaluating waveforms for transthoracic defibrillation as well as electrode size, placement, and composition.

Tissue anchors for transmural gut-wall apposition

With the development of NOTES (natural orifice transluminal endoscopic surgery) and efforts to advance gastric reduction surgery, alternatives for robust tissue apposition apart from suturing and current mucosal clipping devices may be valuable. We attempted to identify functional tissue anchors that could be deployed endoscopically, with the potential to provide transmural tissue apposition. Short-term animal-survival study. Domestic pigs, under general anesthesia, underwent open laparotomy, gastrotomy, and manual placement of prototype tissue anchors. Four tissue-anchor designs were evaluated (T bar, T bar with mesh bolster, star, basket). Full-thickness gastric plications were manually created in the body and the antrum via laparotomy and were secured with sets of paired anchors, also placed manually via a gastrotomy. In 1 test animal, a pilot gastric reduction was created by forming 2 rows of 4 anchor sets on the anterior and posterior walls to create a tubelike gastric lumen. Follow-up endoscopy was performed at 2, 4, and 9 weeks to visually assess the intraluminal appearance of the plications, followed by necropsy and histologic study. There was an overall attrition of the number of anchor sets. At 2 weeks, the T-bar anchors were first to disappear, and the mesh and the star designs began to pull through the gastric folds. At 4 weeks, there was flattening of the plications that involved 6 pairs of mesh anchors. By 9 weeks, 3 pairs of mesh anchors were lost and 3 pairs were associated with flattened folds. At the time of euthanasia, at 4 or 9 weeks, the number of retained anchors associated with intact plications for each group were as follows: T bar, 6 of 9 pairs (67%); mesh, 12 of 18 pairs (67%); basket, 14 of 18 pairs (78%); and star, 2 of 9 pairs (22%). There were no gastric adhesions and no evidence for any inflammatory changes surrounding the stomachs. The tallest plications involved the basket anchors. The basket-anchored plications contained apposed muscularis propria, with serosal fusion evident. The folds from the other anchor types were formed of mucosa and submucosa with or without superficial muscularis propria. The results of this experience are encouraging. The basket tissue anchors appear most promising. These findings suggest that further development of tissue anchors deployed via flexible catheter-based devices may have clinical value for transmural tissue apposition.

Infrainguinal Arterial Intervention: Is There a Role for an Atherectomy Device?

Excision of atheromatous plaque is an attractive option for the minimally invasive treatment of peripheral arterial disease. Approved for use in 2003, the SilverHawk Plaque Exicison System (FoxHollow Technologies, Redwood City, CA) is a catheter-based plaque excision device allowing percutaneous removal of atheromatous material. This device represents the most recent generation of atherectomy tools. Overall experience with plaque debulking in the peripheral arteries spans almost two decades, and understanding of the technique continues to evolve. This article reviews the technology, current practices, and data on plaque excision.

No-reflow phenomenon and prognosis in patients with acute myocardial infarction

The rapid restoration of coronary flow to the jeopardized myocardium has become an essential part of therapy after acute myocardial infarction. Despite an open infarct-related artery, breakdown of or obstruction to coronary microvasculature can markedly reduce blood flow to the infarct zone. This effect is known as the no-reflow phenomenon. Advances in imaging modalities have improved visualization of no reflow, showing its frequency to be higher than was estimated by clinical judgment alone. This phenomenon is important because it correlates with infarct size and provides useful prognostic information. No reflow is associated with reduced left ventricular ejection fraction, left ventricular remodeling, and poor clinical outcomes, placing patients with this effect in a high-risk group among reperfused patients. The focus of reperfusion therapy is shifting towards improved myocardial perfusion, which could promote functional recovery of viable muscle, reduce infarct expansion, and increase the delivery of blood-borne components, thereby accelerating the healing process. Various pharmacologic interventions and catheter-based devices to retrieve embolic materials have been proposed. Further studies to improve understanding of the pathophysiology of microvascular dysfunction will, however, help in the further development of preventive and therapeutic strategies. In this article, I discuss in depth the data available on the no-reflow phenomenon.

Device discordancy: Lost cords, quick-fix seekers, quality, and ethics

doi:10.1016/j.jtcvs.2005.10.031 Our modern world is so accustomed to instant gratification and efficiency with the accompanying expectations of little effort or pain that people will often choose the easy path at the cost of a poorer outcome over the long term. There are many examples of these choices by both consumers and patients, particularly when they are not fully informed, including use of catheter-based devices rather than open procedures. In this issue of the Journal, Flores and colleagues present their experience with combined open aortic arch repair and descending thoracic aortic stenting in the hopes of avoiding a second procedure, either open or endovascular, to treat patients more speedily. The results are sobering. First, their circulatory arrest times must have been prolonged, thus risking greater brain injury to the patients. Second, postoperative spinal cord injury occurred at an unacceptably high percentage of 24%. The finding of an increased complication rate of spinal cord injury is not new. For example, acute aortic dissection repair with replacement of the entire aortic arch (a questionable procedure except in rare cases) and stenting of the descending aorta has resulted in a similarly high rate of lost spinal cord function. Furthermore, in our early experience with the modified inverted elephant trunk insertion method in 84 patients, we noted that too long of an elephant trunk graft in the descending aorta resulted in complete paraplegia in 1 patient and paraparesis in 2 patients. This led to our recommendation that an elephant trunk graft should be no longer than 10 to 15 cm. Why then is stenting or a long elephant trunk graft a problem? The obvious answer is that the intercostal arteries are occluded by the graft material, and the cord becomes dependent on collateral circulation. Second, it is likely that pump-related nonpulsatile hypotension and perioperative hypotension are inadequate for sufficient perfusion of the spinal cord in many patients who are dependent on their collateral arteries. In addition, it is worth noting that the squeezing of atheroma, somewhat akin to the texture of toothpaste, into intercostal arteries by stents could likely cause embolic obstruction of the blood supply. Whether these factors completely explain the high risk of paralysis when stenting is combined with cardiopulmonary bypass cannot be determined from this study. In our review of 832 descending aortic open repairs, paralysis occurred mostly in those patients who underwent replacement of either the entire descending aorta or the distal third or in those patients who had previously undergone abdominal aortic replacements. In 132 patients with descending aortic repairs, Borst and colleagues found paralysis was higher in patients with replacement below T8. Similarly, others noted a higher paralysis rate with distal descending aorta replacements. It appears that these hard lessons are now being relearned for descending aortic stenting. The Stanford group reported in 2004 that the risk of paralysis increased with either distal descending aortic stents or combined descending aortic stents in patients with previous aortic abdominal replacements. In our experience with descending aortic

Imaging techniques in cardiac electrophysiology

Modern cardiac electrophysiology procedures include catheter-based arrhythmia ablation and transvenous device implantation, which are highly dependent on accurate, real-time cardiac imaging. With the realization that anatomic structures are critical to successful electrophysiologic procedures, accurately defining a patient’s cardiac anatomy has become more important. Fluoroscopy allows for 2D imaging of cardiac structures in real-time, and is used to guide catheter and lead placement, but does not allow for visualization of soft tissues. Intracardiac echocardiography allows for both direct visualization of anatomic structures within the heart and real-time imaging during catheter placement. Despite advances in intracardiac echocardiography catheters that allow for larger windows, the ability to accurately delineate anatomic structures depends on the patient’s anatomy and operator experience. Neither of these techniques allows for electrical mapping of the heart; however, both anatomic and electrical intracardiac mapping can be achieved with advanced mapping systems. These systems allow for real-time catheter localization, help elucidate cardiac anatomy, evaluate electrical activation during arrhythmias and guide catheter placement for deliverance of radiofrequency current. More recently, 3D cardiac computed tomography has been used to accurately define intracardiac anatomy; however, catheter tracking and electrical mapping cannot be performed by computed tomography. Mapping systems are now being merged with computed tomography images to produce an accurate anatomic and electrical map of the heart to guide catheter ablations. The objective of this paper is to describe the current imaging and mapping techniques used in electrophysiologic procedures.

Percutaneous In Situ Coronary Venous Arterialization: A Catheter‐Based Procedure for Coronary Artery Bypass

Diffuse coronary artery disease is frequently untreatable by coronary artery bypass or angioplasty. Open chest surgical arterialization of the coronary venous system was successfully performed before the widespread use of coronary artery bypass grafting and has been applied in ungraftable patients thereafter. Percutaneous in situ coronary venous arterialization (PICVA) follows this surgical experience, using a series of unique catheter-based devices to arterialize isolated segments of coronary vein, forcing retroperfusion of severely ischemic myocardium. In a series of animals, this procedure had been shown to reduce ischemia and myocardial damage in an infarction model. In the PICVA European Safety trial, the first 11 percutaneous applications of catheter-based coronary bypass in humans revealed feasibility of the technique in highly symptomatic "no-option" patients. Despite two deaths and six failures to create the bypass, we continue to believe that on further development, the catheter-based coronary bypass can become a broad-based interventional application.

Three-dimensional echo-guided beating heart surgery without cardiopulmonary bypass: Atrial septal defect closure in a swine model

In this study, we tested 3 techniques of atrial septal defect closure under real-time 3-dimensional echocardiography guidance in a swine model. The operations were conducted under the sole guidance of a modified real-time 3-dimensional echocardiography guidance system with a x4 matrix transducer (Sonos 7500, Philips Medical Systems, Andover, Mass). Eighteen swine were anesthetized, and after median sternotomy, the echo probe was applied directly to the surface of the right atrium. To create an atrial septal defect, balloon atrial septostomy and atrial septal defect enlargement were performed. Subsequently, 3 different techniques of atrial septal defect closure were attempted: group I, direct suture closure; group II, closure of the atrial septal defect using the Amplatzer device (AGA Medical Corp, Golden Valley, Minn); and group III, patch closure of the atrial septal defect (n = 6 each). Real-time 3-dimensional echocardiography guidance provided sufficient spatial resolution and a satisfactory frame rate to provide a "virtual surgeon's view" of the relevant anatomy during the entire procedure. All atrial septal defects were enlarged, and the mean final size was 8.5 +/- 1.8 mm. Atrial septal defect closure was successfully accomplished with all the 3 surgical techniques examined. In groups I and III, the needles (1-3 sutures) and staples (6-12 staples) penetrated the tissue and patch material consistently, whereas in group III, the Amplatzer atrial septal defect device was easily deployed. There was no incident device/staple embolization or air introduction. Neither intraoperative 2-dimensional color Doppler echocardiography nor postmortem macro-evaluation revealed any residual shunts. Beating heart atrial septal defect closure under real-time 3-dimensional echocardiographic guidance is feasible and, unlike catheter-based devices, applicable for any type of secundum atrial septal defect.

Interventional Cardiovascular Pharmacotherapy

In the last decade, a variety of novel anticoagulant and antiplatelet agents that improve outcomes in patients undergoing percutaneous coronary revascularization have emerged. During the next decade, continued refinements in catheter-based device technology should lead to further increases in the number of interventional procedures. The use of optimal antithrombotic strategies is pivotal in reducing adverse events among patients undergoing percutaneous coronary intervention (PCI). Our purpose is to review the current evidence regarding the efficacy of available adjunctive anticoagulant and antiplatelet agents in treating patients undergoing percutaneous coronary revascularization. It should be borne in mind that patients undergoing PCI in the midst of an acute coronary event require a different level of coagulation and platelet aggregation inhibition than low-risk patients undergoing elective PCI for stable angina pectoris. Similarly, generalizing antithrombotic regimen safety data to a wide spectrum of catheter-based therapeutic devices should be avoided. A level of anticoagulation that is safe and effective for angioplasty and stent placement may not be sufficient for devices with longer intracoronary dwell times such as brachytherapy catheters. In light of current evidence, activated clotting times should be targeted in the 200- to 250-second range during elective PCI and in the 250- to 300-second range when intervening on a higher-risk lesion, such as one with an angiographically visible thrombus or in patients presenting with an acute coronary syndrome (ACS).Low-dose enoxaparin sodium is an attractive antithrombin strategy in PCI because it is intrinsically adjusted for renal function, age, and concomitant glycoprotein (GP) IIb/IIIa antagonist use. Other low-molecular weight heparins have also been studied as adjunctive anticoagulants during cardiac catheterization. For example, in pilot studies, dalteparin sodium was shown to have a good safety profile when used alone or in combination with abciximab during PCI.A wealth of data supports the use of a GP IIb/IIIa antagonist in patients presenting with ACS, especially those with high-risk features such as elevated cardiac markers; the systematic use of GP IIb/IIIa inhibitors in this population is therefore encouraged. Overall, the use of GP IIb/IIIa inhibitors reduces the incidence of thrombotic complications following PCI, is associated with a mortality benefit, but has no impact on the risk of restenosis.

Closure of Coronary Artery Fistula with Covered Stent and Correction of Stenosed Left Anterior Descending Artery in the Same Procedure

We report a case of closure of the coronary artery fistula with polytetrafluoroethylene (PTFE)-covered stent at the proximal left anterior descending artery along with simultaneous stenting at the stenosed middle segment of the left anterior descending artery. The successful experience proved that this kind of stent is a feasible and safe supplement to catheter-based devices in treating coronary artery fistula, although further evaluation is needed.

Prevention of intimal hyperplasia: Initial results with low-dose beta-radiation applied by an external vascular polymer wrap

Objective Endovascular brachytherapy, delivered by a variety of catheter-based devices, has proven clinically effective for the inhibition of neointimal hyperplasia (NIH) after coronary and peripheral balloon/stent angioplasty. No platform, however, has been developed to deliver low-dose radiation in concert with vascular surgical operations. The purpose of this study was to evaluate the vascular response following balloon injury to the rabbit carotid artery, with and without topical low-dose 45Ca, applied by an external vascular “wrap”. Methods Twelve rabbit carotid arteries were subjected to balloon injury by embolectomy catheter. The common carotid artery was then “wrapped” circumferentially with a biostable polyurethane membrane (Nanoskin Secant Medical, Perkasie, PA), without radiation ( n=6), or with radiation ( n=6) ( 45Ca ∼50 μCi). The animals were sacrificed at 4 weeks for histologic assessment of the treated vessels. Results The 45Ca wrap inhibited NIH evidenced by trends towards reduction of intimal area (0.46±0.19 control carotid vs. 0.35±0.15 45Ca-treated carotid arteries; P=.11), maximal intimal thickness (0.21±0.08 vs. 0.16±0.05; P=.12), average intimal thickness (0.12±0.06 vs. 0.08±0.03; P=.08), marginally significant reduction in percent area stenosis (33±15% vs. 21±9%; P=.06) and marked neointima suppression in areas immediately adjacent to 45Ca wrap remnants. Medial necrosis ( P=.003), however, was observed slightly more for 45Ca-treated carotid arteries versus control arteries. Conclusion Low-dose 45Ca beta-radiation labeled onto a polyurethane membrane appears to inhibit NIH in an animal model.

Secundum ASD closure using a right lateral minithoracotomy: Five-Year experience in 122 patients

Background Surgical closure of secundum atrial septal defect (ASD) is a standard procedure associated with very low mortality and morbidity. We evaluated outcomes in the era of catheter-based interventional closure and minimally invasive techniques. Methods From May 1996, February 2002, 177 patients with a body weight of more than 30 kg underwent surgical ASD closure. A right lateral minithoracotomy (LMT) was used in 122 patients and a conventional approach, in 55. Diagnoses included secundum ASD in 106 patients in the LMT group and 40 in the conventional group, sinus venosus ASD in 13 patients in each group, and status post interventional closure in 3 and 2 patients, respectively. Mean age was 37 ± 17 years in the LMT group and 43 ± 20 years, in the conventional group and mean body weight was 66 ± 17 kg and 70 ± 16 kg, respectively. In the LMT group, femoral cannulation was performed for cardiopulmonary bypass. Results Direct ASD closure was carried out in 67.2% of patients in the LMT group and 58.2% of those in the conventional group. The remaining patients had pericardial patch closure. There was one death: A patient in the conventional group who required explantation of an Amplatzer device because of infection died postoperatively. Average stay in the intensive care unit was 1.2 ± 0.5 days. Two patients required reoperation for residual ASD after direct closure; 1 sustained a temporary neurological deficit that resolved completely. On postoperative echocardiography, a minimal residual shunt was seen in only 3 patients. All patients were in good clinical condition with improved functional status at discharge from the hospital. Conclusions Secundum ASD closure by LMT has become as standard and safe an operation as the conventional technique and achieves good perioperative results and satisfactory long-term outcomes. Thus LMT is an attractive option for patients who are not suitable for closure using catheter-based devices.

Topical application of β-radiation to reduce intimal hyperplasia after carotid artery balloon injury in rabbit: A possible application for brachytherapy in vascular surgery

Purpose: Endovascular brachytherapy for the prevention of intimal hyperplasia (IH) and restenosis after balloon/stent angioplasty has proven effective both in animal preparations and clinical trials. A variety of β-emitting isotopes and catheter-based devices have been developed for the delivery of low-dose radiation in clinical coronary and peripheral trials. No platform, however, has yet been developed for brachytherapy in concert with vascular surgical operations. The purpose of this study was to evaluate the vascular histopathologic response following balloon injury to rabbit carotid arteries with and without topically applied low-dose β-radiation. Methods: The β-emitting isotope strontium-90 (Sr-90) was conjugated onto the matrix of polypropylene (PLYP) mesh. Rabbit carotid arteries were balloon-injured with a #2 embolectomy catheter. Six carotid arteries were wrapped with nonradioactive PLYP mesh (controls) and Sr-90 (∼90 μCi) PLYP mesh in order to deliver low-dose radiation to the vessel wall from the external (adventitial) surface. Tissue was harvested at 6 weeks and processed for histologic examination. Results: There was consistent blockade of fibrocellular neointima formation with virtually no neointima present in all treated segments, compared to moderate neointima formation in controls. Medial thinning and smooth muscle cell (SMC) necrosis were also associated with topical brachytherapy. Conclusion: β-Radiation applied by an externally wrapped PLYP mesh labeled with Sr-90 markedly suppressed neointima formation in an animal vascular surgical injury model. Further studies, however, are necessary to determine a suitable isotope and dosage for clinical application.

Prototype therapeutic ultrasound emitting catheter for accelerating thrombolysis.

The aim of this study was to evaluate the performance of a new therapeutic ultrasound device for accelerating thrombolysis by urokinase. Artificial thrombi were produced in vitro by Chandler's loop method. Urokinase (240 IU) was added to the artificial thrombi (n = 5) before exposure to ultrasound with the new catheter-delivered device. Ultrasound (1.3 MHz) was applied with an intensity of 0.3 W/cm2 for 60 s. The degree of fibrinolysis was obtained by measurement of thrombus weight and calculated as percentages. Fibrinolysis was compared between control thrombus groups (n = 5) treated with urokinase alone or with ultrasound alone (analysis of variance, P < 0.05). Ultrasound plus urokinase (33.1 +/- 6.1% [mean +/- standard deviation]) was significantly different urokinase alone (12.3 +/- 2.4%) after 15 min of incubation. Ultrasound alone resulted in no fibrinolysis (0.9 +/- 2.5%). Ultrasound energy from the catheter-based device was sufficient to induce acceleration of fibrinolysis with urokinase.

Intravascular ultrasound guidance for peripheral vascular interventions.

Intravascular ultrasound (IVUS) imaging during peripheral endovascular interventions adds important information regarding the distribution of disease by providing controlled measurements of the cross-sectional area of the vessel lumen and wall prior to and following procedures. IVUS is useful in determining the mechanism and efficacy of balloon angioplasty, in guiding atherectomy devices, and in assuring appropriate placement of intravascular stents. The incorporation of an IVUS element into catheter-based interventional devices may improve the immediate and long-term results of endovascular interventions by decreasing complications from dissection and perforation of the arterial wall. Combined IVUS-stent prototype catheters are being developed to enable imaging and deployment simultaneously. Similar devices are being explored to enhance expedient, precise delivery of endoluminal grafts. Future studies of endovascular techniques should include IVUS, when possible, to accurately quantitative the initial efficacy of devices and to determine the nature and distribution of recurrent lesions.

Intravascular Ultrasound Guidance for Peripheral Vascular Interventions

Intravascular ultrasound (IVUS) imaging during peripheral endovascular interventions adds important information regarding the distribution of disease by providing controlled measurements of the cross-sectional area of the vessel lumen and wall prior to and following procedures. IVUS is useful in determining the mechanism and efficacy of balloon angioplasty, in guiding atherectomy devices, and in assuring appropriate placement of intravascular stents. The incorporation of an IVUS element into catheter-based interventional devices may improve the immediate and long-term results of endovascular interventions by decreasing complications from dissection and perforation of the arterial wall. Combined IVUS-stent prototype catheters are being developed to enable imaging and deployment simultaneously. Similar devices are being explored to enhance expedient, precise delivery of endoluminal grafts. Future studies of endovascular techniques should include IVUS, when possible, to accurately quantitate the initial efficacy of devices and to determine the nature and distribution of recurrent lesions.