Catheter-based Devices Research Articles

Current developments in transcatheter aortic valve implantation techniques

Transcatheter aortic valve implantation (TAVI) has become a viable treatment option in high-risk patients with symptomatic aortic stenosis. The widespread uses of TAVI procedures in recent years and the steadily growing evolution of numerous new catheter-based devices have led to a remarkable shift in the treatment of this patients group towards TAVI procedures. Several developments have now overcome most of the initial problems with the early devices and have been quickly implemented in clinical routine. Nevertheless, several current TAVI systems have shown a number of limitations and disadvantages relating to valve design, the occurrence of paravalvular leakages, valve positioning and deployment, the occurrence of thromboembolic events during the procedure, as well as vascular or conduction complications. As a result, all current efforts in further development focus primarily on the following issues: (1) the further miniaturization of catheter devices and sheaths not only to facilitate transarterial but also transapical access; (2) the development of a broad variety of valve sizes to cover all aortic annulus sizes; (3) the development of retrievable, repositionable and removable systems; (4) the development or modification of stent design to prevent or reduce paravalvular leakages; (5) the implementation of modern imaging and navigation tools; (6) and finally, the initial development of prophylactic devices to prevent thromboembolic events. The present article provides a review of current developments in the field of TAVI.

Endocervical ultrasound applicator for integrated hyperthermia and HDR brachytherapy in the treatment of locally advanced cervical carcinoma

The clinical success of hyperthermia adjunct to radiotherapy depends on adequate temperature elevation in the tumor with minimal temperature rise in organs at risk. Existing technologies for thermal treatment of the cervix have limited spatial control or rapid energy falloff. The objective of this work is to develop an endocervical applicator using a linear array of multisectored tubular ultrasound transducers to provide 3-D conformal, locally targeted hyperthermia concomitant to radiotherapy in the uterine cervix. The catheter-based device is integrated within a HDR brachytherapy applicator to facilitate sequential and potentially simultaneous heat and radiation delivery. Treatment planning images from 35 patients who underwent HDR brachytherapy for locally advanced cervical cancer were inspected to assess the dimensions of radiation clinical target volumes (CTVs) and gross tumor volumes (GTVs) surrounding the cervix and the proximity of organs at risk. Biothermal simulation was used to identify applicator and catheter material parameters to adequately heat the cervix with minimal thermal dose accumulation in nontargeted structures. A family of ultrasound applicators was fabricated with two to three tubular transducers operating at 6.6-7.4 MHz that are unsectored (360 degrees), bisectored (2 x 180 degrees), or trisectored (3 x 120 degrees) for control of energy deposition in angle and along the device length in order to satisfy anatomical constraints. The device is housed in a 6 mm diameter PET catheter with cooling water flow for endocervical implantation. Devices were characterized by measuring acoustic efficiencies, rotational acoustic intensity distributions, and rotational temperature distributions in phantom. The CTV in HDR brachytherapy plans extends 20.5 +/- 5.0 mm from the endocervical tandem with the rectum and bladder typically <8 mm from the target boundary. The GTV extends 19.4 +/- 7.3 mm from the tandem. Simulations indicate that for 60 min treatments the applicator can heat to 41 degrees C and deliver > 5EM(43 degrees C) over 4-5 cm diameter with Tmax < 45 degrees C and 1 kg m(-3) s(-1) blood perfusion. The 41 degrees C contour diameter is reduced to 3-4 cm at 3 kg m(-3) s(-1) perfusion. Differential power control to transducer elements and sectors demonstrates tailoring of heating along the device length and in angle. Sector cuts are associated with a 14-47 degrees acoustic dead zone, depending on cut width, resulting in a approximately 2-4 degrees C temperature reduction within the dead zone below Tmax. Dead zones can be oriented for thermal protection of the rectum and bladder. Fabricated devices have acoustic efficiencies of 33.4%-51.8% with acoustic output that is well collimated in length, reflects the sectoring strategy, and is strongly correlated with temperature distributions. A catheter-based ultrasound applicator was developed for endocervical implantation with locally targeted, 3-D conformal thermal delivery to the uterine cervix. Feasibility of heating clinically relevant target volumes was demonstrated with power control along the device length and in angle to treat the cervix with minimal thermal dose delivery to the rectum and bladder.

Left Atrial Appendage Closure Devices For Stroke Prevention

Cardioembolic stroke is a major cause of morbidity and mortality in patients with atrial fibrillation (AF). The left atrial appendage (LAA) is the prominent source of clot formation. While systemic anticoagulation is the current standard of care, anticoagulants carry many contraindications and possible complications. Techniques for elimination of the LAA are in various stages of development and early clinical use. In the coming years, accumulating data will help guide the management of AF patients at risk of bleeding as well as potentially become first-line therapy to reduce the risk of thromboembolic stroke. The purpose of this article is to review current endovascular and epicardial catheter-based LAA occlusion devices and the clinical data supporting their use.

The no-reflow phenomenon associated with percutaneous coronary intervention: its mechanisms and treatment

In patients with acute coronary syndrome (ACS), the immediate therapeutic goal is to establish patency of the infarct-related artery and to achieve optimal myocardial tissue reperfusion. Coronary microvasculatures, however, are often damaged irreversibly due to myocardial ischemia and reperfusion, and flow to the previously ischemic myocardium is markedly reduced, a phenomenon known as the "no-reflow phenomenon". In clinical settings, percutaneous coronary intervention (PCI) may accelerate embolization of plaque gruels and microthrombi to the microvessels, which further reduces tissue perfusion. The microvascular dysfunction attenuates the beneficial impact of PCI. The extent of the no-reflow phenomenon correlates with infarct size, and it has additional prognostic information. Patients with the no-reflow phenomenon have poor functional and clinical outcomes. Recent advances in imaging modalities have enabled diagnosis of the no-reflow phenomenon and assessment of the mechanisms of the microvascular dysfunction in patients. Use of pharmacological interventions and catheter-based devices to retrieve embolic materials have been proposed, and some of them are associated with improvement in clinical outcomes. Thus, we should keep in mind that only the achievement of successful myocardial perfusion is associated with better functional and clinical outcomes in patients with ACS.

Endovascular Interventions for Acute Pulmonary Embolism

Massive pulmonary embolism (PE) is a highly lethal condition with clinical manifestations of hemodynamic instability, acute right ventricular (RV) failure, and cardiogenic shock. Submassive PE, as defined by RV failure or troponin elevation, can result in life-threatening sequelae if treatment is not initiated promptly. Current treatment paradigm in patients with massive PE mandates prompt risk stratification with aggressive therapeutic strategies. With the advent of endovascular technologies, various catheter-based thrombectomy and thrombolytic devices are available to treat patients with massive or submassive PE. In this article, a variety of endovascular treatment strategies for PE are analyzed. The authors' institutional experience with ultrasound-accelerated thrombolytic therapy as well as catheter-directed thrombolytic therapy in patients with acute massive PE during a recent 10-year period is discussed. Finally, clinical evidence on the utilization of catheter-based interventions in patients with massive and submassive PE is also analyzed.

Intracardiac Shunts in Children with Sickle Cell Disease and Stroke

Source: Dowling MM, Lee NL, Quinn CT, et al. Prevalence of intracardiac shunting in children with sickle cell disease and stroke. J Pediatr. 2010; 156(4): 646– 650; doi: 10.1016/j.jpeds.2009.10.012Investigators from the University of Texas Southwestern Medical Center studied the prevalence of intracardiac shunts in children, 2 to 19 years old, with sickle cell disease (SCD) and a history of stroke, either symptomatic or silent. All patients underwent transthoracic echocardiography (ECHO) using three techniques to compare their utility for the detection of an intracardiac shunt: conventional 2-dimensional imaging, color Doppler ultrasound, and intravenous contrast injection with agitated saline.A total of 40 children, 39 with SCD and one with sickle beta thalassemia, were enrolled. Ten of these children had either a patent foramen ovale (PFO) or other intracardiac shunt detected. Two-dimensional ECHO was the least sensitive technique, detecting shunts in only 2 of the 10 children with SCD and shunt. Color Doppler was positive in 6 of 10 children, while agitated saline was positive in 5 of 10. Pain crisis at the time of the stroke onset and acute headache were more likely in those with an intracardiac shunt than those with no detectable shunt (40% vs 7%, P=.026, and 40% vs 3%, P=.014, respectively).The authors conclude that intracardiac shunts are common in children with SCD and stroke and that detection requires a combination of imaging techniques. They speculate that early detection and closure of intracardiac shunts in children with SCD might decrease strokes in this high-risk population.SCD is a well-recognized risk factor for pediatric stroke, although the causes of stroke in this population have not been completely delineated. An association between PFO and stroke has been hypothesized for over 20 years.1,2 That a PFO is an independent risk factor for stroke, however, has been more difficult to substantiate3,4 and supporting evidence is based largely on case-control studies. Population-based studies have not demonstrated PFO as an independent risk factor.5 The present study does little to clarify this controversy. For example, the majority (75%) of patients in this series with SCD and stroke did not have a PFO or other identifiable intracardiac shunting. In addition, most of the clinical characteristics of the stroke victims (eg, demographics, vascular infarct distribution, hemoglobin, platelet count, etc.) did not differ between those with a PFO and those without. Finally, no data on the prevalence of PFO in SCD patients who have not had stroke are presented.Presently, the association between PFO and stroke remains too speculative to recommend medical treatment or closure of PFOs for primary prevention. However, catheter-based device closure of PFOs or selective use of anti-platelet and anti-coagulation therapy for secondary prevention in high-risk patients with PFO may reduce recurrent stroke risk.6,7 Defining precisely those SCD patients who will benefit from this therapy remains challenging.4The authors have demonstrated that evaluation for the presence of a PFO in a child with SCD and a stroke may be fruitful. What to do when a PFO is detected in this clinical scenario remains unclear.Routine screening for intracardiac shunts in children with SCD obviously remains investigational. However, transcranial Doppler (TCD) screening, followed by prophylactic transfusion (PT) in patients with increased internal carotid and middle cerebral artery blood flow velocity has documented benefits. A recent retrospective study from The Children’s Hospital of Philadelphia demonstrated a greater than 10-fold reduction in strokes following the institution of TCD screening and PT in their institution.8 Yet, nought comes without a price. PT increases the risk of infection and iron overload, for which the pediatrician must be ever-vigilant.

Predicting Atelectasis by Assessment of Collateral Ventilation prior to Endobronchial Lung Volume Reduction: A Feasibility Study

Background: The advent of endoscopic lung volume reduction (ELVR), especially relying on valve technology to achieve atelectasis, has aroused new interest in the assessment of collateral ventilation, which has been implicated in ELVR failures. We are reporting on the use of a catheter-based device that measures airway pressures and flows, and calculates airway resistance in vivo. Objectives: To assess the safety of this catheter-based system and the feasibility of obtaining measurements predictive of atelectasis after ELVR. Methods: Patients undergoing ELVR were prospectively included in this double-blind cohort study. Each lobe targeted for ELVR was blocked with a catheter system (Chartis® System; Pulmonx, Inc., Redwood, Calif., USA); pressures and flows were assessed continuously. The primary endpoints were to evaluate the safety and feasibility; the secondary endpoint was to assess whether there was a relationship between the measurements and the incidence of atelectasis following ELVR. Results: From June 2008 to November 2008, 25 patients were included in the study. All procedures could be performed without any complications. Due to pneumothorax in 1 case and inability to assess the catheter-based measurements in 4 cases, the final analysis included 20 patients. Atelectasis occurred in 8 out of 20 cases following implantation. In 18 patients (90%), the resistance measurements correlated with the postimplantation atelectasis visualized on a chest X-ray; in 2 patients (10%), a mismatch was detected. Conclusions: Resistance measurements were safely and successfully achieved. In 90% of the analyzable cases, the resistance measurements correlated with the occurrence of atelectasis after ELVR. The clinical impact of these findings will need to be evaluated in subsequent trials.

Pediatric Cardiovascular Device Registries—The Need for Such Data And The Potential Impact

The use of devices to treat disorders and diseases affecting pediatric patients has increased significantly since the 1980s, particularly in the field of pediatric cardiology where interventional procedures have become viable alternatives to open heart surgery for many conditions [1, 2]. Yet as the treatment of congenital heart disease (CHD) with cardiac catheterization and device placement has evolved, there remains a lack of devices on the market that are designed for, studied in, and specifically labeled for pediatric patients and evidence-based data to guide decision making in treating these patients remains scarce. Treatment strategies instead are derived largely from expert opinion— which may not be consistent across locales or widely accessible—and off-label use is not uncommon [3]. With the emphasis on evidence-based practice in medicine today, it is important that pediatrics not be left behind. If the present situation is to change, and the quality and consistency of information about catheter-based device treatment for pediatric cardiology patients is to improve, a method of collecting, analyzing, and widely distributing procedural data becomes essential. The development of more comprehensive pediatric device registries would thus seem a critical part of the progression and of utmost importance to the public health. Registries provide opportunities to collect data from a broader population of patients and physicians than current surveillance mechanisms and could be used to monitor actual practices and practice bias for both onand off-label use of devices used in children—better defining the current clinical landscape so that unmet needs and supportive regulatory initiatives can be more easily and quickly identified. Also, collection of long-term, longitudinal data on significant events, functionality, and quality of care that are so essential to optimizing pediatric care could be attained. The limited numbers of patients with any given congenital cardiac anomaly, and the heterogeneous subpopulations, makes pediatric cardiology an especially challenging area to obtain valid and generalizable data. Thus, it is one in which high-quality registry data would be particularly suitable.

'Edge to edge' percutaneous mitral valve repair in mitral regurgitation: it can be done but should it be done?

This editorial refers to ‘Percutaneous mitral valve repair with the MitraClip system: acute results from a real world setting’[†][1], by C. Tamburino et al. , on page 1382 and ‘Acute outcomes of MitraClip therapy for mitral regurgitation in high-surgical-risk patients: emphasis on adverse valve morphology and severe left ventricular dysfunction’[‡][2], by O. Franzen et al. , on page 1373 The treatment of mitral valve regurgitation (MR) is an important clinical issue as MR represents >30% of native valve diseases.1 The results of surgery, in particular valve repair, are good, which sets a high standard for future innovative interventions.2 However, some observations suggest a potential for new interventions: (i) in current practice worldwide, surgery is denied to many patients with severe MR and symptoms;3 (ii) mitral valve repair is not always used or feasible;4 and (iii) surgical risks remain high in an important percentage of contemporary patients who are elderly with co-morbidities. Two main techniques have been introduced for percutaneous mitral valve repair: the edge to edge technique and the prosthetic ring annuloplasty. The edge to edge technique mimics the surgical procedure introduced by O. Alfieri, which creates a double mitral orifice by means of a few stitches securing the two leaflets together at their mid-part5 ( Figure 1 ). This technique has been performed percutaneously using a clip (E-valve MitraClip) made of a cobalt–chromium alloy and Dacron.6 Another design involved the use of one or two sutures deployed via a catheter-based device, but this has since been abandoned.7 The initial clinical experience with the edge to edge technique is mostly from the USA, including >500 patients; however, the reports in peer-reviewed journals are only based on the first 107 cases in the EVEREST registry.8,9 In addition, 279 patients are included in the EVEREST II … [1]: #fn-1 [2]: #fn-2

Percutaneous approaches to mitral regurgitation

Percutaneous therapy for mitral repair has emerged over the past several years as an investigational option for treating mitral regurgitation (MR). A variety of novel methods to treat MR using a percutaneous route have been developed. Most of these approaches are modifications of surgical techniques, some established and some obscure. The basic surgical approaches to mitral repair are annuloplasty and leaflet repair. Catheter-based devices mimic or approximate these surgical approaches. MR as a disease process is heterogeneous, and different therapeutic approaches are needed for different etiologies of MR and morphologies of the mitral apparatus. Primary leaflet diseases are mitral prolapse and fibroelastic deficiency. Secondary, or functional, MR exists when the leaflets are normal. Functional ischemic MR and functional MR related to heart failure occur in different populations and historically have had different responses to surgical therapy. Leaflet repair using a percutaneous clip has been accomplished for patients with mitral valve prolapse and also some patients with functional MR. Indirect annuloplasty via the coronary sinus has shown promising early human trial results in patients with functional MR. Direct annuloplasty and left ventricular chamber remodeling technologies are in the earliest stages of human application. This group of approaches is being studied as an alternative to surgery for selected patients. The MitraClip (Evalve, Menlo Park, CA) for leaflet repair has been approved for use in Europe and is being applied predominantly to high-risk surgical patients with either functional or degenerative, organic MR. One of the coronary sinus devices has received approval in Europe as well. This complex clinical landscape has made device development, trial design, and patient selection complicated. Steady progress in the field is being made. Many patients with functional MR who are currently treated medically will be the subject of upcoming trials. Catheter methods for mitral repair promise to serve some patients currently considered high risk for surgery, and some patients may have catheter therapy as an alternative to surgery.

A novel endovascular large animal model for testing catheter-based thrombolytics and devices used in acute limb ischemia

A novel endovascular large animal model for testing catheter-based thrombolytics and devices used in acute limb ischemia

No-reflow phenomenon in patients with acute myocardial infarction: its pathophysiology and clinical implications.

For patients with acute myocardial infarction (MI), the immediate therapeutic goal is to establish the patency of the infarct-related artery. Prolonged myocardial ischemia, however, often breaks down the coronary microvasculature, and the flow to the infarct myocardium may be markedly reduced. This is called the no-reflow phenomenon. This phenomenon is important not solely because it correlates with infarct size but because it provides additional prognostic information. With recent advances in imaging modalities, the no-reflow phenomenon is observed more frequently than when clinical judgment alone is used. Patients with this phenomenon are associated with poor functional and clinical outcomes. Now, the no-reflow phenomenon can be a parameter with which to predict high-risk patients. The focus of reperfusion therapy has shifted toward the improvement of myocardial perfusion. The improvement of myocardial perfusion could promote the functional recovery of viable muscle and reduce infarct expansion, which is associated with favorable clinical outcomes. For this purpose, pharmacological interventions and catheter-based devices to retrieve embolic materials have been proposed. Advances in our understanding of the pathophysiology of microvascular dysfunction would aid the development of therapeutic strategies for its prevention and treatment.

Design of a Catheter-Based Device for Performing Percutaneous Chordal-Cutting Procedures

In this paper we detail the rapid design, fabrication and testing of a percutaneous catheterbased device that is envisioned to enable externally controlled manipulation and cutting of specific chordae tendinae within the heart. The importance of this work is that it (a) provides a means that surgeons may use to alleviate problems associated with some forms of mitral valve regurgitation and (b) demonstrates how a deterministic design process may be used to drive design innovation in medical devices while lowering development cost/time/resources. In the United States alone, approximately 500,000 people develop ischemic or functional MR per year. A chordal cutting procedure and device could allow many patients, who would otherwise be unable to survive open-heart surgery, to undergo a potentially life-saving operation at reduced risk. The design process has enabled us to generate a solution to this problem in a relatively short time. A deterministic design process was used to generate several design concepts and then evaluate and compare each concept based on a set of functional requirements. A final concept to be alpha prototyped was then chosen, optimized, and fabricated. The design process made it possible to make rapid progress during the project and to achieve a device design that worked the first time. This approach is important to medical device design as it reduces engineering effort, cost, and the amount of time spent in iterative design cycles. An overview of the design process will be presented and discussed within the context of a specific case study–the rapid design/fabrication of a chordal cutting device. Experimental results will be used to assess: (i) The performance of the catheter in maneuvering into the heart and grasping various structures. (ii) The effectiveness of the catheter's RF ablation tip at cutting chordae inside of a heart. In the first experiment, the catheter was guided to the basal chordae under direct visualization, which showed that the catheter is capable of successfully grasping a chord. During the second experiment, ultrasound was shown to be a viable method of visualizing the catheter within the heart. During this experiment, once contact between the chord and RF ablator tip was confirmed, the chord was successfully ablated. We will also discuss experiments that are currently underway to visualize the catheter utilizing a Trans-Esophageal Echo probe, as well as imaging the mitral valve from the apex of the heart with a laparoscope so that video of the basal chord being grasped and cut can be acquired on a heart whose anatomical structures are intact. A brief synopsis will then be given of how the design process has been used in research and educational collaborations between MIT and local hospitals.

Design of a Catheter-Based Device for Performing Percutaneous Chordal-Cutting Procedures

This paper focuses on the design and implementation of a percutaneous catheter-based device to provide physicians with an externally controlled tool capable of manipulating and cutting specific chordae tendinae within the hear to alleviate problems associated with some forms of mitral valve regurgitationt. In the United States alone, approximately 500,000 people develop ischemic or functional MR per year, and the chordae tendinae cutting procedure and device are needed because many patients do not have the required level of health necessary to survive open-heart surgery. A deterministic design process was used to generate several design concepts and then evaluate and compare each concept based on a set of functional requirements. A final concept to be alpha prototyped was then chosen, further developed, and fabricated. Experiments showed that the design was capable of locating and grabbing a chord and that ultrasound imaging is a viable method for navigating the device inside of the human body. Once contact between the chord and an RF ablator tip was confirmed, the chord was successfully ablated.

Telemetric Catheter-Based Pressure Sensor for Hemodynamic Monitoring: Experimental Experience

The purpose of this study was to evaluate the technical and animal experimental feasibility of a percutaneously implantable pulmonary arterial implant for permanent hemodynamic monitoring. Two systems for measuring pulmonary artery pressure (PAP) as well as pulmonary artery occlusion pressure (PAOP) were developed by modifying a commercially available pulmonary artery catheter (PAC). First, a cable-bound catheter-based system was designed by implementation of a capacitive absolute-pressure sensor in the catheter tip. This system was developed further into a completely implantable telemetric system. The devices were tested in an acute setting in a total of 10 sheep. The implant was placed with its tip in the descending pulmonary artery via the right jugular approach. Results were compared with conventional PAC positioned in the contralateral pulmonary artery using Pearson's correlation coefficients and Bland-Altman plots. Implantation of the monitoring systems was uneventful in 10 animals. Data from two fully functional cable-bound and telemetric pressure monitoring systems were available, with a total of 18,506 measurements. There was an excellent correlation between reference data and the data obtained with the implants (r = 0.9944). Bland-Altman plots indicated a very good agreement between the techniques. We report the development and successful initial test of an implantable catheter-based device for long-term measurement of PAP and PAOP. Both devices may be applicable for hemodynamic monitoring. Further long-term studies for assessing reliability and durability of the device are warranted.

Development of a Prototype Trocar for Translumenal Therapeutic Interventions Using EUS

Introduction: For EUS-guided therapeutic interventions such as pancreatic pseudocyst drainages, current techniques rely on the use of a 19 gauge FNA needle to gain initial access across the GI lumen. However, advancement of catheter-based devices through the incision created by these needles is technically difficult thereby necessitating progressive dilation of the lumenal wall prior to undertaking endotherapy. The EUS 2008 Working Group recommended development of specific devices to facilitate easy endotherapy. An echoendoscope-compatible prototype 19 gauge trocar was designed to create a tissue puncture, significantly larger than its own profile, to facilitate easier passage of larger catheter-based devices for one-step endotherapy. Aim: This study compared a standard 19 gauge FNA needle to three versions of a prototype (“Extending Blade”) trocar based on: (1) the force required to puncture porcine GI lumenal tissue, and (2) the force required to subsequently pass large caliber catheters through the resulting puncture site. Methods: Ex-vivo porcine stomachs were used to compare puncture forces of a 19 gauge EUS-FNA needle with 1, 2 and 3-blade versions of the prototype trocar passed via the biopsy channel of an echoendoscope. Subsequently, the force required to pass a 2.2 mm dilating catheter and a 6mm balloon catheter through the punctures created by the FNA needle and prototype trocars were compared. Results: The force required for initial puncture of the tissue using all three prototype trocars was equal to that applied using a 19 gauge FNA needle. The force required to advance the 2.2 mm dilating catheter through the tissue punctured using the prototype trocars was 8 times (range, 6-11) less than the force required to advance them via the 19 gauge needle puncture site. Also, the force required to advance the 6mm balloon catheter through the tissue punctured by the prototype trocars was 9 times (range 7-11) less than the force required to advance them via the 19 gauge needle puncture site. Conclusion: Initial access created by the echoendoscope compatible prototype trocar obviates the need for progressive dilation of the GI lumenal wall and could potentially facilitate easier one-step translumenal endotherapy.

Intracardiac Echocardiography During Interventional and Electrophysiological Cardiac Catheterization

Just as the growing interest and proliferation of methods to reperfuse the coronary artery system with transcatheter techniques spurred interest and utilization of intracoronary ultrasound (at least in academic centers), so the growth of anatomic cardiac transcatheter interventions and increasingly aggressive transcatheter ablative strategies to treat cardiac arrhythmias has stimulated the use of and development of new methods for intracardiac echocardiography (ICE). This article will review the development, present state of the art, and applications of ICE as well as project its evolution from 2-dimensional to 3-dimensional/4-dimensional visualization and integration of therapy with imaging in the near future. It may be surprising to realize that in the earliest days of ultrasound, as early as 1956, the potential of imaging heart structures with catheter-based devices was explored.1 The earliest investigators used single-crystal probes, some of which were rotated to achieve cardiac imaging.2,3 In the mid-1960s, a mechanically rotating 4-element probe was developed by Eggleton et al,4 and in 1969, a 32-element phased-array coil was developed by Bom and coworkers5,6 in Rotterdam. These interests even preceded the development of interventional catheterization therapy. They were spurred by the problems of angiography in outlining vascular and intracardiac anatomy in large detail as single-plane and eventually biplane angiography. The goal was precise measurement of vascular lumens. Some of the early explorations of intracardiac imaging with phased-array technology and color Doppler were undertaken with miniaturized transesophageal studies in experimental animals.7 Higher-frequency rotating catheter probes in the range of 20 to 30 MHz were developed and marketed for intracoronary investigations that yielded new insights into atherosclerosis, vascular response to stents, and coronary remodeling.8 Lower-frequency (10- to 12.5-MHz) versions of these rotating single-element devices were used for the earliest intracardiac investigations by Pandian et al9 in 1990. Our efforts with an …

Evolving strategies for the treatment of valvular heart disease: Preclinical and clinical pathways for percutaneous aortic valve replacement

To decrease the morbidity associated with conventional surgery for calcific aortic stenosis, there has been increasing interest in catheter-based treatment using a stent or frame mounted bioprosthetic valve. Critical to its success is knowledge of pathoanatomy, risk of embolization of calcific debris, and issues associated with device anchoring and paravalvular leaks. In the absence of a chronic animal model of aortic stenosis, development of a catheter-based device has been an iterative process based on experimental and early clinical data gathered abroad, where marketing may be permitted with less clinical data than required in the United States. This process has persuaded many companies to circumvent the time delays occasioned by the FDA regulatory validation of iterative design changes by performing initial studies outside the United States. Because percutaneous aortic valve replacement is considered a Class III device, premarket approval, including defining the patient population, inclusion and exclusion criteria, control population, and interpretable clinical endpoints, is required. In the early clinical experience, percutaneous aortic valve replacement has been directed at high-risk patients who were considered "very poor" or "non-surgical" candidates. Defining and identifying patients for the clinical trial may be challenging, in part because of the difficult selection of an appropriate control group, e.g., conventional aortic valve replacement, best medical management, and/or balloon valvuloplasty.

Prospects for Percutaneous Valve Therapies

Developmental efforts to achieve percutaneous catheter-based therapies for cardiac valve repair and replacement have advanced rapidly over the past several years. A variety of methods to treat mitral regurgitation (MR) and to replace aortic and pulmonic valves have already been successfully employed in patients. These innovative clinical transcatheter valve therapies were anticipated more than a decade ago by creative experimentalists who helped develop predicate techniques in animal models. For example, in 1992, a catheter-delivered ball-in-cage prosthetic aortic valve was implanted in a canine model by Pavcnik1 and a stent-mounted bioprosthetic valve was placed by Andersen, who used a retrograde transarterial approach in a swine model.2 Clearly, the catheter-based technologies used in clinical studies today in patients with aortic stenosis were derived from the fusion of known successful aortic valve replacement (AVR) surgical devices and adaptive interventional modalities, first studied in experimental animal models. Similarly, approaches for transcatheter treatment of MR have also borrowed heavily from preexisting and accepted surgical techniques, such as the edge-to-edge leaflet coaptation technique and reduction ring mitral annuloplasty.3 Importantly, recognition that the coronary sinus parallels the mitral annulus has spurred unique catheter-based transvenous approaches to treat MR by indirectly reducing mitral annular dimensions.4 Because many of the new percutaneous approaches to valve therapy have been developed by surgeons, a collaboration has emerged between thoughtful surgeons and interventionalists, combining skill sets and experiences to accelerate the developmental pathways of less-invasive transcatheter valve therapies. Growing recognition exists that percutaneous alternatives to surgical therapies are required in some patient subgroups with valvular heart disease. Among patients with either mitral and/or aortic valve disease, an expanding population of elderly patients with significant comorbidities may benefit from traditional surgical methods, but these methods are associated with unacceptable perioperative mortality or prolonged postoperative recoveries. In the EuroHeart Survey …

Reduced regional right ventricular wall motion after transventricular repair of tetralogy of Fallot

ably high. 4 Based on the above facts, we integrated the catheterbased devices and the traditional surgical procedure for PAIVS as initial management. In this hybrid beating-heart procedure, first we perforate the PV with the needle and then deliver the balloon through the RV free wall to the pulmonary trunk. Epicardial echocardiography was used not only to guide the procedure with real-time imaging but also to evaluate the effectiveness of valvuloplasty with monitoring of the trans-PV flow and gradient pressure. In percutaneous catheter therapy, if the newborn could not be weaned from the prostaglandin infusion, an urgent BT shunt would be considered. Such a delayed decision could result in postoperative hypoxia and thus increased mortality. Because the operative field was offered by the open-chest approach, we regularly placed a BT shunt simultaneously. Ligation of the patent ductus arteriosus was performed to prevent the excess augmentation of blood flow to the lung, and then prostaglandin infusion was ceased immediately in the operating room.