Device Size Selection Research Articles

Implantation of Left Atrial Appendage Occlusion Devices and Complex Appendage Anatomy: The Importance of Transesophageal Echocardiography

Percutaneous delivery of left atrial appendage (LAA) occluding devices represents a novel approach for stroke prevention in patients with atrial fibrillation. Transesophageal echocardiography (TEE) has a pivotal role throughout these procedures, facilitating device size selection and ensuring optimal deployment of the device. We report a case of an LAA occluding device implantation in which apparent proper positioning on fluoroscopy was determined by TEE to be malpositioning with a nonocclusive, perpendicular orientation to the plane of the LAA ostium. This problem appeared to be related to a complex, multilobed LAA anatomy and was readily resolved by repositioning of the device under TEE guidance.

Interventional approach to the treatment of aneurysms of the perimembranous ventricular septal defects

To explore applicable protocol for the positioning of ventricular septal defect (VSD) occluder and the selection of the device by retrospective analysis of transcatheter closure approach to the aneurysms of the perimembranous VSD. Thirty-five cases of perimembranous VSD with septal aneurysm (19 males and 16 females) from May, 2004 to May, 2005 were included, with a mean age of 5.3 y and mean weight of 17.6 kg. Their angiographic and ultrasound data, and interventional processes were analyzed. Seven segments of the aneurysms were assessed: the diameter of the defect on the left ventricle, the diameter of the defect on the right ventricle, the thickness of ventricular septum, the distance from the farthest end of the aneurysm to the defect, the diameter of the widest part of the aneurysm and the distance between the two farthest orifices on the aneurysm. Sixteen cystiform aneurysms and nineteen tubiform ones were identified with left ventricular angiography. The diameters of the orifices of aneurysms and the diameters of the VSDs ranged from 1.5 mm to 4.1 mm and 2.7 mm to 11.9 mm, separately, with the mean of 2.9 mm and 4.3 mm. From the echocardiography, the distances of the rim of defect to the aortic valve ranged from 2.0 mm to 7.0 mm, with the mean of 4.3 mm. All the interventions were successfully done with symmetrical devices from 4 mm to 14 mm. The left disc of the device was positioned at the defect surface from the left ventricle in 29 cases, and was released at the left side of the orifice in 3 cases. The positioning of the left disc is mostly determined by the condition for the correct formation of the right disc in the right ventricle after deploying. Generally the defect surface in the left ventricle is most ideal to release the left disc of the device. If the body of aneurysm was too long for the right disc to restore its configuration, the left disc should be released on the left side of the orifice. The selection of device size is determined by the placement of the left disc. When the left disc is to be released at the defect surface in the left ventricle, the device size should be equal to or 1 to 2 mm larger than the diameter of the defect on the left ventricle. When the left disc is to be deployed on the left side of an orifice, the device size should be equal to or 1 mm larger than the defect diameter on the left ventricle when there is a single orifice. In the case of multiple orifices, the minimal size of the device which can cover all the orifices should be selected.

Design and analysis of a 44-GHz MMIC low-loss built-in linearizer for high-linearity medium power amplifiers

A 44-GHz monolithic microwave integrated circuit (MMIC) low-loss built-in linearizer using a shunt cold-mode high-electron mobility transistor (HEMT), based on the predistortion techniques, is presented in this paper. The proposed cold-mode HEMT linearizer can enhance the linearity of the power amplifier (PA) with a low insertion loss (IL<2 dB), a compact die-size, and no additional dc power consumption. These advantages make the linearizer more suitable for millimeter-wave (MMW) applications. The physical mechanism of the gain expansion characteristics of the proposed linearizer is analyzed. A systematic design procedure for a low-loss linearizer is developed, which includes: 1) insertion loss minimization through a device-size selection and 2) linearity optimization through a two-tone test. To demonstrate the general usefulness of the proposed linearizer, the linearizer was applied to a two-stage 44-GHz MMIC medium PA and a commercial MMW PA module. After linearization, the output spectrum regrowth is suppressed by 7-9 dB. To keep the adjacent channel power ratio below -40 dBc, the output power has been doubled from 15 to 18 dBm at 44 GHz. The error vector magnitude of the 16-quadrature amplitude modulation signal can be reduced from 6.11% to 3.87% after linearization. To the best of our knowledge, this is the first multistage MMW PA with a low-loss built-in linearizer

Transcatheter Atrial Septal Defect Closure Assisted by Intracardiac Echocardiography: 3‐Year Follow‐Up

Intracardiac echocardiographic (ICE) evaluation of secundum atrial septal defect (ASDs) shows several advantages over transesophageal echocardiography (TEE). The aim of our study is to describe the 3-year results of transcatheter ASDs closure using the Amplatzer septal occluder (ASO) and ICE as the sole imaging tool both to select the device size and to monitor the procedure. Under local anesthesia, 135 consecutive eligible patients with ASDs (male/female = 45/90; mean age 42.2 +/- 19.2 years; BSA 1.71 +/- 0.7 m(2); mean pulmonary arterial pressure 30.4 +/- 11.5 mmHg; mean Qp/Qs ratio 2.1 +/- 0.6) underwent transcatheter closure using ASO and ICE. A 9F-9MHz mechanical transducer was used. Two orthogonal views on the transverse aortic valve and on the longitudinal four-chamber planes were obtained for quantitative ICE measurements, from which the diameters of the implanting ASO waist were to be derived. In all cases, we obtained a proper evaluation of ICE ASDs dimensions, leading to an optimal device size selection (mean size 25.0 +/- 6.7 mm). Moreover, the ICE allowed us to monitor device deployment and to verify the effectiveness of the ASDs stented by ASO. There were no complications related to the procedure or to the use of ICE. During a mean follow-up period of 21.5 +/- 12 months, the cumulative complete occlusion rates were 97.7, 97.0, 97.1, and 98% at 24 hours, 3 month, and 1 and 3 years, respectively. ICE is an effective and safe alternative to TEE and balloon-sizing maneuver during ASDs transcatheter closure procedures, allowing us to avoid the need of general anesthesia and leading to a similarly high percentage of occlusion rates with respect to the conventional method.

Intervertebral disc prostheses.

This article is based on a comprehensive review of the literature related to intervertebral disc prostheses. To compile an overview of the results and complications related to various types of lumbar and cervical disc replacements. A functional disc prosthesis has been sought since the 1950s. Although there were a few early attempts, disc replacement did not become a viable therapy until the late 1980s. Devices that were used in Europe at that time are now being evaluated in the United States in clinical trials. Cervical disc replacements are currently in the early stages of development and evaluation. A thorough literature search was conducted to identify articles published on intervertebral disc prostheses. Proceedings from conferences were reviewed as well. Articles were classified by topics, including lumbar total disc replacement, disc nucleus replacement, and cervical disc replacement. Results of total disc replacement are favorable, with 63-85% of patients having a good outcome. As with any procedure, issues related to patient selection, operative technique, and device size selection were learned from the early experiences with these devices. There has been only one disc nucleus replacement used in an appreciable number of patients. This has yielded good results, but there have been problems related to device displacement. There are increasing reports on the use of cervical disc replacements, but they are still in the early evaluation phases. However, as with the lumbar counterparts, new designs are being evaluated. Although still in the early phases of development, functional disc replacement will become a part of the spine surgeon's armamentarium for the treatment of patients with disc-related pain unresponsive to nonoperative care. The future in this area is exciting and bright with the introduction of new materials and new designs for implants. However, as with any new technology, there must be careful consideration of the safety of the devices, and their effectiveness will only be determined in long-term follow-up studies.

Echocardiographic estimation of balloon-stretched diameter of secundum atrial septal defect for transcatheter occlusion

Stretched diameter of the atrial septal defect (ASD), determined by balloon sizing at cardiac catheterization, is commonly used to select the sizes of the devices used for transcatheter closure of the secundum ASD. We have previously evaluated the utility of pulmonary/systemic flow ratio and angiographic and echocardiographic (echo) sizes of the ASD in estimating stretched ASD diameter in a group of 16 patients and determined that echo diameter had the best correlation with stretched diameter ( r = 0.82; p < 0.001). The stretched diameter can be estimated: 1.05 × echo diameter in millimeters + 5.49. In this study we have prospectively evaluated this formula in estimating the stretched ASD diameter by two-dimensional echo measurements obtained in two (long and short-axis) subcostal views in another group of 21 patients aged 2.5 to 29 years (median 4.5 years). The echo size of the ASD was 9.7 ± 3.0 mm, whereas the measured stretched diameter was 15.3 ± 4.0 mm. The predicted stretched ASD diameter was calculated according to the above formula and was 15.7 ± 3.1 mm, not significantly different ( p > 0.1) from the measured stretched diameter. The correlation between predicted and measured stretched ASD sizes was excellent ( r = 0.9; p < 0.001). The mean squared error was 2.4. The differences between measured and predicted values were within 2 mm in all but three patients. It is concluded that stretched ASD diameter can be estimated accurately by two-dimensional subcostal echo measurements, which in turn could be used for selection of device size for occlusion of the ASD.