Bryant Lin

Contractile actin expression in torn human menisci.

The human meniscus is subject to injury that necessitates repair or removal. Many aspects of the cellular response to injury have not been well characterized. The purpose of this study was to describe the cellular distributions within the torn human meniscus. In addition to evaluating the cell density in selected regions, we investigated the cellular expression of a contractile actin isoform that has recently been found in the intact human meniscus. Included as a contemporaneous comparative group were torn human meniscal allografts. We hypothesized that a hypercellular surface zone would be found in the torn menisci, with a higher percentage of cells in this peripheral region expressing α‐smooth muscle actin compared with other locations in the interior of the remnant. The rationale for this hypothesis was based on prior immunohistochemical investigations of the distribution of α‐smooth muscle actin–containing cells in the torn human anterior cruciate ligament. Eighteen torn meniscal specimens were obtained from 17 patients, 0.5 to 84 months after injury, and four torn allograft meniscal samples were retrieved from three patients, 11 to 49 months after implantation. Microtomed sections of paraffin‐embedded tissue were stained with hematoxylin and eosin and a monoclonal antibody to α‐smooth muscle actin. The cell density and percentage of cells containing α‐smooth muscle actin were determined in the following zones: synovial, vascular, hypercellular with loose collagen, hypocellular with dense collagen, and organized collagen. A cellular layer that resembled synovium was present on the surface of all but two of the specimens. Vascular regions were often continuous with the synovium abutting the more interior loose collagen zones. The total cell density was greatest in each of the zones closest to the periphery (synovium, vascular, and loose collagen; p < 0.001), when compared to the interior of the tissue. The synovium‐like layer was found to have the highest percentage of α‐smooth muscle actin–expressing cells and the highest α‐smooth muscle actin–containing cell density (p < 0.05). Similar results were found for the torn allograft menisci. These findings confirm the working hypothesis and suggest that the torn human meniscus is capable of mounting a reparative response, including the proliferation of cells capable of contributing to wound closure. This underscores the importance of providing a bridging scaffold into which such cells can migrate. (WOUND REP REG 2002;10:259–266)

Direct Visualization of Cardiac Radiofrequency Ablation Lesions

Effective ablation of atrial fibrillation and other cardiac arrhythmias requires precise catheter navigation and controlled delivery of energy to cardiac tissue. In this study, we summarize our initial experience using a fiber optic direct visualization catheter to evaluate and guide placement of endocardial radiofrequency (RF) ablation lesions. RF lesions were created in cadaveric porcine hearts and examined in a blood-filled field using a direct visualization catheter. Direct visualization of RF lesions was repeated in vivo using an ovine model. Lesions and interlesion gaps were clearly identifiable using the direct visualization catheter. It was possible to place lesions in proximity to anatomical landmarks and in relation to one another. Catheter-generated images correlated well with lesion appearance on gross examination. Direct catheter-based visualization is a feasible technique for guiding RF lesion placement, estimating lesion size, and identifying interlesion gaps. Future work is needed to correlate surface appearance with transmurality and electrical isolation.

A covariance-based algorithm: A novel technique for rhythm discrimination in ICDs

Inappropriate shocks due to misclassification of supraventricular and ventricular arrhythmias remain a major problem in the care of patients with Implantable Cardioverter defibrillators (ICDs). In this study we have investigated the ability of a new covariance-based algorithm, to distinguish Ventricular Tachycardia from other rhythms such as Supraventricular Tachycardia. The proposed algorithm has a low computational demand and with a small adjustment is applicable on both single-chamber and dual-chamber ICDs. The results are promising and suggest that the new covariance-based algorithm may be an effective method for ICD rhythm classification and may decrease inappropriate shocks.

Cryosurgical posterior nasal tissue ablation for the treatment of rhinitis

Endoscopic posterior nasal nerve (PNN) resection has been described as an efficacious surgical treatment of allergic and nonallergic rhinitis, but the requirement for surgery under general anesthesia has limited its acceptance. We report the first series of patients treated for chronic rhinitis using a novel device designed for office‐based cryosurgical ablation of the PNN.

A new approach for ICD rhythm classification based on support vector machines

Inappropriate shocks due to misclassification of supraventricular and ventricular arrhythmias remain a major problem in the care of patients with Implantable Cardioverter Defibrillators (ICDs). The purpose of this study was to investigate the ability of a new covariance-based support vector machine classifier, to distinguish ventricular tachycardia from other rhythms such as supraventricular tachycardia. The proposed algorithm is applicable on both single and dual chamber ICDs and has a low computational demand. The results demonstrate that suggested algorithm has considerable promise and merits further investigation.

Extraction of Buried P Waves from Printed Electrocardiograms

Background: Morphologic identification of ectopic P‐waves from surface ECGs can be challenging, particularly when the P‐wave is buried in the QRST wave complex. Because ECGs are often available on paper and not digitally, we developed a method of subtracting the T‐wave from the buried P‐wave complex on paper ECGs.

Extracting concealed atrial premature contractions from ambulatory Holter data using a PC-based system

Atrial fibrillation may be cured by eliminating triggering atrial premature contractions (APCs.) Characterizing these APCs may help localize triggers, however this is difficult when the APC is obscured by the preceding T-wave. Therefore we sought to develop an inexpensive method to extract APCs from ambulatory Holter monitors in AF patients. We examined 24-hour Holter strips from patients with AF triggered by APCs. Triggering and nontriggering APCs were extracted using a PC-based T-wave subtraction algorithm. The extracted APCs were compared visually as well as by correlation software. The software accurately identified 29 episodes of atrial fibrillation and extracted 76 APCs in 12 patients. In all cases, visual inspection confirmed the presence of atrial fibrillation of APCs. Triggering APCs were similar to other triggering APCs in each patient while nontriggering APCs were less similar to other nontriggering APCs in each patient. Triggering APCs were different from nontriggering APCs. Automated computerized subtraction of T-waves using an inexpensive PC-based system may permit characterization of APCs during ambulatory monitoring.