Biomedical subjects

Pallav Shah

Publications and source records attributed to Pallav Shah.

7 recordsLinked to original sources

PubMed2006

Patient-specific bronchoscopy visualization through BRDF estimation and disocclusion correction.

This paper presents an image-based method for virtual bronchoscope with photo-realistic rendering. The technique is based on recovering bidirectional reflectance distribution function (BRDF) parameters in an environment where the choice of viewing positions, directions, and illumination conditions are restricted. Video images of bronchoscopy examinations are combined with patient-specific three-dimensional (3-D) computed tomography data through two-dimensional (2-D)/3-D registration and shading model parameters are then recovered by exploiting the restricted lighting configurations imposed by the bronchoscope. With the proposed technique, the recovered BRDF is used to predict the expected shading intensity, allowing a texture map independent of lighting conditions to be extracted from each video frame. To correct for disocclusion artefacts, statistical texture synthesis was used to recreate the missing areas. New views not present in the original bronchoscopy video are rendered by evaluating the BRDF with different viewing and illumination parameters. This allows free navigation of the acquired 3-D model with enhanced photo-realism. To assess the practical value of the proposed technique, a detailed visual scoring that involves both real and rendered bronchoscope images is conducted.

Algorithms↗

PubMed2004

Early and midterm results with the Ross procedure: a study of the first 31 cases.

Between 1994 and 2002, 31 patients underwent the Ross procedure by a single surgeon. The mean age was 42 years (24-61), 87% were male and 61% were in New York Heart Association (NYHA) class III-IV. Pure aortic stenosis (AS) was present in 32% of patients, pure aortic regurgitation (AR) in 22% and mixed disease in the rest. The aortic valve was bicuspid in 93.5% of the patients. Autograft implantation was by full root replacement in all cases. Concomitant cardiac surgical procedures were carried out in 10/31 (32%). All patients had at least annual clinical and echocardiographic follow-ups. There was one early death (3%). Overall patient survival was 92.7% at 1 year and 86.1% at 5 years. Twenty-eight (96.55%) were in NYHA class I. Echocardiographic follow-up revealed none to trivial AR in 24/29 (82.75%) and mild AR in 4/29 (13.7%). There was no autograft re-operation before 5 years. The mean gradient across the autograft was low (< 4 mm Hg). There were no incidences of endocarditis or thromboembolism. None of the patients required anticoagulation. Our early experience with the Ross procedure has shown good results in relation to early and midterm morbidity, mortality, autograft, and homograft function.

Adult↗

PubMed2003

HIV-related lung cancer in the era of highly active antiretroviral therapy.

OBJECTIVES: To address the impact of highly active antiretroviral therapy (HAART) on the incidence and outcome of patients with HIV-related lung cancer. DESIGN AND SUBJECTS: Patients with HIV-related lung cancer were identified from a prospective HIV data base of 8400 patients diagnosed between 1986 and 2001. Patients diagnosed with HIV-related lung cancer before 1996 were in the pre-HAART cohort whereas the remainder were in the post-HAART cohort. METHODS: The incidence of HIV-related lung cancer in the pre- and post-HAART cohorts was compared with the age and sex-matched population of south east England. Clinicopathological features, treatments and outcomes were also recorded. RESULTS: The incidence of HIV-related lung cancer increased from 0.8 (95% CI 0.2-3.2)/10(5) patient-years follow-up in the pre-HAART era to 6.7 (95% CI 3.1-13.9)/10(5) patient-years follow-up in the post-HAART era. The age and sex-matched incidence of lung cancer in south east England was 0.75 (95% CI 0.63-0.87)/10(5) patient-years, suggesting that HIV-related lung cancer only occurred more frequently in the post-HAART era (relative risk 8.93, 95% CI 4.92-19.98). The patient characteristics and outcomes were similar in the pre- and post-HAART eras, although the time interval between testing HIV positive and developing HIV-related lung cancer was longer in post-HAART patients. CONCLUSION: In this study HIV-related lung cancer occurred more frequently in the post-HAART era, when compared with the HIV-negative population. Unfortunately, the outcome of these patients remains poor despite HAART.

Antiretroviral Therapy, Highly Active↗

PubMed2003

Mitral regurgitation: comparison between edge-to-edge repair and valve replacement.

Mitral regurgitation due to bileaflet prolapse and ischemic causes can be difficult to repair. Midterm experience of the Alfieri edge-to-edge repair as an alternative to valve replacement is reported. Twenty-six patients with severe mitral regurgitation underwent the Alfieri repair between January 1998 and December 2000 (group 1); 15 cases were due to bileaflet prolapse and 7 were of ischemic origin. During the same period, valve replacement was performed in 36 patients (group 2), 20 of whom had similar indications. Follow-up was complete to a mean of 15 months (range, 1-28 months). There was no early death in either group. During follow-up, there was no reoperation in group 1, while 2 patients in group 2 required reoperations due to prosthetic valve endocarditis. There were 4 major thromboembolic or bleeding events in group 2, and none in group 1. All patients in group 1 had trivial to mild mitral regurgitation on follow-up echocardiography. The mean mitral valve gradient was significantly higher in group 2 compared to group 1 (7.2 versus 3.2 mm Hg, p = 0.001). The edge-to-edge repair is associated with good early and midterm results. Long-term follow-up is required to evaluate the durability of this technique.

Aged↗

PubMed2002

Impaired inhibition by dexamethasone of cytokine release by alveolar macrophages from patients with chronic obstructive pulmonary disease.

Chronic obstructive pulmonary disease (COPD) is characterized by inflammation of the respiratory tract in which macrophages are the predominant inflammatory cell and for which the efficacy of treatment with corticosteroids is controversial. We investigated the effect of dexamethasone on basal and interleukin (IL)-1beta or cigarette smoke media (CSM)-stimulated release of IL-8 and granulocyte macrophage-colony stimulating factor (GM-CSF) by bronchoalveolar lavage macrophages from cigarette smokers and patients with COPD (n = 15). Basal release of IL-8 was approximately fivefold greater in patients with COPD than smokers, whereas GM-CSF was similar for each group. IL-1beta and CSM increased IL-8 and GM-CSF release by macrophages from both smokers and patients with COPD. Dexamethasone did not inhibit basal or stimulated IL-8 release from macrophages from patients with COPD but inhibited release in smokers. In contrast, basal and IL-1beta-stimulated GM-CSF release, but not CSM-stimulated release, was inhibited by dexamethasone. We conclude that the lack of efficacy of corticosteroids in COPD might be due to the relative steroid insensitivity of macrophages in the respiratory tract.

Aged↗

PubMed2002

Double-breasted repair of the posterior mitral valve leaflet.

The double-breasted repair of the posterior leaflet of the mitral valve is an alternative technique for correction of mitral regurgitation in selected patients. This new technique has the advantage of avoiding distortion of the posterior annulus and simplifies the repair, especially in complex posterior leaflet prolapse.

Cardiac Surgical Procedures↗

PubMed2002

Avoiding the pump in tricuspid valve endocarditis--vegetectomy under inflow occlusion.

BACKGROUND: Surgical treatment of tricuspid valve endocarditis (TVE) ranges from vegetectomy to valve replacement with the use of cardiopulmonary bypass (CPB), accompanied by risks of systemic and lung complications. We present our experience with tricuspid valve vegetectomy under inflow occlusion without CPB. METHODS: Between July 1998 and July 2001, seven patients with a mean age of 26 years underwent tricuspid valve vegetectomy under vena caval inflow occlusion (VCIO). Five patients were intravenous drug users. None of them had left-sided heart valve involvement. The clinical indications for operating were recurrent septic pulmonary emboli with significant bilateral lung infiltrates and intractable infection with signs of severe systemic sepsis, despite treatment with appropriate intravenous antibiotics for a mean duration of 126 hours. The echocardiographic indication was very large localized >1 cm vegetations in all patients. Six patients had methicillin sensitive staphylococcus aureus and one had streptococcus viridans positive blood cultures. Five patients had postoperative high volume veno-venous hemofiltration (HVVF). RESULTS: There were no deaths. VCIO time did not exceed 2 minutes (range time was 45 seconds to 2 minutes). All patients had resolution of sepsis and improvement in respiratory status within 48 hours. Five patients had trivial and two moderate tricuspid regurgitation. Six patients were discharged home within 14 days with no long-term sequelae. One patient required long-term dialysis for renal failure. One patient required a late thoracotomy for drainage of a loculated empyema. CONCLUSIONS: Tricuspid valve vegetectomy can be performed safely under VCIO. HVVF promotes removal of inflammatory mediators, thus improving recovery.

Adolescent↗